Heat Therapy Alters the Expression of Myogenic and Angiogenic Factors and Accelerates Functional Recovery Following Exercise-Induced Muscle Damage in Humans

Introduction Exposure to a single session of heat therapy (HT) promotes the mRNA expression of pivotal angiogenic and inflammatory mediators in human skeletal muscle. We investigated the effects of repeated HT on functional recovery and the expression of select genes involved in myogenesis, angiogenesis and inflammation following exercise‐induced muscle damage (EIMD). Methods Eleven healthy young adults (23.8±0.6yrs, BMI 23.7±0.6) performed 300 maximal eccentric contractions of the knee extensors with both legs. One randomly selected thigh was treated with HT immediately after the exercise bout and 4 additional consecutive days while the opposite thigh served as a control. A water‐circulating garment perfused with water at ~52°C was used to apply HT for 90 min. Thermoneutral water (33°C) was circulated through the garment in the control thigh. Biopsies from the vastus lateralis muscle were obtained 2 weeks prior to and 1 and 5 days after the eccentric exercise bout. The mRNA expression of myogenic, angiogenic and inflammatory factors was determined using real‐time polymerase chain reaction. Perceived pain (visual analog scale) and fatigue resistance (total work amount during 28 repetition maximums at 180°/s) were assessed before, during and after the intervention. Results A similar reduction in fatigue resistance (Control: −27.1±3.7% vs. HT: −21.4±4.6%, p>0.05) and an increase in perceived muscle pain (Control: 4.3±0.7 vs. HT: 4.2±0.7, p>0.05) were observed in both legs 1 day after the exercise bout. However, the thigh treated with HT had greater fatigue resistance than the control thigh (Control: −15.9±2.8% vs. HT: −9.6±1.9%, p=0.04) 4 days after the EIMD protocol. Perceived muscle pain was also lower in the thigh exposed to HT at 4 (Control: 2.9±0.6 vs. HT: 2.3±0.4, p=0.02) and 5 days (Control: 1.8±0.4 vs. HT: 1.3±0.3, p=0.02) after the exercise bout. When compared to the control thigh, the change in mRNA expression from baseline of paired box 7 (Control: 0.9±0.1 vs. HT: 1.3±0.1, p=0.04), vascular endothelial growth factor (Control: 0.8±0.1 vs. HT: 1.2±0.1, p<0.01), and angiopoietin 1 (Control: 0.3±0.1 vs. HT: 0.5±0.1, p=0.02) was higher in the thigh exposed to HT 1 day after the exercise bout. After 5 consecutive days of HT, the change in mRNA expression from baseline of monocyte chemoattractant protein 1 (Control: 1.3±0.3 vs. HT: 0.5±0.1, p<0.01) and myostatin (Control: 0.6±0.1 vs. HT: 0.3±0.1, p<0.01) were significantly lower in the thigh treated with HT. Conclusion Taken together, these results suggest that application of HT accelerates functional recovery following EIMD in humans, possibly by enhancing the expression angiogenic and myogenic factors early in the repair process.