Cold-Water Immersion Impairs Power Earlier than Strength Through Time-Dependent Reductions in Intramuscular...

We aimed to investigate the time- and intramuscular temperature-dependent changes in neuromuscular function throughout 1 h of cold-water immersion (CWI) at 10°C. It was hypothesized that acute CWI (<30 min) would not affect neuromuscular function due to limited reductions in intramuscular temperature, whereas prolonged CWI (>30 min) would impair muscle contractility by drastically reducing intramuscular temperature.

Twelve healthy participants (nine males and three females) partook in a randomized crossover design study involving 1-h CWI at 10°C of their lower leg, with three experimental visits consisting of 1) 1-h CWI at 10°C (CWI-only), 2) nonfatiguing exercise followed by 1-h CWI at 10°C to mimic the use of postexercise CWI (Ex + CWI), and 3) passive muscle preheating followed by 1-h CWI at 10°C (Heat + CWI). Skin temperature, intramuscular temperature, and neuromuscular function were periodically assessed in the dorsiflexors throughout the 1 h of CWI.

Decreased peak power was observed after 10 min of CWI, CWI-only (50.3 ± 16.0%, P < 0.05), Ex + CWI (55.0 ± 18.3%, P < 0.05), and Heat + CWI (62.0 ± 16.8%, P < 0.05), whereas maximal isometric torque decreased after ≥30 min of CWI, CWI-only (81.1 ± 9.1%, P < 0.05), Ex + CWI (86.6 ± 14.3%, P < 0.05), and Heat + CWI (88.7 ± 10.0%, P < 0.05). Decreases in M-wave peak-to-peak amplitude, 50-Hz torque, and postactivation potentiation were only evident following prolonged CWI (P < 0.05).

These results highlight that peak power is more sensitive to reductions in intramuscular temperature than maximal isometric strength, reflecting a time- and temperature-dependent effect on skeletal muscle function.