Abstract

Purpose

The sensorimotor system is a subcomponent of the comprehensive motor control system of the body. However, the complex nature of the sensorimotor system makes it difficult to interpret findings for clinical application. The purpose of this study was to utilize principal component analysis (PCA) to identify sex differences and relationships between sensorimotor variables during a dynamic perturbation.

Materials and methods

Thirty physically active individuals (15 males and 15 females) were blindfolded and positioned on an isokinetic dynamometer with their knee flexed to 70°. At random, the dynamometer moved rapidly towards knee extension. Subjects were asked to resist the dynamometer as it would randomly and rapidly move towards knee extension. Torque and position values were used to calculate stiffness values.

Results

PCA revealed sex differences in two principal components (PCs): PC2 in female was comprised from higher position, torque, and time values (p = .038), PC4 in females was comprised from higher active stiffness and lower short-range stiffness values (p = .032) compared to males. Torque at the resting position was correlated to the short-range passive stiffness (ρ = 0.539, p = .002), time to peak torque (ρ = −0.375, p = .003), and reactive stiffness (ρ = 0.526, p = .041).

Conclusions

Females had later reaction time and lower short-range passive stiffness and they resisted the dynamometer by their voluntary activation compared to the males thus requiring muscle activation for meaningful response. In addition, the higher resting muscle activities may correlate to short-range passive stiffness and quicker active stiffness. Abbreviations: ACL: anterior cruciate ligament; EEG: electroencephalogram; EMG: electromyography; ICC: intraclass correlation coefficient; MDC₉₅: minimally detectable differences at 95% confidence intervals; PC: principal component; PCA: principal component analysis; POS₅₀: position value at 50 ms; POS₁₀₀: position value at 100 ms; POS_prop: position value at TIME_prop; POS_pk: position value at TIME_pk; POS_prop-pk: position difference between POS_prop and POS_pk; SEM: standard error of measurements; STIFF₅₀: short-range-stiffness at 50 ms; STIFF₁₀₀: short-range-stiffness at 100 ms; STIFF_reac: reactive knee stiffness (stiffness between TIME_prop to TIME_pk); TIME_prop: threshold-to-detect passive movement as the time point; TIME_pk: time at which peak hamstrings torque occurred; TIME_prop-pk: time between TIME_prop to TIME_pk; TORQ₀: torque value at time zero; TORQ₅₀: torque value at 50 ms; TORQ₁₀₀: torque value at 100 ms; TORQ_prop: torque value at TIME_prop; TORQ_pk: torque value at TIME_pk; TORQ_50diff: torque difference between TORQ₀ and TORQ5₀; TORQ_100diff: torque difference between TORQ₀ and TORQ₁₀₀

中文翻译：

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动态扰动试验中膝屈肌被动和主动刚度的性别差异：主成分分析。

摘要

目的

感觉运动系统是身体综合运动控制系统的一个子组件。然而，感觉运动系统的复杂性质使得难以解释临床应用的结果。本研究的目的是利用主成分分析 (PCA) 来确定动态扰动期间感觉运动变量之间的性别差异和关系。

材料和方法

30 名身体活跃的人（15 名男性和 15 名女性）被蒙住眼睛，放在等速测功机上，膝盖弯曲至 70°。随机地，测功机迅速向伸膝方向移动。受试者被要求抵抗测力计，因为它会随机且快速地向伸膝方向移动。扭矩和位置值用于计算刚度值。

结果

PCA 揭示了两个主要成分 (PC) 的性别差异：女性的 PC2 由较高的位置、扭矩和时间值组成（p  = .038），女性的 PC4 由较高的主动刚度和较低的短程刚度值组成（p  = .032) 与男性相比。静止位置的扭矩与短程被动刚度 ( ρ = 0.539, p  = .002)、达到峰值扭矩的时间 ( ρ = -0.375, p  = .003) 和反应刚度 ( ρ  = 0.526, p  = .041）。

结论

与男性相比，女性的反应时间较晚，短程被动刚度较低，并且她们通过自愿激活来抵抗测功机，因此需要肌肉激活才能做出有意义的反应。此外，较高的静息肌肉活动可能与短程被动僵硬和较快的主动僵硬相关。缩写： ACL：前交叉韧带；EEG：脑电图；EMG：肌电图；ICC：组内相关系数；MDC ₉₅：在 95% 置信区间的最小可检测差异；PC：主成分；PCA：主成分分析；POS ₅₀ : 50 ms 时的位置值；POS ₁₀₀ : 100 ms 时的位置值；POS _prop : TIME 位置值_道具; POS _pk : TIME _{pk 的}位置值；POS _prop-pk : POS _prop和 POS _{pk 的}位置差；SEM：测量的标准误差；STIFF ₅₀ : 50 ms 时的短程刚度；STIFF ₁₀₀ : 100 ms 时的短程刚度；STIFF _reac：反应性膝关节刚度（TIME _prop到 TIME _pk之间的刚度）；TIME _prop : 检测被动运动的阈值作为时间点；TIME _pk : 出现腘绳肌峰值扭矩的时间；TIME _prop-pk : TIME _prop到 TIME之间的时间_pk ; TORQ ₀ : 零时刻的扭矩值；TORQ ₅₀ : 50 ms 时的扭矩值；TORQ ₁₀₀ : 100 ms 时的扭矩值；TORQ _prop : TIME _prop处的扭矩值；TORQ _pk : TIME _pk处的扭矩值；TORQ _50diff：TORQ ₀和TORQ5 ₀之间的扭矩差；TORQ _100diff : TORQ ₀和 TORQ ₁₀₀之间的扭矩差