Is active recovery during cold water immersion better than active or passive recovery in thermoneutral water for postrecovery high-intensity sprint interval performance?

Functional Impact of Post-exercise Cooling and Heating on Recovery and Training Adaptations: Application to Resistance, Endurance, and Sprint Exercise

The application of post-exercise cooling (e.g., cold water immersion) and post-exercise heating has become a popular intervention which is assumed to increase functional recovery and may improve chronic training adaptations. However, the effectiveness of such post-exercise temperature manipulations remains uncertain. The aim of this comprehensive review was to analyze the effects of post-exercise cooling and post-exercise heating on neuromuscular function (maximal strength and power), fatigue resistance, exercise performance, and training adaptations. We focused on three exercise types (resistance, endurance and sprint exercises) and included studies investigating (1) the early recovery phase, (2) the late recovery phase, and (3) repeated application of the treatment. We identified that the primary benefit of cooling was in the early recovery phase (< 1 h post-exercise) in improving fatigue resistance in hot ambient conditions following endurance exercise and possibly enhancing the recovery of maximal strength following resistance exercise. The primary negative impact of cooling was with chronic exposure which impaired strength adaptations and decreased fatigue resistance following resistance training intervention (12 weeks and 4–12 weeks, respectively). In the early recovery phase, cooling could also impair sprint performance following sprint exercise and could possibly reduce neuromuscular function immediately after endurance exercise. Generally, no benefits of acute cooling were observed during the 24–72-h recovery period following resistance and endurance exercises, while it could have some benefits on the recovery of neuromuscular function during the 24–48-h recovery period following sprint exercise. Most studies indicated that chronic cooling does not affect endurance training adaptations following 4–6 week training intervention. We identified limited data employing heating as a recovery intervention, but some indications suggest promise in its application to endurance and sprint exercise.

Spinal and corticospinal excitability in response to reductions in skin and core temperature via whole-body cooling

Cold stress impairs fine and gross motor movements. Although peripheral effects of muscle cooling on performance are well understood, less is known about central mechanisms. This study characterized corticospinal and spinal excitability during surface cooling, reducing skin (Tsk) and core (Tes) temperature. Ten subjects (3 female) wore a liquid-perfused suit and were cooled (9°C perfusate, 90 min) and rewarmed (41°C perfusate, 30 min). Transcranial magnetic stimulation [eliciting motor evoked potentials (MEPs)], as well as transmastoid [eliciting cervicomedullary evoked potentials (CMEPs)] and brachial plexus [eliciting maximal compound motor action potentials (Mmax)] electrical stimulation, were applied at baseline, every 20 min during cooling, and following rewarming. Sixty minutes of cooling, reduced Tsk by 9.6°C (P<0.001) but Tes remained unchanged (P=0.92). Tes then decreased ~0.6℃ in the next 30 minutes of cooling (P<0.001). Eight subjects shivered. During rewarming, shivering was abolished, and Tsk returned to baseline while Tes did not increase. During cooling and rewarming, Mmax, MEP, and MEP/Mmax were unchanged from baseline. However, CMEP and CMEP/Mmax increased during cooling by ~85% and 79% (P<0.001) respectively, and remained elevated post-rewarming. Results suggest that spinal excitability is facilitated by reduced Tsk during cooling, and reduced Tes during warming, while corticospinal excitability remains unchanged. ClinicalTrials.gov ID NCT04253730 Novelty: • This is the first study to characterize corticospinal, and spinal excitability during whole body cooling, and rewarming in humans. • Whole body cooling did not affect corticospinal excitability. • Spinal excitability was facilitated during reductions in both skin and core temperatures.