Hot But Not Cold Water Immersion Mitigates the Decline in Rate of Force Development Following Exercise-Induced Muscle Damage

Purpose: In recent years, there has been significant advancement in the guidelines for recovery protocols involving heat or cold water immersion. However, comparison between the effects of hot and cold water immersion on key markers of neuromuscular recovery following exercise-induced muscle damage (EIMD) is lacking. Methods: Thirty physically active males completed an individualized and tailored EIMD protocol immediately followed by one of the following recovery interventions: cold water immersion (11 degrees C, CWI11), hot water immersion (41 degrees C, HWI41), or warm-bath control (36 degrees C, CON36). Gastrointestinal temperature was tracked throughout HWI41 . Knee extensors' maximal isokinetic strength (peak torque (T-peak)) and explosive strength (late-phase rate of force development (RFD 100-200 )) were measured before EIMD (pre-), 24 h (post-24 h), and 48 h (post-48 h) post-EIMD. In addition, pressure pain threshold (PPT) was measured to quantify the recovery from muscle soreness. Surface electromyography signals (sEMG) from the vastus lateralis were captured to extract the rates of electromyography rise (REMGR) and the spectral power in the low-frequency band. Results: At post-48 h, T-peak returned to baseline values following both CWI 11 (-8.3% +/- 6.8%, P = 0.079) and HWI 41 (-1.4% +/- 4.1%, P = 1). In contrast, RFD 100-200 (-2.3% +/- 29.3%, P = 1) and PPT (+5.6% +/- 14.6%, P = 1) returned to baseline values at post-48 h only following HWI41. Spectral analysis of the sEMG signal revealed that the low-frequency band was significantly increased following CWI 11 (+9.0% +/- 0.52%, P = 0.012). REMGR was unchanged regardless of the condition (all P > 0.05). Conclusions: A single session of HWI 41 , rather than CWI11, improved the recovery of the late-phase rate of force development following EIMD in physically active males. This suggests that in athletic contexts where a rapid force development is a key performance determinant, hot bath should be preferred over cold bath.