Аннотация:The aim of the present study was to examine the associations between adaptive responses to an in‐season soccer training camp in the heat and changes in submaximal exercising heart rate ( HRex , 5‐min run at 9 km/h), postexercise HR recovery ( HRR ) and HR variability ( HRV ). Fifteen well‐trained but non‐heat‐acclimatized male adult players performed a training week in Q atar (34.6 ± 1.9°C wet bulb globe temperature). HRex , HRR , HRV (i.e. the standard deviation of instantaneous beat‐to‐beat R – R interval variability measured from P oincaré plots SD 1, a vagal‐related index), creatine kinase ( CK ) activity, plasma volume ( PV ) changes, and post‐5‐min run rate of perceived exertion ( RPE ) were collected at six occasions in temperate environmental conditions (22°C). Players also performed the yo‐yo intermittent recovery test level 1 ( Yo‐Yo IR1 ) in the same environmental conditions (22°C), both at the beginning and at the end of the training week. Throughout the intervention, HRex and HRV showed decreasing ( P < 0.001) and increasing ( P < 0.001) trends, respectively, while HRR remained unaffected ( P = 0.84). Changes in HRex [−0.52, 90% confidence limits (−0.64; −0.38), P < 0.001] and SD 1 [0.35 (0.19; 0.49), P < 0.001] were correlated with those in PV . There was no change in RPE ( P = 0.92), while CK varied according to training contents ( P < 0.001), without association with HR ‐derived measures. Yo‐Yo IR1 performance increased by 7 ± 9% ( P = 0.009), which was correlated with changes in HRex [−0.64 (−0.84; −0.28), P = 0.01]. In conclusion, we found that an in‐season soccer training camp in the heat can significantly improve PV and soccer‐specific physical performance; both of which are associated with changes in HRex during a 5‐min submaximal run.
