Using skin temperature and muscle thickness to assess muscle response to strength training

ABSTRACT Introduction: Several studies already reported the response of many biomarkers after strength training, but studies using low cost diagnostic imaging tools are rare. Objective: To evaluate the usage of skin temperature and muscle thickness (MT) to monitor muscle response (until 96 hours after) to high-intensity strength training. Methods: This is a short-term longitudinal study with 13 trained, healthy male volunteers. Volunteers performed five sets of biceps bi-set exercise with their dominant arm with dumbbells, with load of 70% of one-repetition maximum (1RM). The ultrasound (US) and thermal images were acquired before and immediately after the last set, 24, 48, 72 and 96 hours after exercise. Results: The analysis was divided in two stages: acute muscle response (until 24 hours after training) and delayed muscle response (from 24 to 96 hours after training). The elbow flexors thickness showed the peak value immediately after the last set of training. Skin temperature (on elbow flexors) and the elbow flexors thickness grew continuously from 24 to 96 hours after strength training. There is a high correlation (r=0.941, p=0.017) between skin temperature and muscle thickness from the end of exercise until 96 hours after strength training. Conclusions: The US images showed high sensibility for muscle physiological changes on the first 24 hours after exercise. On the other hand, the thermal images had higher sensibility for muscle physiological changes than US images from 24 to 96 hours after training.

摘要
引言：已有多项研究报道了力量训练后多种生物标志物的响应特征，但针对低成本诊断成像工具的相关研究仍较为匮乏。
研究目的：评估皮肤温度与肌肉厚度（muscle thickness，MT）在监测高强度力量训练后肌肉响应（直至训练后96小时）方面的应用价值。
研究方法：本研究为一项短期纵向研究，共纳入13名具备训练经验的健康男性志愿者。志愿者以惯用手臂持哑铃完成5组肱二头肌双组训练，训练负荷为单次最大重复重量（one-repetition maximum，1RM）的70%。分别于最后一组训练前、训练后即刻，以及训练后24、48、72、96小时采集超声（ultrasound，US）与热成像图像。
研究结果：分析分为两个阶段：急性肌肉响应阶段（训练后24小时内）与迟发性肌肉响应阶段（训练后24至96小时）。肘屈肌厚度在最后一组训练后即刻达到峰值。训练后24至96小时，肘屈肌部位的皮肤温度与肘屈肌厚度呈持续升高趋势。自训练结束至训练后96小时，皮肤温度与肌肉厚度之间存在高度相关性（r=0.941，p=0.017）。
研究结论：超声图像在训练后最初24小时内对肌肉生理变化具有较高的敏感性；与之相对，训练后24至96小时，热成像图像对肌肉生理变化的敏感性优于超声图像。