Plasma TSH, T3, T4 and cortisol responses to swimming at varying water temperatures

Abstract

The acute effect of 30-min swimming at a moderate speed, at three water temperatures (20, 26 and 32 °C) on plasma thyroid stimulating hormone (TSH), free thyroxine (F.T4), triiodothyronine (T3) and cortisol concentrations was studied in 15 élite male swimmers. Blood was sampled before and immediately after the events. The heart rate, which was continuously monitored during exercise, had the highest response at 32 °C and the lowest at 20 °C. Blood lactate concentrations were found to be similar after the three tests. Plasma TSH and F.T4 were found to be significantly increased (by 90.4% and 45.7% respectively) after swimming at 20 °C, decreased at 32 °C (by 22.3% and 10.1% respectively) and unchanged at 26 °C. Exercise at these three water temperatures did not significantly affect T3. Finally, plasma cortisol was found to be increased after swimming at 32 °C (by 82.8%) and 26 °C (by 46.9%), but decreased at 20 °C (by 6.1%). © 1993.