Short-Term Repeated-Sprint Training in Hot and Cool Conditions Similarly Benefits Performance in Team-Sport Athletes

Abstract

This study compared the performance and physiological adaptations of short-term repeated-sprint training in HOT [40°C and 40% relative humidity (RH)] and COOL (20°C and 40% RH) conditions in team-sport athletes. Twenty-five trained males completed five training sessions of 60 min over 7 days in HOT (n = 13) or COOL (n = 12) conditions, consisting of a submaximal warm-up and four sets of maximal sprints. Before and after the intervention, intermittent shuttle running performance was assessed in cool and repeated-sprint ability in hot conditions; the latter preceded and followed by neuromuscular function testing. During the repeated-sprint training sessions, skin (~8.4°C) and core (~0.17°C) temperatures were higher in HOT than COOL (p < 0.05) conditions. Shuttle running distance increased after both interventions (p < 0.001), with a non-significant (p = 0.131) but larger effect in HOT (315 m, d = 1.18) than COOL (207 m, d = 0.51) conditions. Mean (~7%, p < 0.001) and peak (~5%, p < 0.05) power during repeatedsprinting increased following both interventions, whereas peak twitch force before the repeated-sprint assessment was ~10% lower after the interventions (p = 0.001). Heart rate during the repeated-sprint warm-up was reduced (~6 beats.min −1) following both interventions (p < 0.01). Rectal temperature was ~0.14°C lower throughout the repeatedsprint assessment after the interventions (p < 0.001), with larger effects in HOT than COOL during the warm-up (p = 0.082; d = −0.53 vs. d = −0.15) and repeated-sprints (p = 0.081; d = −0.54 vs. d = −0.02). Skin temperature (p = 0.004, d = −1.11) and thermal sensation (p = 0.015, d = −0.93) were lower during the repeated-sprints after training in HOT than COOL. Sweat rate increased (0.2 L.h −1) only after training in HOT (p = 0.027; d = 0.72). The intensive nature of brief repeated-sprint training induces similar improvements in repeated-sprint cycling ability in hot conditions and intermittent running performance in cool conditions, along with analogous physiological adaptations, irrespective of the environmental conditions in which training is undertaken.

Active Heat Acclimation Does Not Alter Muscle–Tendon Unit Properties

“…Nevertheless, 6 wk of local heat therapy on plantarflexors (i.e., 8 h·d −1 using heat pads, 5 d·wk −1 ) induced no effect on strength and contractile properties of plantarflexors in active participants (44). Active short-term HA also showed no effect on knee extensor maximal force and VA (45). Recent studies also showed that adding local repeated heat stress during a long period (i.e., 10–12 wk) of resistance training had no effect on muscle strength production (46,47).…”

Cooling during short‐term heat acclimation enhances aerobic capacity but not sweat capacity

“…Conversely, Gale, Etxebarria, Pumpa, and Pyne (2020) demonstrated that the six repeated‐sprint training sessions in 34°C over 12 days resulted in an 8–13% greater improvement in running capacity, while HA was unaffected. The five repeated‐sprint training over 7 days under heat stress in 40°C elicited partial heat adaptation, in turn improved running distance during the Yo‐Yo IR1 Tests (Périard et al, 2020). Altogether, it appears the threshold required for heat adaptation via repeated‐sprint training is higher than the threshold needed for improvements in aerobic fitness.…”

“…For example, short‐term training in thermoneutral environments led to improvements in aerobic performance; however, it did not elicit heat adaptation (Cheung & McLellan, 1998; McGarr, Hartley, & Cheung, 2014). Previous study utilizing short‐term repeated‐sprint training (total 300 min) in 40°C have demonstrated evidence of enhancement of endurance performance and attainment of partial heat adaptation (Périard et al, 2020). In this study, total exposure time during the short‐term HA training was 410 min.…”

“…Improving the exercise performance is an important consideration when athletes undergo field training or major sporting competitions in summer, such as the 2020 Olympics in Tokyo, which will be held in hot conditions. When racket‐sport or team‐sport athletes undertake consecutive relevant sprint‐based field training in hot and humid environments, natural heat acclimatization from repeated prolonged exposure to exercise‐heat stress will induce biological adaptations that reduce physiological strain, and enhance repeated‐sprint performance in the heat (Périard, Pyne, Bishop, Wallett, & Girard, 2020). Athletes involuntarily acclimate to the heat over a short‐term because of repeated field training during summer (Lee et al, 2012).…”