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 repeated-sprinting 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 repeated-sprint 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.
Highlights
COOL conditions improved Yo-Yo IR1 distance covered in cool conditions by ~23
Repeated-sprint ability in the heat was also improved in both groups
prior to the RST conducted after the training intervention
Summary
Exercise-heat acclimation is used by endurance athletes to optimize performance when competing in the heat. The training required to optimize performance and heat tolerance in team-sport athletes, may differ to that commonly prescribed for endurance athletes For sports such as rugby sevens, soccer, and field hockey, high-level performance involves the ability to repeat maximal or near-maximal sprint efforts (Girard et al, 2015). When playing under heat stress, repeated-sprinting and jumping ability are compromised to a greater extent than when playing in temperate conditions (Mohr et al, 2010) This compromise occurs despite evidence that players adjust their physical activity patterns (e.g., decrease total and high-intensity running distance) in the heat to maintain the capacity to perform periodic sprint efforts when required at key moments in a match (i.e., pacing; Duffield et al, 2009; Mohr et al, 2012; Nassis et al, 2015). Repeated-sprint heat acclimation may be an approach that minimizes the impact of hot environmental conditions on repeated-sprint ability and low-to-moderate intensity exercise, whereby the pace and physical activity patterns adopted by team-sport athletes can be maintained throughout a match
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