Functional muscle asymmetries and laterality in Latin American formation dancers

Abstract

BACKGROUND:

Despite the high popularity of Latin American dance and the specific movement patterns characteristic of this dance discipline, studies on the physical effects of these dance style specific movement patterns are still lacking.

OBJECTIVE:

The purpose of the present study is to analyze strength level differences and shortening of relevant muscle groups resulting from formation dance, taking performance standard and gender into consideration. Furthermore, the correlation between the findings of muscle function tests (MFT) and the occurrence of lumbar spine complaints is evaluated.

METHODS:

A total of 66 participants (m: $n=$ 31, f: $n=$ 35) volunteered for this cross-sectional study (examination group, $n=$ 39, m: $n=$ 19, f: $n=$ 20). The control group consisted of $n=$ 27 participants (m: $n=$ 12, f: $n=$ 15). Besides isometric maximal strength tests (Digi Max system, mechaTronic), relevant muscle groups were examined for shortenings (hip flexors, hamstrings).

RESULTS:

The male participants in dance sport reached a significantly higher strength level in the muscles of the spine region ( $p=$ 0.011) than the participants of the control group. The female elite dance athletes developed a significantly higher strength level in the knee flexors on the right side than the dancers of the advanced group (NL) ( $p=$ 0.021). At that, muscle shortening were observed that seem to be specific to dance sport. In addition, gender specific differences were observed both in strength levels and in tendency to shortenings.

CONCLUSION:

The specific requirements profile of Latin American formation dance seems to produce affects in the form of muscular imbalance on both sides of the body. These differences of muscular status were mainly observed between dance sport competitors and non-dancers rather than between performance levels. Future investigations with higher numbers of participants would be necessary here.

Keywords

Dance sport isometric maximal strength lateralization muscle imbalance

1. Background

In Latin American formation dance six to eight couples of a team aim at moving synchronously and precisely, as well as mainly symmetrically, on a dance floor while performing the five Latin American dances (Samba, Rumba, Jive, Cha-Cha-Cha, Paso Doble) [1]. Particularly during the fast dances (e.g. Jive) cardiovascular impact reaches the maximum intensity level during the six-minutes presentation [2, 3].

Beyond the movement patterns in the single pair dance and the gender-specific tasks and movement- and gait characteristics combined therewith, there are specific movement elements for all participating couples in the formation. Compared to single pair dance these elements occur more frequently (e.g. Lankenau-Pirouette, Cha-Cha spins) but also as parts of special elements, so called ‘highlights’ (e.g. wandered or flung round about, pot stir) typical of formation dance. These elements, as the highest level of difficulty, are essential components of judges’ decisions. According to [4, 5] formation dance sport is the discipline with the highest injury risk within the field of dance sport.

2. Objective

It is not only that movement elements typical in formation dance show a high movement dynamic, but also that stabilization and development are exclusively performed unilaterally by the right upper extremity. Unlike other dance styles, this results in a specific type of load to the movement and support system of either dance partner (Figs 1 and 2). Initial investigations showed that injuries to the upper extremities seem to be characteristic of formation dance sport [6, 7] compared with other disciplines of dance sport [3, 5] and other dance styles [8, 9, 10, 11].

Figure 1.

Round about. The male dancer is directing his female partner clockwise around his body in the dance position shown above. Stabilization is ensured only via right arm contact and is combined with a high load of the shoulder-arm region and spine.

Figure 2.

Pot stir. The male dancer is rapidly stirring his female partner, who is in a deep one-legged squat sitting on her right leg, rotating around her own body axis.

Although there are investigations on other dance styles that suggest a morphological laterality of the body (e.g. in terms of a higher right side strength level, f $>$ m) resulting from gender specific and dance style specific movement components [12, 13, 14, 15], investigations on dance sport are still lacking. In parallel with the high popularity of formation dance, the aforementioned existing specific characteristics and requirements for technical capability have significantly increased in the past decade. Physical effects in terms of strength level and muscle function/-shortenings of specific muscle groups have not been investigated yet.

The aim of the present study is to analyze strength level differences and shortening of relevant muscle groups resulting from formation dance, taking performance standard and gender into consideration. Furthermore, the correlation between the findings of muscle function tests (MFT) and the occurrence of lumbar spine complaints is evaluated.

Table 1

Characteristics of study participants ( $n=$ 66). Mean value and standard deviation

	Examination group (EG)								Control group (CG)
	Men				Women				Men		Women
	IL ( $n=$ 8)		NL ( $n=$ 11)		IL ( $n=$ 8)		NL ( $n=$ 12)		CG ( $n=$ 12)		CG ( $n=$ 15)
Age (yrs)	27.5	$\pm$ 6.6	19.6	$\pm$ 3.2	22.3	$\pm$ 2.5	20.2	$\pm$ 3.9	25.5	$\pm$ 5.7	25.1	$\pm$ 3.6
Height (cm)	182.4	$\pm$ 5.8	183.0	$\pm$ 10.1	168.0	$\pm$ 4.4	165.3	$\pm$ 6.8	180.0	$\pm$ 5.4	171.1	$\pm$ 7.1
Weight (kg)	76.9	$\pm$ 9.8	71.6	$\pm$ 10.3	54.6	$\pm$ 6.2	54.7	$\pm$ 7.2	72.8	$\pm$ 5.2	62.0	$\pm$ 7.1
Training (yrs)	13.0	$\pm$ 5.0	4.0	$\pm$ 2.2	7.9	$\pm$ 2.2	4.9	$\pm$ 4.1	n/a		n/a
Sports activity (hrs/week)	11.6	$\pm$ 7.1	7.5	$\pm$ 2.4	10.9	$\pm$ 5.5	6.0	$\pm$ 2.5	4.5	$\pm$ 5.0	6.9	$\pm$ 5.0

IL: International level, NL: National level.

3. Methods

3.1 Subjects

A total of 66 (m: $n=$ 31, f: $n=$ 35) subjects participated in this study with 39 (m: $n=$ 19, f: $n=$ 20) in the examination group (EG) and 27 (m: $n=$ 12, f: $n=$ 15) in the control group (CG). All subjects participated on a voluntary basis. Study procedures were approved by the University Research Ethics Committee (Charité – Medical school, Berlin, Germany). Informed consent was given prior to the first tests.

All 39 subjects of the EG were members of competitive Latin American dance formations and danced at elite performance level (international standard, IL) (m: $n=$ 8, f: $n=$ 8) and advanced (national) level (NL) (m: $n=$ 11, f: $n=$ 12). All 27 participants of the control group consisted of non-athletes and recreational athletes of other types of sport (Table 1).

3.2 Examinations

The study consisted of three parts:

a)
Experimental strength diagnostics
b)
Muscle function and shortening tests [16, 17]
c)
Questionnaire on complaints in the lumbar spine region

3.2.1 Experimental strength diagnostics

All subjects successfully completed a total of seven isometric maximum strength tests (Digi Max Meßsystem from mechaTronic) of various muscle groups, which affect either stability and symmetry of the spine (M. latissimus, shoulder extensors, M. trapezius) or muscle groups physically challenged by dance sport specific activities (internal rotators of shoulders, elbow flexors, knee extensors and – flexors) [6, 7]. All muscle tests were carried out twice with both body/shoulder sides. The higher value of each examination measured at each trial was evaluated.

The mobile measuring system consisted of a strength sensor fitted between two pulling systems (here: wall bars and subject). Kilogram output was calibrated in 0.5 kg increments, using a digital output device. The strength sensor was attached by a spring hook to a continuously variable mounting at the wall bars and connected to a cuff by a rope. The cuff was placed on the subjects’ body in accordance with the muscle groups to be measured.

3.2.2 Muscle function and shortening tests

A test version by Janda [17] was used to check existing muscle shortenings of the hip joint flexors (here: M. iliopsoas and M. rectus femoris) of all participants in supine position. In addition, the finger-floor distance (FFD) as indicator of a posterior femur or lower back muscle shortening was recorded. In order to test the FFD the test persons stood on a 25 cm high bench. It was only differentiated between “shortened” and “not shortened” [16, 17].

The hip flexors were tested according to Janda [17] with the following ranking:

Level 0: No shortening Level 1: Slight shortening Level 2: Significant shortening

3.2.3 Questionnaire on complaints in the lumbar spine region

The questionnaire provided personalized data as well as traumatic injuries and chronic complaints of either side of the body. For this purpose, the body was divided in single segments according to Strauß [5]. The present evaluation comprises complaints in the lumbar spine region whose resulting data were then correlated to the determined values of strength and the results of the muscle function test.

Table 2
Relative strength differences of combined muscle groups (%) comparing both body sides

	Men						Women
	EG IL	EG NL	p value	EG total	CG	p value	EG IL	EG NL	p value	EG total	CG	p value
Spine	10.5	10.6	0.974	10.6	2.8	0.011 ${}^{*}$	6.8	4.7	0.284	5.5	4.6	0.762
Upper extremity	7.7	6.2	0.749	6.9	5.0	0.597	6.0	8.9	0.734	7.7	5.0	0.444
Lower extremity	$-$ 1.5	5.0	0.222	2.3	1.0	0.764	2.0	9.3	0.967	6.4	3.1	0.369

${}^{*}p<$ 0.05, ${}^{**}p<$ 0.001.

Table 3

Relative strength differences of selected muscle groups (%) comparing both body sides

	Male						Female
Muscle group	EG IL	EG NL	p value	EG total	CG	p value	EG IL	EG NL	p value	EG total	CG	p value
M. latissmus dorsi	6.2	12.3	0.431	9.8	$-$ 0.4	0.071	10.9	3.0	0.284	6.2	6.1	0.995
Shoulder extensors	12.9	7.9	0.388	10.0	2.5	0.108	6.3	3.9	0.734	4.9	2.2	0.595
Shoulder internal rotators	5.7	3.0	0.693	4.1	3.1	0.838	7.8	7.4	0.967	7.6	7.0	0.930
Elbow flexors	9.8	9.4	0.940	9.6	7.0	0.445	4.3	10.3	0.164	7.9	3.1	0.163
M. trapezius	12.7	12.5	0.972	12.6	6.3	0.111	3.1	7.2	0.581	5.6	5.3	0.967
Knee extensors	$-$ 1.6	8.5	0.136	4.2	$-$ 0.0	0.454	$-$ 6.0	7.2	0.021 ${}^{*}$	1.9	2.7	0.859
Knee flexors	$-$ 1.4	1.6	0.747	0.03	1.9	0.823	10.0	13.4	0.612	12.1	3.6	0.137

${}^{*}p<$ 0.05, ${}^{**}p<$ 0.001.

3.3 Statistical evaluation

3.3.1 Strength measurements

Given the research question the strength differences assessed between the right and left side of the body were recorded as percentages. For this purpose, the strength values of the various muscle groups obtained from the maximum strength test were summed up against each other and proportionally related to the total performance. A positive value shows a right sided laterality in respect of strength capability, with a negative value on the left. In order to create a relation between laterality in strength level and injury frequency, the various muscle groups were combined and allocated to the specific body segment:

•
Spine: M. trapezius, shoulder extensors, M. latissimus, M. erector trunci
•
Upper extremity: elbow flexors, shoulder internal rotators
•
Lower extremity/hip: knee extensors, knee flexors, M. iliopsoas

3.3.2 Muscle function and shortening tests

As the subjects of the present study were young, athletically active people, it was determined that all positive values show a finger-floor distance as zero or above zero, i.e. that neither the hamstrings nor the lower back extensors are shortened. Negative values indicated that the subject being tested was not capable of touching the floor with his/her fingertips which suggests a shortening of the muscles involved.

Four categories were established: right: ‘only right laterally shortened’; left: ‘only left laterally shortened’; bilateral: ‘bilaterally shortened’, neither side: ‘not shortened’. Comparing both sides of the muscle groups of the hamstrings and the lower back extensor (lumbar part of the M. erector trunci) by the finger-floor distance test was determined as neither feasible nor practicable. Therefore, the only differentiation recorded was between ‘shortened’ and ‘not shortened’.

All analyses were conducted in SPSS Version 18.0. Difference hypotheses were tested by T-Tests for independent samples, or by non parametric tests (Mann-Whitney-U-Test), respectively, when results were not normally distributed. Significance level was determined at $p\leqslant$ 0.05.

Table 4
Results of muscle functioning tests for shortening (%) comparing men versus women

	EG			CG
Muscle	Men	Women	p value	Men	Women	p value
M. iliopsoas	n (%)	n (%)		n (%)	n (%)
Right	9 (47.4)	2 (10.0)	0.010 ${}^{*}$	2 (16.7)	1 (6.7)	0.411
Left	5 (26.3)	2 (10.0)	0.184	3 (25.0)	0 (0.0)	0.040 ${}^{*}$
Bilateral	5 (26.3)	0 (0.0)	0.014 ${}^{*}$	1 (6.7)	0 (0.0)	0.255
M. rectus femoris
Right	18 (94.7)	9 (45.0)	0.001 ${}^{**}$	8 (66.7)	12 (80.0)	0.432
Left	14 (73.7)	14 (70.0)	0.798	6 (50.0)	12 (80.0)	0.100
Bilateral	14 (73.7)	9 (45.0)	0.069	6 (50.0)	12 (80.0)	0.100

${}^{*}p<$ 0.05, ${}^{**}p<$ 0.001.

Table 5

Results of muscle functioning tests for shortening (%) comparing study groups

	Men			Women
	EG	CG	p value	EG	CG	p value
Illiopsoas	n (%)	n (%)		n (%)	n (%)
Right	9 (47.4)	2 (16.7)	0.082	2 (10.0)	1 (6.7)	0.727
Left	5 (26.3)	3 (25.0)	0.935	2 (10.0)	0 (0.0)	0.207
Bilateral	5 (26.3)	1 (8.3)	0.217	0 (0.0)	0 (0.0)
Rectus femoris
Right	18 (94.7)	8 (66.7)	0.038 ${}^{*}$	9 (45.0)	12 (80.0)	0.039 ${}^{*}$
Left	14 (73.7)	6 (50.0)	0.179	14 (70.0)	12 (80.0)	0.503
Bilateral	14 (73.7)	6 (50.0)	0.179	9 (45.0)	15 (100.0)	0.036 ${}^{*}$

${}^{*}p<$ 0.05, ${}^{**}p<$ 0.001.

4. Results

4.1 General

Descriptive data of the subjects and results as to training age and scope is shown in Table 1. Comparison of the mean values indicates that males and females of the performance level are older than those of the non-athletic level. This difference is also reflected in the training age. As expected, weekly training scope increases with the rising performance level.

4.2 Relative strength differences of the muscle groups

Unlike their female counterparts (EG vs. CG, $p=$ 0.762), only male dancers achieved a significantly higher strength level in the musculature of the spine region compared to the subjects of the control group ( $p=$ 0.011). This can be regarded as a result of the challenging movement elements. A significant higher strength level at the upper extremity as well as the lower extremity between the evaluated groups (IL vs. NL and EG vs. CG) could not be observed (Table 2).

Detailed analysis of the individual muscle groups showed that the female elite dance athletes (IL) developed a significantly higher strength level in the knee flexors on the right side than the dancers of the advanced group (NL) ( $p=$ 0.021). This difference could not be seen in the males. In addition, a tendency towards a significant result could be observed in the M. latissimus dorsi of the male dancers’ group compared to the control group ( $p=$ 0.71). This could suggest an increase load in favor of the right side of the body in dance athletes with a higher performance capability. This difference could not be found in the females (Table 3).

As a whole, only few significant results were found between the performance groups (IL/NL) as well as comparing dancers and the control groups.

4.3 Muscle function and shortening tests

Tables 4 and 5 show the results of muscle functioning tests.

4.4 Hip flexors

Regarding shortening tendencies in the M. iliopsoas region, a clear picture emerged. In either group (examination and control group), a shortening of this muscle was found less often in females than in their male counterparts. Within in the group of male dancers, gender specific significant muscle shortening on the right side could be observed (47.4% vs. 10%, $p=$ 0.01) compared to female dancers. Comparing males and females of the CG, the left sides were significantly more often affected in the males (25%, $p=$ 0.04).

A significant difference between men and women regarding a bilateral shortening was only accounted for in the dancers’ group (26.3% vs. 0%, $p=$ 0.014).

Comparing the groups (EG and CG), only a tendency of increased shortening of the right hip musculature was recognized in the male dance athletes of the examination group (47.4% vs. 16.7%, $p=$ 0.082). All other results were found to be without any significant differences.

Table 6
Results of muscle functioning tests for shortening in cm (hamstrings and M erector trunci) comparing study groups (a) and gender (b)

a)	EG			CG
	Men mean	Women mean	p value	Men mean	Women mean	p value
	value (%)	value (%)		value (%)	value (%)
Hamstrings and M. erector trunci	$-$ 1.7 (36.8)	7.1 (5.0)	0.001 ${}^{**}$	7.4 (25.0)	12.2 (6.7)	0.244
b)	Men			Women
	EG mean	CG mean	p value	EG mean	CG mean	p value
	value (%)	value (%)		value (%)	value (%)
Hamstrings and M. erector trunci	$-$ 1.7 (36.8)	7.4 (25.0)	0.021 ${}^{*}$	7.1 (5.0)	12.2 (6.7)	0.049 ${}^{*}$

${}^{*}p<$ 0.05, ${}^{**}p<$ 0.001.

4.5 M. rectus femoris

Here again, a clear picture emerged. In contrast to the control group, a shortening of the M. rectus femoris was found more often in males than in females of the examination group.

In this muscle region, significantly more shortenings were found in males compared to female dance athletes (94.7% vs. 45%, $p=$ 0.001). Although not significantly, the bilateral shortening in male athletes was higher than in their female counterparts ( $p=$ 0.069). No gender specific significant results could be found in the CG.

Comparing the two groups, significant differences could especially be observed in the right M. rectus femoris in the females of the CG ( $p=$ 0.039) and the males of the EG ( $p=$ 0.038) showing more muscle shortening. A significant bilateral shortening was found in the female CG ( $p=$ 0.036).

4.6 Hamstrings and M. erector trunci

Unlike females, an increasing tendency to shortening in the hamstrings and the lower back extensors (M. erector trunci) was observed in male dance athletes ( $p=$ 0.001) of the examination group and the control group ( $p=$ 0.244) compared to their female counterparts (Table 6). In addition to that, a more frequent shortening in the males of the examination group could be observed (36.8% vs. 25%, $p=$ 0.021) compared to the control group. The same is valid for differences in mobility in the female subjects of the two groups (5.0% vs. 6.7%, $p=$ 0.049).

4.7 Muscle shortenings and lumbar spine complaints

Of all subjects, 37.8% ( $n=$ 25) reported recurrent lumbar spine complaints subjectively impairing their physical performance, with 62.2% ( $n=$ 41) not stating any complaints. A correlation between the shortenings of anterior hip flexors and occurrence of lumbar spine complaints could not be statistically accounted for in the present study.

However, a significant difference in the results of the finger floor distance test ( $p=$ 0.015) between subjects with lumbar spine complaints and those without such could be determined. Subjects with lumbar spine complaints in the lower back region and hamstrings were more mobile than subjects without any complaints in those regions. Both genders showed the same tendencies, however, case data were too small to achieve significant results. Therefore, a differentiation between examination group and control group was waived.

5. Discussion

Significant differences as to strength level favoring the right side of the body in the spinal musculature region (m) and upper extremity musculature (f) were observed in the dancers in comparison with the control group. This phenomenon was more pronounced in the spine region of male dancers than in their female counterparts. The different results within the groups (elite performance level and advanced level) are connected with the relatively low case data in the individual groups. By contrast, no significant differences in strength levels could be determined in the control group in terms of the division of muscle groups of the spine into upper and lower extremity. Consequently, the higher right strength level of spine and upper extremity musculature can be associated with increased static strain to male dancers’ while particularly performing the ‘highlights’ of a choreographic sequence [6].

As the movement description shows, it costs male dance athletes enormous effort to lead and stabilize their female partners during the various elements of the choreography. This effort is mainly exerted by the right arm and right side of the body [6, 7]. The higher strength level of the upper extremities in female dance athletes can be similarly explained. In Latin American formations, both male and female dancers maintain contact by the right arm, with the male dancer directing movement impulses to his female partner in this way. Average training workload of a dance formation is 11 hours weekly; it can easily be imagined that the surplus load to the right side of the body results in a higher strength level due to the process of morphological adjustment. The differences regarding strength relations and shortening tendencies of the lower extremities between male and female dancers reflect the different load profiles in Latin American formation dance [6, 7].

Comparing the sides of the lower extremities (knee extensors, knee flexors), strength significant differences could neither be found in male nor in female dancers for the most part.

However, they are too striking to be ignored. One explanation for the left lateral higher strength level of knee extensors in females of the elite performance group, for example, could be the increased isometric strain work load during the compulsory elements (e.g. round about, pirouette, pot sti rrer). Similar results of strength measurements in classical dance were found by [12, 18]. Female dancers showed a 21% higher strength level of the abductors, which – according to the authors – resulted from an increased isometric load during unilateral work.

This phenomenon was observed only in the performance level group and can be explained by higher daily workload of this group and the fact that these elements of the choreography are demanded with increasing performance standard as compulsory elements. These considerations are also supported by the significantly more frequent shortening of the anterior hip flexor in subjects of performance level IL.

However, the right laterality of the knee flexors again suggests an increased load of the right leg during the whole body turns (pirouettes) principally performed on the right leg as working/supporting leg. On the other hand, it obviously not an easy matter to straighten out the generally higher – however not significantly – right lateral strength level in the lower extremity region of male dance athletes of the performance level.

It can only be estimated that these differences – also in the advanced level – result from choreographies. As a rule, only one single choreography is danced for an entire year which allows adjustments in terms of strength imbalances [6]. Further investigations with other choreographies are suggested here. This is also valid for the significantly more frequent shortening of the hip flexors of male participants in the examination group.

Furthermore, the correlation between lumbar spine complaints and higher flexibility in the ischiocrural musculature region and lower back extensors was striking. Although the correlation with other dance styles is presented [19, 20, 21, 22, 23], investigations from dance sport are still lacking here. There are a number of studies on laterality of injuries as a result of muscle imbalance in other types of sport [24, 25, 26, 27].

5.1 Limitations of the study

This study has a few limitations. Self reported injuries that consult personal assessments may lead to incorrect information by trivializing and not reporting a subjectively minor injury which can not be ruled completely. In contrast with questionnaires that consult objective findings were evaluated in the strength tests. As the authors were seeking identical test conditions, a mobile strength testing system was used. It cannot be totally excluded that mobile testing holds a risk of inaccurate results. In addition to that, power measurements and partly also muscle shortening tests are subject to motivation which could have had an adversely affect on the results, too. However, despite the limitations the study provides important clues about the impact of specific dance elements on muscles and therefore offers several starting points for further research.

6. Conclusion

The specific efficiency profile in Latin American formation dance seems to initiate a muscular imbalance of the sides of the body. Differences of muscular status were mainly observed between dance sport athletes and non-dancers or cross gender. There were hardly any significant differences observed between the various performance classes. Further investigations with higher subject numbers are suggested here.

Footnotes

Conflict of interest

None to report.

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Functional muscle asymmetries and laterality in Latin American formation dancers

Abstract

BACKGROUND:

OBJECTIVE:

METHODS:

RESULTS:

CONCLUSION:

Keywords

1. Background

2. Objective

3.1 Subjects

3.2 Examinations

a) Experimental strength diagnostics b) Muscle function and shortening tests [16, 17] c) Questionnaire on complaints in the lumbar spine region 3.2.1 Experimental strength diagnostics

3.2.2 Muscle function and shortening tests

3.2.3 Questionnaire on complaints in the lumbar spine region

Table 2 Relative strength differences of combined muscle groups (%) comparing both body sides

3.3.1 Strength measurements

• Spine: M. trapezius, shoulder extensors, M. latissimus, M. erector trunci • Upper extremity: elbow flexors, shoulder internal rotators • Lower extremity/hip: knee extensors, knee flexors, M. iliopsoas 3.3.2 Muscle function and shortening tests

Table 4 Results of muscle functioning tests for shortening (%) comparing men versus women

4.1 General

4.2 Relative strength differences of the muscle groups

4.3 Muscle function and shortening tests

4.4 Hip flexors

Table 6 Results of muscle functioning tests for shortening in cm (hamstrings and M erector trunci) comparing study groups (a) and gender (b)

4.6 Hamstrings and M. erector trunci

4.7 Muscle shortenings and lumbar spine complaints

5. Discussion

5.1 Limitations of the study

6. Conclusion

Footnotes

Conflict of interest

References

a)
Experimental strength diagnostics
b)
Muscle function and shortening tests [16, 17]
c)
Questionnaire on complaints in the lumbar spine region

3.2.1 Experimental strength diagnostics

Table 2
Relative strength differences of combined muscle groups (%) comparing both body sides

•
Spine: M. trapezius, shoulder extensors, M. latissimus, M. erector trunci
•
Upper extremity: elbow flexors, shoulder internal rotators
•
Lower extremity/hip: knee extensors, knee flexors, M. iliopsoas

3.3.2 Muscle function and shortening tests

Table 4
Results of muscle functioning tests for shortening (%) comparing men versus women

Table 6
Results of muscle functioning tests for shortening in cm (hamstrings and M erector trunci) comparing study groups (a) and gender (b)