Prolonged cooling with phase change material enhances recovery and does not affect the subsequent repeated bout effect following exercise.

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The aim of this investigation was twofold: (1) to examine the effect of prolonged phase change material (PCM) cooling following eccentric exercise of the quadriceps on indices of muscle damage, and (2) to elucidate whether application of PCM cooling blunted the acute adaptive response to eccentric exercise, known as the repeated bout effect (RBE). Twenty-six males (25 ± 6years) performed an initial bout (B1) of 120 eccentric quadriceps contractions on each leg at 90% of their isometric strength and were then randomized to receive PCM packs frozen at 15°C (treatment) or melted packs (control) worn directly on the skin under shorts for 6h. The protocol was repeated 14days later (B2) with all participants receiving the control condition. PCM cooling provided protection against strength loss in B1 (P = 0.005) with no difference in strength between treatment groups in B2 (P = 0.172; bout by treatment by time P = 0.008). PCM cooling reduced soreness in B1 (P = 0.009) with no difference between treatment groups in B2 (P = 0.061). Soreness was overall lower following B2 than B1 (P < 0.001). CK was elevated in B1 (P < 0.0001) and reduced in B2 (P < 0.001) with no difference between treatments. The damage protocol did not elevate hsCRP in B1, with no difference between treatments or between bouts. This work provides further evidence that PCM cooling enhances recovery of strength and reduces soreness following eccentric exercise. Importantly, these data show for the first time that prolonged PCM cooling does not compromise the adaptive response associated with the RBE.