Manual handling in child care work: components of back...

Manual handling in child care work:

components of back injury risk during

the task of nappy changing

Adele Stewart B.P.E.

This thesis is presented for the degree of

Master of Science of

The University of Western Australia,

School of Sport Science, Exercise and Health

December 2009.

ii

Executive Summary

Manual handling is a duty inherent to child care. Whether it is domestic or

occupational, the manual handling work involved in caring for young children

doesnt differ. The lifting and handling of young children and interaction with infant

nursery equipment and childrens furniture is relentless. General manual handling (MH)

work is associated with higher than normal levels of musculoskeletal disorder (MSD).

Occupational health and work safety (OHS) practices have been created to identify,

assess and minimise injury risk to workers. The key variables taken into account are the

characteristics of the loads, equipment, job design and the anthropometry and ability

of those doing the work. Although there is no apparent lack of OHS regulations applied

to child care work, unusually high rates of MSD continue to be reported (Owen, 1992;

Bright & Colabro, 1999; King et al., 2006) with lower back injury (LBI) being the main

contributor (Brown & Gerbrick, 1993). The exceptionally high rates of injury for workers

employed in child care, the majority of whom are female, exposes an implication of

injury risk to women caring for young children in the domestic environment. Many of

these women in domestic child care will be pregnant or postpartum and as such

likely to already have some LBI or transient physical disability (Pheasant, 1986). Past

studies of MH in child care have observed likely implications for LBI from lifting children

and interaction with equipment, but to date there has been no biomechanical analysis

or objective measurement of the tasks or the components. That being said, lifting

children is not a standardised activity and therefore difficult to measure. Nappy

changing however, is one MH child care task that is performed frequently and includes

variables that are quantifiable. The aim of this research was to establish an

understanding of the complexities involved in nappy changing and to explore the

biomechanical risk hazards for LBI. Due to the significant number of women involved in

domestic child care and occupational MH work, this study has implications for the child

care environment as well as the broader workplace.

Method: The research comprised of two separate but interrelated studies. Study One, a

self responded questionnaire, was designed to gather information from women (n=411)

who were regularly involved in the task of nappy changing. It also provided frequency

and duration data as well as scaled response feedback on associated lower back pain

(LBP); all of which were used to provide perspective and validity to the overall study.

The data regarding equipment, load and task variables were used to develop the

control variables for the second study. Study Two was a biomechanical analysis using

3DSSPP Version 5.0.4 (University of Michigan, 2005) of the common nappy change task

scenarios. Participants (n=10) included pregnant, postpartum and nulliparae women.

The biomechanical analysis measured posture and spinal loading when lifting a 3

month and an 18 month simulated baby load from three heights of purpose built

nappy change furniture, and repeated the test for the two stance alignments. Study

iii

Two also assessed biomechanical outcomes for a floor reaching posture common

when using this change furniture.

Results: Study One indicated that most women in the domestic child care environment

(i) use purpose built nappy change furniture that is around waist height which required

either a symmetric or asymmetric stance; (ii) were working with two or more children

under the age of three; and (iii) associated some level of LBP with the posture and the

lift components of this task. This study also revealed that women have a 50% risk of

developing LBP during and/or subsequent to pregnancy. Furthermore, those who

reported high levels of LBP rated pain associated with posture and lifting components

of the nappy change task as severe. Study Two established that spinal compression

and shear force, ligament strain and torso muscle fatigue were increased to potentially

hazardous levels when lifting the heavy baby load regardless of bench height or

stance alignment. The results also indicated that whilst there was a statistically

significant difference between the two stance alignments, there were both positive

and negative attributes for both stance conditions in terms of injury risk. The results

suggest that some purpose built furniture may be hazardous to LBI. Although not

directly tested, the results indicate that the frequency and duration of the task may

compound the outcomes and that nappy change furniture with the work surface of

waist height may not be optimum for these women when performing this task.

Conclusion: Our results demonstrate that a considerable number of women (i)

experience LBP during and subsequent to pregnancy; (ii) associate the task of nappy

changing with heightened LBP; and (iii) have increased difficulty changing older

babies as they are physically challenging and the task takes longer. Furthermore, these

data indicated that waist height nappy change furniture may be associated with

posture related LBP. The results of Study Two revealed there are several biomechanical

risk consequences for LBI from both the lifting and posture components of this task.

These risks for the operator may be compounded due to the design of equipment, the

nature of the baby loads being handled and for operators who are carrying

abdominal, pelvic and/or lower back injuries. These problems may also be

exacerbated by the frequency and duration of this task. The long term implications of

unresolved LBI in these women are unknown, but may have repercussions for future

workplace injury. This study has highlighted the urgent need for OHS strategies to

address the unique requirements of the individual populations of women working in

child care and manual handling roles and strongly recommend further biomechanics

studies of this nature.

iv

Table of Contents Page

Executive Summary... ii

Table of Contents.. iv

Acknowledgements.. vii

List of Tables. viii

List of Figures ix

List of Abbreviations.. xiv

Chapter One Introduction.

1

Statement of the Problem... 4

Significance of the Study. 4

Overview of the Thesis Structure 4

Aims 5

Hypotheses.. 6

Delimitations. 7

Limitations. 8

Chapter Two - Review of Literature

9

Manual Handling 9

Women in Child care Work. 10

Identifying the Risk. 12

Operator characteristics. 12

Difficult loads.. 17

Equipment... 20

Occupational health and safety issues.. 26

Task of nappy changing. 27

Assessing the Risk 30

The biomechanics of standing lifts: implications for LBI 30

Posture strength and lifting 33

Implications 37

Chapter Three Methods...

40

Study One.. 40

Participants... 40

Survey design 41

v

Distribution. 42

Data Analysis 43

Study Two... 44

Participants... 44

Instruments and apparatus.. 45

Procedures 47

Treatment of the data... 51

Statistical analysis 53

Chapter Four - Study One Results..

55

Demographics 55

Equipment 57

Task Frequency and Duration 59

Rating of Task Difficulty Associated with Equipment... 60

Rating of Pain and Dysfunction Associated with the Task. 61

Pain and Dysfunction Associated with Respondent Characteristics.. 64

Qualitative Summary 68

Chapter Five - Study Two Results

72

Scenario One Symmetric Lift.. 74

Scenario Two Asymmetric Lift. 82

Comparison of Symmetric and Asymmetric Lift 90

Scenario Three Mid-Calf Reach. 98

Chapter Six Discussion

106

Outcome of Study One 107

Outcome of Study Two. 108

Synthesis of the Studies. 113

Load.. 113

Equipment... 114

Frequency, duration and fatigue. 117

Operator Characteristics 119

Summary of Discussion. 120

Recommendations. 121

Conclusion.. 124

vi

References. 125

Appendices.. 132

Appendix A: Subject Information Sheet Study One 132

Appendix B: Study One Questionnaire 135

Appendix C: Subject Information Sheet Study Two. 140

Appendix D: Participant Consent Form Study Two.. 142

vii

Acknowledgements

To my three girls Dempsey, Audrey and Lily for giving me the opportunity to

experience and learn so much more than I could ever have imagined

To my friends and family for their endless support

To my Mother Julie, who has always encouraged me and enabled the

freedom and certainty for me to pursue my challenges

I love you and sincerely thank you all.

To Brian, for having faith in my abilities when mine was faltering

And to my supervisors Tim and Siobhan, who have completed a manual

handling marathon, ever so gently pushing me on through the long and

winding tunnel toward that light

I am so grateful to have been allowed this indulgence.

Finally, to the many women who so willingly participated in this study, and to

those who will hopefully benefit from it.the work you all do is amazing!

viii

List of Tables Page

Table 2.1

The Average Expected Somatic Growth Measures for children

New Born to 24 Months

19

Table 3.1 Dimensions Used for Baby Load Manikins

46

Table 4.1 Number of Pregnancies to Full term for Each Respondent group

56

Table 4.2 Respondent Characteristics relative to task Associated Low back Pain

65

Table 4.3 Age and BMI Status Relative to Perceived Task-Associated Low Back Pain/Disability

67

Table 4.4 Pregnancy status and Number of Births Relative to Perceived Task-Associated Low back Pain/Disability

68

Table 4.5 Qualitative Theme Summary and Percentage of Responses to general Dimensions Categories

71

Table 5.1 Participants Demographic and Girth Measurement Information

72

Table 5.2 Repeated Measures ANOVA Summary of Bench Height and Load Main Effects for Scenario One, the Symmetric Lift

75

Table 5.3 Repeated Measures ANOVA Summary of Bench Height and Load Main Effects for Scenario Two, the Asymmetric Lift

83

Table 5.4 Repeated Measures ANOVA Summary of Stance Alignment with Bench Height Main Effects for the Comparison of Symmetric and

Asymmetric Lift at Load 2

91

Table 5.5 Repeated Measures ANOVA Summary of Bench Height Effect Scenario Three, the Mid-calf Reach

99

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List of Figures Page

Figure 2.1 2/3 Tier change table

21

Figure 2.2 Bath and change table

22

Figure 2.3 Fold out frame and sling

23

Figure 2.4 Drawer top changer or changing chest

23

Figure 2.5 Cot top changer or changing board

24

Figure 2.6 Drop down suspended bench top perpendicular or horizontal to the wall

25

Figure 2.7 Instructions for nappy changing

29

Figure 3.1 Change bench apparatus shown in the Scenario One symmetric lift with an 18 month baby load manikin (11.5 kg

load) at 80 cm, 95 cm and 110 cm bench surface heights.

45

Figure 3.2 Three month baby load manikin. Rump placement position is marked on the surface of the change bench

47

Figure 3.3 Eighteen month baby load manikin. Rump placement position is marked on the surface of the change bench

47

Figure 3.4 Scenario One Symmetric lift position

49

Figure 3.5 Scenario Two Asymmetric lift position

50

Figure 3.6 Scenario Three Mid-calf reach

51

Figure 3.7 Example of 3D SSPP Version 5.0.4 application window depicting modelling file for a pregnant participant performing a

symmetric lift at the 95 cm bench height with an 18 month baby

load manikin

52

Figure 4.1 Respondent age group frequencies

55

Figure 4.2 Respondent height group frequencies

56

Figure 4.3 Change furniture styles as reported, used in the domestic environment

57

Figure 4.4 Change surface heights as reported, used in the domestic environment

57

Figure 4.5 Domestic furniture example of 2/3 tier change unit

58

x

Figure 4.6 Domestic furniture example of drawer top change unit

58

Figure 4.7 Domestic furniture example of bath/change unit

58

Figure 4.8 Domestic furniture example of frame sling change unit

58

Figure 4.9 Public change unit example of wall mounted, vertical

59

Figure 4.10 Public change unit example of wall mounted, horizontal

59

Figure 4.11 Reported daily task frequency per baby load

60

Figure 4.12 Reported task duration per baby load

60

Figure 4.13 Difficulty associated with using Public furniture styles

61

Figure 4.14 Difficulty associated with using Domestic furniture styles

61

Figure 4.15 Low back pain/dysfunction associated with Lift of load and Posture associated with the nappy change task

62

Figure 4.16 Low back pain/dysfunction as a result of posture used with each furniture style

63

Figure 4.17 Low back pain/dysfunction as a result of lift used with each furniture style

63

Figure 4.18 Low back pain/dysfunction as a result of lifting and relative height of the furniture used by each respondent. Furniture

height is expressed as a proportion of individual stature

64

Figure 4.19 Low back pain/dysfunction as a result of posture and relative height of the furniture used by each respondent. Furniture

height is expressed as a proportion of individual stature

64

Figure 4.20 Summary of raw data from written responses and first order key components of themes making up the general dimensions

of observations

70

Figure 5.1 Representation of Scenario One Symmetric Lift. Sagittal and Frontal views at 80 cm bench height

74

Figure 5.2 Mean torso extension as a result of load and height changes in Scenario One Symmetric lift

76

Figure 5.3 Mean compression force (N) at L5/S1 as a result of load and height changes in Scenario One Symmetric lift

77

Figure 5.4 Mean shear force (N) at L5/S1 as a result of load and height changes in Scenario One Symmetric lift

77

Figure 5.5 Mean ligament strain at L5/S1 as a result of load and height changes in Scenario One Symmetric lift

78

Figure 5.6 Mean torso flexion/extension muscle fatigue (%MVC) at L5/S1 as a result of load and height changes in Scenario One

Symmetric lift

79

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Figure 5.7 Mean torso lateral bending muscle fatigue (%MVC) at L5/S1 as a result of load and height changes in Scenario One

Symmetric lift

80

Figure 5.8 Mean torso rotation muscle fatigue (%MVC) at L5/S1 as a result of load and height changes in Scenario One

Symmetric lift

80

Figure 5.9 Mean right shoulder abduction/adduction muscle fatigue (%MVC) as a result of load and height changes in Scenario

One Symmetric lift

81

Figure 5.10 Mean right shoulder flexion/extension muscle fatigue (%MVC) as a result of load and height changes in Scenario One

Symmetric lift

81

Figure 5.11 Mean right shoulder humeral rotation muscle fatigue (%MVC) as a result of load and height changes in Scenario One

Symmetric lift

81

Figure 5.12 Representation of Scenario Two Asymmetric Lift. Sagittal and Frontal views at 80 cm bench height

82

Figure 5.13 Mean torso extension as a result of load and height changes in Scenario Two Asymmetric lift

84

Figure 5.14 Mean compression force (N) at L5/S1 as a result of load and height changes in Scenario Two Asymmetric lift

85

Figure 5.15 Mean shear force (N) at L5/S1 as a result of load and height changes in Scenario Two Asymmetric lift

85

Figure 5.16 Mean ligament strain at L5/S1 as a result of load and height changes in Scenario Two Asymmetric lift

86

Figure 5.17 Mean torso flexion/extension muscle fatigue (%MVC) at L5/S1 as a result of load and height changes in Scenario Two

Asymmetric lift

87

Figure 5.18 Mean torso lateral bending muscle fatigue (%MVC) at L5/S1 as a result of load and height changes in Scenario Two

Asymmetric lift

87

Figure 5.19 Mean torso rotation muscle fatigue (%MVC) at L5/S1 as a result of load and height changes in Scenario Two

Asymmetric lift

88

Figure 5.20 Mean right shoulder abduction/adduction muscle fatigue (%MVC) as a result of load and height changes in Scenario

Two Asymmetric lift

89

Figure 5.21 Mean right shoulder flexion/extension muscle fatigue (%MVC) as a result of load and height changes in Scenario Two

Asymmetric lift

89

Figure 5.22 Mean right shoulder humeral rotation muscle fatigue (%MVC) as a result of load and height changes in Scenario Two

Asymmetric lift

89

xii

Figure 5.23 Representation of Symmetric and Asymmetric Lifts. Sagittal and Frontal views at 80 cm bench height

90

Figure 5.24 Mean torso extension as a result of stance alignment and height changes in Symmetric vs Asymmetric lift

92

Figure 5.25 Mean compression force (N) at L5/S1 as a result of stance alignment and height changes in Symmetric vs Asymmetric lift

92

Figure 5.26 Mean shear force (N) at L5/S1 as a result of stance alignment and height changes in Symmetric vs Asymmetric lift

93

Figure 5.27 Mean ligament strain at L5/S1 as a result of stance alignment and height changes in Symmetric vs Asymmetric lift

94

Figure 5.28 Mean torso flexion/extension muscle fatigue (%MVC) at L5/S1 as a result of stance alignment and height changes in

Symmetric vs Asymmetric lift

94

Figure 5.29 Mean torso lateral bending muscle fatigue (%MVC) at L5/S1 as a result of stance alignment and height changes in


95

Figure 5.30 Mean torso rotation muscle fatigue (%MVC) at L5/S1 as a result of stance alignment and height changes in Symmetric vs

Asymmetric lift

95

Figure 5.31 Mean right shoulder abduction/adduction muscle fatigue (%MVC) as a result of stance alignment and height changes in


96

Figure 5.32 Mean right shoulder flexion/extension muscle fatigue (%MVC) as a result of stance alignment and height changes in


96

Figure 5.33 Mean right shoulder humeral rotation muscle fatigue (%MVC) as a result of stance alignment and height changes in


97

Figure 5.34 Representation of Scenario Three, Mid-calf Reach. Sagittal and Frontal views at 80 cm bench height

98

Figure 5.35 Mean torso extension as a result of bench height in Scenario Three, Mid-calf Reach.

100

Figure 5.36 Mean compression force (N) at L5/S1 as a result of bench height in Scenario Three, Mid-calf Reach.

100

Figure 5.37 Mean shear force (N) at L5/S1 as a result of bench height in Scenario Three, Mid-calf Reach.

101

Figure 5.38 Mean ligament strain at L5/S1 as a result of of bench height in Scenario Three, Mid-calf Reach.

102

Figure 5.39 Mean torso flexion/extension muscle fatigue (%MVC) at L5/S1 as a result of bench height in Scenario Three, Mid-calf Reach.

102

xiii

Figure 5.40 Mean torso lateral bending muscle fatigue (%MVC) at L5/S1 as a result of bench height in Scenario Three, Mid-calf Reach.

103

Figure 5.41 Mean torso rotation muscle fatigue (%MVC) at L5/S1 as a result of bench height in Scenario Three, Mid-calf Reach.

103

Figure 5.42 Mean right shoulder abduction/adduction muscle fatigue (%MVC) as a result of bench height in Scenario Three, Mid-calf

Reach.

104

Figure 5.43 Mean right shoulder flexion/extension muscle fatigue (%MVC) as a result of bench height in Scenario Three, Mid-calf Reach.

104

Figure 5.44 Mean right shoulder humeral rotation muscle fatigue (%MVC) as a result of bench height in Scenario Three, Mid-calf Reach.

105

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Definition of Key Terms and Abbreviations

ABS Australian Bureau of Statistics

AL Action Limit (NIOSH)

ANOVA Analysis of variance

ASCC Australian safety and Compensation Council

BCDL Back compression design limit (NIOSH)

CCCL Australian Child Care Centre License

CF Spinal compression force

CNS Central Nervous System

CoG Centre of gravity

CoM Centre of mass

DL Design limit (NIOSH)

DOCEP Department of Consumer and Employment Protection

GLBP Gestational lower back pain

INPAA Infant and Nursery Products Association of Australia Inc

IV Intervertebral

LBD Lower back disorder

LBI Lower back injury

LSAC Longitudinal Study of Australian Children

MH Manual handling

MPL Maximum permissible limit (now AL NIOSH)

MSD Musculoskeletal disorder

MSI Musculoskeletal injury

MVC Maximum Voluntary Contraction

NIOSH National Institute for Occupational Safety and Health

OHS Occupational health and safety

RWL Recommended Weight Limit

RCN Raising Children Network

SF Spinal shear force

WHO World Health Organisation

1

CHAPTER ONE

INTRODUCTION

Nappy changing One of the ultimate joys of parenting is undoubtedly

nappy changing. Its a skill that can be quickly acquired with a few basic rules

to make this unavoidable and essential daily task a straight forward and

relaxed time for both baby and parents

(http://www.howto.tv/show/how_to_change_a_nappy).

Contrary to this statement, nappy changing is a complex manual handling

task, revealing some underestimated occupational hazards and classic

components of risk for lower back injury.

Any work deemed to be MH, is work that requires the use of body force to lift,

lower or in any way move a load, either inanimate or live (Chaffin & Andersson,

1991; Kroemer & Grandjean, 2001). In the work place, MH is associated with

higher than normal occupational health and safety (OHS) hazards (NIOSH,

1994; NIOSH, 2004; Miller et al., 2006) and as a result workers are faced with a

higher than normal risk of sustaining a musculoskeletal injury (MSI) (McGill, 1997;

Dempsey, 1998). The most problematic MSI or musculoskeletal disorder (MSD)

associated with MH is lower back injury (LBI) (NIOSH, 1994; Dempsey & Hashemi,

1999; ASCC1, 2007). LBI and lower back disorders (LBD) are complex to

diagnose (Karwowski, 2006), frequently result in long periods of absence from

the work place and present an enormous cost to industry (NIOSH, 2004; ASCC,

2007; EASHW, 2007).

Industries that principally involve MH work have typically been linked with part-

time work, shift work and occupational gender segregation (Preston &

Whitehouse, 2004). For example 70% of employees in the transport, mining,

manufacturing and construction industries are men; and 80% of employees

within the health and community service, retail or service industry groups are

women (ABS, 2004; WorkCover, 2007). Furthermore, women currently make up

almost half of the Australian work force and the majority are employed in MH

industries (ABS, 2004). And although OHS policies attempt to standardise safe

work practices in all work place populations, women currently account for 55%

of all lost time work claims from MSD (Miller et al., 2006). Additionally, in the past

2

10 years, Government OHS policies have specifically addressed MH related

LBD (ASCC3, 2007). During this period, although there has been a significant

decline in the rate of LBD among men, the rate in women has slightly

increased (ASCC1, 2007; Hawkes, 2007).

MSI are particularly high among child care workers (King et al. 1996; Wortman,

2003; Gratz et al., 2002). Given the nature of child care, it is perhaps not

surprising that 95% of these employees are women (Wortman, 2003; Gratz et

al., 2002). Of interest though, is the significant risk of injury that the child care

environment poses to the workers (Owen, 1992; Gratz & Claffey, 1996;

Wortman, 2003). Although there is no apparent lack of safety controls and

regulations (ASCC2, 2007), this population of workers consistently present with

unusually high rates of LBD (NIOSH, 1994; Owen, 1994; Bright & Calabro, 1999;

King et al., 2006). With over 115,000 women employed in registered child care

work in Australia (ABS, 2007), the potential cost of injury associated with MH

work in this industry alone is substantial. The exceptionally high rates of injury

for workers employed in child care also exposes an implication of injury risk to

a much broader population that being women involved in unpaid child

care within the domestic environment. Although there are no statistics on MH

related injuries for women in home duties, the high rate of injury in child care

occupations would indicate that there may be similar injury risks for women

caring for young children at home.

Whether in the domestic or formal child care environments though, MH work

involving very young children doesnt differ: the objective is to meet their

needs and the work is relentless (Griffin & Price, 2000; Craig, 2007). This MH is

an on-going relay of lifting and carrying children or manipulating these live

loads into or onto furniture and equipment that have been purpose built with

mainly the child in mind (Wortman, 2003; Gratz et al., 2002; King et al., 2006).

The situation is further compounded since work place safety in the child care

industry is focused more on safety of the children being handled, rather than

those doing the handling (Griffin, 2006). The task, which involves children as

live loads and the purpose built equipment are MH variables unique to this

work environment and clearly present exceptional problems.

In the domestic child care environment, regardless of whether they are stay-

at-home mothers or in paid employment as well, women are the primary

3

care providers for infants (012 months) and young children ((Preston &

Whitehouse, 2004; ABS, 2005; Baxter et al., 2007). In Australia 10% of adult

women are pregnant at any one time (ABS, 2007), with more than half of

these women already caring for at least one child under the age of 3 years

(ABS, 2005; ABS, 2007). It is now well documented that between 5090% of

pregnant women will experience lower back pain (LBP) during pregnancy

(Ostgaard et al., 1996; Sweden, 2003; Carlson et al., 2003; Wang, 2003) which

more than likely will commence within the first trimester (Wu et al., 2004).

Having pregnancy related LBP is the greatest predictor for women suffering

LBP following the birth of a child (Ostgaard & Anderson, 1992; Ostgaard et al.,

1997; Noren et al., 2002; Ostgaard et al., 2002). However, although the cause

for pregnancy related LBP remains uncertain, the severity and duration of this

LBP is a real concern for at least 20% of post partum women (Noren et al.,

2002). Complicating this problem is the fact that many women develop

functional disabilities associated with pelvic floor insufficiency (Mast, 1999;

Newman, 2000; Neuman & Gill, 2002) and abdominal muscle diastases

(Kotarinos, 2003) that can only be repaired through surgery (Mast, 1999).

To date there is no published research that objectively quantifies the MH work

when caring for young children. Lifting and lowering of children is undoubtedly

the most frequent and at times, the most strenuous of these MH tasks (Hostetler,

1984; Kuczmarski et al., 2000; Morehead, 2004), but in child care, lifting children

is not generally a standardised activity. It is possible that because of the

continuous, random and combined nature of lifting tasks in child care, defining

an assessment that is valid and reliable could prove difficult. However, nappy

changing is one MH task that is performed frequently and includes variables

that are quantifiable. Nappy change furniture is used to elevate the working

surface when changing a young childs nappy and the carer will lower the

child to this surface, and then lift the child from this surface on completion of

the task. The components of this task are measurable and biomechanically

quantifiable in relation to injury risk and therefore, may provide some indication

of the implications for women when lifting young children.

4

Statement of the Problem

We do not know if women working in child care view the task of nappy

changing on a young child as difficult, nor if purpose built nappy change

furniture is problematic to them. Also we have very limited understanding of the

biomechanics of the nappy change task and the spinal loads resulting from the

lifting actions and postures. Handling a young child as a load has not been

investigated scientifically and purpose built nappy change furniture designs

have never been scrutinised in relation to their effect on the operator. Nor do

we know the implications of spinal loading on women whose anatomy may be

compromised due to pregnancy or childbirth; or if these women are at an

increased risk of LBI from MH. These factors all have implications for the child

care environment as well as the broader workplace.

Significance of the Study

There is a heightened risk of LBI for workers employed in child care that appears

to be unaltered by conventional MH risk control protocols. The problems

appear unique to this work and there are several issues of concern that have

never been investigated scientifically. This research will be of significance to:

professionals involved in ergonomics and the development of occupational

health and safety policy; those responsible for nursery furniture design and

manufacturing standards; professionals working in parenting education; and for

anyone undertaking the task of nappy changing in both occupational and

domestic child care settings.

Overview of the Thesis Structure

This introduction is followed by a comprehensive review of literature

investigating relevant aspects of MH; women in MH work, MH involved in child

care and the issues relating to the task of nappy changing. The review will also

address three of the independent variables related to the nappy changing

task that will be tested in this study: the operators, loads and equipment. This is

followed by is an overview of the available OHS publications referring to child

care tasks and a description of nappy changing and finally, a review of

biomechanical outcome measures and a summary of the implications for

women involved in this work.

5

This research comprised of two separate, but interrelated studies. Chapter 3

presents the methods used for Studies One and Two. Study One employed a

questionnaire designed to gather information from women who were regularly

involved in the task of nappy changing. Quantitative data from this study

(Study One) regarding equipment and task variables were used to develop the

control variables for Study Two. Other task related information from Study One

supplied qualitative feedback which was used to provide perspective and

validity to the overall project. Study Two involved a biomechanical analysis of

various nappy changing task scenarios, in which we measured movements

and postures, and estimated spinal loading on women when lifting a child from

purpose built nappy change furniture. Chapters 4 and 5 present the results for

Studies One and Two respectively. Finally Chapter 6 will connect both studies

together highlighting and discussing the main outcome points of interest from

this research.

Aims

The aims of Study One were to gather quantitative and quantitative

information:

from experienced women in relation to the physical difficulty and LBP

associated with the nappy change task;

on the task of nappy changing from which to build the test variables

for the biomechanical analysis in Study Two; and

regarding a range of other lifting tasks involved in child care, in order

to provide a comparison perspective for the task of nappy changing.

The aims for Study Two were to:

assess biomechanically the act of lifting a young child from the

surface of commonly used purpose built change furniture;

assess biomechanically the postures involved in the task of nappy

changing when using common purpose built change furniture; and

assess and quantify the spinal loadings and therefore, potential LBI

risk from the task of nappy changing when using common purpose

built change furniture.

6

Hypotheses

1) Following biomechanical simulation of lifting a baby load from purpose built

nappy change furniture, there will be a difference (p < 0.017) in the angle of

torso extension as a result of three variations in height; two variations in baby

load size and two variations in lifting stance alignment.


nappy change furniture, there will be a difference (p < 0.017) in compression

force at L5/S1 as a result of three variations in height; two variations in baby

load size and two variations in lifting stance alignment.


nappy change furniture, there will be a difference (p < 0.017) in shear force at

L5/S1 as a result of three variations in height; two variations in baby load size

and two variations in lifting stance alignment.


nappy change furniture, there will be a difference (p < 0.017) in ligament strain

at L5/S1 as a result of three variations in height; two variations in baby load size

and two variations in lifting stance alignment.


nappy change furniture, there will be a difference (p < 0.017) in the estimated

percentage of torso muscle fatigue as a result of three variations in height; two

variations in baby load size and two variations in lifting stance alignment.



percentage of (right) shoulder muscle fatigue as a result of three variations in

height; two variations in baby load size and two variations in lifting stance

alignment.


nappy change furniture, there will be a difference (p < 0.017) in the angle of

torso extension as a result of three variations in height during a hold and reach

posture.

7


nappy change furniture, there will be a difference (p < 0.017) in the

compression force at L5/S1 as a result of three variations in height during a hold

and reach posture.


nappy change furniture, there will be a difference (p < 0.017) in the shear force

at L5/S1 as a result of three variations in height during a hold and reach

posture.


nappy change furniture, there will be a difference (p < 0.017) in the ligament

strain at L5/S1 as a result of three variations in height during a hold and reach

posture.



percentage of torso muscle fatigue as a result of three variations in height

during a hold and reach posture.



percentage of (right) shoulder muscle fatigue as a result of three variations in

height during a hold and reach posture.

Delimitations

Study One

This questionnaire involved only women who had recent experience in the task

of nappy changing on a young child and was made available for a collection

period of four months.

Study Two

Participants in this study were either pregnant or post partum with experience in

the task of nappy changing; and nulliparae women who represent

occupational child care workers who have never been pregnant. They were

aged between 20 and 45 years, of average height and within a BMI range of

8

1825. The biomechanical outcomes were measured at the L5/S1 joint in the

lumbar spine.

Limitations

Study One

The respondents to the questionnaire were self-selected and the question

responses were self-assessed. The respondent sample may be biased and may

not adequately represent the target population which could limit the strength

of the qualitative component of this questionnaire. The validity and reliability of

the questionnaire was not known or tested.

Study Two

The sample size for this study was small and as such all participant data for

each lifting task was combined and presented as average data, thus being a

stronger representation of the outcome measures, but possibly lacking

accuracy in relation to the individual populations concerned. The

biomechanical analyses were performed using static measures, not dynamic

motion and measures of shoulder muscle fatigue were reported for the right

shoulder muscle groups only. The static strength prediction program cannot

recreate the frontal mass increase or simulate the pregnant and postpartum

weight distribution. This may have underestimating true values for subject

anthropometry and the inertial parameters input to the model.

9

CHAPTER TWO

REVIEW OF LITERATURE

MANUAL HANDLING

When reviewing the literature on occupational health and safety, it is clear that

MH has provided a rich field for research. Equally, when considering themes

within MH; lifting tasks, associated MSD and the enormous costs incurred from

lost time due to injuries, seem to dominate the literature (ABS, 2003).

Although MH work is generally referred to in an occupational sense, it may be

equally relevant to unpaid work in the domestic environment. According to the

(ABS, 2005), at least 80% of Australian women will experience motherhood and

the majority of 25 to 50 year old women not employed in paid work, will be

occupied full time in caring for their young children (Chaffin & Andersson, 1991;

McGill, 1997; Kroemer & Grandjean, 2001). Although there are few studies

reporting the specifics of tasks involved in child care, there is little doubt that

lifting is a frequent requirement when working with babies and young children

(NIOSH, 1994; Dempsey & Hashemi, 1999; WorkCover, 2004)

Lifting is reported to be a significant contributor to MSD (Marras et al., 1995) of

which LBI is the most frequently sustained, prolonged and costly work related

health problem (Karwowski, 2006). Unresolved injury to the spine can reduce an

individuals capacity to perform physical activity and increase the likelihood of

developing chronic disability (ASCC1, 2007; Hawkes, 2007). Furthermore a

history of LBD heightens the risk of serious acute back injury (ASCC1, 2007;

Hawkes, 2007).

In Australia in 2006, 61% of all lost time workers compensation claims made by

women were for MSI, with more than a third of those resulting from LBD

associated with lifting (ABS, 1998; ABS, 2007). Whats more, the highest rate of

lost time claims for MSD over the past 10 years was recorded by women

between the ages of 35 to 54 years (ABS, 1998). Although in the same period,

the number of LBD compensation claims made by men decreased by 18%, the

percentage of those made by women increased by 1% (ABS, 2005).

10

WOMEN IN CHILD CARE WORK

Over the last 30 to 40 years there has been a notable change in the

participation rate of women in the work force (Baxter & Gray, 2008). In 1960 less

than 33% of Australian women (aged 15 to 64) were employed and only 31% of

these were married women (Pocock, 2003; Craig, 2007). Currently in Australia

70% of women are employed (Baxter et al., 2007; Craig, 2007) with the largest

employer groups being Health and Community Services, Retail and

Manufacturing (ABS, 2005). Because women in Australia are still the primary

care providers to their children (ABS, 2005), working women are combining

paid work with family responsibilities (Craig, 2007). It is no surprise then that the

demand for secondary child care support has also changed.

In Australia, mothers of children up to 12 months of age will generally be the full

time carer for this child (ABS, 2003) with grandmothers being the preferred

secondary support (Whitebook & Ginsburg, 1983; Hostetler, 1984; Moorehead,

2004). The Longitudinal Study of Australian Children (LSAC) (ABS, 2005) reported

that mothers working at home with an infant (012 months) spent 10 hours per

day in high contact activities which included bathing, changing nappies and

feeding; and holding, carrying or cuddling the child (ABS, 2005). In addition

though, over half of the pregnant and early post partum women working at

home will also be caring for at least one other child between the ages of 12

and 24 months (Brown & Gerberich, 1993). Although children of this age have

more developed cognitive processes, they are still fully dependent and require

constant supervision (Griffin & Price, 2000; Sanders & Morse, 2005). However, as

the age of children increases out of infancy the use of formal day care as the

secondary support also increases (ABS, 2005). Indeed the largest group of

children attending formal day care centres in Australia is represented by the

one to three year olds with more than 62% of them being in care for some

period (Brown & Gerberich, 1993; Gratz et al., 2002).

Caring for young children is extremely demanding, the physical work of which is

often relentless (Shultz et al., 2004; Karageanes, 2005) It requires the continuous

necessity for lifting, bending, carrying, reaching, stooping, pushing and pulling

awkward and heavy loads; getting children in and out of prams, high chairs

and cots as well as interacting with equipment, purpose built for children

(Charlton et al., 2001; Palejwala et al., 2001). There are relatively few studies

11

reporting the specific physical demands of child care, but perhaps because of

the non-specific and continual nature of the tasks throughout a day,

formulating a research perspective is difficult. According to Hostetler (1984), the

first empirical study of this MH work; a worker employed within formal child care

and responsible for eight children, will bend and lift at least 200 times in an

eight hour day, potentially lifting around 4,350 kg in that time. In addition to the

handling of children, is the regular moving of furniture, equipment and toys; the

use of child size furniture and spending large amounts of time sitting on the floor

(Dragoo et al., 2003).

Much of the manual handling required of all child care workers, presents classic

LBD and other physical risk (Owen, 1992; Gratz & Claffey, 1996; Wortman, 2003).

A five year study by (Pheasant, 1988; ABS, 2006) reviewing the cause and rate

of injuries in American child care workers, reported that LBD accounted for the

greatest proportion of the total injuries, and that 68 percent of all MSD involved

lifting or lowering children. Regardless of this only a handful of published studies

have since attempted to reveal the ergonomic and issues for child care

workers (Baxter & Gray, 2008) and fewer published studies have attempted to

quantify the MSD associated with these workers (Foti et al., 2000). In an effort to

identify and reduce risk to occupational child care workers, King et al. (2006)

designed a program of ergonomic intervention, introducing alternative

methods of manual handling. The program participants (95% women) all of

whom reported some level of work related MSD were surveyed before and

after the prescribed changes. The majority of the 258 respondents had, where

possible, implemented the ergonomic interventions, but at the end of the six

month program there was little empirical data to support any change to

reported rates of MSD. King et al. (2006) noted that a number of factors may

have confounded the results, but also that some of the advised changes could

not be implemented. The changes not undertaken were those that required

the use of two adult workers to lift or lower children when using equipment such

as prams, cots and change tables. Of the tasks reported to contribute most to

lower back pain (LBP) as well as upper back and shoulder pain, nappy

changing and the working height of change bench furniture presented

significant risk (King et al., 2006). Concerns raised by other observers include the

lifting and lowering of children onto the change furniture and the awkward

and sustained postures maintained during the change task (Owen, 1992; Grant

12

et al., 1995; Wortman, 2003; Gratz et al., 2002; King et al., 2006). Wortman (2003)

and King et al. (2006) suggested using waist height furniture when lifting heavy

items and change tables should adjusted so that the carer is working at waist

level with the child. Generally though, the results from these few studies have

highlighting the clear MH risk to workers with recommendations for further

research as well as the need for teaching proper lifting techniques.

It is perhaps not surprising therefore, that the rates of occupational sick leave

and compensation in formal child care workers remains unusually high

(Kristiansson et al., 1996) with the most serious health problem for employees in

formal child care being LBD (Charlton et al., 2001; Shultz et al., 2004). It seems

also somewhat obvious that the same cause for LBD in occupational child care

is surely duplicated in those working with young children in the domestic

environment although this has to date, not been acknowledged. Plainly there

are a number of possible contributing factors to LBD from lifting tasks in child

care and nappy changing is just one of them. However, lifting a child after

nappy changing is the most frequent, repetitive task that engages the use of

purpose built furniture (National Childbirth Trust (NCT), 2004) and provides an

opportunity for research that is both observable and measurable. Hence, in this

thesis we are reviewing the lifting involved in nappy changing.

IDENTIFYING THE RISK

This literature review will explore three main ergonomic considerations that may

have influence on lower back injury in women in this lifting task. It will then

review the task of nappy changing, and then follow with a review of the

biomechanical variables of interest in relation to standing lifting postures.

Operator Characteristics

The ability to perform lifting work is affected by the anthropometry, strength,

age, and physical ability of an individual (Chaffin & Andersson, 1991; Kroemer

& Grandjean, 2001). In women though, the periodical increase in oestrogen

and relaxin may influence the strength of the musculoskeletal system

(Karageanes, 2005). These hormones have a softening effect on elastin and

collagen, increasing connective tissue laxity (Jang et al., 2008) altering the

structure and integrity of ligament tissues (Pheasant, 1988). Increased relaxin is

13

an influencing factor in the high rate of sport associated knee, ankle (Pheasant,

1988; Jang et al., 2008) and lower back joint injuries suffered by women as

opposed to men (Dragoo et al., 2003). Therefore, it is possible that some

women may have a heightened risk of work related musculoskeletal injury

during periods of elevated hormones (Dragoo et al., 2003).

Pregnant women

Ten percent of women in western countries between the ages of 25 to 35 will

be pregnant at any one time (Foti et al., 2000) with the average age for a first

pregnancy currently being 32.5 years (ABS, 2007). Approximately two thirds of

Australian women are employed during pregnancy (Sweden, 2001; Jang et al.,

2008). The physical changes in a pregnant womans body occurring from early

in the first trimester are vast and dynamic (Sweden, 2001; Jang et al., 2008). At

around 12 weeks gestation, the level of serum relaxin is most potent, having

increased ten fold from that before pregnancy (Wu et al., 2004; Jang et al.,

2008). At this time, connective tissues start softening (Wu et al., 2004) creating

separation, movement and laxity in spinal, lumbo-pelvic and the other core

stability ligaments and joints (Gutke et al., 2006).

From around 12 weeks gestation, the uterus expands anteriorly, laterally and

superiorly (Carlson et al., 2003), eventually increasing the abdominal depth by

20 cm or more (Ostgaard et al., 1994; Colliton, 1996; Kristiansson et al., 1996).

Through a singleton pregnancy, a womans weight will increase by around 16

kg (Perkins et al., 1998; Noren et al., 2002) with the majority of this being located

as a frontal mass (Sweden, 2001). As a result of the increased frontal load, the

centre of mass (CoM) shifts and may affect the pregnant womans balance

(Ostgaard et al., 1997; Wu et al., 2004). As her weight increases, so too does the

work load on her musculoskeletal system, increasing at the same time as the

load bearing capacity is decreasing (Perkins et al., 1998). Because of laxity in

core stabilisers, the spreading symphysis pubis and forwardly rotating pelvis, the

lumbar lordosis is disturbed and her ability to walk and stand with ease are also

increasingly challenged (Karageanes, 2005).

Frequently coinciding with the early peaking of serum relaxin levels is the onset

of pregnancy related pelvic pain (Fast et al., 1987) and gestational lower back

pain (GLBP). LBP is often considered an inevitable consequence of pregnancy

(Nicholls & Grieve, 1992). However, LBP is a debilitating disorder experienced by

14

5090 percent of pregnant women(Paul & Frings-Dresen, 1994) and is their most

frequent cause of sick leave (OHCOW, 2008). Compared to the expected rate

of 2025 percent in non-pregnant women of the same age (OHCOW, 2008)

back pain during pregnancy is not trivial (Schytt et al., 2008) and for some

women may be the beginning of life long chronic back pain (McGovan et al.,

2007).

There are many possible contributing factors to GLBP; biomechanical changes,

muscle fatigue, radiated pain and ligament laxity are all potential contributors

(Kristiansson et al., 1996; Sweden, 2001; Sloane, 2002; Qu et al., 2006).

Additionally, multiparae women and those who have experienced LBD prior to

pregnancy are more likely than not, to suffer from GLBP (Liu et al., 2002; Sloane,

2002). The significant point is that women are pre-disposed to LBP during

pregnancy and from around 1218 weeks gestation, this condition can be

severe and debilitating (Ostgaard et al., 1997; Karageanes, 2005; Gutke et al.,

2006).

A woman in advanced pregnancy is considered anthropometrically extreme

(Pheasant, 1988; Paul et al., 1994). The new physical shape restricts her ability to

perform tasks that require reaching, lifting, bending and twisting, and these

limitations classify her as disabled (Liu et al., 2002; Sloane, 2002). In a study of

200 pregnant women, (Ostgaard & Andersson, 1992; Ostgaard et al., 1997)

identified 48 common domestic duties that they regularly engage in. The task

of lifting items from floor level was rated by 98% of participants as extremely

difficult, but amongst the most strenuous were those tasks that required

standing and reaching postures, including ironing and washing dishes. A more

complex study by (Mast, 1999) reviewed standing work postures in a group of

27 women in their third trimester of pregnancy compared with non-pregnant

women. Three table heights were imposed; waist height (the apex of the

abdomen); a height set in accordance with Dutch ergonomic guidelines

(approximately 90 cm); and a self-selected table height (average 13.8 cm

under the apex of the abdomen). The women were required to engage in a

variety of six task positions, the most frequently encountered in their workplace.

The postural differences between participants demonstrated that the pregnant

women stood with their feet further from the table edge; the calf angles were

smaller as a result of a backward lean; the trunk was flexed more (with

15

pregnant women also keeping their abdomen away from the edge of the

table) with hips being in a more backward position; the upper arms and

forearms were more raised and extended. Furthermore, the self selected height

chosen by the pregnant women, although being the lowest of the three

heights, allowed them to stand closer to the table in a more upright position

and with their arms more relaxed, resulting in the least postural difference

between the pregnant and non-pregnant women.

Having made similar observations in regard to the postural consequences for

pregnant women in standing bench work, Nicholls and Grieve (1992) pointed

out that lifting any load from a flexed; reaching posture may substantially

increase the torque about the lumbo-sacral joint. Although increasing the

height of the bench would put operators into a more upright stance (Nicholls &

Grieve, 1992), this may impact on the muscle strength requirements to

complete the task. In ironing for example, Paul and Frings-Dresen, (1994)

suggested that raising the height of the work surface may restrict the subjects

ability to exert downward pressure when performing the work. This point relates

to our study in that it is often necessary for a carer, standing at a change

bench, to apply a securing force to the baby with one hand while reaching to

access change items on a lower level.

Occupational Health Clinics for Ontario Workers, Ergonomics and Pregnancy

Policy (Boissonault & Blaschak, 1988; Kotarinos, 2003), makes the following

recommendations: women in the third trimester of pregnancy should not

perform jobs that require balance, lifting weights over 10 Kg, awkward postures,

high force, no rest or repetitive work. Workstations should be adjustable to

reduce any awkward postures and to accommodate the pregnant womans

body. Unfortunately, there appears to be very few published papers regarding

biomechanics of pregnant women. Equally, no publication has been found

that mentions MH restrictions in the first or second term of pregnancy. The

concerns here perhaps are two fold: general OHS practices view the third

trimester as the time to limit physically strenuous work (Neumann & Gill, 2002);

pregnant women in domestic environments generally have no option but to

engage in MH work throughout their pregnancy.

16

Post partum women

The physical strain associated with birth is often extreme (Richardson et al.,

2002) and traumas associated with parturition frequently include: episiotomy

repair weakened pelvic floor, general body pain, back pain and fatigue

(Neumann & Gill, 2002). Prior to the mid 1960s, it was common for a woman to

recover in hospital for 10 days following the birth of a baby (Wijma et al., 2001;

Neumann & Gill, 2002). However, the average hospital stay following an

uncomplicated vaginal delivery is now 1248 hours (Carriere & Feldt, 2006). Also

around 35 percent of births are through caesarean section, from which the

recovery is reportedly longer and more complex (Qu et al., 2006), nevertheless

the hospital recovery time for these women is three to five days (Sloane, 2002).

Upon leaving hospital most women will be released into home care to

complete their recovery.

Many women can suffer the physical side effects of pregnancy and child birth

for 12 months or more (McGill, 1997; Kroemer & Grandjean, 2001). Around 40%

of women will continue to experience back pain for at least three months

following delivery (McGovan et al., 2007), with the greatest predictor of

postpartum back pain being the occurrence of GLBP (Pheasant, 1988; Chaffin,

2005). A prospective follow up study by Noren et al. (2002) reviewed 800

postpartum women and showed that 20% of those who had GLBP continued to

experience moderate to severe LBP symptoms three years on from parturition.

However, an explanation for the long duration and severity of postpartum LBD

remains elusive.

Some injuries resulting from pregnancy or the birth can linger for years, often

requiring surgical repair to assist recovery (Fathallah et al., 1998). The most

common of these are diastasis rectus (Mital et al., 1997), pelvic floor

insufficiency and prolapse (Mast, 1999; Waters et al., 1993) and lower back

disorders (Davis & Marras, 2005). Boisannault and Blaschak (1988) reported that

36% of women dont spontaneously reduce during the postpartum period and

subsequent prevailing abdominal muscle separations can vary from one to

several centimetres. In cases of obese women, multiparas women or those with

multiple birth pregnancies, the separation can extend from the umbilicus down

to the pubis (Kotarinos, 2003). As a result the rectus sheath can diverge enough

to allow the herniation of abdominal contents to occur (Kotarinos, 2003).

17

The functioning of the abdominal wall in relation to posture, trunk stability and

movement is well established (Waters et al., 1994). As the transverse

abdominals and oblique muscles are recruited with pelvic floor contractions, a

weakened abdominal wall also augments pelvic floor weakness (Davis &

Stubbs, 1977; Sapsford & Hodges, 2001). About 60% of postpartum women

experience pelvic floor weaknesses and 30% of all women will develop chronic

disabilities associated with pelvic floor insufficiency (Pheasant, 1988; Eveleth &

Tanner, 1990). There appears to be a relationship between pelvic floor pain

and LBP (Kramer et al., 2002) and it is possible that pelvic floor weakness may

facilitate instability of the lumbar spine, but there is no apparent study on this

topic. Richardson et al. (2002) researched the relationship between abdominal

strength, LBP and sacroiliac joint mechanics. She suggested the contraction of

transversus abdominis increased stability of the sacroiliac joints more than the

activation of all the lateral abdominals, potentially alleviating pain during lifting

work.

Postpartum women are advised that the body will take between three to six

months to recover (Sweden, 2001; NCT, 2004), and weight bearing activity

should be kept to a minimum for the first eight weeks (NCT, 2004). Following a

short hospital stay, 50% of women will return to households to care for at least

one child less than two years of age, as well as the new born. It is likely that

these women will be involved in tasks that necessitate the lifting and lowering

of young children and the interaction with purpose built furniture. Sanders &

Morse, (2005) noted that there is a high risk of mothers developing MSD as a

result of child care work.

Difficult Loads

When assessing loads for task management the dimensions, weight, CoM and

coupling of the item need to be taken into account (Moorhead, 2005). Loads

of greater than 10 kg are generally considered heavy (NCHS, 2000) but

perhaps one of the more significant factors in relation to handling is the inertial

qualities of a load (HealthWest, 2000). Ergonomically, the CoM should be

located near the centre of a load (Kroemer & Grandjean, 2001) and it should

be stable. Unpredictable and unexpected inertial characteristics should be

avoided (Pheasant, 1988; ACA, 2004).

18

According to the American National Institute for Occupational Safety and

Health (NIOSH) (INPAA, 1998.), the maximum recommended weight for a single

lift in optimum conditions, is 23 kg. In reality this figure is an overestimate and

the application in a work environment is very limited (OHCOW, 2008). However,

the NIOSH lifting equation (1993) in which the recommended weight limit for a

given task is calculated, has been adopted into occupational ergonomics as

the standard for evaluating load limits in various lifting scenarios (ACA, 2004;

NCT, 2004). The lifting equation takes into account the coupling as well as the

horizontal and vertical location of the load at origin. It also considers the

duration of the task, the frequency of the lift and the symmetry of the posture

(Waters, Putz-Anderson et al., 1994). Unfortunately, the NIOSH lifting equation

(1993) cannot be applied if the task involves one handed lifting, restricted

workspace, unstable loads, pulling the load before lifting or awkward postures

(Chaffin & Andersson, 1991). According to Chaffin and Andersson, (1991) and

Jorgensen et al. (2005), the maximal acceptable load for healthy women

under 50 years of age, in optimum lifting posture is 18 kg. However, guidelines

for maximal acceptable weights in lifting are useful in the sense that the limit

provides an indication of safe limits in optimum conditions, and therefore the

limits make obvious where load weights should be reduced for conditions that

are less than optimum (Pheasant, 1988). Applying these guidelines though to

animate or live loads is theoretically accounted for, but in reality perhaps not

so easy, particularly in the case of young children.

Growth in young children is complex and rapid and in order to understand the

implications for managing a child as a MH load, it is fundamental to be aware

of the behavioural as well as the physical changes in their development

(Bogduk & Endres, 2005). Growth and development rates in children are not

universal (Dempsey, 1998) therefore, references regarding child growth are

reflective of population averages. During the first year, growth is more

advanced in proximo-distal direction and from the midline to extremities, with

the region of greatest mass being located within the torso and head

(Pheasant, 1988). By the time a child is two years old it will have a body 10% the

size of its adult potential (Pheasant, 1988).

The following (Table 2.1) is a compilation of the average expected somatic

growth, measurements and developmental stages of a young child. The

19

information provided is drawn from Pheasant (1988); NIOSH (1981); the United

States National Centre of Health Statistics revised data, collected between

1988 to 1994 by the Growth Chart Working Group; Bogduk and Endres, (2005);

and the Health West Child Health Record (2000).

Table 2.1 The Average Expected Somatic Growth Measures for Children New Born to 24 Months.

Infant Health Growth Chart Measures Baby Age Head Weight Crown to Heal Circumference (cm) (kg) Length (cm)

Neonate

(first four weeks)

36 to 40

3.5 to 6.0

50 to 57

One to three months

38 to 44

4.5 to 7.5

55 to 66

Three to six months

41 to 47

6.0 to 10.0

60 to 73

Six to 12 months

43 to 50

7.5 to 12.5

66 to 82

12 to 24 months

46 to 52

10.0 to 18.0

75 to 95

During the first two years the child also develops movement skills that

commence as rudimentary involuntary reflexes. A neonate can be a

surprisingly lively and spontaneous with an array of reflexes including a walking

reflex; startle reflex; tonic-labyrinthine reflex, in which the baby will try to lift its

head when placed in a prone or supine position; and a palmer grasp so strong

that it can lift its own body weight. From around six to eight weeks the cylinder

shaped baby load will start rolling movements. By six months the child can

move into crawling position and the lumbar curvature is developing shape and

strength. From 6 to 12 months the child is sitting and pulling to a stand position;

is becoming independently mobile (crawling) to a point of learning to walk;

and develops from reaching to grasping objects with fine motor skills. From 18

to 24 months physical development is slowing but motor and cognitive abilities

are rapidly developing. These children are top heavy, 11 to 18 kg in weight

with a body length of up to a metre long.

20

Because of the pattern of body growth in the first two years, the CoM in the

baby load remains high in the torso. The implication for the task of lifting from a

change table surface is that as the baby is growing, the CoM of the load is

becoming more distal to the operator. This is further complicated by the

behavioural characteristics of the baby load, which at 12 months is mobile and

unpredictable, socially interactive, increasingly independent, thinking

strategically, behaviourally demanding and has no concept of danger (NCT

2004).

Equipment

In a work situation specifically designed for standing bench work, good

ergonomic design (NIOSH, 1991; Kroemer & Grandjean, 2001) would be

considerate of:

the operator maintaining an upright trunk posture.

the work surface height being relative to the task.

the available horizontal foot space.

the available horizontal knee space.

reach and access to other levels.

allowable symmetry of operator posture.

available space for operator to move in.

Anecdotal information suggests that purpose built change bench furniture, is

the most frequently used equipment in paediatric and formal child care work

places. It is a mandatory requirement in all commercial locations (AS1428.1/

Australian Building Codes Board) and recommended by consumer advice

authorities as a necessity in the domestic environment (Dolan et al., 1994).

Information regarding change bench furniture for this review has come from

popular press sources; the European Standard EN 12221-1:1999 Changing units

for domestic use Part 1: Safety requirements (2000); and anecdotal advice and

experience.

Domestic furniture

Over the past 30 years, change furniture has becoming more elaborate, more

available and according the Infant and Nursery Products Association of

Australia Incorporated (McGill et al., 1998; Mital, 1999) designed to improve

child safety, versatility and aesthetic appeal. Domestic change units are

21

available in various designs, but in general, all provide a baby change surface

space with width of 380550 mm and length of 650 750 mm (EN 12221-2, 1999);

the working change surface height is generally 800950 mm from the ground;

the surface provides enough space for the baby only and accessory change

items are usually positioned for access somewhere other than the change

surface. Change furniture should be made from either wood, plastic or metal or

a combination of these materials (EN 12221-2, 1999). The popular purpose built

change furniture designs include the following.

2/3 Tier change table (Figure 2.1)

As the name suggests, this trolley framed furniture has one or two shelves

beneath the top work surface. The lower shelves are designed to store change

items within easy reach however, the operator will be reaching, usually with

one hand, to a level lower than work height in order to access these items. The

unit may or may not be on caster wheels, but will generally have space for the

operators feet underneath the bottom shelf.

Figure 2.1. 2/3 Tier change table (picture from Glenhuntly Baby Carriages retail catalogue, Melbourne, Australia. 2005).

22

Bath and change table unit (Figure 2.2)

This has a similar construction and user functionality as the 2/3 tier unit, but

usually with the padded change surface hinged on one long side. Underneath

the baby bath are generally one or two shelves or drawers.

Fold out frame and sling (Figure 2.3)

This consists of a sling of textile across a collapsible A frame. The sling has a

natural dip like a hammock. The frame legs spread, opening the area of the

change surface and allowing the operator to move their feet and body close

to the work area. The hammock provides a natural resistance to baby sitting up

or rolling over and out. A low level shelf may or may not be provided for

accessory change items. Foot space is available, but knee and leg space may

be inhibited.

Figure 2.2. Bath and change table (picture from Glenhuntly Baby Carriages retail catalogue, Melbourne, Australia. 2005).

23

Drawer top changer (Figure 2.4)

This is either a rectangular shallow box with padded change mat insert that sits

on top of a set of drawers or a semi enclosed area on top of a set of drawers.

The height of this surface is generally dependent on the height of the drawer

set. Usually this change situation does not allow for knee space, the operators

feet may not fit under the drawer unit and there is no obvious location for

accessory change items. The operator is positioned either along side the baby

load or symmetric to the baby load with movement usually confined by the

wall barrier.

Figure 2.3. Fold out frame and sling (picture from Glenhuntly Baby Carriages retail catalogue, Melbourne, Australia. 2005).

.

Figure 2.4. Drawer top changer or changing chest (picture from Glenhuntly Baby Carriages retail catalogue, Melbourne, Australia. 2005).

24

Cot top changer (Figure 2.5)

This is a firm rectangular change board surface designed to fit over the rails of a

standard cot. The height of this surface is dependent on the height of the cot

sides. The operator can generally fit the feet under the cot, but the dropped

side of the cot inhibits knee space. No obvious easy access to change items

exists.

Commercial and public change facility furniture

It is a mandatory requirement for public locations and commercial and

buildings in Australia to have adequate parent and baby change facilities

available (AS1428.1/ Australian Building Codes Board). Of the locations that

have facilities for changing baby, according to sales figures from Baby

Changers (2006), approximately 80% provide a drop down suspended bench

top (Figure 2.6). The drop down bench will be mounted on the wall either

horizontal or perpendicular to the wall. With the majority of these units, the

change surface provides enough space for the baby only (no standardised

dimensions or work surface height available) and accessory change items must

be positioned for access somewhere other than the change surface. Some

nappy change stations consist of a built-in counter top surface and others

consist of domestic furniture. Generally the work surface height for the drop

down units is a standard 800850 mm from the ground.

Figure 2.5. Cot top changer or changing board (picture from Glenhuntly Baby Carriages retail catalogue, Melbourne, Australia. 2005).

25

Child care and paediatric furniture

Nappy change stations within these work locations are not standardised and

vary according to facilities available in each work place. In the paediatric

health care environment, babies and young children are changed either in

their bed, cot or bassinet, or on a work bench surface which may not allow for

horizontal knee and foot space. In formal child care environments sanitation,

safety and supervision are key criteria (Dolan & Adams, 1993) for the design

and location of nappy change furniture. Child care occupational health and

safety guidelines usually include comments on the height of the nappy change

surface, suggesting it be at a height that will minimize back injury (Aronson,

1999), but no mention of knee or foot placement or lift symmetry have been

observed in the available literature.

Safety and design standards

The only design standards available for nappy change furniture are the

European Standard EN 12221-1:1999 Changing units for domestic use safety

requirements and EN 12221-2:1999 Changing units for domestic use test

methods. These standards are bound by CEN/CENELEC Internal Regulation

(1998) to be implemented by the countries of the European Union and have

been adopted and published in Britain as the British Standards.

Figure 2.6. Drop down suspended bench top perpendicular or horizontal to the wall (picture from Janitorial Direct trade catalogue, U.K. 2006).

26

The scope of Changing Units specifies safety requirements for all types of

changing units for children with a body weight of up to 15 kg. The Standard

specifies minimum change surface dimensions for 12 month and 36 month old

children; it defines a variety of change unit types and provides design

recommendations for child safety such as child roll barriers, restrictions to child

body part access and the assembly, strength, stability and general design of

the change furniture. The final section of the Standard provides instructions for

use in which the warning: Do Not Leave the Child Unattended must be

included, as well as the requirement of information concerning the adequate

height of the unit (BS 12221-1:2000, 2000. p14). However, there is no

recommendation for the working height of a change unit. In relation to working

height, the regular advice is when changing a babys nappy on a change

bench use a bench that is waist height (Wortman, 2003; King et al., 2006).

In Australia, there are currently 25 organisations involved in the revision process

of design standards for nursery equipment. These organisations include: Infant

and Nursery Products Association of Australia Incorporated (INPAA), The

Childrens Hospital of Westmead, Consumers Federation of Australia, Australian

Chamber of Commerce and Industry and the National Council of Women of

Australia. Additionally, consumer occupational safety and health information in

relation to the purchase and use of domestic equipment is scant. The INPAA

advises that, the onus is on the consumer to make sure that the change

bench furniture they buy for their children is safe, and that invariably means

buying a premium product (Nursery Furniture How safe is it? INPAA, 1998. p5).

It is clear though that the focus of equipment specification is on child safety

and not the safety of the operator.

Occupational Health and Safety Issues

Popular press articles (Marras et al., 1998) that instruct on nappy changing

often refer to choosing furniture that is waist height, and that which allows

change items to be kept within reach to avoid unnecessary twisting and

turning (Birthnet:birth.com.au.,p3). Published advise also suggests that

operators avoid leaning over and over reaching when changing a nappy,

and for new mothers the advice includes having someone else lift heavy

objects (NCT, 2004; Raising Children Network, 2006; Birthnet:birth.com.au). In

27

contrast to this advice however, the most common change furniture styles

available for domestic and public use (Figures 2.12.6), require operators to

flex, reach, twist, turn and sustain awkward postures whilst carrying out the

nappy change task.

Furthermore, even though it is a mandatory requirement for change furniture to

be available in public and commercial locations in Australia (AS1428.1/

Australian Building Codes Board), there is no Standard for the design of the

furniture. Neither is there a Standard for change benches being used in day

care centres or hospitals or any other location. Currently in Australia there is no

national, independent nursery equipment safety framework and there is no

occupational health and safety guideline for the use of change furniture by

adults working with young children. In relation to the MH work performed by

child care workers, there are no relative occupational guidelines for task

design, the handling of live loads, or equipment design (Gratz & Claffey, 1996;

Bright & Calabro, 1999; King et al., 2006). It is relevant that consideration should

be for the safety of the child, but there is nothing that indicates consideration

for the safety of the operator.

Task of Nappy Changing

The following instructional diagram (Figure 2.7), is an extract from a popular

child care education internet site (abc.net.au/articles/babies_dailycare.htm), it

has been included in this review to demonstrate a typical information

publication for parents. The nappy change task sequence commences with a

pre-change lift then lowering of the child to the change surface. Then follows

the nappy change during which time the operator may be required to hold

the child down with one hand, and perhaps reach asymmetrically to a lower

level in order to access change items. After completing the change, the child is

finally lifted from the change surface and carried or lowered again. An infant

child will require nappy changing between eight to12 times a day; a young

toddler 12 to 24 months, will require changing 6 to 8 times a day and an older

toddler of 24 to 36 months will require changing 4 to 6 times per day (NCT,

2004). There is no information regarding the duration of this task however,

popular press publications make regular mention that as a child gets older, the

task can become more complicated.

28

In formal child care, the number of children per carer varies, but the Australian

Child Care Centre Licence (CCCI 46-05D, 2004) allows for eight children under

the age of two per carer. And for those over 2 years, one carer can be

responsible for up to 16 children (CCCI 46-05D, 2004). Anecdotal information

from child care workers in Western Australia suggests though, that nappy

changing of toddlers is attended to every 3 to 4 hours with one carer often

changing nappies consecutively on 20 children.

29

Set-up and strip off

Before you change a nappy, make sure you have everything you need within arm's reach of the

change area. This includes: a fresh nappy, baby wipes and baby cream. Lie baby down on the

change table. If she grizzles, sing her a song or give her a favourite toy to keep her entertained.

Undress baby's bottom half and unfasten the nappy. Use the front of the nappy to wipe off any

poo, then fold the nappy into a tight bundle before putting it in a plastic bag.

Cleanse and apply cream

Gently cleanse baby's bottom using baby wipes. Make sure you get into the crevices but avoid

separating a baby girl's labia to 'clean inside'. Likewise, a boy's foreskin should never be

pushed back. To wipe the back of baby's bottom, hold her by the legs with your fingers between

her ankles and gently lift so her bottom comes slightly off the change table. Wiping girls front to

back will help avoid vaginal infections. Apply a dollop of baby cream to prevent against nappy

rash.

Applying the new nappy

Open a clean nappy, making sure the fastening tabs are towards the top. Lift baby up by the

ankles and slip the nappy beneath her bottom. Fold the front flap up, tuck it firmly around

baby's waist and secure each tab. Once you've dressed baby, secure her in a bouncer or cot and

dispose of the nappy. Wash your hands before touching baby's hands or face. Remember: never

leave a baby unattended on a change table. They can squirm or roll off in seconds. If you have

to take your eyes off baby, keep your hands on.

Figure 2.7. Instructions for nappy changing (ref: web site abc.net.au/articles/babies

_dailycare.htm).

http://www.abc.net.au/parenting/tools_and_activities/

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ASSESSING THE RISK

We know the spinal column carries the weight of the trunk and upper body

and in neutral stance; forces are cushioned uniformly within intervertebral (IV)

joint structures. Moving into a non-neutral stance, changes in body weight

distribution, or lifting a load destabilises the force through the lumbar spine

(Dolan & Adams, 1993; Delleman et al., 2004; Genaidy et al., 2006) It is an

individuals capacity to manage the variations of force in the lumbar spine

which influences the process of LBD or injury (McGill et al., 1998). We have

reviewed the task of nappy changing and identified characteristics of each of

the three main variables; the operators, the loads and the equipment. Clearly

there are elements in each of these variables that make the task of nappy

changing difficult and an injury risk. A biomechanical assessment is one way of

measuring the risk from lifting (Kingma et al., 2006) following the task of nappy

changing.

The Biomechanics of Standing Lifts: Implications for LBI

Lifting frequently engages the whole body, but it is the upper body that

manipulates the load. The lumbar spine is the region of greatest mobility yet it

sustains the largest forces under loading (Chaffin & Andersson, 1991; Jorgensen

et al., 2005). The biomechanical outcome measures most familiar to risk

assessment in lifting are compression force (CF), shear forces (SF) and spinal

ligament tension (Dempsey, 1998). Measuring these parameters provides an

indication of mechanical stress on th

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