The effectiveness of strength-related quality in daily life, exercise, and prevention and treatment of chronic diseases has increasingly been recognized [
Ample research has been conducted on the criterion-related validity of SMST test indicators [
However, there are two main defects in previous studies. Firstly, there were no tests for two or more than two blocks and no single test can assess the overall strength of the body. It is necessary to study the validity of the SMST to reflect the whole body muscle strength. Secondly, residence differences are not considered in the study of validity. Fan et al. [
The aims of the present study, therefore, were to
In order to study the validity of SMST indicators to assess whole body muscle strength, we tested the isokinetic muscle strength of the six joints’ flexion and extension movements of the whole body. The isokinetic strength test (IST) has been demonstrated to be valid for assessing muscle strength and muscle function in the knee joint [
Fifth and sixth graders, aged 10 to 12 years, were recruited from the Hunan Normal University Affiliated Primary School (Changsha City, urban) and Liuyang Kouchong Primary School (Liuyang, rural) using a stratified random sampling method. In total, 240 students participated in the study and were divided into four groups which were urban boys (UB), urban girls (UG), rural boys (RB), and rural girls (RG). Each group contained 60 students. All participants met the following criteria:
The Biodex system 3 is a multijoint, constant velocity testing and training system (Biodex Medical Systems New York, USA) and was used to assess IST in the present study. The test indicators for IST were based on the six joints (shoulder, elbow, wrist, marrow, knee, and ankle) for peak torque (PT) and unit weight torque (UWT). PT is the maximum torque output produced by muscle contraction throughout the joint activity, that is, the highest point of the torque curve [
Range of motion (ROM), also known as the range of joint activity, refers to the maximum radian that can be achieved during joint activity [
The introduction of SMST is presented in Table
Indicators and test methods of the SMST.
Test site | Indicators | Test methods | Instruments |
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Upper limbs | Hand-grip (kg) [ |
The participant stood, relaxed, with his/her arms naturally drooped to the sides of the body, palms inward, the hand to be tested holding the grip dynamometer, holding the strength measuring site, reaching slightly out. The range did not exceed 30°. When the participant was ready, he/she was required to use their maximum strength to grip the grip dynamometer once and read the record. Left and right hands were measured alternately. | The Hui Hai student physical quality evaluation system (Hui Hai Electronics, Shanghai, China) |
Knee bent push-up (times) [ |
The participant began prone on the mat, with ten fingers forward and shoulder-width apart, on the ground. The arms were straight and the knees were on the mat. The feet were off the ground and overlapped each other and maintained a straight line from the head and the back to the knee. After hearing the signal, the participant flexed his/her arms to about 90° before pushing the body up and straightening his/her arms. This was counted as a push-up. Throughout the test, the participant held a straight line from the head and back to the knee, and there was no obvious pause between the movements of kneeing push-up. It took 1 minute to complete the knee bent push-up. | The Hui Hai student physical quality evaluation system (Hui Hai Electronics, Shanghai, China) | |
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Trunk | Back muscle strength (kg) [ |
The participants stood and adjusted the handle height of the back dynamometer to make the upper limb of the participant lean forward at 30°. During the test, the participants had both hands clenched on the handle and kept their legs straight, using the maximum strength of the arm, pulling up the back dynamometer. After pulling up the back dynamometer, the participants could not bend their arms or knees, or fall backwards. | BCS-400 electronic back dynamometer (Hengqi Weighing Factory, Nantong, Jiangsu, China) |
Sit-up (times) [ |
The participant lied on his/her back on the mat with knees bent, with his/her fingers grasping the head (back of the head) in the ready posture. When the time started, the participant sat up as quickly as possible, with two elbows touching the outer sides of the two legs. Both shoulders, back, and head must be clenched to the mat in the ready posture. It took 1-minute to complete the sit-up. | The Hui Hai student physical quality evaluation system (Hui Hai Electronics, Shanghai, China) | |
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Lower limbs | Standing long jump (m) [ |
The participant stood behind the jump line, with feet naturally apart. The toes should not step on the line (preferably using a rope as the jump line). Both feet jump simultaneously from the standing point; taking a step or successive jumping was not allowed. The vertical distance from the trailing edge of jump line to the nearest landing point was measured. | The Hui Hai student physical quality evaluation system (Hui Hai Electronics, Shanghai, China) |
Leg muscle strength (kg) [ |
The leg muscle strength test also uses the back dynamometer, but the test method is different. The participant handle height of the back dynamometer was adjusted to make the participant bend the knee at ~115°–125°. During the test, the participants had both hands clenched on the handle, holding the upper body upright and using their maximum strength of the arm to pull the back dynamometer. When pulling up the back dynamometer, the participants could not bend their arms, bend their body, or fall backwards. | BCS-400 electronic back dynamometer (Hengqi Weighing Factory, Nantong, Jiangsu, China) |
Before conducting the factor analysis, the correlation analyses, Kaiser-Meyer-Olkin (KMO) test and Bartlett test, were used to test whether the data met the criteria for conducting a factor analysis. The Bartlett’s sphericity test showed whether the data was suitable for factor analysis. According to the principle of factor analysis, when the cumulative contribution rate of extracted common factor was over 80%, this factor could explain most of the information [
To study the validity of the SMST indicators, Pearson correlation analyses were used to analyze the correlation of the SMST indicators and the
As shown in Table
The anthropometry characteristics of participants.
UB | RB | UG | RG | |
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Height (cm) |
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140.2 ± 4.05 |
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139.93 ± 6.78 |
Weight (kg) |
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35.2 ± 8.02 | 35.98 ± 9.73 | 33.16 ± 6.07 |
Vital capacity (ml) |
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1695.9 ± 273.15 |
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1669 ± 307.01 |
As shown in Table
The results of SMST.
UB | RB | UG | RG | |
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Hand-grip (kg) |
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12.75 ± 4.10 | 10.24 ± 3.25 |
Knee bent push-ups (kg) |
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11.16 ± 3.49 | 9.87 ± 2.32 |
Back muscle strength (kg) |
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39.2 ± 9.78 | 42.8 ± 8.13 |
Sit-ups (times) | 32.14 ± 8.22 | 33.32 ± 7.56 | 32.76 ± 7.87 | 31.59 ± 9.05 |
Leg muscle strength (kg) |
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55.3 ± 15.22 |
Standing long jump (m) | 1.67 ± 0.45 |
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1.53 ± 0.34 | 1.46 ± 0.49 |
The results of IST are presented in Table
The peak torques of six joints.
Extensor PT | Flexor PT | |||||
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90°/S | 180°/s | 240°/s | 90°/S | 180°/s | 240°/s | |
Left shoulder |
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Right shoulder |
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Left elbow |
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Right elbow |
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Left wrist |
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Right wrist |
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Left hip |
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Right hip |
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Left knee |
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Right knee |
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Left ankle |
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Right ankle |
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Compared with the right knee, the 90°/s PT (
The results of unit weight torque (UWT) are similar to those of PT (Table
The unit weight torque of six joints.
Extensor UWT | Flexor UWT | |||||
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90°/S | 180°/s | 240°/s | 90°/S | 180°/s | 240°/s | |
Left shoulder |
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Right shoulder |
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Left elbow |
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Right elbow |
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Left wrist |
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Right wrist |
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Left hip |
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Right hip |
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Left knee |
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Right knee |
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Left ankle |
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Right ankle |
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Compared with the right knee, the 90°/s UWT of left knee flexor under working condition was significantly lower (
The correlation coefficients between indictors of SMST are presented in Table
Correlation between indicators of SMST.
Hand-grip | Knee bent push-up | Back muscle strength | Sit-ups | Leg muscle strength | Standing long jump | |
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Hand-grip | 1 |
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Knee bent push-up |
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1 |
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Back muscle strength |
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1 | 0.378 |
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0.096 | |
Sit-ups |
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0.378 | 1 |
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Leg muscle strength |
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1 | 0.151 | |
Standing long jump |
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0.096 |
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0.151 | 1 |
The KMO and Bartlett test results showed that all correlation coefficients between each indicator of IST were greater than 0.3 for UB, UG, rural boys, and RG. The KMO test results for UB, UG, RB, and RG were, respectively, 0.876, 0.833, 0.856, and 0.872. Bartlett’s sphericity test showed that the data was suitable for factor analysis (
Common factor and feature scatter plot. (a) Urban boys, common factors = 7; (b) urban girls, common factors = 6; (c) rural boys, common factors = 5; (d) rural girls, common factors = 5.
There were seven common factors for urban boys (Table
Factor analysis of IST among urban boys.
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.716 | −.032 | .020 | −.227 | .199 | −.484 | .202 |
.692 | .078 | .127 | −.193 | .164 | −.562 | .260 |
.761 | −.426 | .023 | −.086 | .028 | .221 | .010 |
.678 | −.458 | −.070 | .005 | −.101 | .111 | −.091 |
.676 | −.246 | −.021 | .493 | .342 | .002 | −.115 |
.716 | −.446 | .052 | .235 | .389 | .038 | −.018 |
.326 | .513 | −.476 | −.400 | .131 | .393 | .142 |
.450 | .567 | −.437 | −.300 | −.032 | .323 | .157 |
−.052 | −.462 | −.083 | .204 | .114 | .303 | .072 |
.649 | −.200 | −.518 | .214 | .346 | −.036 | −.122 |
.432 | −.648 | .087 | −.013 | −.075 | .003 | .487 |
.570 | −.263 | .171 | −.320 | −.283 | .466 | .194 |
.081 | .510 | .729 | .104 | .119 | .193 | .178 |
.102 | .356 | .731 | .364 | .001 | .059 | .339 |
.069 | .479 | .207 | −.001 | .446 | .116 | −.445 |
.230 | .728 | .202 | .204 | .306 | .076 | .133 |
.528 | .133 | .279 | −.600 | −.017 | −.119 | −.311 |
.728 | .088 | .320 | −.348 | −.017 | .008 | −.393 |
.701 | .500 | −.313 | .083 | −.069 | −.084 | .156 |
.730 | .474 | −.012 | .028 | −.309 | .041 | .025 |
.446 | −.303 | .417 | .253 | −.097 | .394 | −.197 |
.460 | −.091 | .223 | .008 | −.667 | −.247 | −.206 |
.301 | .406 | −.374 | .540 | −.376 | .035 | −.041 |
.470 | .316 | −.144 | .640 | −.265 | −.152 | −.142 |
Factor analysis of IST among urban girls.
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.894 | −.029 | .046 | .013 | .180 | −.255 |
.870 | −.116 | −.034 | −.256 | .089 | −.196 |
.613 | −.293 | −.628 | .065 | −.134 | .093 |
.410 | .085 | −.363 | −.580 | .024 | .162 |
.150 | .766 | −.017 | .142 | .327 | .273 |
.081 | .637 | .404 | −.353 | .321 | .175 |
.897 | −.056 | −.158 | .042 | .084 | .101 |
.767 | .363 | −.173 | −.232 | .167 | −.107 |
.745 | .141 | .199 | −.380 | −.046 | .097 |
.325 | .662 | .242 | −.053 | −.222 | .185 |
.668 | −.375 | −.111 | .544 | .108 | −.031 |
.666 | −.435 | .142 | .175 | .139 | .363 |
−.089 | .708 | .239 | .205 | −.154 | −.166 |
.494 | .316 | .225 | .095 | −.418 | −.042 |
−.064 | .436 | −.600 | .435 | .167 | .000 |
−.214 | .317 | −.420 | .295 | .624 | −.109 |
−.055 | −.083 | .861 | .046 | .151 | −.316 |
−.059 | −.211 | .710 | −.309 | .445 | .000 |
.822 | −.332 | .135 | −.064 | .035 | .083 |
.817 | .010 | −.019 | .126 | −.018 | −.326 |
−.200 | −.387 | .115 | −.010 | .002 | .791 |
−.056 | −.569 | .494 | .371 | .233 | −.107 |
.421 | .335 | .346 | .539 | .175 | .339 |
.412 | .238 | .485 | .398 | −.497 | .076 |
Factor analysis of IST among rural boys.
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.769 | −.247 | .005 | .317 | −.175 |
.792 | −.224 | −.198 | .418 | −.257 |
−.219 | .746 | −.072 | .245 | −.118 |
.870 | −.094 | −.206 | .073 | −.368 |
.389 | .712 | −.189 | −.009 | −.164 |
.400 | .786 | −.242 | −.308 | −.092 |
.340 | .641 | −.097 | .660 | .042 |
.753 | .441 | −.061 | .230 | .097 |
.711 | .039 | .095 | .049 | .150 |
.688 | .289 | −.391 | −.181 | .199 |
−.553 | .338 | .093 | −.015 | .512 |
−.444 | .515 | −.465 | −.237 | −.014 |
.895 | −.036 | −.062 | −.127 | −.089 |
.769 | .064 | −.293 | −.290 | .115 |
.946 | −.179 | .032 | .047 | −.084 |
.906 | −.217 | .022 | .025 | .096 |
.870 | −.112 | −.104 | .002 | −.030 |
.856 | −.113 | .210 | −.317 | .090 |
.516 | .372 | .627 | −.240 | −.005 |
.785 | .028 | −.004 | −.279 | .299 |
.252 | .278 | .897 | .024 | −.099 |
.288 | .306 | .889 | −.005 | −.090 |
.859 | −.162 | −.071 | −.198 | .248 |
.319 | −.096 | .042 | .523 | .684 |
Factor analysis of IST among rural girls.
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.688 | .352 | −.083 | .096 | −.301 | −.105 |
.733 | .352 | .104 | −.176 | .087 | −.411 |
.856 | −.167 | −.204 | .208 | .006 | −.123 |
.709 | −.405 | −.357 | −.210 | −.085 | .019 |
.479 | −.478 | −.376 | −.468 | −.025 | .254 |
.721 | .101 | −.470 | .200 | .318 | −.100 |
.562 | .302 | −.362 | .543 | −.259 | −.054 |
.530 | .365 | .566 | −.072 | −.109 | .410 |
.545 | .574 | .130 | −.027 | .253 | .204 |
−.043 | .528 | .660 | .227 | −.017 | −.173 |
−.039 | .145 | .182 | .358 | .799 | .283 |
.445 | −.638 | .352 | .448 | .033 | −.124 |
.464 | −.662 | .260 | .479 | −.028 | −.092 |
.877 | −.369 | −.011 | .015 | .002 | −.096 |
.919 | −.239 | −.094 | .040 | −.017 | .079 |
.767 | .142 | −.093 | .267 | −.132 | .050 |
.853 | .282 | .085 | −.019 | .203 | −.097 |
.476 | −.442 | .662 | −.246 | −.124 | −.070 |
.664 | −.374 | .577 | −.255 | −.021 | −.007 |
.802 | .388 | .147 | −.092 | −.079 | .054 |
.623 | .237 | .052 | −.517 | −.025 | .047 |
.634 | −.269 | −.143 | −.157 | .559 | .179 |
.374 | .072 | −.051 | .299 | −.427 | .671 |
.672 | .547 | −.187 | −.154 | −.037 | −.187 |
The correlation coefficients were shown in Table
Results of the correlation analyses of SMST indicators and
AC | UB | UG | RB | RG | ||||||
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Hand-grip | 0.455 | <0.01 | 0.411 | <0.01 | 0.507 | <0.01 | 0.435 | <0.01 | 0.389 | <0.01 |
Knee bent push-ups | 0.608 | <0.01 | 0.678 | <0.01 | 0.691 | <0.01 | 0.522 | <0.01 | 0.539 | <0.01 |
Back muscle strength | 0.80 | <0.01 | 0.774 | <0.01 | 0.803 | <0.01 | 0.824 | <0.01 | 0.799 | <0.01 |
Leg muscle strength | 0.811 | <0.01 | 0.811 | <0.01 | 0.789 | <0.01 | 0.837 | <0.01 | 0.801 | <0.01 |
Standing long jump | 0.465 | <0.01 | 0.438 | <0.01 | 0.367 | <0.01 | 0.567 | <0.01 | 0.478 | <0.01 |
Sit-ups | 0.425 | <0.01 | 0.345 | <0.01 | 0.428 | <0.01 | 0.389 | <0.01 | 0.516 | <0.01 |
The main purpose of this study was to determine the criterion-related validity of the SMST indicators for hand-grip strength, knee bent pull-up, back muscle strength, leg muscle strength, standing long jump, and sit-up to assess whole body muscle strength in Chinese children aged 10 to 12 years. Gender and residence were included as between-subject factors because earlier studies have shown differences in the concurrent validity between males and females and urban and rural populations in muscle strength [
The results showed that the criterion-related validity of SMST indicators to assess whole body muscle strength was moderate to high. The correlation SMST and
Similar results were found in several other studies. For instance, in Japan, back, hand-grip, wrist, leg, and abdominal muscle strength were adopted as indicators [
The present study also sought to compare the validity of SMST indicators to assess whole body muscle strength in different genders and residences. The results for back muscle strength demonstrated the highest validity scores for UB, RB, and RG,
There were differences in anthropometric characteristics between urban and rural children, and also differences in the SMST results. The evaluation of physical quality fitness tests for students has been concentrated on the adaptability of the test among children of different ages and genders around the world. Generally speaking, there were three kinds of situations in terms of the difference of indicators across age and gender. First, the indicators of test for junior students were same across gender, while the indicator for senior students was different from that of junior students, and there were differences in indicators between male and female senior students. For instance, in the School Physical Fitness Rewards Program of Hong Kong [
Back muscle strength and leg muscle strength can give the highest validity for assessing whole body muscle strength and also have higher validity in both urban and rural children. For urban children, the knee bent push-up also has a high validity indicator but poor validity for rural children.
In the future, back muscle strength and leg muscle strength can be considered as strength test indicators for Chinese student’s physical fitness test. Meanwhile, residential differences in SMST indicators should be considered when setting up the physical fitness test evaluation indicators of students, especially for knee bent push-up.
The authors have no conflicts of interest to disclose in relation to the current research.
During the construction of this study, Liqin Yin played a role in data collection, sorting, analysis, and writing the article. Changfa Tang played a role in developing the idea, overseeing data collection and analysis, and helping to edit the article. Xia Tao played a role in data collection, testing, and analysis.
The authors gratefully acknowledge the financial support from the national social science foundation of China (no. BLA090074). Liqin Yin would like to thank the coauthors for their generous support in conducting this study.