Effects of Hot Baths Prior or After a Damaging Protocol on Muscle Function and HSP70 Expression

Muscle lengthening contractions lead to physiological responses such as strength loss, soreness, immune cell infiltration, and CK production, along with elevated heat shock proteins (HSPs), which protect and regenerate cells. Passive heating before or after exercise can aid in recovery by restoring strength and reducing soreness, requiring a core temperature of over 38.5°C for 20 minutes to be effective. Studies show that combined mechanical and thermal stress induces a cumulative HSP response, enhancing cellular protection. Thermal stress alone peaks at 16- 24 hours, whereas mechanical stress shows a biphasic response, with peaks at 3-6 hours and around 39 hours. Thus, combining heat with exercise could optimize HSP production, improving recovery by increasing and accelerating the HSP response. However, more research is needed to determine the best timing for thermal stress in human applications, especially in sports and therapy contexts. This study aimed to compare the effects of hot-water immersion administered before versus after muscle-lengthening exercise on muscle function and HSP70 expression in healthy young athletes.