EXERCISING THE MIDSECTION MUSCLES USING THE SPINEGYM

DEVICE

Effects on muscle strength and EMG activity

Iita Aho

Master’s thesis in biomechanics

Spring 2016

Institute for Biology of Physical Activity

University of Jyväskylä

SUMMARY

Iita Aho (2016). Exercising the midsection muscles using the SpineGym device: Effects on muscle strength and EMG activity. Institute for Biology of Physical Activity, University of Jyväskylä, Master’s thesis in biomechanics, 60 pgs., 4 appendices.

The muscles of the midsection are of great importance in everyday life because of their role in supporting the body and maintaining balance. The importance of exercising the midsection muscles is highlighted when one observes people who suffer from back problems and balance disorders, for whom the resulting muscle weakness has begun to cause problems. For these people, the exercising of the muscles may be more difficult due to the limits imposed by said weakness. The SpineGym device allows the muscles to be exercised in a vertical position (i.e. standing), in their natural position of use, and with small trajectories of movement, which makes the exercising easier both for those suffering from back problems and for others.

A study was conducted that investigated how two weeks of SpineGym exercises would affect the EMG activity of the midsection muscles; how much, when a person is exercising with the SpineGym device, the various abdominal and back muscles would work relative to their activity during a person’s isometric maximum-force compression; and, how two weeks of daily exercise with the SpineGym device would affect maximum force in torso-straightening and -bending exercises. The subjects included 20 men and women with sedentary jobs who did not typically engage in muscle fitness exercise (age: 47.5 ± 12.5 years). At the start and end of the study period, maximum-force measurements were performed, and EMG activity was measured, in the following muscles: the abdominal external oblique muscle, the rectus abdominis, the abdominal internal/transverse oblique muscle, the rectus femoris, the trapezius, the spinal erector muscle, the gluteus maximus, and the biceps femoris. The measurements were performed while the subjects were doing abdominal and back muscle exercises with the SpineGym device, and during maximum-force tests. The SpineGym was given to the subjects to use, and the subjects’ objective was to do an approximately 5-minute exercise routine every day for a period of two weeks. The exercise routine included six exercises, three of which focused on the abdominal muscles and quadriceps femoris, and three on the back muscles, gluteal muscles and biceps femoris. Each exercise involved 20 repetitions. According to the exercise journals that were kept, 97% of the exercises were performed.

Over the 2-week study period, the observed change in maximum force was 16.2% (p < 0.001) on average in the torso-bending exercises; in the torso-straightening exercises, the change averaged 9.0% (p < 0.001). The activity of various different muscles in the SpineGym exercises relative to maximum force varied depending on the exercise in question; however, the activity level with the device relative to that seen in the maximum-force test was 57%, on average, for the abdominal external oblique muscle, 80% on average for the rectus abdominis muscles, 61% on average for the abdominal transverse/internal oblique muscle, and 34% on average for the rectus femoris muscle. With the backside muscles, the following average ratios (relative to the maximum-force test activity level) were achieved: 77% for the trapezius, 51% for the spinal erector muscle, 39% for the gluteus maximus, and 47% for the biceps femoris. The subjects’ EMG activity increased between the initial and final measurement by 179%, on average, in the abdominal external oblique muscles, by 157% on average in the rectus abdominis muscles, by 88% on average in the abdominal transverse/internal oblique muscle, and by 199% on average in the quadriceps femoris. On the backside, the change relative to the initially-measured EMG activity was 151% for the trapezius, 9% for the spinal erector muscles, and 582% for the gluteus maximus after the period of SpineGym exercises. The changes were statistically significant (p < 0.05). It was found that, during the period of the SpineGym study, the strength of the midsection muscles developed, and muscle activity improved.

Keywords: SpineGym, midsection muscles, muscle fitness exercises, abdominal muscles, back muscles

CONTENTS

SUMMARY ................................................................................................................................... 2

1 INTRODUCTION .................................................................................................................... 1

2 OPERATING PRINCIPLE OF THE MUSCLES ........................................................................... 3

3 ANATOMY OF THE MIDSECTION ......................................................................................... 5

3.1 Abdominal muscles ...................................................................................................... 5

3.2 Back muscles .............................................................................................................. 10

3.3 Other posture-maintaining muscles .......................................................................... 16

4 IMPORTANCE OF THE MIDSECTION MUSCLES .................................................................. 23

5 EXERCISING THE MIDSECTION MUSCLES .......................................................................... 25

5.1 Various exercise methods .......................................................................................... 25

5.2 Exercising the midsection brings quick results .......................................................... 29

1

1 INTRODUCTION

The midsection muscles, as defined here, include the muscles that support the backbone and

pelvis. Due to their location, they are very important to the kinetic muscle chain, and they

play a part in all movements as well. As the muscles of the lower limbs have an important

role (due to their size) in stabilising the body’s posture, or in inciting and supporting

movement in nearly all activities, these muscles will also be examined here as part of the

structure that supports the body’s midsection.

If the musculature of the midsection is weak, this weakens one’s balance and can increase

the risk of lower back pain, which is often strong enough to inhibit movement. This leads to

a spiralling effect, since back pain can make it more difficult to exercise the midsection

muscles than would otherwise be the case. Additionally, the strength of the midsection

muscles is highly important in the transfer of force from the lower to the upper limbs. Several

different muscles, on both the dorsal and abdominal side, are involved in supporting and

moving the midsection of the body. There are many different methods of exercising these

muscles.

The midsection muscles can be exercised as a unified whole, or one can target certain of

these muscles for exercises and attempt to exclude the other ones. The transverse

abdominal muscle and the oblique abdominal muscles can be exercised simply by tensing

the abdomen in various different positions, and using various stable or labile bases, and

the entire midsection can be exercised using various different holds wherein one tries to

hold one’s torso in a straightened position (supported on one’s toes and elbows, for

2

example). Dynamic abdominal muscle exercises can involve various kinds of abdominal

curls, exercises where one straightens the opposite arm and leg in crawling position, or

sideways turns.

The SpineGym device consists of two strong, upright poles with a safety belt between them,

firmly attached to a standing-platform. By supporting oneself against the belt, and using

the poles as resistance, one can exercise one’s midsection muscles without having to make

any major movements. This way, the muscles can be exercised in a standing position – a

position in which there is a practical need for the muscles' support – and via small

movements, which makes it easier for people with back problems, the elderly, or others

suffering from balance disorders, to develop these muscles, and thus promotes the healing

of back problems or the correction of balance. Many may find exercises done in a standing

position to be more reasonable, and less demanding, than the more traditional midsection

exercises, which are often done lying on the floor or (e.g.) on top of an exercise ball.

3

2 OPERATING PRINCIPLE OF THE MUSCLES

There are three types of muscle tissue: heart muscle, smooth muscle and skeletal muscle,

which is also referred to as striated muscle. Smooth muscle is internal organ muscle

innervated by nerves of the autonomic nervous system; it cannot be voluntarily moved.

Heart muscle is found only in the heart. The striated muscles under consideration here are

innervated by nerves of the somatic (i.e., voluntary) nervous system – they can be voluntarily

moved, and they are used to perform all the body’s voluntary movements. Striated muscles

are attached to bones mainly via tendons, crossing over the joint between the bones.

(Nienstedt et al. 2006, 76-83.)

Striated muscle tissue consists of 5-50 mm-long and 10-100 µm-thick muscle fibres. The

muscle fibres travel, in a lengthwise direction, between a muscle’s point of departure and

point of attachment, and they are full of parallel myofibrils, which consist of parallel

myofilaments. Myofilaments are divided into actin and myosin filaments, which slide

between each other when they are in a resting state. (Nienstedt et al. 2006, 76-78.)

When muscles are activated, actin and myosin filaments slide past each other, so that the

length of the muscle fibres and the entire muscle is shortened, adducting the muscle's point

of origin and point of attachment, thereby causing movement (Nienstedt et al. 2006, 78-80).

A muscle’s contractive force depends on how many motor units, muscle cells innervated by

a single nerve cell, are active; it is also affected by the speed of the movement in question,

the length of the muscle fibres before the start of the movement, and the quality of the

muscle fibres (Nienstedt et al. 2006, 144).

4

By exercising one’s muscles, one can have an effect on the activation of motor units, the

amount of filaments, and muscle metabolism. Muscle contractions can be divided into

isometric, concentric and eccentric contractions. In an isometric contraction, the muscle

cells contract but the tendon stretches, and thus the length of the muscle-tendon complex

does not change. Thus, the contraction does not cause movement, but rather maintains a

given posture. Isometric contraction also occurs in cases where the load one is trying to

move is too big to be moved. When a muscle works concentrically, it shortens during

contraction, whereas when it works eccentrically, it lengthens. It is in eccentric action that

a muscle is able to produce the greatest contractive force. (Nienstedt et al. 2006, 146.) An

example of several different types of muscle action is a chin-up: in the phase involving

concentric muscle action, the person pulls him-/herself up; in the isometric phase, the

person holds him-/herself in place above the bar; and, in the eccentric phase, he/she slowly

goes down, controlling the speed with little "braking" actions.

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3 ANATOMY OF THE MIDSECTION

In this study, the term “midsection” is used to refer to the spine and pelvis, and the

musculature that supports them. The muscles of the midsection are often divided into local

and global muscles, the global muscles being large and more superficial, and the local

muscles being smaller and located deeper in the body (Czaprowski et al. 2014). On the front

side, the midsection is moved and supported by the abdominal muscles located between the

sternum on the one hand, and the pubic bone and iliac ridge on the other (Kathle 1986, 84).

On the back side, the muscles responsible for support and movement are located between

the skull and sacrum (Nienstedt et al. 2006, 149). Some of the midsection muscles, both on

the abdominal side and the back side, are muscles that primarily serve to support the spine,

and play virtually no part in generating movement (Basset & Leach 2011).

There are individual differences in the precise attachment points of the muscles (Kathle et

al. 1986, 84, 88, 94). With regard to muscle functioning, the most significant factor is which

joint a muscle crosses over, and therefore which joint a muscle flexes when it contracts, and

therefore what movement a muscle produces when it contracts. The attachment points

mentioned here are based on the stated source text; however, different sources sometimes

give different attachment points, and therefore, the precision used here when discussing

attachment points does not go beyond what is essential to a muscle’s function, and what is

significant in view of the nature of the study.

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3.1 Abdominal muscles

The white line, or linea alba, travels vertically down the mid-line of the abdominal muscles

and divides them into left and right halves; it is a “tendon-seam” that arises from the

merging of the abdominal muscles on each side. Medially and superficially, on each side of

the white line, are the rectus abdominis muscles, which typically start at the cartilage of

the 5th, 6th and 7th ribs and end at the pubic bone. Depending on the individual, there

may be additional ribs that they attach to. Normally, there are three tendon lines attached

to the white line that travel horizontally across the rectus abdominis muscles. These lines

give the muscles their typical shape. Depending on the individual, there may also be four

or five tendon-seams. (Kathle et al. 1986,88.)

The most important function of the rectus abdominis muscles is the anterior flexion of the

straightened spine, the adduction of the chest towards the pelvis. Additionally, the rectus

abdominis muscles play a part in exhalation, excretion, childbirth and the regulation of

pressure in the abdominal cavity. On top of the rectus abdominis muscles, there is the

pyramid muscle, which starts at the pubic bone and attaches to the white line; in up to 25%

of people, the pyramid muscle may be missing or underdeveloped. The pyramid muscle

assists the rectus abdominis muscles in the flexion of the back. (Kathle et al. 1986, 88.)

The abdominal external oblique muscle starts at the anterior surface of the 5th-12th ribs,

at the latissimus dorsi muscle, and the spaces between the attachment points of the

serratus anterior muscle. Depending on the individual, the number of attachment points

may differ from the eight aforementioned ones. The abdominal external oblique muscle

attaches, fan-like, to the iliac ridge, the inguinal ligament, and the synovium of the rectus

7

abdominis. (Kathle et al. 1986, 84.) Figure 1 shows the rectus abdominis muscles and the

abdominal external oblique muscles.

FIGURE 1. The rectus abdominis muscles, between which one can see the white line, and

which are divided up (by means of tendon lines) into the typical “six-pack” form on the

abdomen. The abdominal external oblique muscles. (Carter & Gray 1918a. Image has been

modified.)

Tendon line

Abdominal external

oblique muscle Rectus abdominis

White line

8

The abdominal internal oblique muscle (Figure 2) is located between the abdominal external

oblique muscle and the transverse abdominal muscle. It starts from the membrane structure

of the pelvic region, the inguinal ligament, and the iliac ridge, and attaches to the lowest ribs

and the synovium of the rectus abdominis. When they contract, the abdominal external and

internal oblique muscles cause rotation of the torso, and help the torso flex (both

downwards and sideways). They function as a kinetic muscle pair, and work simultaneously

with each other. (Kathle et al. 1986, 86.)

FIGURE 2. Abdominal internal oblique muscle. (Carter & Gray 1918b. Image has been

modified.)

Abdominal

internal

oblique

muscle

9

The transverse abdominal muscle, also referred to as the deep abdominal muscle, is located

at the deepest point relative to the other abdominal muscles. It starts from the inner surface

of the cartilage of the 7th-12th rib and from the hip bones and membrane structure of the

lumbar region, and attaches directly to the synovium of the abdominal muscles. This muscle

has a very important role in the stabilisation of the spine, and it also plays a part in regulating

the pressure of the abdominal cavity. In contrast to the other abdominal muscles, the

horizontal direction of the muscle fibres of the transverse abdominal muscle allows the

midsection of the body to be supported in a transverse (crosswise) direction. (Kathle 1986,

86.) Figure 3 shows the transverse abdominal muscle.

FIGURE 3. The transverse abdominal muscle, rectus abdominis and abdominal internal

oblique muscle. (Berichard. Traité d'anatomie topographique. Paulet 1867. Image has been

modified.)

The diaphragm muscle is an important supporter of the body’s midsection (Figure 4). It is

located below the lungs, on the inner side of the lowest rib, and separates the abdominal

Rectus

abdominis

Abdominal

internal

oblique muscle

Transverse

abdominal

muscle

10

cavity from the chest cavity. The diaphragm consists of a central tendon and a muscular

component, which is divided into three parts based on where it is attached: the sternum

component, which attaches to the xiphoid process; the costal component, which attaches

to the 7th-12th ribs; and the lumbar vertebral component. When it tenses, it raises the

internal pressure of the abdominal cavity, which supports the spine from the front. The

diaphragm tenses inward when one breathes and holds one’s breath; this generally

happens automatically when one lifts a heavy load or prepares to throw something. (Kathle

et al. 1986, 102.)

FIGURE 4. The diaphragm. (Carter & Gray 1918c.)

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3.2 Back muscles

The spinal erector muscles (Figure 5) are a group of muscles that consist of multiple

separate muscles, and that extend from the base of the skull to the pelvis. The spinal

erector muscles include the spinalis dorsi muscles, the longissimus dorsi muscles, and the

iliocostalis dorsi muscles. The iliocostalis lumborum muscle starts at the iliac ridge and

attaches to the corner of the 7th-12th rib; the iliocostalis thoracis muscle starts from the

corner of the 7th-12th rib and attaches to the corner of the 1st-6th rib, and the iliocostalis

cervicis muscle starts from the corner of the 3rd-6th rib and attaches to the transverse

processes of the 4th-6th vertebra. The chest component of the longissimus dorsi muscles,

the longissimus thoracis muscle, travels from the transverse processes of vertebrae L1-5 to

those of vertebrae TH1-12; their neck component, the longissimus cervicis muscle, travels

from the transverse processes of vertebrae TH1-5 to those of vertebrae C2-6; and their

head component, the longissimus capitis muscle, starts from the transverse processes of

vertebrae TH1-5 and attaches to the mastoid processes of the temporal bone. The spinalis

thoracis muscle starts from the spinous processes of vertebra TH11-L2, and attaches to

those of TH2-9, whereas the spinalis cervicis muscle starts from the spinous process of

vertebra C7 and ends at that of vertebra C2. The function of the spinal erector muscles is

to straighten the spine when it is in a flexed position, and also, with the iliocostalis cervicis

and longissimus capitis muscles, sideways bending. The long spinalis cervicis muscle only

takes part in sideways bending. It is a powerful group of muscles, and is highly important

to the maintenance of upright posture. (Nienstedt et al. 2006, 149; Kathle et al. 1986, 74.)

12

FIGURE 5. Spinal erector muscles. (Gilroy et al. 2008, 26. Image has been modified.)

The latissimus dorsi muscle (Figure 6) starts from the spinous processes of the 7th-12th

vertebrae, the membrane structure of the lumbar vertebrae, the iliac ridge, the two

lowest ribs, and often also the shoulder blade, and attaches to the upper part of the

humerus bone. The latissimus dorsi muscle is responsible for pulling an outstretched arm

down from an upward position, plays a part in the adduction of outstretched arms and

the medial rotation of the upper arms, and pushes the shoulders downwards and

backwards. It also assists in exhalation and coughing. (Kathle et al. 1986, 138.)

Spinous

process

muscles Iliocostalis dorsi

muscles Longissimus

dorsi muscles

13

FIGURE 6. The latissimus dorsi muscle. (Häggström s.a. Image has been modified.)

The trapezius muscle is divided into upper, middle and lower components (Figure 7). The

upper part starts in the upper section of the nape-of-neck line at the back of the head, and

attaches to the lateral third of the collarbone. The starting points of the middle component

are the spinous processes between the 7th cervical and 3rd thoracic vertebrae, and the

attachment point is the acromion, the end of the collarbone, and the ridge of the shoulder

blade. The lower component of the trapezius starts at the spinous processes of the 2nd and

12th pectoral vertebrae, and attaches to the ridge of the shoulder blade. The main role of

the trapezius is to stabilise the shoulder blade in place. It also pulls the shoulder blades

backwards, turns them, and raises the shoulders. (Kathle et al. 1986, 144.)

Latissimus dorsi

muscle

14

FIGURE 7. The trapezius muscle. (Häggström 2014. Image has been modified.)

The multifidus muscles (Figure 8) are a numerous group of small and deeper back muscles.

They start at the upper transverse process of two overlapping vertebrae, and attach to

the spinous process of the lower vertebra, starting from the second cervical vertebra and

ending at the sacrum. These muscles are active in all the movements of the back, and

cause vertebra-level turning motion. They have an important role in the maintenance of

posture. (Kathle et al. 1986, 74.)

Trapezius

15

FIGURE 8. Multifidus muscles. (Pilates Tonic s.a. Image has been modified.)

The quadratus lumborum muscle (Figure 9) starts at the lowest rib and the vertebrae of the

lumbar vertebrae, and attaches to the iliac ridge. Its function is to straighten the torso from

a sideways-bending position, and to support the side that is opposite to the bent side.

(Kathle et al. 1986, 94.)

Multifidus

muscles

16

FIGURE 9. The quadratus lumborum. (“Muscle system pro 3” iPad application.)

3.3 Other posture-maintaining muscles

The gluteal area consists of three muscles: the gluteus maximus, the gluteus medius, and

the gluteus minimus. The gluteus maximus muscle starts from the ilium, the membrane

structure of the lumbar vertebrae, the sacrum, the coccyx, and the muscle membrane of

the gluteus medius, and attaches to the outer edge of the femur. The main function of the

gluteus maximus is the straightening and outward turning of the hip. It also acts to prevent

the pelvis from inclining forward too much. The gluteus medius and gluteus minimus start

at the ilium and attach to the end of the femur. Both are involved in the medial and lateral

rotation and abduction of the hip, and they also play a part in the straightening of the hip.

(Kathle et al. 1986, 232.) Figure 10 shows the gluteus maximus and medius muscles.

Quadratus lumborum

17

FIGURE 10. The gluteus maximus and medius. (Posterior Hip Muscles 3 s.a. Image has been

modified.)

The quadriceps femoris – the anterior thigh muscle – is divided into four parts (as its name

suggests), which have a shared point of attachment at the upper end of the tibia. At the

front of the thigh muscle, the part that is most visible on the surface is the rectus femoris

muscle, which starts at the most anterior lower peak of the ilium and at the rim of the

acetabulum. The vastus intermedius muscle is located below the rectus femoris, and

Gluteus maximus Gluteus medius

18

starts from the anterior surface of the trunk of the femur. The vastus lateralis muscle is

located on the outer side of the thigh, on the surface, and starts from the trochanter

major located at the end of the femur, the femoral ridge, and the ridge between

trochanters. The vastus medialis muscle is located at the inner edge of the thigh, on the

surface, and starts from the femoral ridge and the ridge between trochanters. (Kathle et

al. 1986, 244.) Figure 11 shows the vastus intermedius, vastus lateralis and vastus medialis

muscles; the rectus femoris, which would be in front of them, has been removed from the

image.

Sartorius muscle

Vastus intermedius

Vastus lateralis

Vastus medialis

Gastrocnemius

muscle Frontmost lower-leg muscle

Soleus muscle

19

FIGURE 11. The quadriceps femoris consists of four parts; the part that is most on the

surface, the rectus femoris, has been removed from the image so that the other parts can

be seen. (Illu lower extremity muscles s.a. Image has been modified.)

The quadriceps femoris straightens the knee, and the rectus femoris also plays a part in

the flexion of the hip. The vastus medialis also has a role in stabilising the knee. Also

located on the front side of the thigh, in addition to the quadriceps femoris, is the

sartorius muscle, which is a long, thin muscle that travels from the hindmost upper peak

of the ilium to the inner side of the upper tibia (Figure 11). The sartorius muscle travels,

at an angle, from the frontal side of the other anterior thigh muscles , playing a part in the

flexion of the hips and knees, the abduction and outward turning of the hips, and the

inward turning of the knee. (Kathle et al. 1986, 244.)

Also located in the anterior muscle chamber is the iliopsoas muscle (Figure 12), which

consists of the psoas major, iliacus, and psoas minor muscles. The psoas major muscle

starts from the main body of the TH12-L4 vertebrae and the L1-L4 costal processes, and

attaches to the trochanter minor of the femur. Its function involves the outward turning,

adduction and flexion of the hips, as well as the flexion of the lumbar spine. The iliacus

muscle travels from the surface of the ilium to the trochanter minor; it plays a part in the

flexion, outward turning, and adduction of the hips. More than 50% of people do not have

a psoas minor. It starts from the trunk of the TH12-L1 vertebrae to the obturator

membrane of the ilium, and plays a part in the flexion of the lumbar spine. (Kathle et al.

1986, 94.)

20

FIGURE 12. Iliopsoas muscle. (Ohara s.a. Image has been modified.)

On the posterior side of the thigh, there is the biceps femoris muscle (Figure 13). This

muscle is divided into two parts, which attach to the end of the fibula; its long end (Latin:

caput longum) starts from the ischial tuberosity of the hip bone, and its short end (Latin:

caput breve) starts from the ridge of the femur. Both ends of the biceps femoris muscle

flex and turn the knee joint, and the long end also plays a role in straightening the hip. On

the posterior side of the thigh are the semitendinosus muscle and semimembranosus

muscle. Both these muscles start from the ischium and attach to the tibia; the

semimembranosus muscle also attaches to the fibula. The function of these muscles

involves the straightening of the hip joints, flexion of the knees, and the inward turning

of the knees. The term “hamstring” is often used when speaking about the posterior thigh

muscles as a group. (Kathle et al. 1986, 246.)

Tensor fasciae latae muscle

Iliacus muscle

Psoas major

Piriformis muscle

21

FIGURE 13. Biceps femoris. (Rolfing Wellness Bringing Alignment and Resolving Tension in

your Body s.a. Image has been modified.)

On the medial side of the thigh are the thigh’s adductor longus muscle, adductor brevis

muscle, and adductor magnus muscle, the function of which is the adduction of the thighs.

The adductor longus muscle travels from the ischial tuberosity to the central third of the

linea aspera; the adductor brevis travels from the pubic bone to the linea aspera, and the

adductor magnus travels from the ischial tuberosity to the linea aspera and the medial

epicondyle of the femur. The medial thigh also includes the gracilis muscle, the pectineus

muscle, and the external obturator muscle. The gracilis muscle starts from the ischium

and attaches to the medial surface of the tibia; it plays a role in the adduction of the hips,

the flexion of the hips and knees, and the inward turning of the knees. The pectineus

muscle starts at the of the pubic bone, ends at the femur, and plays a part in the adduction,

flexion and supination of the hip. The external obturator muscle starts from the obturator

membrane of the foramen obturatorium, attaches to the femur at the trochanteric fossa;

Biceps femoris

Semitendinosus muscle

Semimembranosus muscle

22

its functions include adduction and outward turning of the hips. (Kathle et al. 1986, 236-

238.)

The triceps surae is a three-part muscle consisting of the gastrocnemius and soleus

muscles (Kathle et al. 1986, 258). Figure 11 shows the triceps surae muscles. All the triceps

surae muscles attach to the knob of the heel-bone via the Achilles' tendon. The lateral

end of the gastrocnemius muscle attaches to the femur from above the lateral condyle,

and the medial end attaches from above the medial condyle. (Kathle et al. 1986, 258.)

23

4 IMPORTANCE OF THE MIDSECTION MUSCLES

Here, the stability of the midsection means the ability to control the posture of the

midsection, and to transfer motion from one part of the body to another as one

intends to, using kinetic muscle chains and the concerted action of the torso muscles.

The muscles of the body’s midsection are highly important to maintaining a stable

posture, and to controlling posture during movement. Running, throwing and kicking

are examples of movements in which the body’s midsection is a key component, even

though the motion itself is not regarded as a midsection exercise. (Kibler et al. 2006.)

By exercising the deep muscles of the abdomen, one can improve the support for

one’s spine, lumbar vertebrae and even shoulders, and thus create a basis for all types

of movement (Omkar & Vishwas 2009). Leetun et al. (2004) showed that proper

support for the body’s midsection significantly reduces the risk of injuries to the lower

limbs. Because the spine is fairly unstable compared to the other bones, the

importance of muscles in supporting the spine is highlighted all the more (Gong 2012;

Hodges 1997).

Panjabi divides the system that maintains the midsection’s stability into a passive,

active and neural component (Panjabi 1992, according to Willardson 2007). The

passive component includes the bones and ligaments of the spine that are able to

support weights that are considerably lower than the body’s weight. The active

component includes muscles that provide enough support to carry loads even greater

than the body’s weight. The neural component comprises the nervous system, which

serves to monitor and regulate the muscles’ use of force depending on the changing

24

situation, in various different balancing situations or as the load one is supporting

changes. (Willardson 2007.)

For the current purpose, “balance” refers to the ability to keep the body’s centre of

gravity within certain bounds, such that one’s posture can be stably maintained and

one’s desired motions are possible. Strengthening of the midsection muscles can

promote one’s ability to maintain balance in the midst of challenging movements

(Kibler et al. 2006; Ko et al. 2014). In older people, fitness of the midsection muscles

also appears to increase trust in one’s own balance, it can therefore reduce one’s fear

of falling down and embolden one to move more freely (Ko et al. 2014). Lack of

confidence in one’s ability to maintain balance, and fear of falling, may explain why

weakness of the midsection is one of the main problems that causes elderly persons to

avoid performing daily tasks (Mashall et al. 2005).

Lower-back pain is a common problem caused by weakness of the midsection’s

musculature (Hides et al. 2006; Cairns et al. 2006). Exercise is considered an effective

aid for back problems, but not enough is known to provide precise recommendations

on the nature of the exercises (Airaksinen et al. 2006; Bliven et al. 2013). Strengthening

of the midsection seems to have its own role in the prevention of accidents and strain

injuries. Studies performed with athletes show that exercising the torso reduces the

incidence of accidents and injuries, and also the number of resulting sick days

(Chaudhari et al. 2014).

It is also the role of the midsection to transmit force between the lower and upper limbs

through various kinds of movements – a good example of this is a throwing movement.

25

A javelin-thrower, using his midsection, transfers and strengthens the force produced

by his lower limbs to his throwing arm, so that his throwing arm gets as much force as

possible to hurl the javelin onto its trajectory. If one has a strong midsection, the

transfer of force, and production of extra force, is more efficient than with a weaker

midsection musculature (Kibler et al. 2006; Abt et al. 2007). Abt et al. (2007) have also

shown that having a powerful midsection can increase one’s fortitude in long

endurance tasks.

26

5 EXERCISING THE MIDSECTION MUSCLES

There are conflicting views as to whether one should exercise one’s midsection as a unified

whole, or with exclusive focus on global and local muscles. All the muscles of the midsection

jointly participate in supporting the midsection, and no one muscle, on its own, clearly has

the greatest importance as a muscle – instead, as a person’s load changes, the muscles are

activated in different proportions. (Cholewicki 2002; Marshall et al. 2005.) Attempts are

often made to exclude large, global muscles from exercises wherein the goal is to exercise

local muscles that are focused towards support for the midsection (Chanthapetch et al.

2009; Bjerkefors et al. 2010).

5.1 Various exercise methods

Exercises done on a stable platform and with a stable load are common and traditional

methods of midsection exercise, for the purpose of improving the midsection’s support

(Escamilla et al. 2010; Czabrowski et al. 2012). With the increase in functional exercises,

people have begun shifting from the traditional stable strength exercises to more unstable

types(Kohler et al. 2010; Basnet et al. 2013). A labile base, such as an exercise ball, is often

recommended as an alternative and more efficient base for exercises (Escamilla et al. 2010).

On the other hand, there is evidence that a labile base does not necessarily bring any

significant increase in efficiency of exercise, but instead may even be a drawback, insofar

as it increases the risk of lower-back injuries (Drake et al. 2006; Wahl et al. 2008; Desai et

al. 2010).

27

Bjerkefors et al. (2010) showed that the activation of the transverse abdominal muscle – at

least during various exercises that place a load on the midsection – can be improved simply

by tensing the abdomen. When, during movement and normally during breathing, one

slowly and gently pulls the lower abdomen inward from below the navel without

simultaneously moving the upper abdomen or other parts of the body, the activation of the

transverse abdominal muscle is increased considerably, but not that of the rectus abdominis

muscles. (Bjerkefors et al. 2010.) Tensing of the abdominal muscles also works as an

independent exercise, particularly for the transverse abdominal muscle and the abdominal

internal oblique muscle. (Lee et al. 2011).

A common abdominal muscle exercise is to pull the navel towards the back and towards the

ribs, in such a way that no movement occurs in the back, pelvis, sternum or elsewhere in the

body. This exercise can be done in various different positions: lying on one’s back, lying on

one’s stomach, in a crawling position, or lying supine or prone with one’s legs bent. (Ko et al.

2014; Chanthapetch et al. 2009.) Slightly more demanding abdominal exercises include holds,

wherein one tries to hold one's torso completely straight, normally with one’s weight on the

toes and elbows. Variations on this include (e.g.) a side-hold, wherein one holds the torso in

a straight position with one's weight on one elbow and foot; or, a hold done in a supine

position. Holds can be done on a stable and unstable base. (Czaprowski et al. 2012.) Figure

14 shows examples of various different holds.

28

FIGURE 14. Abdominal muscle exercises. A: front-support hold on a stable base; B: front-leaning hold

with a BOSU ball; C: front-support hold with an exercise ball; D: sideways hold on a stable platform;

E: sideways hold with a BOSU ball; F: hold in a supine position on a stable platform; G: supine hold

with a BOSU ball; and H: supine hold with an exercise ball. (Czaprowski et al. 2012.)

More dynamic abdominal muscle exercises include (e.g.) straightening the opposite arm and leg in a

crawling position on a stable base or on a balancing board; various abdominal curls wherein one

elevates one of the shoulders towards the opposite knee, or both shoulders towards both knees; or

the raising of the legs while keeping them straight, in a supine position (Kahle et al. 2009). Figure 15

shows abdominal curls and the raising of the legs. In the “boat” position, one leans backward with

one’s back straight on a level base, or (for example) on an exercise ball. The boat position can also be

made more effective with sideways turns. Sideways turns can also be done on (e.g.) an exercise ball,

with a weight in one’s outstretched hands, turning from one side to the other. (Kahle et al. 2009.)

Figure 16 shows the “boat” position, and the turning of the body while one is sitting on the exercise

ball.

29

FIGURE 15. Abdominal muscle exercises. Abdominal curling wherein the shoulder approaches

the knee; and the raising of the legs while in supine position. (Kahle et al. 2009.)

FIGURE 16. The “boat” position, and the turning of the body with a hand-held weight. (Kahle et al.

2009.)

5.2 Exercising the midsection brings quick results

By exercising one’s midsection muscles, one can make a positive difference in one’s balance, regardless

of age, in only a few weeks. Basset and Leach (2011) showed that 8 weeks of traditional midsection

exercises, done three times a week for 30 minutes each time, could result in significant development

of young exercisers’ midsection stability. Stability was measured with the “Bunkie” test, wherein

subjects assumed four different hold positions and attempted to maintain their position for 20 seconds.

30

Kim, Yong and Na (2014) observed that half an hour’s exercise three times a week was enough to

produce significant development in the midsection musculature of elderly subjects, who did exercises

on an exercise ball for 20 minutes five times a week. For healthy adults, improvement of balance is

possible in six weeks, if the exercises are done three times per week (Kahle et al. 2009). For aged

subjects, 30 minutes of exercise three times a week resulted in an improvement after six weeks, both

in their physical balance and in how sure they felt of their own balance. The fear of falling down

decreased after the exercise. (Ko et al. 2014.)

Clear results from the exercise of the abdominal muscles can be obtained very quickly. As little as two

weeks of daily, 20-minute exercises involving tensing of the abdominal muscles can produce

improvements in these muscles’ functioning (Lee et al. 2011). With the short exercise periods, the

biggest result is likely due to improvement in the nervous-system regulation of the muscles. The size

of the abdominal muscles probably does not develop enough with two weeks of exercising to be

measurable with an ultrasound device – for that, a longer exercise period would be needed (Lee et al.

2011).

31

6 RESEARCH PURPOSE

The purpose of the research was to determine the effects of the SpineGym muscle exercise

equipment on the strengthening of the core muscles. According to the feedback the manufacturer

has received from their clients, two weeks of exercise with the equipment yield clear, positive

results for posture and muscle condition. The SpineGym equipment can be used to exercise the

core muscles in a standing position and with minor movements, which makes it easier for people

with back problems or the elderly and those suffering from balance problems to exercise their

muscles and therefore promote the correction of back and balance problems.

Research questions:

1. How are muscles activated by the SpineGym equipment with different movements in relation to

their activity in maximum force compression?

2. What kind of an effect does daily SpineGym exercise over a period of two weeks have on core

muscle activity during exercise in persons who work sitting down and do not exercise their

muscles?

3. What kind of an effect does daily SpineGym exercise over a period of two weeks have on core

muscle maximum strength production in persons who work sitting down and do not exercise

their muscles?

The research hypothesis was that SpineGym exercise will increase maximum strength and muscle

activity during the exercise period in persons who do not exercise their muscles previously or exercise

at all actively.

32

7 RESEARCH METHODS

The research setting constituted a group of people who carried out a daily SpineGym

exercise of five minutes for two weeks. The laboratory measurements were carried out

before and after the exercise period. There was no control group.

7.1 Research subjects

20 volunteers were recruited for the study among employees of companies in Jyväskylä.

They had to be people who work sitting down and do not exercise actively in their free time.

Minor back problems were not an obstacle to participation.

The subjects were informed of the study process, its associated disadvantages, the

expectations and risks facing the subjects and any possible unpleasant measurements. They

signed a consent form for participation and were informed that they may discontinue their

participation at any time (appendix 1).

The subjects (14 women and 6 men) were 47.5±12.5 years of age on average. Their body

mass indices were calculated on the basis of the height and weight reported by the subjects

themselves, and averaged at 28±7 kg/m2. Figure 17 shows a more detailed distribution of

the subjects’ weight indices and ages. 13 of the subjects reported mild back problems on

the anamnesis form (appendix 2). The back problems were non-specific symptoms of

stiffness and earlier diagnosed non-acute intervertebral disc slips. The subjects estimated

that they sit down for 50 to 90 % of their working hours, the average time spent sitting down

was calculated at 77±12 % of the working hours. Standing up was estimated to average

14±13 % of the working hours, and walking 8±5 %.

33

Age (years)

FIGURE 17. The age distribution of the subjects’ body mass indices.

7.2 Research protocol

During their first laboratory visit the subjects filled out the anamnesis forms, received

guidance in the use of the SpineGym equipment (SpineGym Oy, Finland) and the equipment

was adjusted to fit each individual. Then EMG electrodes were attached to 8 of their muscles

(see section 7.4) and they warmed up their muscles for maximum strength output under

guidance, carrying out the daily exercise regime to be used in the intervention, constituting

of 20 repeats of each motion used in the study. At the same time, instructions were given

related to the exercise regime (see section 7.3). After the initial warm-up, the subjects

received an isometric maximum body extension and curl measurements by a strength

dynamometer made at the University of Jyväskylä (figure 18).

34

FIGURE 18. The strength dynamometer.

The subjects were asked to squeeze as hard as they can for about three seconds, from which

input the maximum strength was analysed as a one-second average. EMG signals were

registered during the measurements. The best result of three was recorded as the subject’s

maximum strength. After this, the subjects performed muscle exercises on the SpineGym

equipment according to the manufacturer’s instructions, their muscle activity being

recorded by the MegaWin software (Megaelektroniikka Oy, Kuopio, Finland).

The subjects were provided with a SpineGym equipment and they carried out the same

initial five-minute muscle exercise at home once per day every day for the next two weeks.

The subjects kept exercise diaries (appendix 3), and filled out a feedback survey at the end

of the regime concerning the sensibility of the regime (appendix 4). After the two-week

research period, they performed the above maximum strength and muscle condition

exercises again.

35

7.3 Exercise intervention

7.3.1 Back muscle exercises

According to the manufacturer’s instructions, the exercise period included back arching,

upper back exercises and back rotation for the back muscles, the glutes and the hamstrings.

For the back arching, one stands on the platform in an upright position with the support belt

in the front at pelvic height and with the padded staves behind the shoulders. The pelvis is

thrust forward against the support belt, while the back is being arched with tense abdominal

muscles. (Figure 19.) The exercise is repeated 20 times. (SpineGym Core exerciser 2013.)

FIGURE 19. Back arching

36

For the upper back exercise the SpineGym equipment is set up in the same way as for the

back arching. The arms are lifted up to shoulder height, and the elbows brought back by

pressing the shoulder blades together as far as possible. (Figure 20.) The exercise is repeated

20 times. (SpineGym Core exerciser 2013.)

FIGURE 20. Upper back exercise.

For back rotation the settings are the same as for the previous back muscle exercises. The

body is held upright and slowly rotated to the side as far as possible. The motion is held

constant all the way, and the rotations go both ways in turns. (Figure 21.) The exercise is

repeated 20 times for both sides. (SpineGym Core exerciser 2013.)

37

FIGURE 21. Back rotation.

7.3.2 Abdominal muscle exercises

The abdominal muscle and quadriceps exercises recommended by the manufacturer

include transverse abdominal muscle activation, straight abdominal muscle exercises and

oblique abdominal muscle exercises, i.e. abdominal rotation. For the transverse muscle

activation one stands in the SpineGym with the support belt against the lower back and

the padded staves on the front of the shoulders. The belt length is adjusted in a way that

allows for good posture, but minimal tension in the initial stage. The arms are straight at

the sides, palms forward. The back is pushed against the belt while the arms are being

pushed forward, while the shoulders should not move. (Figure 22.) The exercise is

repeated 20 times. (SpineGym Core exerciser 2013.)

38

FIGURE 22. Transverse abdominal muscle activation.

In the straight abdominal muscle exercise the support belt remains behind the lower

back and the padded staves on the front of the shoulders. The pelvis is held in place

while the upper body is bent forward and down, pressing the shoulders forward

diagonally towards a point on the floor approximately 1 to 1.5 meters away. (Figure 23.)

The exercise is repeated 20 times. (SpineGym Core exerciser 2013.)

39

FIGURE 23. Straight abdominal muscle exercise.

For the abdominal rotation the SpineGym is set up in the same way as for the previous

abdominal exercises. The body is kept upright and rotated to both sides as far as it can

go without problems. The motion is briefly stopped in the middle before rotating the

other way. (Figure 24.) The exercise is repeated 20 times to both sides. (SpineGym Core

exerciser 2013.)

40

FIGURE 24. Oblique abdominal muscle exercise, i.e. abdominal rotation.

All exercises are carried out at a peaceful tempo to avoid jerking or sudden and

uncontrolled movements. Movements are reset calmly, constantly feeling the resistance

from the staves. The exercises are carried out in a way that ensures that the concentric,

isometric and eccentric phases are clearly articulated.

7.4 EMG

The EMG electrodes (Ambu Blue Sensor N, Ambu) were attached to the musculus

trapezius, the musculus gluteus maximus and the musculus erector spinae as well as the

musculus biceps femoris on the back. On the abdominal side the electrodes were placed

on the musculus transversus abdominis, the musculus rectus abdominis, the musculus

obliquus external abdominis and the musculus quadriceps femoris in the thigh. In practice,

the electrode on the musculus transversus abdominis also receives a stimulus from the

musculus obliquus internal abdominis and the electrode on the musculus erector spinae

receives a stimulus from the musculus latissimus dorsi. (Figure 25.)

41

FIGURE 25. Placement of the EMG electrodes.

The applied electrodes were bipolar surface electrodes. They were placed as shown in the

pictures. Dead cells were removed and the skin treated with wound disinfectant before the

electrodes were attached. If necessary, any hair was shaved off before the electrodes were

attached. Finally, the electrodes were placed at carefully considered locations. The EMG

measurements were carried out by the ME6000 device (Megaelektroniikka Oy, Kuopio,

Finland).

7.5 Statistical analysis

Excel Office was used for the statistical processing and analysis of the research data. The

results are presented as averages, standard deviations and percent changes (formula: (final

measurement/initial measurement-1) *100). The EMG values measured during the

SpineGym exercises were normalized according to the EMG values measured in the

isometric situation and presented as percentages. The significance of the results was tested

by interdependent sample t-testing. The limit for statistical significance was set at p<0.05.

42

8 RESULTS

Two men discontinued the study. The other’s SpineGym shaft broke in the middle of an

exercise on the second day of the study, presumably due to a manufacturing fault, and

because he was away from town another set of equipment could not be delivered, so he

could not continue. The other man’s pre-existing herniated disc got worse during the

exercises and he had to discontinue because of it. Their initial results have been included

in determining what the muscle activity percentage is during SpineGym exercises in

comparison to maximum strength measurements, but not in the analysis of the effects of

the exercise. No successful muscle activity curve could be obtained from two subjects

during the initial measurements, so no muscle activity change percentages could be

obtained either. For some subject the activity of all muscles could not be reliably measured

due to high body fat or other problems, so certain individual subjects’ measurements have

not been included in the calculations. Changes in maximum strength were monitored for

all those involved in the study of the whole exercise period. Data on the relation of muscle

activity during exercise to maximum strength were obtained from 18 subjects, changes in

muscle activity over the two week period for 16 subjects, and maximum strength changes

during the period for 18 subjects.

According to the exercise diaries, 97 % of the planned exercises were carried out. Nine

subjects completed the exercises daily according to the program, a total of three exercises

were missed due to forgetfulness and five due to travels. One subject’s exercise session

had to be aborted once due to back pains which had been caused earlier by unrelated

reasons and made worse by some of the exercises. The pains lasted for only one day. One

subject had the flu with fever for two days and did not exercise during that time, but they

also extended the exercising period for two days and completed 14 exercises in 16 days.

One subject missed one day’s session,

43

but they exercised in the morning and evening of the following day. The results showed no

discernible difference in muscle strength, growth or muscle activity changes between those

who exercised every day and those who missed one or two sessions, so they have all been

included in the same group for the purpose of analysing the results.

8.1 Muscle activity for different SpineGym exercises in relation to activity

during maximum strength

Table 1 presents the average abdominal muscle and quadriceps activity during SpineGym

exercises in comparison to the activity of the same muscles during maximum strength

curling motions. Depending on the muscle, the activity during SpineGym exercises is

between 23 % and 80 % of the activity during maximum strength. The lowest activity values

relative to maximum strength were measured at the musculus rectus femoris, which is not

a primary exercise target for the SpineGym. For abdominal muscles, the average variable

range of muscle activity measured on the SpineGym and the maximum strength curl motion

was between 32 and 80 %.

44

TABLE 1. Abdominal and quadriceps muscle activity and standard deviation in percentages

of activity during maximum strength body curls for various SpineGym exercises and in

terms of different muscles. Oe = m. obliquus external abdominis, ra = m. rectus

abdominis, tra = m. transversus abdominis, oi = obliquus internal abdominis, rf = rectus

femoris.

Exercise oe ra tra/oi rf

Transverse abdominal activation 39±20 46±30 40±22 23±21

Straight abdominal exercise 57±30 80±28 61±35 34±23

Oblique abdominal exercise 39±24 32±13 49±26 33±34

Table 2 presents the activity of back muscles, glutes and hamstrings during SpineGym

exercises in comparison to the activity of the same muscles during maximum strength

extension exercises. Depending on the muscle, the activity during SpineGym exercises is

between 29 % and 80 % of the activity during maximum strength. The weakest activities

in relation to maximum strength are for the musculus gluteus maximus and the musculus

biceps femoris during the upper back exercise, which is not expected to target the glutes

anyway. The highest activity in relation to maximum strength during the upper back

exercise is for the musculus trapezius, which is specifically targeted by the upper back

exercise.

45

TABLE 2. Back muscle, glutes and hamstrings activity and standard deviation in percentages

of activity during maximum strength body extensions for various SpineGym exercises and in

terms of different muscles. tr = m. trapezius, es = m. erector spinae, gm = m. gluteus

maximus, bf = biceps femoris.

Exercise tr es gm bf

Back arching 49±36 51±18 27±19 42±19

Back rotation 40±25 38±15 39±25 47±18

Upper back exercise 80±65 46±25 29±32 30±19

8.2 Exercise effects on core muscle activity

A statistically significant growth was detected in the activity of the subjects’ abdominal and

quadriceps muscles during the two-week exercise period (Table 3). The highest average

muscle activity growth was measured in the quadriceps during transverse abdominal muscle

activation and straight abdominal muscle exercises. The highest average muscle activity

growth was measured in the subjects’ outer oblique abdominal muscles. The activity in the

subjects’ outer oblique abdominal muscles and quadriceps during all three abdominal

exercises grew to a statistically significant degree. The muscle activity of the

transverse/inner oblique abdominal muscle improved to a statistically significant degree

during the straight abdominal muscle exercise and the oblique abdominal muscle exercise,

the activity of the subjects’ straight abdominal muscles only improved to a statistically

significant degree during the transverse abdominal muscle activation exercise. During

maximum curl exercises, the only statistically significant muscle activity increase was

detected, on average in the subjects’ quadriceps. (Table 3.)

46

TABLE 3. Abdominal and quadriceps muscle activity changes in percentages after the two-

week exercise period. *=p<0.05 statistically significant between initial and final

measurements. Oe = m. obliquus external abdominis, ra = m. rectus abdominis, tra = m.

transversus abdominis, oi = obliquus internal abdominis, rf = rectus femoris

Exercise oe ra tra/oi rf

Transversal abdominal activation 179±224* 157±349* 69±94 199±385*

Straight abdominal exercise 173±149* 111±180 69±103* 180±209*

Oblique abdominal exercise 106±76* 19±83 88±98* 165±165*

Maximum curl 98±106 32±61 48±78 134±246*

The activity of back muscles, glutes and hamstrings are in table 4. Statistically significant muscle

activity increase was detected in the trapezius, glutes and the erector spinae, but not in the

hamstrings. The upper back exercise did not generate statistically significant muscle activity

increase in any muscle. The greatest muscle activity increase occurred in the gluteus maximus,

the activity of which for back rotation grew on average 582 % from the initial measurement

during the two-week period (p<0.05).

47

TABLE 4. Activity changes and standard deviation in percentage for back muscles, glutes and

hamstring after the two-week exercise period. *=p<0.05 statistically significant difference

between initial and final measurements.

Tr = m. trapezius, bf = biceps femoris. es = m. erector spinae, gm = m.

gluteus

Exercise tr es gm bf

Back arching 151±463* 36±71 155±375* 17±62

Back rotation 28±101* 9±29* 582±655* 92±74

Upper back exercise 175±154 -43±40 7±71 -27±72

Maximum extension 58±92* 13±34* 142±315* 58±165

8.3 Exercise effects on maximum strength

The maximum strength for the 18 subjects who remained in the study for the entire time

improved for body curls (bending forward) by 16.2 % on average during the two-week period

(standard deviation (SD) 12.7 %, p < 0.001). The maximum strength change range was -2.1

to 45.9 %. The subjects’ maximum strength for body extensions (bending backwards)

improved by 9.0 % on average (SD 9.4 %, p < 0.001). The range was -2.1 to 31.2 %. There

were two worse results in both measurements (not the same person for the curl and the

extension), other results were improved. Figures 26 and 27 present the subjects’ individual

maximum strength changes during the exercise period for curls and extensions.

48

Individual changes

FIGURE 26. Subjects’ body curl maximum strength changes during the two-week exercise

period.

FIGURE 27. Subjects’ body extension maximum strength changes during the two-week

exercise period.

-10% Individual changes

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49

8.4 Subject experiences

Based on a survey conducted at the end of the research period, 90 % of the subjects felt

that the exercises were good or very good, and 10 % felt that they were moderate. 79 % of

the subjects felt that the amount of exercise was good, the remaining 21 % felt that it was

low or very low. 95 % of the subjects felt that their success in the exercise was good or

excellent, only 5 % felt that their success was only moderate.

Of the 13 subjects who reported back pains before the study, 5 (38 %) felt that the exercises

improved their problems a little. 7 (54 %) of these subjects felt that the exercises did not

affect their back problems at all, and 1 (8 %) felt that the exercises worsened their back

problem to such a degree that they had to discontinue the study because of it. 84 % of the

surveyed subjects stated that they would continue exercising or could continue exercising

with the SpineGym even after the study. 16 % could not say whether they would want to

continue exercising. 32 % of the subjects purchased a SpineGym for themselves after the

study.

50

9 DISCUSSION

The purpose of the study was to investigate the activation of core muscles during SpineGym

exercises and the changes to muscle activation and maximum strength during a two-week

exercise period with the SpineGym equipment. Based on the results, it is possible to use the

SpineGym equipment to exercise effectively enough to make progress in relation to

maximum strength, at least for those who have not exercised previously. The study showed

that the subjects’ maximum strength increased by 16 % for body curl exercises and 9 % for

body extension exercises during the two-week period.

Compared to other studies investigating core muscle exercises, the intervening period of

this study was short and its exercise amount low. Another two-week intervention study has

been published, but the exercise session length there was 20 minutes per day, or

approximately four times longer than the session length in this study (Lee et al. 2011). The

length of the other studies has usually been 6 to 8 weeks, and they have contained 3 to 6

exercise sessions per week for 20 to 30 minutes at a time (Kim et al. 2014; Kahle et al. 2009;

Ko et al. 2014). In the study by Lee et al. (2011) a significant change was detected in the EMG

activity of exterior oblique abdominal muscles and erector spinae muscles over a two-week

exercise period. The study sought to exclude other muscles from the intervention and

focused only on transverse abdominals, oblique abdominals and erector spinae. The daily

exercise amount of the study was longer than that of the SpineGym study, and all of its

subjects were young adults with an average age of 24.4 years. (Lee et al. 2011.) Much of the

exercise effects detected during a short exercise period take place in the nervous system

and are related to learning. Exercising with the SpineGym would seem to produce a similar

exercise effect in the short term as the core exercise methods employed in the other studies,

but a longer study period would make it possible to better compare the effectiveness of

SpineGym exercises with other methods.

51

Kim et al. (2014) detected a statistically significant change in the EMG activity of elderly

people during an eight-week exercise period in the abdominal muscles, erector spinae,

quadratus lumborum and gluteus maximus. The standard deviation in their study was clearly

smaller than in the SpineGym study. The research subjects were elderly people with an

average age of approximately 76.5 years, so their expected progress has probably not been

as good as that of the working age subjects in the SpineGym study.

The difference between the SpineGym and other commonly used core muscle exercise

methods is that the SpineGym is used standing up and in a mostly isometric manner. It is

therefore suitable for people with back problems who may experience pain with extensive

motions or troublesome poses. Stable exercise motions can also be carried out under

various tensions (Chanthapetch et al. 2009). In this case the challenge may be managing the

pose and tensions. Beginners may find it hard to carry out the tensions properly, and may

thus need more guidance than when using the SpineGym. In addition, the tensions may not

feel right or effective since there is no actual motion or any equipment which may make it

harder to keep up the motivation to carry on exercising. Various planking exercises use the

core muscles to keep up stable poses (Czaprowski et al. 2012). There is no motion involved,

which would prevent people with back problems to do them, but they do require strength,

and if one does not have any the pose may begin to fail, causing the back to end up in a bad

position and especially existing back problems to cause pain. Plankings also put quite a lot

of strain on the wrists or shoulders, so people with related problems may not be able to

carry them out. If the muscles are too weak planking is not possible due to requiring quite a

lot of strength. The SpineGym makes it possible to carry out almost fully stable core

exercises without the problems associated with tension and planking.

52

Exercising core muscles and any other muscles can be done by several different methods,

but the essential aspect of all exercise is to actually do the exercise, because only completed

exercise has any effect. Sticking to an exercise regime is influenced by whether it is possible

to carry out the regime due to physical or mental limitations, usually lack of motivation. It is

of course personal how one gets motivated. If motivation requires equipment that serves as

a reminder for exercising and possibly makes the exercise feel more efficient, right or

sensible than exercise without equipment, then using such equipment is justified. The

SpineGym might make exercising easier and more fun by, for example not requiring one to

lie down on the floor and enabling resistance to be adjusted in a gradual and stepless way.

The SpineGym study did not include a control group, which means that the reason for the

changes cannot be determined on the basis of the results. The results may have been affected

by learning the test setting and the possibly different physical state of the subjects during the

different study occasions. One of subjects receiving the worst maximum strength result in the

final measurement had had the flu with fever a few days before, and despite they had felt better

by the time of the measurement, they may still have felt weaker and therefore get worse results.

No data is available for illnesses or other factors influencing the study in the case of the other

subjects, but possible differences in tiredness, oncoming flus or other unconscious

encumbrances may have affected the results. All of the subjects worked sitting down and did

not exercise, so their muscle activity and strength probably improved more during the two

weeks than the activity or strength of such people who actually do exercise regularly anyway.

Learning may have been a possible explanation for the improvement of maximum strength

results, and its significance cannot be reliably determined in the absence of a control group. The

position of the subjects’ feet during the maximum strength extension motion had been

standardised by marking the floor with tape.

53

Some subjects attempted to move their feet over the tape to get more strength out of their

feet into the motion itself, and their pose had to be corrected throughout the measurements.

It is possible that the feet of the subjects were not sufficiently supervised, especially during the

early initial measurements, so some of them were able to carry out the extension exercise

initially with more strength than in the final measurement. This possibility is supported also by

the fact that those who got the worst results in the final measurement in relation to the initial

measurement tried to reposition their feet several times during maximum strength

measurements and had to be corrected. This may have worsened the back extension maximum

strength results for some subjects, which of course also lowers the average. The correct height

for the support belt and the upper support structure was determined and recorded during the

first maximum strength measurements and the same height used in the re-measurements.

Shoes however, were not standardised, so it is possible that some subjects wore different

during the first and second measurements, in which case the different shoes may have affected

the height of the maximum strength support in relation to the first measurement. The tightness

of the support belt was also not standardised but simply tightened by hand, but because there

were several persons carrying out the measurements and tightening the belts, it is possible that

the support belt was not equally tight during initial and final measurements.

In the maximum strength measurement, we asked the subjects to press as hard as possible

while we provided positive feedback. This yielded long and even maximum strength curves,

from which one-second averages were taken as the result. Despite guidance, the subjects used

the SpineGym to carry out significantly shorter stable phases with muscle tension, and the

result had to be a half-second average as the activation even though the original goal was to

get a one-second average here as well as in the maximum strength test.

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Even half a second turned out to be a long time for some subjects during certain exercises, the

curves showing a clear strength spike during the half a second which went up and down. This

being the case, the muscle activation average for the exercises measured at the equipment,

especially for the rotation exercises, was probably not as good in all cases as it could have been

had the subjects maintained their tension for a little longer. The actual muscle tension is

probably slightly higher than the measured values.

The body mass index of some subject was high, which was detrimental to the reliable muscle

activity measurements by the electrodes. Clearly isolated deviating results for some exercises

were left out of the results as anomalies, but it is probable that fatty tissue between the muscle

and the electrode and other interferences have caused inaccuracies in included results as well.

The EMG activity curves of the gluteus maximus for subjects with high body mass index turned

out to be quite difficult as well. Measuring the transverse abdominal muscle by EMG surface

electrodes without the interior oblique abdominal muscle interfering is presumably not possible.

The effects the SpineGym on the transverse abdominal muscle should be investigated further

by other methods.

It was ensured during the initial measurements that each subject can carry out the exercises

correctly and perform the motions cleanly during the actual measurement. By the time of the

final measurements several different versions of the exercises were observed, as many subjects

had not stuck to the instructed exercises. The results might have been different and better for

some subjects if the exercises had been carried out as instructed and without taking shortcuts.

Despite these variations, no-one reported any problems concerning the use of the equipment

or carrying out the exercises in the final survey.

An interesting group whose SpineGym exercising could be studied is pregnant women for whom

exercising the straight abdominal muscles is not recommended due to the separation of the

abdominal muscles, but whose supporting muscles come to play an increasing role due to the

pregnancy. They often suffer from back problems and difficulties with different poses and

balance as the pregnancy progresses, so a simple upright posture and small movements could

make it possible to exercise supporting abdominal muscles in a differentiated manner.

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Reference Picture: EMG Monitoring on SpineGym Tester

Reference Picture: Measuring Results of SpineGym Tester