Research Article Peak Vertical Ground Reaction Force ...

Research ArticlePeak Vertical Ground Reaction Force during Two-Leg LandingA Systematic Review and Mathematical Modeling

Wenxin Niu123 Tienan Feng4 Chenghua Jiang4 and Ming Zhang2

1 Tongji Hospital Tongji University School of Medicine Shanghai 200455 China2 Interdisciplinary Division of Biomedical Engineering The Hong Kong Polytechnic University Hong Kong3 Shanghai Key Laboratory of Orthopaedic Implants Shanghai 200011 China4Department of Disaster and Emergency Medicine Eastern Hospital Tongji University School of Medicine Shanghai 200120 China

Correspondence should be addressed to Chenghua Jiang jchtongjieducn

Received 3 June 2014 Revised 19 July 2014 Accepted 5 August 2014 Published 26 August 2014

Academic Editor Ali A Khraibi

Copyright copy 2014 Wenxin Niu et al This is an open access article distributed under the Creative Commons Attribution Licensewhich permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited

Objectives (1) To systematically review peak vertical ground reaction force (PvGRF) during two-leg drop landing from specificdrop height (DH) (2) to construct a mathematical model describing correlations between PvGRF and DH and (3) to analyze theeffects of some factors on the pooled PvGRF regardless of DH Methods A computerized bibliographical search was conductedto extract PvGRF data on a single foot when participants landed with both feet from various DHs An innovative mathematicalmodel was constructed to analyze effects of gender landing type shoes ankle stabilizers surface stiffness and sample frequency onPvGRF based on the pooled data Results Pooled PvGRF and DH data of 26 articles showed that the square root function fits theirrelationship well An experimental validation was also done on the regression equation for themedicum frequencyThe PvGRFwasnot significantly affected by surface stiffness but was significantly higher inmen thanwomen the platform than suspended landingthe barefoot than shod condition and ankle stabilizer than control condition and higher than lower frequencies Conclusions ThePvGRF and root DH showed a linear relationshipThemathematical modeling method with systematic review is helpful to analyzethe influence factors during landing movement without considering DH

1 Introduction

Landingmovement has been thoroughly researched in sportsbiomechanics because it is very important in gymnastics [12] parachuting [3 4] Parkour [5] volleyball [6 7] basketball[8 9] soccer [10] Australian football [11] and netball [1213] In these studies the landing risk or performance wasvaluated with various kinetic kinematic and electromyo-graphic parameters among which the ground reaction forces(GRF) is very important and fundamental [13 14] The GRFparameters are often compared between or among differentparticipant groups or trial conditions to draw intuitional con-clusions regarding biomechanical evaluation [15ndash21] Becausethe vertical GRF (vGRF) is markedly larger compared tothe anterior-posterior or medial-lateral component its peakvalue (PvGRF) has been favored in most studies

To realize different mechanical demands in laboratorythe drop height (DH) differed greatly in various studies

Hoffren et al [22] studied drop landing from a 10-cm DHwhile Zhang et al [23] measured GRF of landing from a103-cm DH The DH range was so large that PvGRF wasalso widely distributed Even for the same DH of 60 cmas an example the mean PvGRF ranged from 238 to 491times body weight (BW) [1 17 24ndash34] The wide rangeof PvGRF restricted the data comparison among variousstudies and the development of a consensus It is necessary tocomprehensively integrate and analyze the published PvGRFdata during drop landing

Though with a wide range DH adopted in the controlledlab setting is still unavailable to reproduce most movementsin the real world To our knowledge the maximum DH ofdrop landing performed in kinematic laboratory was 200 cm[35] Also fundamental backward rotating dismounts frombeam have been measured with the mean peak centre ofmass of 222 cm high [36] However the GRF data were notmeasured by the researchers Considering safety issues the

Hindawi Publishing CorporationBioMed Research InternationalVolume 2014 Article ID 126860 10 pageshttpdxdoiorg1011552014126860

2 BioMed Research International

DH higher than 100 cm was rarely adopted in laboratoryHowever the practical height was higher than the testingDH in many sports such as gymnastics [35] and parachuting[15] The PvGRF is still unknown for a DH higher than theexperimental limit [15] This leads to invalid analyses for thepractical condition It is useful to predict PvGRF for anydemanding landing based on current knowledge

In 1942 De Haven [37] used the acceleration equation(V = radic2119892119904) and an inversion of the equation for acceleration(V2 = 2119892119904) to estimate the impact force in falls from heightsFor the normal landing with autonomic posture regulationNiu et al [15] described the mean impact force determinedby the initial landing velocity and buffer distance using anequation 119866 = 1198812(2119878119892) where 119866119881 119878 and 119892 represent meanimpact force initial velocity buffer distance and gravitationalacceleration respectively Both methods are only used forestimating themean force in thewhole impact process but areunable to provide the peak value Yeow et al [38] determinedregression relationships of DH with peak GRF GRF slopeand impulse during landing However as there were onlyfive participants it is difficult to form a general conclusionA large sample through various DHs is needed to predictthe information when individuals land from a more practicalDH

A valid predicting method should be also helpful forcomparing PvGRF between or among different groups orconditions The landing biomechanics is often affected bythe landing type [1 23] instruction [14] shoe [39] anklestabilizer [16] surface stiffness [2] and participantrsquos age[40] sex [41] fatigue [42] and vision [43] In many casesresearchers tried to find some evidences in PvGRF to evaluatecertain influential factors but many conflicting conclusionshave been obtained in these studies For example someauthors reported that women produced significantly higherPvGRF [6 28 29] while Blackburn and Padua [32] detectedsignificantly higher PvGRF in men and also some found nostatistically significant differences in PvGRF between genders[8 41 42] These contradictories may be related to differentDHs in different studies There was no effective method tocompare the PvGRF data between different groups or landingconditions without considering DH Based on abundantpooled data from systematic review a mathematic modelingmay provide some helpful clue to deal with this question

Therefore the purposes of this studywere to (1) systemat-ically review PvGRF data when participants landed from spe-cific DHs with two legs (2) construct a mathematical modeldescribing the constitutive relationship between PvGRF andDH and (3) analyze the effects of gender landing type shoesankle stabilizers and surface stiffness on PvGRF regardless ofDH based on the proposed models

2 Material and Methods

21 Systematic Review In April 2014 two independentreviewers (WNandTF) performed a computerized search forpeer-reviewed journal articles published in English to iden-tify studies reporting drop landing with both legs Searcheswere performed using the following databases PubMed

ScienceDirect Ovid and ISI Web of Knowledge As the highperformance force plate had seldom been used prior to 1980the publication range was between 1980 and April 10 2014Keywords used included ldquolandingrdquo and ldquobiomechanicsrdquo incombination Furthermore relevant articles were identifiedby cross-referencing the citation lists of the articles identifiedin the electronic search In addition authors in the field werecontacted and the authors also searched their own files

Articles retrieved in the original search were exportedinto a single Endnote file (Thomson Reuters CarlsbadCA) and duplicate articles were removed The title andabstract of each record were screened and irrelevant articleswere excluded Where insufficient information was availablefrom the title and abstract the full text was inspected Theremaining full-text articles were assessed for inclusion by oneauthor (WN) Articles selected for exclusion were verifiedby another author (CJ) and any discrepancies were resolvedthrough discussion involving all authors

Studies that met the following criteria were included (1)the studywas conducted on humans (2) the participant num-ber was reported (3) all participants were adults (12ndash60 yr)healthy and with normal vision in the trials (4) participantslanded with both legs and stabilized themselves after contactwhile the single-leg landing countermovement-jump (CMJ)landing or special type of landing (eg Parkour or parachut-ing roll fall) was excluded (5) only the anticipated droplanding was included while jump landing or unanticipatedlanding was excluded (6) DH was reported (7) PvGRF wasprovided with numerical presentation and was normalized toBW (8) the impact force on one foot (left or right dominantor nondominant) was independently measured with oneforce plate

22 Mathematical Modeling Using the principle of conser-vation of energy gravitational potential energy equals thekinetic energy in the vertical direction As described by deHaven [37] the impact velocity from DH in the ideal statecan be calculated as follows

V0= radic2119892 sdot DH (1)

where V0is the impact velocity at initial contact and 119892

is the gravitational acceleration According to the law ofconservation of momentum

int

119905

0

119865119889119905 = int

0

V0119898119889V (2)

where 119865 is the vertical force on one leg and can be calculatedas the difference of themeasured vGRF andBW2At the timeof 119905 = 0 V = V

0 In the impact process F is a continuous

function of the time (t) Based on themean value theorem forintegrals there would exist a 1198651015840 such as 1198651015840Δ119905 = 119898V

0 Then

119865

1015840

119898

= V0

1198981PvGRF = radic2119892 sdot DH

PvGRF =radic2119892

1198981

radicDH

(3)

BioMed Research International 3

where1198981is a modified parameterTherefore the relationship

between PvGRF and DH was deduced as a square root formAt the end of the landing impact process the subject getshisher stability and then 119865 is about BW2 rather than 0Therefore another parameter should be added into the squareroot equation Then

PvGRF = 119886radicDH + 119887 (4)

where 119886 sim radic21198921198981and 119887 sim BW2 The values of 119886 and 119887 can

be calculated by the maximum likelihood method based onexperimental data

This mathematical model is proposed to illuminate thecorrelation between PvGRF and DH during a double-legdrop landing Using the available data from pooled studiesthe nonlinear regression can be transformed into linearregression in this model R language team [44] and SPSS 170(SPSS Inc Chicago IL USA) were used to find the best fitand to statistically analyze the dataThe1198772 value was adjustedbased on the standard deviation and the sample count fromeach study and it indicated a linear regression relationshipbetween the independent and dependent variables when itapproached one A 119875 value less than 005 implied that theindependent variable could be used to predict the dependentvalue A smaller root mean squared error (RMSE) indicateda more accurate prediction

To validate the mathematic model we used the meanvalues of PvGRF measured by McNitt-Gray [45] in whosestudy six gymnasts and six recreational athletes performeddrop landings Because the GRF data were measured on bothfeet together theywere not included in this systematic reviewThese data were used to validate our mathematic model forthe following reasons (1) they were not used to construct themodel (2) this study accords with the all other seven (1ndash7)criteria described above and (3) one DH in this study was128 cm and far beyond the maximum DH (103 cm) in ourpooled data

23 Influential Factors If the gender was not explicitlyreported or two genders were mixed in the same experimentthe data were excluded when the factor of gender wasanalyzed Two types of drop landing with specific DHs havebeen customarily studied The first is the suspended landingmeaning that participants are suspended above the force platebefore dropping and are released to land autonomously Thesecond is the platform landing meaning that participantsinitially stand on a platform and step or jump from it to land

Therewere two conditions related to shoe condition shodand barefoot If this factor was not reported in the studythe data were excluded when shoe condition was analyzedTwo conditions were related to ankle protection use of anankle stabilizer (tape or brace) and a control without astabilizer Two conditions were classified according to thelanding surface stiffness hard and soft If no mat or pad wasused to cover the force plate the surface was classified ashardThree levels of sample frequencywere considered as low(lt1000Hz) medium (1000ndash1200Hz) and high frequencies(gt1200Hz)

When a participant dropped from a zero DH (DH = 0)then the formula would produce PvGRF = 119887 (4) This criticalcondition actually represents static standing with two legswhich is seldom influenced by the other factors Thereforethe variable 119887 in the function is nearly unchangeable withinvarious conditions This means the variance of PvGRF atthe same DH under different conditions could be explainedby the variable 119886 Therefore we used the modified PvGRF(mPvGRF) calculated by the below equation to determinethe impact of other factors described above

mPvGRF = PvGRF minus 119887radicDH

(5)

where 119887 is the weighted mean of 119887 Accordingly datacollected from different heights could be analyzed togetherThe mPvGRF was used to analyze the effects of variousfactors The means and standard errors of PvGRF could becollected from all pooled papers Based on the property ofnormal distribution we could combine the datasets underthe same condition and calculate the values of means andstandard errors In comparison between two conditions theindependent t-test was used to calculate the 119875 value Incomparison among multiple conditions analysis of variance(ANOVA) was used to calculate the 119875 value

3 Results

31 Systematic Review The study selection process wasdescribed in Figure 1 The computerized literature searchfrom all databases yielded 4673 articles After the removal ofduplicates and irrelevant articles based on title and abstractscreening 189 articles remained of which an additional 163articles were removed on the basis of inclusion and exclusioncriteria leaving a final yield of 26 articles [1 3 15 16 1820 22ndash34 39 42 46ndash50] The characteristics of all includedarticles were listed as Table 1

Groups of male participants were measured in 16 articles[3 15 16 23ndash26 28 29 31ndash34 42 47 48] while groups offemale participants were measured in 11 articles [1 3 15 1628ndash30 32 42 46 50] In one article [27] the gender was notexplicitly reported In five articles [18 20 30 39 49] bothgenders were mixed in the same experimental group In fivearticles [26 29 46 49 50] participantswere suspended abovethe force plate before dropping In the remaining 21 articlesthe platform landing was studied

In seven articles [1 3 15 16 18 34 50] the participantswere shoeless In thirteen articles [20 24 25 27ndash29 32 3942 47ndash49] the participants wore shoes Shultz et al [39]measured the same group of participants with and withoutshoes In the other 7 articles [22 25 26 30 35 48 50]shoe conditions were not reported The participants weremeasured without any ankle stabilizers in all 26 articles Infour articles [16 20 46 49] the same groups of participantswere also protected by ankle taping or bracing Separate 16-cm rubber pads were used by Seegmiller and McCaw [1] toprovide a nonslip visually identical landing surface In theother 25 articles the landing surface was determined as hard


Records identified throughdatabase searching

Additional records identifiedthrough other sources

Records after duplicates removed

Records screened(n = 3020)

Full-text articles assessedfor eligibility

Studies included inqualitative synthesis

Studies included inquantitative synthesis

Records excluded

Full-text articles excluded(n = 163)

∙ Animals 2∙ Children or elders 7∙ Subjects number was

unknown 8

∙ Single-leg landing 43∙ CMJ 38∙ Special type landing 8∙ Jump or unanticipated

landing 39∙ DH was unreported 3

∙ PvGRF1PvGRF were

∙ 2 feet measured 6

Scre

enin

gIn

clude

dEl

igib

ility

Iden

tifica

tion

(n = 108)(n = 4673)

(n = 3020)

(n = 2831)

(n = 26)

(n = 26)

(n = 189)

unreported orunnormalized 9

Figure 1 Identification of relevant publications (the PRISMA flow diagram)

except that in one study [3] the hard surface and two types ofsoft surface were compared

The sample frequencies were explicitly reported in allstudies Four studies were measured with sample frequencieslt1000Hz [1 24 25 46] The frequencies ranged between1000 and 1200Hz in 20 articles [3 15 16 18 20 23 26ndash30 32ndash34 39 42 47ndash50] Additionally 2000Hz and 3000Hzwere respectively reported by Hoffren et al [22] and Zhanget al [31] who together provided eight groups of data witheight DH levels (15ndash90 cm)

32 Mathematical Modeling The regression results of thethree groups divided by sampling frequency are shown inFigure 2The RMSE values of the three regressions were 083037 and 046 for the low medium and high frequenciesrespectivelyThe corresponding adjusted-1198772 values were 073094 and 046The119875 value for each frequencywaslt0001TheANOVA found the statistical significance in the values of ldquoardquoamong three regressions (119875 lt 0001) The difference of ldquobrdquoamong three regressions was not statistically significant (119875 =035) The weighted mean of the three ldquobrdquo values was 034

The data measured by McNitt-Gray [45] was used tovalidate the regression model In his study the samplefrequency was 1000Hz so the regression equation for themedium frequency (PvGRF = 049radicDH + 037) was usedto calculate the PvGRF As shown in Figure 3 the calculatedPvGRF mean was 59 BW for the 128 cm DH McNitt-Gray[45] measured the PvGRF data on two feet which were110 and 91 BW for the gymnasts and recreational athletesrespectively The calculated predictive value agreed with thehalf of experimental values well

33 Influential Factors The effects of all involved factorswere listed in Figure 4 The PvGRF was not significantlyaffected by the surface stiffness but was significantly higherin men than women the platform than suspended landingthe barefoot than shod condition and ankle stabilizer thancontrol condition and higher than lower sample frequencies

4 Discussion

41 Systematic Review We selected 26 articles to make thissystematic review As seen in Table 1 and Figure 2 the large


Table1Ch

aracteris

ticso

fincludedarticles

References

(autho

rsyear)

Subjects(119899sex)

DH(cm)

Land

ingtype

Shoe

Ank

lestabilizer

Surfa

cestiffness

Frequency(H

z)Dufek

andBa

tes19901992[2425]

3M

4060100

PFShoe

Con

trol

Hard

500

Caste

rand

Bates1995[26]

4M

60SP

US

Con

trol

Hard

1000

Zhangetal2000

[23]

9M

3262103

PFUS

Con

trol

Hard

1000

Riem

annetal2002

[20]

9M5

F59

PFShoe

Both

Hard

1000

Deckere

tal2002

[27]

11US

60PF

Shoe

Con

trol

Hard

1200

Deckere

tal2003

[28]

12M9

F60

PFShoe

Con

trol

Hard

1200

Seegmiller

andMcC

aw2003[1]

20F

306090

PFBa

refoot

Con

trol

Soft

960

Kernozek

etal2005

[29]

15M15

F60

SPShoe

Con

trol

Hard

1200

Hod

gson

etal2005

[46]

12F

61SP

Shoe

Both

Hard

600

Kulase

tal2006

[30]

20F

60PF

US

Con

trol

Hard

1000

Hoff

renetal2007

[22]

5M7

F1015

20

PFUS

Con

trol

Hard

2000

Zhangetal2008

[31]

10M

3045607590

PFUS

Con

trol

Hard

3000

BlackburnandPadu

a2009

[32]

20M20F

60SP

Shoe

Con

trol

Hard

1000

Gehrin

getal2009

[42]

13M13

F52

PFShoe

Con

trol

Hard

1080

Niu

etal2010

[15]

8M8

F325272

PFBa

refoot

Con

trol

Hard

1000

Selletal2010

[47]

70M

50PF

Shoe

Con

trol

Hard

1200

Wallace

etal2010

[33]

14M

306090

PFShoe

Con

trol

Hard

1200

Niu

etal2011[16]

8M8

F325272

PFBa

refoot

Both

Hard

1000

Niu

etal2011[18]

8M8

F325272

PFBa

refoot

Con

trol

Hard

1000

Torryetal2011[48]

6M

40PF

US

Con

trol

Hard

1200

Changetal2012

[34]

10M

204060

PFBa

refoot

Con

trol

Hard

1000

Zhangetal2012

[49]

5M5

F60

SPShoe

Both

Hard

1200

Shultzetal2012

[39]

10M10

F45

PFBa

refoot

Con

trol

Hard

1000

Niu

andFan2013

[3]

8M8

F325272

PFBa

refoot

Con

trol

Both

1000

Simpson

etal2013

[50]

16F

43SP

US

Both

Hard

1200

Mm

aleFfemalePF

platform

land

ingSP

suspend

edland

ingUSun

specified

intheo

riginalarticle


00

00

25

25

50

50

75

75

00

25

50

75

100

PvG

RF (B

W)

PvG

RF (B

W)

DH (cm)

LowMedium

High

LowMedium

High

0 25 50 75 100

Sqrt DH (cm12)

Figure 2 Regression between the sqrt drop height (DH) and thepeak vertical ground reaction force (PvGRF) classified by samplefrequency (low frequency PvGRF = 044radicDH + 045 RMSE =083 adjusted-1198772 = 073 119875 lt 0001 medium frequency PvGRF =049radicDH + 037 RMSE = 094 adjusted-1198772 = 045 119875 lt 0001

high frequency PvGRF = 075radicDH+017 RMSE = 046 adjusted-119877

2= 096 119875 lt 0001)

ranges of PvGRF and DH were included in these pooleddata Though there are also many other similar articlesthey do not completely meet the criteria For example somestudies measured resultant GRF on double feet [5 45 5152] According to Criterion 8 they were all excluded in ouranalysis The standard of landing posture and trial processshould be constructed for convenience of comparison amongdifferent studies

Fifteen articles about single-leg landing were recentlysystematically reviewed to compareGRF parameters betweenpatients with footankle pathology and healthy controls [53]They found that PvGRF yielded small significant pooledeffect size of 038 but concluded the GRF parameters oftime to stabilization further met the criteria for proven orcandidate relevant parameters Niu et al [21] concludedthat parameters of time to stabilization were not sensitivefor two-leg landing This study showed satisfying sensitivitywhen evaluating most influential factors during two-leglanding However more kinematic kinetic and electromyo-graphic parameters should be systematically reviewed and

00

25

50

75

0 50 100 128 150

PvG

RF (B

W)

DH (cm)

Figure 3 The validation of regression equation Two star markersrepresent the measurement mean values of peak vertical groundreaction force (PvGRF) for the drop height of 128 cm The shadedarea represents the 95 confidence interval

evaluated to construct a full biomechanical view of thismovement

42 Mathematical Modeling Yeow et al [38] used a simplelinear exponential and natural logarithmic function to fit therelationship of peak GRF and DH of the experimental dataand finally found that they typically followed an exponentialregression relationship of

119910 = 119886119890

119887119909 (6)

where 119910 = GRF and 119909 = DH The exponential function fitonly considered the mathematical implications but not thepractical significance For example in the critical conditionwhen a zero DH (119909 = 0) is considered the exponentialfunction would produce 119910 = 119886 The regression coefficient(a) ranged from 119 to 152 according to the experimentaldata [38] In other words when the participant stands quietlyon both feet the force plate would measure 119ndash152 BWbelow each foot according to the exponential function Thisis understandable When DH = 0 the square root functionwould give PvGRF = b According to the present fit theintercept 119887 values were all in a reasonable interval around theoptimal value in most conditions

Another practical significance of the square root functionwas its domain (DH ge 0) It is impossible for a participant ina traditional landing rather than jumpingmovement to dropfrom a lower height onto a higher position It is necessary toreflect this principle in the mathematic formula Our squareroot function did it because a negative DH is senseless to bea radicand From amathematical aspect there was no similarlimitation in the exponential function proposed byYeow et al[38] Additionally the exponential function was based onfitting of measurement on a certain individual For the sameparticipant the GRF pattern was very similar when landingfrom different DHs but the individual variation amongdifferent participants was not considered Yeow et al [38] alsofound great variations in the regression parameters amongdifferent participants In the present study as many data as


0

02

04

06

Male FemaleGender

mPv

GRF

0

02

04

06

mPv

GRF

0

02

04

06

mPv

GRF

0

02

04

06

mPv

GRF

0

02

04

06

mPv

GRF

0

02

04

06

mPv

GRF

Suspending PlatformLanding type

P = 0042 P = 0001

Barefoot ShoeShoe

No stabilizer StabilizerAnkle stabilizer

Soft HardSurface stiffness

Low Medium HighSample frequency

P = 0027 P = 0047

P = 0820 P = 0031

Figure 4 The effects of all involving factors on the modified peak vertical ground reaction force (mPvGRF)

possible were gathered together to avoid the influence ofindividual variations and produce more satisfactory results

The regression equation for medium frequency was alsovalidated by an experimental measurement done by McNitt-Gray [45] He measured the resultant GRF on double feetfor drop landing while we modeled the peak value onsingle foot Based on the hypothesis proposed by Niu et al[18] that impact forces on both limbs got their imperfectly

simultaneous peaks during landing the calculated predictivePvGRF on one foot should be slightly higher than half ofresultant PvGRF on two feet As seen in Figure 3 the resultwas very satisfactory

43 Influential Factors It is well known that women have anincreased risk for lower-extremity injury while performinglanding movement [15 28 51] Many studies have been done


to investigate the biomechanical differences between twogenders in landing [6 8 29 32 41 42] As seen in theexample listed above there was no consensus on which onegender has higher PvGRF than the other This study showedhigher PvGRF in men compared to women Thereforethe higher injury risk in women has no correlation withPvGRF Scientists should search for a relationship with otherparameters such as jointmotion andmuscle activities [15 16]Based on the finding of higher GRF in men a former studyconcluded that men are more likely to transform the kineticenergy to impact [15]This conclusion was validated becausethe same evidence was confirmed in the present study

A significantly higher mean PvGRF was detected in theplatform landing compared to the suspended landing Theplatform landing is normally accompanied with a steppingor jumping movement through a reaction force from theplatformThismakes the subject leave the platform ahead andupward In most conditions the accompanied stepping orjumping movement would produce an extra vertical heightwhich leads to an actual DH higher than the reported valueduring platform landing Relatively the similar problem isnot seen in the study of suspending landing Therefore thesuspended landing is more reliable than the platform landingwhen considering the influence of DH

Wearing shoes significantly decreased PvGRF comparedto barefoot This result is different from that of Shultzet al [39] and LaPorta et al [52] Shultz et al [39] foundsignificantly higher PvGRF in a shod compared to a barefootlanding while LaPorta et al [52] found no significant differ-ence between them In our opinions the shoe provides a softand flat buffer between the foot and the ground and wouldprotect the foot from injury due to a high impact force

As opposed to the shoe the ankle stabilizer significantlyincreased PvGRF during landingThis is consistent with sev-eral previous reports [16 49 50 53 54] Niu et al [16] foundthat semirigid ankle stabilizer could significantly increasePvGRF Because the ankle stabilizer can effectually protectthe ligamentous structure from spraining by controlling theankle joint the kinetic energy originally absorbed by jointmotion has to be released through increased impact forceafter stabilizer using [16] The increased force may influencethe biomechanics of bones and cartilages in footankle oreven other adjacent regions It should be seen as an adverseeffect of the protection Therefore an optimal design shouldbe considered for an ideal prophylactic ankle support to limitthe excessive joint motion and meanwhile to allow necessaryjoint motion

Surface stiffness had no significant effect on PvGRFThe same conclusion was also obtained in some controlstudies [3 55] Someone may think that there would be adecreased PvGRF with a soft surface because of bufferingIn contrast McNitt-Gray et al [2] found that using matssignificantly increased PvGRF during gymnast landing Theauthors considered that participants modulated total bodystiffness in responses to changes in landing surface conditionsby using amultijoint solution It is possible that this postural-coordination mechanism and the buffering effect of matshad opposing effects that counteracted the influence onPvGRF

Hori et al [56] examined the influences of sample frequ-ency on GRF during CMJ and found that the differenceof GRF peaks was minimal between frequencies of 25Hzand 500Hz They thought that sampling could be as low as200Hz depending on the purpose of measurement duringCMJ In the present study however PvGRF was significantlysmaller when sample frequencies were lt1000Hz comparedwith that gt1200Hz Therefore a sample frequency of at least1000Hz was recommended for the application because nosignificant difference was found between the medium andhigh frequency

44 Limitations There are some limitations in the currentstudy Firstly the variations among various studies were verylarge and it influenced the analyses To avoid the subjectiveinfluence we tried to use all available data in our analysisWe had to construct three regression equations dependenton sample frequency because the variation for certain rangeof sample frequency was greatly less than that for full dataSecondly only PvGRF values were collected and analyzedin the present study There are many other parameters todescribe the biomechanical feature of landing movement Acomplete overview should include all the kinetic kinematicand neuromuscular characteristics An innovative methodwas constructed in the present study to analyze the influencesof various factors on the PvGRF involving all DH situationsThis method can be applied to analyze other parametersduring landing or other similar questions

5 Conclusion

Twenty-six articles reported PvGRF during a double-leg droplanding from different DHs Based on the pooled data a newstatistical method was developed to provide the correlationof peak vertical ground reaction force and drop heightduring two-leg landing and the influences of some factorson the peak vertical ground reaction force regardless of dropheight The PvGRF was not significantly affected by surfacestiffness but was significantly greater in men than womenthe platform than suspended landing the barefoot than shodcondition and ankle stabilizer than control condition andhigher than lower frequencies

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Authorsrsquo Contribution

Wenxin Niu and Tienan Feng contributed equally to thiswork

Acknowledgments

This study was funded by the National Natural ScienceFoundation of China (NSFC 1130215411272273) OpeningProject of Shanghai Key Laboratory of Orthopaedic Implants


(KFKT2013002) and the Fundamental Research Funds forthe Central Universities

References

[1] J G Seegmiller and S T McCaw ldquoGround reaction forcesamong gymnasts and recreational athletes in drop landingsrdquoJournal of Athletic Training vol 38 no 4 pp 311ndash314 2003

[2] J LMcNitt-Gray T Yokoi andCMillward ldquoLanding strategiesused by gymnasts on different surfacesrdquo Journal of AppliedBiomechanics vol 10 no 3 pp 237ndash252 1994

[3] W Niu and Y Fan ldquoTerrain stiffness and ankle biomechanicsduring simulated half-squat parachute landingrdquoAviation Spaceand EnvironmentalMedicine vol 84 no 12 pp 1262ndash1267 2013

[4] J W Whitting J R Steele M Jaffrey and B J MunroldquoDoes foot pitch at grorund contact affect parachute landingtechniquerdquoMilitaryMedicine vol 174 no 8 pp 832ndash837 2009

[5] D L Puddle and P S Maulder ldquoGround reaction forces andloading rates associated with parkour and traditional droplanding techniquesrdquo Journal of Sports Science andMedicine vol12 no 1 pp 122ndash129 2013

[6] Y Salci B B Kentel C Heycan S Akin and F KorkusuzldquoComparison of landing maneuvers between male and femalecollege volleyball playersrdquo Clinical Biomechanics vol 19 no 6pp 622ndash628 2004

[7] R W Bisseling A L Hof S W Bredeweg J Zwerver andT Mulder ldquoRelationship between landing strategy and patellartendinopathy in volleyballrdquo British Journal of Sports Medicinevol 41 article e8 no 7 2007

[8] K R Ford G D Myer and T E Hewett ldquoValgus knee motionduring landing in high school female and male basketballplayersrdquoMedicine and Science in Sports and Exercise vol 35 no10 pp 1745ndash1750 2003

[9] S N Fu and C W Y Hui-Chan ldquoModulation of prelandinglower-limb muscle responses in athletes with multiple anklesprainsrdquo Medicine amp Science in Sports amp Exercise vol 39 no10 pp 1774ndash1783 2007

[10] N Cortes S Morrison B L van Lunen and J A OnateldquoLanding technique affects knee loading and position duringathletic tasksrdquo Journal of Science and Medicine in Sport vol 15no 2 pp 175ndash181 2012

[11] E Scase J Cook M Makdissi B Gabbe and L ShuckldquoTeaching landing skills in elite junior Australian footballevaluation of an injury prevention strategyrdquo British Journal ofSports Medicine vol 40 no 10 pp 834ndash838 2006

[12] D M Hopper P McNair and B C Elliott ldquoLanding in netballeffects of taping and bracing the anklerdquo British Journal of SportsMedicine vol 33 no 6 pp 409ndash413 1999

[13] G A Mothersole J B Cronin and N K Harris ldquoKey prerequi-site factors influencing landing forces in netballrdquo Strength andConditioning Journal vol 35 no 2 pp 47ndash54 2013

[14] P J McNair H Prapavessis and K Callendar ldquoDecreasinglanding forces effect of instructionrdquo British Journal of SportsMedicine vol 34 no 4 pp 293ndash296 2000

[15] W Niu Y Wang Y He Y Fan and Q Zhao ldquoBiomechanicalgender differences of the ankle joint during simulated half-squat parachute landingrdquo Aviation Space and EnvironmentalMedicine vol 81 no 8 pp 761ndash767 2010

[16] W Niu Y Wang J Yao M Zhang Y Fan and Q ZhaoldquoConsideration of gender differences in ankle stabilizer selec-tion for half-squat parachute landingrdquo Aviation Space andEnvironmental Medicine vol 82 no 12 pp 1118ndash1124 2011

[17] M A Pflum K B Shelburne M R Torry M J Decker andM G Pandy ldquoModel prediction of anterior cruciate ligamentforce during drop-landingsrdquoMedicine and Science in Sports andExercise vol 36 no 11 pp 1949ndash1958 2004

[18] W Niu Y Wang Y He Y Fan and Q Zhao ldquoKinematicskinetics and electromyogram of ankle during drop landinga comparison between dominant and non-dominant limbrdquoHuman Movement Science vol 30 no 3 pp 614ndash623 2011

[19] H N Ozguven and N Berme ldquoAn experimental and analyticalstudy of impact forces during human jumpingrdquo Journal ofBiomechanics vol 21 no 12 pp 1061ndash1066 1988

[20] B L Riemann R J Schmitz M Gale and S T McCawldquoEffect of ankle taping and bracing on vertical ground reactionforces during drop landings before and after treadmill joggingrdquoJournal of Orthopaedic and Sports Physical Therapy vol 32 no12 pp 628ndash635 2002

[21] W Niu M Zhang Y Fan and Q Zhao ldquoDynamic posturalstability for double-leg drop landingrdquo Journal of Sports Sciencesvol 31 no 10 pp 1074ndash1081 2013

[22] M Hoffren M Ishikawa and P V Komi ldquoAge-related neu-romuscular function during drop jumpsrdquo Journal of AppliedPhysiology vol 103 no 4 pp 1276ndash1283 2007

[23] S N Zhang B T Bates and J S Dufek ldquoContributions oflower extremity joints to energy dissipation during landingsrdquoMedicine amp Science in Sports amp Exercise vol 32 no 4 pp 812ndash819 2000

[24] J S Dufek and B T Bates ldquoThe evaluation and prediction ofimpact forces during landingsrdquo Medicine and Science in Sportsand Exercise vol 22 no 3 pp 370ndash377 1990

[25] J S Dufek and B T Bates ldquoLower extremity performancemodels for landingrdquo Human Movement Science vol 11 no 3pp 299ndash318 1992

[26] B L Caster and B T Bates ldquoThe assessment of mechanical andneuromuscular response strategies during landingrdquo Medicineand Science in Sports and Exercise vol 27 no 5 pp 736ndash7441995

[27] M J Decker M R Torry T J Noonan A Riviere andW I Sterett ldquoLanding adaptations after ACL reconstructionrdquoMedicine amp Science in Sports amp Exercise vol 34 no 9 pp 1408ndash1413 2002

[28] M J Decker M R Torry D J Wyland W I Sterett and J RSteadman ldquoGender differences in lower extremity kinematicskinetics and energy absorption during landingrdquoClinical Biome-chanics vol 18 no 7 pp 662ndash669 2003

[29] T W Kernozek M R Torry H Van Hoof H Cowley andS Tanner ldquoGender differences in frontal and sagittal planebiomechanics during drop landingsrdquo Medicine and Science inSports and Exercise vol 37 no 6 pp 1003ndash1012 2005

[30] A S Kulas R J Schmitz S J Shultz M A Watson and D HPerrin ldquoEnergy absorption as a predictor of leg impedance inhighly trained femalesrdquo Journal of Applied Biomechanics vol 22no 3 pp 177ndash185 2006

[31] S Zhang T R DerrickW Evans and Y Yu ldquoShock and impactreduction in moderate and strenuous landing activitiesrdquo SportsBiomechanics vol 7 no 2 pp 296ndash309 2008

[32] J T Blackburn and D A Padua ldquoSagittal-plane trunk positionlanding forces and quadriceps electromyographic activityrdquoJournal of Athletic Training vol 44 no 2 pp 174ndash179 2009

[33] B J Wallace T W Kernozek J M White et al ldquoQuantificationof vertical ground reaction forces of popular bilateral plyomet-ric exercisesrdquo Journal of Strength andConditioning Research vol24 no 1 pp 207ndash212 2010


[34] J S Chang Y H Kwon C S Kim S Ahn and S H ParkldquoDifferences of ground reaction forces and kinematics of lowerextremity according to landing height between flat and normalfeetrdquo Journal of Back andMusculoskeletal Rehabilitation vol 25no 1 pp 21ndash26 2012

[35] A Arampatzis G Morey-Klapsing and G P BruggemannldquoThe effect of falling height on muscle activity and foot motionduring landingsrdquo Journal of Electromyography and Kinesiologyvol 13 no 6 pp 533ndash544 2003

[36] M J R Gittoes G Irwin D R Mullineaux and D G Ker-win ldquoWhole-body and multi-joint kinematic control strategyvariability during backward rotating dismounts from beamrdquoJournal of Sports Sciences vol 29 no 10 pp 1051ndash1058 2011

[37] H De Haven ldquoMechanical analysis of survival in falls fromheights of fifty to one hundred and fifty feet 1942rdquo InjuryPrevention vol 6 no 1 pp 62ndash68 2000

[38] C H Yeow P V S Lee and J C H Goh ldquoRegressionrelationships of landing height with ground reaction forcesknee flexion angles angular velocities and joint powers duringdouble-leg landingrdquoThe Knee vol 16 no 5 pp 381ndash386 2009

[39] S J Shultz R J Schmitz A J Tritsch and M M MontgomeryldquoMethodological considerations of task and shoe wear on jointenergetics during landingrdquo Journal of Electromyography andKinesiology vol 22 no 1 pp 124ndash130 2012

[40] C J Hass E A Schick M D Tillman J W Chow D Bruntand J H Cauraugh ldquoKnee biomechanics during landingscomparison of pre- and postpubescent femalesrdquo Medicine ampScience in Sports amp Exercise vol 37 no 1 pp 100ndash107 2005

[41] E E Swartz L CDecoster P J Russell andRV Croce ldquoEffectsof developmental stage and sex on lower extremity kinematicsand vertical ground reaction forces during landingrdquo Journal ofAthletic Training vol 40 no 1 pp 9ndash14 2005

[42] D Gehring M Melnyk and A Gollhofer ldquoGender and fatiguehave influence on knee joint control strategies during landingrdquoClinical Biomechanics vol 24 no 1 pp 82ndash87 2009

[43] M Santello M J N McDonagh and J H Challis ldquoVisual andnon-visual control of landing movements in humansrdquo Journalof Physiology vol 537 no 1 pp 313ndash327 2001

[44] R C Team ldquoR a language and environment for statisticalcomputingrdquo R Foundation for Statistical Computing ViennaAustria httpwwwr-projectorg

[45] J LMcNitt-Gray ldquoKinetics of the lower extremities during droplandings from three heightsrdquo Journal of Biomechanics vol 26no 9 pp 1037ndash1046 1993

[46] B Hodgson L Tis S Cobb and E Higbie ldquoThe effect ofexternal ankle support on vertical ground-reaction force andlower body kinematicsrdquo Journal of Sport Rehabilitation vol 14no 4 pp 301ndash312 2005

[47] T C Sell Y Chu J P Abt et al ldquoMinimal additional weightof combat equipment alters air assault soldiersrsquo landing biome-chanicsrdquoMilitary Medicine vol 175 no 1 pp 41ndash47 2010

[48] M R Torry K B Shelburne D S Peterson et al ldquoKneekinematic profiles during drop landings a biplane fluoroscopystudyrdquoMedicine and Science in Sports and Exercise vol 43 no3 pp 533ndash541 2011

[49] S Zhang M Wortley J F Slivernail D Carson and M RPaquette ldquoDo ankle braces provide similar effects on anklebiomechanical variables in subjects with and without chronicankle instability during landingrdquo Journal of Sport and HealthScience vol 1 no 2 pp 114ndash120 2012

[50] K J Simpson J P Yom Y Fu S W Arnett S OrsquoRourke andC N Brown ldquoDoes wearing a prophylactic ankle brace duringdrop landings affect lower extremity kinematics and groundreaction forcesrdquo Journal of Applied Biomechanics vol 29 no2 pp 205ndash213 2013

[51] Y Iida H Kanehisa Y Inaba and K Nakazawa ldquoActivitymodulations of trunk and lower limb muscles during impact-absorbing landingrdquo Journal of Electromyography and Kinesiol-ogy vol 21 no 4 pp 602ndash609 2011

[52] J W LaPorta L E Brown J W Coburn et al ldquoEffects ofdifferent footwear on vertical jump and landing parametersrdquoThe Journal of Strength amp Conditioning Research vol 27 no 3pp 733ndash737 2013

[53] J Abian-Vicen J Alegre J M Fernandez-Rodrıguez A J LaraM Meana and X Aguado ldquoAnkle taping does not impairperformance in jump or balance testsrdquo Journal of Sports Scienceand Medicine vol 7 no 3 pp 350ndash356 2008

[54] C Y Huang T H Hsieh S C Lu and F C Su ldquoEffect of thekinesio tape to muscle activity and vertical jump performancein healthy inactive peoplerdquo BioMedical Engineering vol 10 no2 p 70 2011

[55] AArampatzis G P Bruggemann andGMKlapsing ldquoA three-dimensional shank-foot model to determine the foot motionduring landingrdquo Medicine amp Science in Sports amp Exercise vol34 no 1 pp 130ndash138 2012

[56] N Hori R U Newton N Kawamori and M R McGuiganldquoReliability of performancemeasurements derived fromgroundreaction force datardquo Journal of Strength and ConditioningResearch vol 23 no 3 pp 874ndash882 2009

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Anatomy Research International

PeptidesInternational Journal of


Hindawi Publishing Corporation httpwwwhindawicom

International Journal of

Volume 2014

Zoology


Molecular Biology International

GenomicsInternational Journal of


The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014


BioinformaticsAdvances in

Marine BiologyJournal of



Signal TransductionJournal of


BioMed Research International

Evolutionary BiologyInternational Journal of



Biochemistry Research International

ArchaeaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014


Genetics Research International


Advances in

Virolog y

Hindawi Publishing Corporationhttpwwwhindawicom

Nucleic AcidsJournal of

Volume 2014

Stem CellsInternational



Enzyme Research



Microbiology


DH higher than 100 cm was rarely adopted in laboratoryHowever the practical height was higher than the testingDH in many sports such as gymnastics [35] and parachuting[15] The PvGRF is still unknown for a DH higher than theexperimental limit [15] This leads to invalid analyses for thepractical condition It is useful to predict PvGRF for anydemanding landing based on current knowledge

In 1942 De Haven [37] used the acceleration equation(V = radic2119892119904) and an inversion of the equation for acceleration(V2 = 2119892119904) to estimate the impact force in falls from heightsFor the normal landing with autonomic posture regulationNiu et al [15] described the mean impact force determinedby the initial landing velocity and buffer distance using anequation 119866 = 1198812(2119878119892) where 119866119881 119878 and 119892 represent meanimpact force initial velocity buffer distance and gravitationalacceleration respectively Both methods are only used forestimating themean force in thewhole impact process but areunable to provide the peak value Yeow et al [38] determinedregression relationships of DH with peak GRF GRF slopeand impulse during landing However as there were onlyfive participants it is difficult to form a general conclusionA large sample through various DHs is needed to predictthe information when individuals land from a more practicalDH

A valid predicting method should be also helpful forcomparing PvGRF between or among different groups orconditions The landing biomechanics is often affected bythe landing type [1 23] instruction [14] shoe [39] anklestabilizer [16] surface stiffness [2] and participantrsquos age[40] sex [41] fatigue [42] and vision [43] In many casesresearchers tried to find some evidences in PvGRF to evaluatecertain influential factors but many conflicting conclusionshave been obtained in these studies For example someauthors reported that women produced significantly higherPvGRF [6 28 29] while Blackburn and Padua [32] detectedsignificantly higher PvGRF in men and also some found nostatistically significant differences in PvGRF between genders[8 41 42] These contradictories may be related to differentDHs in different studies There was no effective method tocompare the PvGRF data between different groups or landingconditions without considering DH Based on abundantpooled data from systematic review a mathematic modelingmay provide some helpful clue to deal with this question

Therefore the purposes of this studywere to (1) systemat-ically review PvGRF data when participants landed from spe-cific DHs with two legs (2) construct a mathematical modeldescribing the constitutive relationship between PvGRF andDH and (3) analyze the effects of gender landing type shoesankle stabilizers and surface stiffness on PvGRF regardless ofDH based on the proposed models

2 Material and Methods

21 Systematic Review In April 2014 two independentreviewers (WNandTF) performed a computerized search forpeer-reviewed journal articles published in English to iden-tify studies reporting drop landing with both legs Searcheswere performed using the following databases PubMed

ScienceDirect Ovid and ISI Web of Knowledge As the highperformance force plate had seldom been used prior to 1980the publication range was between 1980 and April 10 2014Keywords used included ldquolandingrdquo and ldquobiomechanicsrdquo incombination Furthermore relevant articles were identifiedby cross-referencing the citation lists of the articles identifiedin the electronic search In addition authors in the field werecontacted and the authors also searched their own files

Articles retrieved in the original search were exportedinto a single Endnote file (Thomson Reuters CarlsbadCA) and duplicate articles were removed The title andabstract of each record were screened and irrelevant articleswere excluded Where insufficient information was availablefrom the title and abstract the full text was inspected Theremaining full-text articles were assessed for inclusion by oneauthor (WN) Articles selected for exclusion were verifiedby another author (CJ) and any discrepancies were resolvedthrough discussion involving all authors

Studies that met the following criteria were included (1)the studywas conducted on humans (2) the participant num-ber was reported (3) all participants were adults (12ndash60 yr)healthy and with normal vision in the trials (4) participantslanded with both legs and stabilized themselves after contactwhile the single-leg landing countermovement-jump (CMJ)landing or special type of landing (eg Parkour or parachut-ing roll fall) was excluded (5) only the anticipated droplanding was included while jump landing or unanticipatedlanding was excluded (6) DH was reported (7) PvGRF wasprovided with numerical presentation and was normalized toBW (8) the impact force on one foot (left or right dominantor nondominant) was independently measured with oneforce plate

22 Mathematical Modeling Using the principle of conser-vation of energy gravitational potential energy equals thekinetic energy in the vertical direction As described by deHaven [37] the impact velocity from DH in the ideal statecan be calculated as follows

V0= radic2119892 sdot DH (1)

where V0is the impact velocity at initial contact and 119892

is the gravitational acceleration According to the law ofconservation of momentum

int

119905

0

119865119889119905 = int

0

V0119898119889V (2)

where 119865 is the vertical force on one leg and can be calculatedas the difference of themeasured vGRF andBW2At the timeof 119905 = 0 V = V

0 In the impact process F is a continuous

function of the time (t) Based on themean value theorem forintegrals there would exist a 1198651015840 such as 1198651015840Δ119905 = 119898V

0 Then

119865

1015840

119898

= V0

1198981PvGRF = radic2119892 sdot DH

PvGRF =radic2119892

1198981

radicDH

(3)




PvGRF = 119886radicDH + 119887 (4)









(5)


3 Results












Records excluded



unknown 8





Scre

enin

gIn

clude

dEl

igib

ility

Iden

tifica

tion

(n = 108)(n = 4673)

(n = 3020)

(n = 2831)

(n = 26)

(n = 26)

(n = 189)








4 Discussion



Table1Ch

aracteris

ticso

fincludedarticles

References

(autho

rsyear)

Subjects(119899sex)

DH(cm)

Land

ingtype

Shoe

Ank

lestabilizer

Surfa

cestiffness

Frequency(H

z)Dufek

andBa

tes19901992[2425]

3M

4060100

PFShoe

Con

trol

Hard

500

Caste

rand

Bates1995[26]

4M

60SP

US

Con

trol

Hard

1000

Zhangetal2000

[23]

9M

3262103

PFUS

Con

trol

Hard

1000

Riem

annetal2002

[20]

9M5

F59

PFShoe

Both

Hard

1000

Deckere

tal2002

[27]

11US

60PF

Shoe

Con

trol

Hard

1200

Deckere

tal2003

[28]

12M9

F60

PFShoe

Con

trol

Hard

1200

Seegmiller

andMcC

aw2003[1]

20F

306090

PFBa

refoot

Con

trol

Soft

960

Kernozek

etal2005

[29]

15M15

F60

SPShoe

Con

trol

Hard

1200

Hod

gson

etal2005

[46]

12F

61SP

Shoe

Both

Hard

600

Kulase

tal2006

[30]

20F

60PF

US

Con

trol

Hard

1000

Hoff

renetal2007

[22]

5M7

F1015

20

PFUS

Con

trol

Hard

2000

Zhangetal2008

[31]

10M

3045607590

PFUS

Con

trol

Hard

3000

BlackburnandPadu

a2009

[32]

20M20F

60SP

Shoe

Con

trol

Hard

1000

Gehrin

getal2009

[42]

13M13

F52

PFShoe

Con

trol

Hard

1080

Niu

etal2010

[15]

8M8

F325272

PFBa

refoot

Con

trol

Hard

1000

Selletal2010

[47]

70M

50PF

Shoe

Con

trol

Hard

1200

Wallace

etal2010

[33]

14M

306090

PFShoe

Con

trol

Hard

1200

Niu

etal2011[16]

8M8

F325272

PFBa

refoot

Both

Hard

1000

Niu

etal2011[18]

8M8

F325272

PFBa

refoot

Con

trol

Hard

1000

Torryetal2011[48]

6M

40PF

US

Con

trol

Hard

1200

Changetal2012

[34]

10M

204060

PFBa

refoot

Con

trol

Hard

1000

Zhangetal2012

[49]

5M5

F60

SPShoe

Both

Hard

1200

Shultzetal2012

[39]

10M10

F45

PFBa

refoot

Con

trol

Hard

1000

Niu

andFan2013

[3]

8M8

F325272

PFBa

refoot

Con

trol

Both

1000

Simpson

etal2013

[50]

16F

43SP

US

Both

Hard

1200

Mm

aleFfemalePF

platform

land

ingSP

suspend

edland

ingUSun

specified

intheo

riginalarticle


00

00

25

25

50

50

75

75

00

25

50

75

100

PvG

RF (B

W)

PvG

RF (B

W)

DH (cm)

LowMedium

High

LowMedium

High

0 25 50 75 100

Sqrt DH (cm12)



2= 096 119875 lt 0001)



00

25

50

75

0 50 100 128 150

PvG

RF (B

W)

DH (cm)




119910 = 119886119890

119887119909 (6)




0

02

04

06

Male FemaleGender

mPv

GRF

0

02

04

06

mPv

GRF

0

02

04

06

mPv

GRF

0

02

04

06

mPv

GRF

0

02

04

06

mPv

GRF

0

02

04

06

mPv

GRF


P = 0042 P = 0001

Barefoot ShoeShoe




P = 0027 P = 0047

P = 0820 P = 0031














5 Conclusion






Acknowledgments




References

































































Volume 2014

Zoology






















Advances in

Virolog y



Volume 2014




Enzyme Research



Microbiology




PvGRF = 119886radicDH + 119887 (4)









(5)


3 Results












Records excluded



unknown 8





Scre

enin

gIn

clude

dEl

igib

ility

Iden

tifica

tion

(n = 108)(n = 4673)

(n = 3020)

(n = 2831)

(n = 26)

(n = 26)

(n = 189)








4 Discussion



Table1Ch

aracteris

ticso

fincludedarticles

References

(autho

rsyear)

Subjects(119899sex)

DH(cm)

Land

ingtype

Shoe

Ank

lestabilizer

Surfa

cestiffness

Frequency(H

z)Dufek

andBa

tes19901992[2425]

3M

4060100

PFShoe

Con

trol

Hard

500

Caste

rand

Bates1995[26]

4M

60SP

US

Con

trol

Hard

1000

Zhangetal2000

[23]

9M

3262103

PFUS

Con

trol

Hard

1000

Riem

annetal2002

[20]

9M5

F59

PFShoe

Both

Hard

1000

Deckere

tal2002

[27]

11US

60PF

Shoe

Con

trol

Hard

1200

Deckere

tal2003

[28]

12M9

F60

PFShoe

Con

trol

Hard

1200

Seegmiller

andMcC

aw2003[1]

20F

306090

PFBa

refoot

Con

trol

Soft

960

Kernozek

etal2005

[29]

15M15

F60

SPShoe

Con

trol

Hard

1200

Hod

gson

etal2005

[46]

12F

61SP

Shoe

Both

Hard

600

Kulase

tal2006

[30]

20F

60PF

US

Con

trol

Hard

1000

Hoff

renetal2007

[22]

5M7

F1015

20

PFUS

Con

trol

Hard

2000

Zhangetal2008

[31]

10M

3045607590

PFUS

Con

trol

Hard

3000

BlackburnandPadu

a2009

[32]

20M20F

60SP

Shoe

Con

trol

Hard

1000

Gehrin

getal2009

[42]

13M13

F52

PFShoe

Con

trol

Hard

1080

Niu

etal2010

[15]

8M8

F325272

PFBa

refoot

Con

trol

Hard

1000

Selletal2010

[47]

70M

50PF

Shoe

Con

trol

Hard

1200

Wallace

etal2010

[33]

14M

306090

PFShoe

Con

trol

Hard

1200

Niu

etal2011[16]

8M8

F325272

PFBa

refoot

Both

Hard

1000

Niu

etal2011[18]

8M8

F325272

PFBa

refoot

Con

trol

Hard

1000

Torryetal2011[48]

6M

40PF

US

Con

trol

Hard

1200

Changetal2012

[34]

10M

204060

PFBa

refoot

Con

trol

Hard

1000

Zhangetal2012

[49]

5M5

F60

SPShoe

Both

Hard

1200

Shultzetal2012

[39]

10M10

F45

PFBa

refoot

Con

trol

Hard

1000

Niu

andFan2013

[3]

8M8

F325272

PFBa

refoot

Con

trol

Both

1000

Simpson

etal2013

[50]

16F

43SP

US

Both

Hard

1200

Mm

aleFfemalePF

platform

land

ingSP

suspend

edland

ingUSun

specified

intheo

riginalarticle


00

00

25

25

50

50

75

75

00

25

50

75

100

PvG

RF (B

W)

PvG

RF (B

W)

DH (cm)

LowMedium

High

LowMedium

High

0 25 50 75 100

Sqrt DH (cm12)



2= 096 119875 lt 0001)



00

25

50

75

0 50 100 128 150

PvG

RF (B

W)

DH (cm)




119910 = 119886119890

119887119909 (6)




0

02

04

06

Male FemaleGender

mPv

GRF

0

02

04

06

mPv

GRF

0

02

04

06

mPv

GRF

0

02

04

06

mPv

GRF

0

02

04

06

mPv

GRF

0

02

04

06

mPv

GRF


P = 0042 P = 0001

Barefoot ShoeShoe




P = 0027 P = 0047

P = 0820 P = 0031














5 Conclusion






Acknowledgments




References

































































Volume 2014

Zoology






















Advances in

Virolog y



Volume 2014




Enzyme Research



Microbiology









Records excluded



unknown 8





Scre

enin

gIn

clude

dEl

igib

ility

Iden

tifica

tion

(n = 108)(n = 4673)

(n = 3020)

(n = 2831)

(n = 26)

(n = 26)

(n = 189)








4 Discussion



Table1Ch

aracteris

ticso

fincludedarticles

References

(autho

rsyear)

Subjects(119899sex)

DH(cm)

Land

ingtype

Shoe

Ank

lestabilizer

Surfa

cestiffness

Frequency(H

z)Dufek

andBa

tes19901992[2425]

3M

4060100

PFShoe

Con

trol

Hard

500

Caste

rand

Bates1995[26]

4M

60SP

US

Con

trol

Hard

1000

Zhangetal2000

[23]

9M

3262103

PFUS

Con

trol

Hard

1000

Riem

annetal2002

[20]

9M5

F59

PFShoe

Both

Hard

1000

Deckere

tal2002

[27]

11US

60PF

Shoe

Con

trol

Hard

1200

Deckere

tal2003

[28]

12M9

F60

PFShoe

Con

trol

Hard

1200

Seegmiller

andMcC

aw2003[1]

20F

306090

PFBa

refoot

Con

trol

Soft

960

Kernozek

etal2005

[29]

15M15

F60

SPShoe

Con

trol

Hard

1200

Hod

gson

etal2005

[46]

12F

61SP

Shoe

Both

Hard

600

Kulase

tal2006

[30]

20F

60PF

US

Con

trol

Hard

1000

Hoff

renetal2007

[22]

5M7

F1015

20

PFUS

Con

trol

Hard

2000

Zhangetal2008

[31]

10M

3045607590

PFUS

Con

trol

Hard

3000

BlackburnandPadu

a2009

[32]

20M20F

60SP

Shoe

Con

trol

Hard

1000

Gehrin

getal2009

[42]

13M13

F52

PFShoe

Con

trol

Hard

1080

Niu

etal2010

[15]

8M8

F325272

PFBa

refoot

Con

trol

Hard

1000

Selletal2010

[47]

70M

50PF

Shoe

Con

trol

Hard

1200

Wallace

etal2010

[33]

14M

306090

PFShoe

Con

trol

Hard

1200

Niu

etal2011[16]

8M8

F325272

PFBa

refoot

Both

Hard

1000

Niu

etal2011[18]

8M8

F325272

PFBa

refoot

Con

trol

Hard

1000

Torryetal2011[48]

6M

40PF

US

Con

trol

Hard

1200

Changetal2012

[34]

10M

204060

PFBa

refoot

Con

trol

Hard

1000

Zhangetal2012

[49]

5M5

F60

SPShoe

Both

Hard

1200

Shultzetal2012

[39]

10M10

F45

PFBa

refoot

Con

trol

Hard

1000

Niu

andFan2013

[3]

8M8

F325272

PFBa

refoot

Con

trol

Both

1000

Simpson

etal2013

[50]

16F

43SP

US

Both

Hard

1200

Mm

aleFfemalePF

platform

land

ingSP

suspend

edland

ingUSun

specified

intheo

riginalarticle


00

00

25

25

50

50

75

75

00

25

50

75

100

PvG

RF (B

W)

PvG

RF (B

W)

DH (cm)

LowMedium

High

LowMedium

High

0 25 50 75 100

Sqrt DH (cm12)



2= 096 119875 lt 0001)



00

25

50

75

0 50 100 128 150

PvG

RF (B

W)

DH (cm)




119910 = 119886119890

119887119909 (6)




0

02

04

06

Male FemaleGender

mPv

GRF

0

02

04

06

mPv

GRF

0

02

04

06

mPv

GRF

0

02

04

06

mPv

GRF

0

02

04

06

mPv

GRF

0

02

04

06

mPv

GRF


P = 0042 P = 0001

Barefoot ShoeShoe




P = 0027 P = 0047

P = 0820 P = 0031














5 Conclusion






Acknowledgments




References

































































Volume 2014

Zoology






















Advances in

Virolog y



Volume 2014




Enzyme Research



Microbiology


Table1Ch

aracteris

ticso

fincludedarticles

References

(autho

rsyear)

Subjects(119899sex)

DH(cm)

Land

ingtype

Shoe

Ank

lestabilizer

Surfa

cestiffness

Frequency(H

z)Dufek

andBa

tes19901992[2425]

3M

4060100

PFShoe

Con

trol

Hard

500

Caste

rand

Bates1995[26]

4M

60SP

US

Con

trol

Hard

1000

Zhangetal2000

[23]

9M

3262103

PFUS

Con

trol

Hard

1000

Riem

annetal2002

[20]

9M5

F59

PFShoe

Both

Hard

1000

Deckere

tal2002

[27]

11US

60PF

Shoe

Con

trol

Hard

1200

Deckere

tal2003

[28]

12M9

F60

PFShoe

Con

trol

Hard

1200

Seegmiller

andMcC

aw2003[1]

20F

306090

PFBa

refoot

Con

trol

Soft

960

Kernozek

etal2005

[29]

15M15

F60

SPShoe

Con

trol

Hard

1200

Hod

gson

etal2005

[46]

12F

61SP

Shoe

Both

Hard

600

Kulase

tal2006

[30]

20F

60PF

US

Con

trol

Hard

1000

Hoff

renetal2007

[22]

5M7

F1015

20

PFUS

Con

trol

Hard

2000

Zhangetal2008

[31]

10M

3045607590

PFUS

Con

trol

Hard

3000

BlackburnandPadu

a2009

[32]

20M20F

60SP

Shoe

Con

trol

Hard

1000

Gehrin

getal2009

[42]

13M13

F52

PFShoe

Con

trol

Hard

1080

Niu

etal2010

[15]

8M8

F325272

PFBa

refoot

Con

trol

Hard

1000

Selletal2010

[47]

70M

50PF

Shoe

Con

trol

Hard

1200

Wallace

etal2010

[33]

14M

306090

PFShoe

Con

trol

Hard

1200

Niu

etal2011[16]

8M8

F325272

PFBa

refoot

Both

Hard

1000

Niu

etal2011[18]

8M8

F325272

PFBa

refoot

Con

trol

Hard

1000

Torryetal2011[48]

6M

40PF

US

Con

trol

Hard

1200

Changetal2012

[34]

10M

204060

PFBa

refoot

Con

trol

Hard

1000

Zhangetal2012

[49]

5M5

F60

SPShoe

Both

Hard

1200

Shultzetal2012

[39]

10M10

F45

PFBa

refoot

Con

trol

Hard

1000

Niu

andFan2013

[3]

8M8

F325272

PFBa

refoot

Con

trol

Both

1000

Simpson

etal2013

[50]

16F

43SP

US

Both

Hard

1200

Mm

aleFfemalePF

platform

land

ingSP

suspend

edland

ingUSun

specified

intheo

riginalarticle


00

00

25

25

50

50

75

75

00

25

50

75

100

PvG

RF (B

W)

PvG

RF (B

W)

DH (cm)

LowMedium

High

LowMedium

High

0 25 50 75 100

Sqrt DH (cm12)



2= 096 119875 lt 0001)



00

25

50

75

0 50 100 128 150

PvG

RF (B

W)

DH (cm)




119910 = 119886119890

119887119909 (6)




0

02

04

06

Male FemaleGender

mPv

GRF

0

02

04

06

mPv

GRF

0

02

04

06

mPv

GRF

0

02

04

06

mPv

GRF

0

02

04

06

mPv

GRF

0

02

04

06

mPv

GRF


P = 0042 P = 0001

Barefoot ShoeShoe




P = 0027 P = 0047

P = 0820 P = 0031














5 Conclusion






Acknowledgments




References

































































Volume 2014

Zoology






















Advances in

Virolog y



Volume 2014




Enzyme Research



Microbiology


00

00

25

25

50

50

75

75

00

25

50

75

100

PvG

RF (B

W)

PvG

RF (B

W)

DH (cm)

LowMedium

High

LowMedium

High

0 25 50 75 100

Sqrt DH (cm12)



2= 096 119875 lt 0001)



00

25

50

75

0 50 100 128 150

PvG

RF (B

W)

DH (cm)




119910 = 119886119890

119887119909 (6)




0

02

04

06

Male FemaleGender

mPv

GRF

0

02

04

06

mPv

GRF

0

02

04

06

mPv

GRF

0

02

04

06

mPv

GRF

0

02

04

06

mPv

GRF

0

02

04

06

mPv

GRF


P = 0042 P = 0001

Barefoot ShoeShoe




P = 0027 P = 0047

P = 0820 P = 0031














5 Conclusion






Acknowledgments




References

































































Volume 2014

Zoology






















Advances in

Virolog y



Volume 2014




Enzyme Research



Microbiology


0

02

04

06

Male FemaleGender

mPv

GRF

0

02

04

06

mPv

GRF

0

02

04

06

mPv

GRF

0

02

04

06

mPv

GRF

0

02

04

06

mPv

GRF

0

02

04

06

mPv

GRF


P = 0042 P = 0001

Barefoot ShoeShoe




P = 0027 P = 0047

P = 0820 P = 0031














5 Conclusion






Acknowledgments




References

































































Volume 2014

Zoology






















Advances in

Virolog y



Volume 2014




Enzyme Research



Microbiology









5 Conclusion






Acknowledgments




References

































































Volume 2014

Zoology






















Advances in

Virolog y



Volume 2014




Enzyme Research



Microbiology



References

































































Volume 2014

Zoology






















Advances in

Virolog y



Volume 2014




Enzyme Research



Microbiology
































Volume 2014

Zoology






















Advances in

Virolog y



Volume 2014




Enzyme Research



Microbiology

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