Wood Louise E, Dixon Sharon, Grant Chris, Armstrong Neil
Department of Sport and Exercise Science, University of Portsmouth, Portsmouth, UK.
Med Sci Sports Exerc. 2004 Nov;36(11):1977-84. doi: 10.1249/01.mss.0000145453.02598.7e.
The purpose of this study was to examine gender- and age-related differences in elbow flexion and extension strength in children, when linear size measurements and actual measurements of muscle size were used as explanatory variables in a multilevel model.
Thirty-seven children participated in a 3-yr longitudinal study (18 boys and 19 girls). The average age +/- SD at the first test occasion was 13.0 +/- 0.3 yr. Stature, arm length, isokinetic concentric and isometric elbow extension and flexion torques, and MRI-determined elbow flexor and extensor muscle cross-sectional areas (CSAs) were assessed annually. Multilevel modeling was used to describe the relationship between the measured torques and body/muscle size variables, incorporating age, age by gender, and gender as additional explanatory variables.
When muscle CSA was included in the static and dynamic torque multilevel models, gender differences in strength were nonsignificant. In contrast, use of stature or arm length alone, suggested gender differences in strength that could not be explained by differences in body size. All torque measures were best explained by inclusion of muscle CSA and a linear dimension in the models. Age also explained additional variance in torque, but the influence of age was action and muscle specific.
Use of only linear dimensions rather than muscle CSA to account for differences in size may have clouded our understanding of strength development in children.
本研究的目的是，在多水平模型中将线性尺寸测量和肌肉大小的实际测量作为解释变量，检验儿童肘部屈伸力量的性别和年龄差异。
37名儿童参与了一项为期3年的纵向研究（18名男孩和19名女孩）。首次测试时的平均年龄±标准差为13.0±0.3岁。每年评估身高、臂长、等速向心和等长肘部伸展及屈曲扭矩，以及通过MRI测定的肘部屈肌和伸肌横截面积（CSA）。多水平模型用于描述测量扭矩与身体/肌肉大小变量之间的关系，将年龄、年龄与性别的交互作用以及性别作为额外的解释变量纳入其中。
当肌肉CSA纳入静态和动态扭矩多水平模型时，力量的性别差异不显著。相比之下，仅使用身高或臂长表明力量存在性别差异，而这种差异无法用身体大小的差异来解释。在模型中纳入肌肉CSA和一个线性维度能最好地解释所有扭矩测量值。年龄也解释了扭矩的额外变异，但年龄的影响因动作和肌肉而异。
仅使用线性维度而非肌肉CSA来解释大小差异，可能会使我们对儿童力量发展的理解变得模糊。
