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

Background: Technological limitations associated with oesophageal and rectal temperature probes have previously limited match play observations of body temperature. Objective: To investigate the application of an intestinal pill system to measure core temperature during dynamic, field based, soccer matches. Methods: Core temperature (T-c) was assessed using the intestinal pill system (CorTemp 2000) and changes in plasma volume were calculated using the values for haemoglobin and packed cell volume obtained before and after recreational (n = 8) and the professional soccer ( n = 7) matches. Results: In the recreational match, there were significant post-match reductions in body mass (-1.6%, p< 0.05) and plasma volume (-7.2%, p< 0.01). Significant increases were observed in T-c from rest to half time ( p, 0.01) and from half time to full time ( p, 0.05). In the professional match, body mass decreased by 1.9% ( p< 0.05) and plasma volume by 11.6% ( p< 0.01). T-c increased from rest to half time ( p< 0.01) but was unchanged from half time to full time. Significant associations were observed between maximum oxygen consumption and match play heart rates in the second half of each match but these were not related to changes in plasma volume or T-c. Conclusions: Intestinal temperature proved a useful method of recording core temperature during soccer match play and assisted in the measurement of alterations in thermoregulatory variables in response to both professional and recreational level soccer matches; however, technological limitations still restrict the wider application of this method, especially at a competitive level.