Thermoregulation in soccer match-play: professional and recreational level applications using an intestinal pill system to measure core temperature

Introduction: The thermoregulatory stresses associated with soccer match-play have typically been estimated by focusing on the responses to match simulation in laboratories. Comparatively, in out-of-doors match-play, soccer players are exposed to environmental conditions that increase the capacity to lose heat; particularly through convective cooling whereby the evaporative capacity of the environment is increased with higher air velocities than those experienced in laboratories with near windstill conditions. Also, the competitive element of match-play presents an intensity of physical challenge and psychological stress that is difficult to replicate in a laboratory and, therefore, the comparison between settings is problematic. The purpose of the present study was to investigate the application of an intestinal pill system to measure core temperature during dynamic, field-based, soccer matches where technological limitations have previously limited match-play observations. The procedure was assessed in both a recreational level match and also in a pre-season professional game between an English Premier League team and an English Championship team. Methodology: Core temperature (TC) was assessed via the intestinal pill system (CorTemp 2000) and changes in plasma volume (PV) were calculated using the values for haemoglobin and haematocrit obtained before and after both recreational (n=8) and the professional soccer (n=7; English Championship team) matches. Match-play heart rates were measured at 5-s intervals using the Polar Team heart rate system. Baseline maximal aerobic power for all subjects was assessed using an online gas analyser and an incremental exercise protocol on a treadmill. Results and Discussion: In the recreational match, significant post-match reductions were observed in body mass (BM) (-1.6%, P<0.05) and PV (-7.2%, P<0.01). Significant increases were observed in TC from rest to half -time (P<0.01) and from half-time to full-time(P<0.05). In response to the professional match, BM decreased by 1.9% (P<0.05) and PV decreased by 11.6%(P<0.01). TC increased from rest to half -time (P