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 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.

Keywords: heat acclimation; intermittent sports; repeated-sprint ability; running; thermoregulation.

Figure 1

Experimental overview of the repeated-sprint exercise (RSE) training protocol undertaken by separate groups in either HOT (40°C and 40% RH) or COOL (20°C and 40% RH) conditions, as well as the pre‐ and post-training assessments performed in conditions as indicated. $\dot{\mathrm{V}}$O_2peak, peak oxygen consumption test; RST, repeated-sprint test; Neuro, neuromuscular function assessment; and Yo-Yo 1, intermittent recovery test level 1.

Figure 2

Individual and mean Yo-Yo intermittent recovery test (level 1) distance covered prior to (pre-training) and following (post-training) a repeated-sprint training intervention undertaken in COOL (20°C and 40% RH) or HOT (40°C and 40% RH) conditions. Open squares and solid lines are means within each group. Symbols omitted for clarity. Post‐ vs. pre-intervention main effect (p < 0.001, d = 0.78).

Figure 3

Heart rate, rectal temperature, and mean skin temperature during a RST including a 22 min submaximal warm-up and four sets of repeated sprints performed in 40°C and 40% RH prior to and following a repeated-sprint training intervention undertaken in COOL (20°C and 40% RH) or HOT (40°C and 40% RH) conditions. Data are mean with 95% CI. Symbols omitted for clarity. Heart rate: post‐ vs. pre-intervention main effect (warm-up: p < 0.001, d = −0.35; sprints: p < 0.001, d = −0.24). Rectal temperature: post‐ vs. pre-intervention main effect (warm-up: p < 0.001, d = −0.33; sprints: p < 0.001, d = −0.26). Skin temperature: post‐ vs. pre-intervention within condition effect for HOT (warm-up: p < 0.001, d = −0.59; sprints: p < 0.001, d = −1.03).

Figure 4

Rating of perceived exertion and thermal sensation during a RST including a 22 min submaximal warm-up and four sets of repeated sprints performed in 40°C and 40% RH prior to and following a repeated-sprint training intervention undertaken in COOL (20°C and 40% RH) or HOT (40°C and 40% RH) conditions. Data are mean with 95% CI. Symbols omitted for clarity. Thermal sensation: post-intervention HOT and COOL between condition effects (warm-up: p < 0.016, d = −0.81; sprints: p < 0.015, d = −0.93).

Figure 5

Mean and peak power output across sets during a four-set RST performed in 40°C and 40% RH prior to and following a repeated-sprint training protocol undertaken in COOL (20°C and 40% RH) or HOT (40°C and 40% RH) conditions. Data are mean with 95% CI. Symbols omitted for clarity. Mean power output: post‐ vs. pre-intervention main effect (p < 0.001, d = 0.45). Peak power output: post‐ vs. pre-intervention main effect (p < 0.001, d = 0.28).