Proper body posture is very important for human health. It is influenced by various factors that can be divided into morphological, psychological, and environmental ones. Daily habits, lifestyle, as well as the nature of physical activity, including various sports fields are also important [
Karate is one of the most popular martial arts in the world, practiced by children, adolescents, adults, and seniors [
Karate is a method of complex movements, where the techniques of attack and defence are characterized by maximum intensity, intertwined with short breaks, which makes the character of this sport comparable to intermittent and intensive exercises [
152 people aged 6 to 16 years, mean age 10.5 ± 3.03, were enrolled in the study. The study group included people attending traditional karate classes for at least one year, twice a week for 60 minutes (76 people, 120 boys and 32 girls). The study was carried out prior to a traditional karate class in Rzeszów in 2015-2017. The control group were children not physically active according to the MVPA (Moderate-to-Vigorous Physical Activity) index [
The inclusion criteria in the study group were the consent of parents and children for examination, regular participation in traditional karate classes for more than 1 year, and lack of neurological and orthopaedic diseases affecting the shape of curvatures of the spine. Inclusion criteria of in the control group were as follows: age, gender matched to the study group, lack of neurological and orthopaedic diseases affecting the posture, and lack of sufficient level of physical activity with MVPA. Moderate physical activity was defined as more than 1 hour a day of cumulative motor activity in the 5 days of the week, whereby motor activity is understood as all forms of physical activity that speed up respiration, e.g., PE classes, sports activities, intense activity during school breaks, walking, and running to or from school. It has been assumed that the response of 5 days or more (MVPA ≤ 5) means physical activity satisfying the minimum needs of adolescents [
Exclusion criteria from both groups were the lack of consent, lower limb injuries (dislocation, sprain) one month before the examination, fractures of the lower limbs in the last 6 months, tactile hypersensitivity resulting in inability of adopting free, habitual posture, and simultaneous regular practice of a sport other than traditional karate.
The flow of the subjects were as follows: Based on the eligibility criteria, 102 karatekas were preliminarily qualified for the study. However, 17 people did not report to the study, 3 people refused to take part on the examination day, and 5 showed tactile hypersensitivity preventing examination. Finally, 76 people from the study group participated in the study.
All the measurements were performed on the same day, starting with anthropometric measurements. Body height was measured with Seca 213 mobile stadiometer, with an accuracy of 0.1 cm. Body mass was measured using electronic scale OMRON BF 500, with an accuracy of 0.1 kg. The measurements were performed in standard conditions; children in underwear and barefoot were standing in upright position, without bending knees. Anthropometric measures of both groups are shown in Table
Characteristics of anthropometric parameters depending on the group.
Variables | Group | N | | Median | Min | Max | Z | p |
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Body weight [kg] | karate | 76 | 38.67±12.56 | 36.85 | 19.90 | 66.80 | -0.226 | 0.820 |
Body weight [kg] | controls | 76 | 39.79±14.90 | 36.05 | 20.00 | 93.00 | ||
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Body height [m] | karate | 76 | 1.41±0.16 | 1.38 | 1.12 | 1.78 | -2.134 | 0,031 |
Body height [m] | controls | 76 | 1.47±0.17 | 1.47 | 1.00 | 1.86 | ||
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BMI | karate | 76 | 18.77±3.06 | 18.24 | 14.51 | 26.37 | 2.027 | 0,041 |
BMI | controls | 76 | 18.00±3.15 | 17.38 | 11.76 | 27.08 |
Z - result of Mann–Whitney
Body posture was examined using inclinometer techniques which is reliable [
The assessment was made in a free standing position, with legs extended in the knees with the eyes directed to the point placed straight ahead of the subject at a distance of 1.5 m. The following instructions were given: “stand in a comfortable manner”; “do not bend your knees”; and “look straight.” The children were not instructed to straighten up [
Correct measurement was when the inclinometer was targeted vertically and the measurement observation was perpendicular to the device. The tests were performed by a physiotherapist with five years of experience as an operator of the equipment and 15 years of experience in testing body posture.
The following parameters were examined by the study: ALPHA angle 1 (ALPHA 1), sacral inclination (the upper inclinometer foot in the middle of the intervertebral space on the line connecting of the posterior superior iliac spines), the ALPHA angle 2 (ALPHA 2), the medial point of the sacrum on the line connecting the so-called Venus dimples (between the inclinometer feet), the BETA angle (BETA Th/L) intervertebral space Th12- L1 (inclinometer on thoracolumbar transition in the middle between the inclinometer feet), GAMMA angle (GAMMA C7) intervertebral space C7-Th1 (top inclinometer foot on C7), DELTA angle (DELTA Th3) intervertebral space Th3-Th4, inclinometer in the plateau of kyphosis, the upper foot right at the end of the convexity forming Dowager’s hump. Lumbar lordosis angle was calculated as (S2) + (Th/L), the thoracic kyphosis angle TKA, (Th/ L) + (C7); Dowager’s hump angle (TKA DH), (C7) + (Th3) [Figure
Measurement with gravity inclinometer.
Changes in the curvature of the spine were evaluated on the basis of the general guidelines for inclinometers acc. to Sauder’s, where the following values were assumed normal: lumbosacral angle (ALPHA angle 1) 15–30°; curvature of the lumbar lordosis, TKA (ALPHA angle 2 + BETA angel) 30–40°; curvature of the thoracic kyphosis (BETA angle + GAMMA angle) 30–40° [
Statistical analyses of the collected material were performed using Statistica 13.1 from StatSoft. Both parametric and nonparametric tests were applied in the analysis of the variables. The choice of parametric test depended on the fulfilment of its basic assumptions, i.e., conformity of the distributions of the examined variables with normal distribution, which was verified with Shapiro-Wilk W-test. The evaluation of the significance level of differences between groups was performed with Mann-Whitney U test or Student t-test for independent variables,
Significant differences were observed between the groups in the inclination of lumbosacral section ALPHA1 p <0.001; karatekas had significantly lower ALPHA 1 inclination and greater inclination of the upper thoracic section (GAMMA TH / L) p=0.023 (Table
Comparison of spine parameters in the sagittal plane depending on the group.
Variables | Group | n | | Me | Min | Max | Z/ | p |
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ALPHA 1 | karate | 76 | 8.79±7.94 | 8.00 | 0.00 | 32.00 | -4.46 | <0.0001 |
ALPHA 1 | controls | 76 | 13.47±6.53 | 12.00 | 1.00 | 26.00 | ||
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ALPHA 2 | karate | 76 | 14.71±6.52 | 14.00 | 2.00 | 32.00 | -0.65 | 0.518 |
ALPHA 2 | controls | 76 | 15.34±5.68 | 15.50 | 6.00 | 29.00 | ||
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BETA Th/L | karate | 76 | 14.26±5.50 | 14.00 | 4.00 | 28.00 | 2.28 | 0,023 |
BETA Th/L | controls | 76 | 11.97±5.62 | 12.00 | 0.00 | 24.00 | ||
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GAMMA C7 | karate | 76 | 22.37±5.32 | 22.00 | 12.00 | 38.00 | -1.84 | 0.066 |
GAMMA C7 | controls | 76 | 24.67±8.28 | 24.00 | 8.00 | 40.00 | ||
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DELTA Th3 | karate | 76 | 17.26±6.42 | 18.00 | 0.00 | 30.00 | -0.66 | 0.508 |
DELTA Th3 | controls | 76 | 18.36±6.89 | 18.00 | 4.00 | 34.00 | ||
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LLA | karate | 76 | 28.97±7.70 | 29.50 | 12.00 | 50.00 | | |
LLA | controls | 76 | 27.32±7.90 | 28.00 | 10.00 | 52.00 | ||
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TKA | karate | 76 | 36.63±8.44 | 36.00 | 24.00 | 58.00 | -0.34 | 0.733 |
TKA | controls | 76 | 36.64±11.10 | 36.00 | 10.00 | 60.00 | ||
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TKA DH | karate | 76 | 31.53±8.70 | 32.00 | 12.00 | 54.00 | | |
TKA DH | controls | 76 | 30.33±8.89 | 31.00 | 10.00 | 54.00 |
ALPHA - sacral inclination; ALPHA 2 – angle of the medial point of the sacrum on the line connecting the so-called Venus dimples; BETA TH /L - intervertebral space Th12- L1; GAMMA C7 - intervertebral space C7-Th1, DELTA Th3 - intervertebral space Th3-Th4 - inclinometer in the plateau of kyphosis; LLA - To obtain the lumbar lordosis on angle – ALPHA 2 + BETA Th / L; TKA - the thoracic kyphosis angle BETA Th12 / L1 + GAMMA C7; TKA DH - Dowager's hump angle GAMMA C7 + DELTA Th3/Th4); n - number of observations;
In the case of the subjects from the karate group, ALPHA 2 flattening was more frequently reported (81.6%) than in the control group (56.6%). In the control group, normal ALPHA 2 was more frequently observed (43.4%). Increased ALPHA 2 was reported only among the karate group (2.6%). The differences were statistically significant (
Characteristics of changes in the inclination of the sacrum depending on the group.
Sacrum ALPHA 1 | Karate Group | Controls Group | Total |
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Normal (15°-30°) | |||
FLATTENING | 62 | 43 | 105 |
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Column % | 81.58 | 56.58 | |
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Total % | 40.79 | 28.29 | 69.08 |
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NORMAL | 12 | 33 | 45 |
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Column % | 15.79 | 43.42 | |
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Total % | 7.89 | 21.71 | 29.61 |
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INCREASED | 2 | 0 | 2 |
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Column % | 2.63 | 0.00 | |
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Total % | 1.32 | 0.00 | 1.32 |
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Total | 76 | 76 | 152 |
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Chi square | 15.238 | ||
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P | 0,0005 | ||
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Cramér’s V | 0.316 |
p - level of probability;
Characteristics of changes in the size of the lumbar lordosis depending on the group.
Lumbar Lordosis Angle (LLA) | Karate Group | Control Group | Total |
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Normal (30°-40°) | |||
FLATTENING | 38 | 50 | 88 |
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Column % | 50.00 | 65.79 | |
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Total % | 25.00 | 32.89 | 57.89 |
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NORMAL | 34 | 24 | 58 |
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Column % | 44.74 | 31.58 | |
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Total % | 22.37 | 15.79 | 38.16 |
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INCREASED | 4 | 2 | 6 |
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Column % | 5.26 | 2.63 | |
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Total % | 2.63 | 1.32 | 3.95 |
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Total | 76 | 76 | 152 |
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Chi square | 4.027 | ||
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P | 0.133 | ||
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Cramér’s V | 0.162 |
P - level of probability
Characteristics of changes in the size of the thoracic kyphosis depending on the group.
Thoracic Kyphosis Angle (TKA) | Karate Group | Control Group | Total |
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Normal (30°-40°) | |||
FLATTENING | 16 | 16 | 32 |
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Column % | 21.05 | 21.05 | |
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Total % | 10.53 | 10.53 | 21.05 |
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NORMAL | 38 | 32 | 70 |
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Column % | 50.00 | 42.11 | |
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Total % | 25.00 | 21.05 | 46.05 |
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INCREASED | 22 | 28 | 50 |
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Column % | 28.95 | 36.84 | |
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Total % | 14.47 | 18.42 | 32.09 |
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Total | 76 | 76 | 152 |
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Chi square | 1.234 | ||
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P | 0.539 | ||
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Cramér’s V | 0.093 |
P - level of probability
Analysing the influence of body mass and height and BMI on the parameters characterizing curvature of the spine, statistically significant relationships were demonstrated in the following range: ALPHA 1 angle, which increased with body weight and BMI in the study group; lumbosacral angle (ALPHA 2), increased with the body height in the study group; the angle of thoracic kyphosis between the scapulae (DELTA Th3) decreased with the increase of body weight and height in the study group. In the control group, there was a significant relationship between the inclination of the upper thoracic segment (GAMMA C7) and the increase in body weight and height and BMI (Table
Relationship between parameters characterizing the shape of the spine in the sagittal plane with body height and mass, BMI depending on the group.
Spearman’s rank-order correlation | ||||
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A pair of variables | Karate group (N=76) | Control group (N=76) | ||
R Spearman | p | R Spearman | p | |
Body weight & ALPHA 1 | 0.31 | 0,007 | -0.02 | 0.897 |
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Body weight & ALPHA 2 | 0.19 | 0.102 | 0.02 | 0.840 |
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Body weight & BETA Th/L | -0.12 | 0.313 | -0.04 | 0.747 |
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Body weight & GAMMA C7 | 0.16 | 0.164 | 0.31 | 0,007 |
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Body weight & DELTA Th3 | -0.17 | 0.147 | 0.01 | 0.919 |
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Body weight & LLA | 0.13 | 0.271 | -0.08 | 0.503 |
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Body weight & KTA | 0.04 | 0.763 | 0.21 | 0.065 |
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Body weight & KTA DH | -0.24 | 0,038 | -0.02 | 0.840 |
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Body height & ALPHA 1 | 0.09 | 0.460 | 0.1 | 0.389 |
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Body weight & ALPHA 2 | 0.28 | 0,015 | 0.06 | 0.597 |
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Body height & BETA Th/L | -0.16 | 0.179 | -0.06 | 0.635 |
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Body height & GAMMA C7 | 0.08 | 0.480 | 0.23 | 0,041 |
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Body height & DELTA Th3 | -0.09 | 0.433 | -0.01 | 0.936 |
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Body height & LLA | 0.2 | 0.080 | -0.03 | 0.806 |
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Body height & KTA | -0.05 | 0.677 | 0.14 | 0.221 |
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Body height & KTA DH | -0.23 | 0.047 | -0.05 | 0.641 |
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BMI & ALPHA 1 | 0.46 | 0,000 | -0.11 | 0.338 |
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BMI & ALPHA 2 | -0.03 | 0.775 | 0.03 | 0.827 |
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BMI & BETA Th/L | -0.09 | 0.452 | -0.04 | 0.703 |
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BMI & GAMMA C7 | 0.2 | 0.086 | 0.28 | 0,014 |
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BMI & DELTA Th3 | -0.2 | 0.084 | 0.02 | 0.891 |
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BMI & LLA | -0.09 | 0.426 | -0.11 | 0.336 |
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BMI &TKA | 0.09 | 0.441 | 0.20 | 0.087 |
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BMI &TKA DH | -0.21 | 0.068 | -0.02 | 0.865 |
ALPHA - sacral inclination; ALPHA 2 - angle of the medial point of the sacrum on the line connecting the so-called Venus dimples; BETA TH /L - intervertebral space Th12- L1; GAMMA C7 - intervertebral space C7-Th1, DELTA Th3 - intervertebral space Th3-Th4 - inclinometer in the plateau of kyphosis; LLA - To obtain the lumbar lordosis on angle – ALPHA 2 + BETA Th / L; TKA - the thoracic kyphosis angle BETA Th12 / L1 + GAMMA C7; TKA DH - Dowager’s hump angle GAMMA C7 + DELTA Th3/Th4); N - number of observations; p - level of probability;
Numerous reports on the impact of martial arts, including karate on the biomechanical, morphological, or psychophysical state of the body are available in the literature [
Our studies showed statistically significant differences in the size of sacral angle parameter (ALPHA 1). The karatekas had significantly lower anterior tilt of sacrum and greater inclination of the thoracic-lumbar transition compared to the control group. In the case of the subjects from the karate group, sacral flattening was more frequently reported (81.6%) than in the control group (56.6%). Increased inclination of lumbosacral section was reported only among the karate group (2.6%). In terms of curvature, thoracic kyphosis and lumbar lordosis, there were no statistically significant differences between the groups.
Mucha et al. reported that unilateral training often leads to reduction in the physiological curvature of the spine, which is the result of excessive strengthening of the Erector spina muscles [
In our studies, the analysis of the influence of body mass, height, and BMI on curvature of the spine showed statistically significant relationships in the following parameters: sacral inclination (ALPHA 1), which increased with body weight and BMI in the study group, lumbosacral angle (ALPHA 2), which increased with the body height in the study group, the angle of the middle thoracic Kyphosis TKA DH, which decreased with body weight and height in the study group, and the inclination of the upper thoracic segment (GAMMA C7), which increased with body weight, height, and BMI in the control group.
Grabara et al. analysed the influence of body mass, height, and BMI on the curvature of the spine in children who do not participate in professional sports training and found weak correlations between curvatures in the sagittal plane and somatic parameters such as height, weight, and BMI [
Summing up, it can be concluded that the results of our research do not confirm the few reports available in the literature, indicating lack of statistically significant differences between the size of lumbar lordosis and thoracic kyphosis between children practicing karate and the control group. Traditional Karate affects the pelvis tilt leading to posterior tilt, at the same time correlating with somatic parameters such as height, body mass, and BMI in terms of spine curvatures. It is assumed that this may be the result of differences in the time of practicing karate in the above quoted reports, since they cover a time interval of 2 to 10 years of regular participation in training. Therefore, further research is necessary considering the division into groups depending on the time of practicing this martial art.
Traditional karate affects the change of pelvis tilt to posterior tilt. Among children practicing traditional karate, body height, body mass, and BMI correlate with parameters characterizing spine curvatures in the thoracic and lumbar-sacral segments. The size of the lumbar lordosis and the thoracic kyphosis in people training traditional karate is comparable to that of a group not practicing sport. Frequent incidence of reduced pelvic tilt in traditional karate practitioners requires introduction of exercises activating anterior tilt in a training session.
An instrument for measuring inclination of surface with respect to vertical line
(Moderate-to-Vigorous Physical Activity) indicator of the level of cumulative motor activity performed with the intensity leading to respiratory increase, considered sufficient for children and adolescents, e.g., sport activities, running from school to school, and PE lessons.
The data used to support the findings of this study are available from the corresponding author upon request.
The authors declare that there are no conflicts of interest regarding the publication of this paper.
This study was funded using the authors’ own resources.