Dotan Raffy, Woods Stacey, Langille Jordan, Falk Bareket
Kinesiology Department, Faculty of Applied Health Sciences, Brock University, St Catharines, ON, Canada.
Eur J Appl Physiol. 2024 Feb;124(2):491-505. doi: 10.1007/s00421-023-05292-3. Epub 2023 Aug 9.
Only scant research has compared children's mean power frequency (MPF) to adults', with a clear overview still lacking. A significant obstacle has been MPF's high variability, which this study aimed to overcome by elucidating the MPF characteristics distinguishing boys from men in progressive exhaustive exercise.
Electromyographic (EMG) data of 20 men (23.5 ± 2.5yrs) and 17 boys (10.2 ± 1.0 yrs), who performed progressively exhausting, intermittent isometric knee extensions, were subjected to secondary MPF analysis. Participants' vastus lateralis MPF data series were transformed to third-order polynomial regressions and expressed as percentages of the peak polynomial MPF values (%MPF). The resulting curves were compared at 5-% time-to-exhaustion (TTE) intervals, using repeated-measures ANOVA. Raw MPF values were adiposity corrected to 0% fat and used to convert the %MPF data back to absolute MPF values (Hz) for estimating muscle-level MPF.
No overall interaction or group effects could be shown between the %MPF plots, but pairwise comparisons revealed significantly higher men's values at 50-70%TTE and lower at 100%TTE, i.e. boys' shallower MPF rise and decline. The adiposity-corrected boys' and men's composite MPF values peaked at 125.7 ± 2.5 and 166.0 ± 2.4 Hz, respectively (110.7 ± 1.7 and 122.5 ± 2.1 Hz, uncorrected), with a significant group effect (p < 0.05) and pairwise differences at all %TTE points.
The boys were lower than the men in both the observed and, more so, in the adiposity-corrected MPF values that presumably estimate muscle-level MPF. The boys' shallower MPF rise and decline conform to children's claimed type-II motor-unit activation and/or compositional deficits and their related known advantage in muscular endurance.
仅有少量研究对儿童与成人的平均功率频率（MPF）进行了比较，目前仍缺乏清晰的概述。一个重大障碍是MPF的高变异性，本研究旨在通过阐明在渐进性力竭运动中区分男孩与男性的MPF特征来克服这一障碍。
对20名男性（23.5±2.5岁）和17名男孩（10.2±1.0岁）进行了肌电图（EMG）数据采集，他们进行了渐进性力竭的间歇性等长膝关节伸展运动，并对其进行了二次MPF分析。将参与者的股外侧肌MPF数据系列转换为三阶多项式回归，并表示为多项式MPF峰值的百分比（%MPF）。使用重复测量方差分析，在5%力竭时间（TTE）间隔内比较所得曲线。将原始MPF值进行肥胖校正至0%脂肪，并用于将%MPF数据转换回绝对MPF值（Hz），以估计肌肉水平的MPF。
在%MPF图之间未显示出总体交互作用或组效应，但成对比较显示，男性在50%-70%TTE时的值显著更高，而在100%TTE时更低，即男孩的MPF上升和下降较平缓。肥胖校正后的男孩和男性的综合MPF值分别在125.7±2.5和166.0±2.4 Hz时达到峰值（未校正时分别为110.7±1.7和122.5±2.1 Hz），在所有%TTE点均有显著的组效应（p<0.05）和成对差异。
在观察到的MPF值以及更重要的是在可能估计肌肉水平MPF的肥胖校正后的MPF值方面，男孩均低于男性。男孩MPF上升和下降较平缓，这与儿童所谓的II型运动单位激活和/或组成缺陷以及他们在肌肉耐力方面已知的相关优势相符。
