PLASMA TSH, T-3, T-4 AND CORTISOL RESPONSES TO SWIMMING AT VARYING WATER TEMPERATURES

The acute effect of 30-min swimming at a moderate speed, at three wate r temperatures (20, 26 and 32 degrees C) on plasma thyroid stimulating hormone (TSH), free thyroxine (F.T-4), triiodothyronine (T-3) and cor tisol concentrations was studied in 15 elite 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 degrees C and the lowest at 20 degrees C. Blood lactate concentr ations were found to be similar after the three tests. Plasma TSH and F.T-4 were found to be significantly increased (by 90.4% and 45.7% res pectively) after swimming at 20 degrees C, decreased at 32 degrees C ( by 22.3% and 10.1% respectively) and unchanged at 26 degrees C. Exerci se at these three water temperatures did not significantly affect T-3 Finally, plasma cortisol was found to be increased after swimming at 3 2 degrees C (by 82.8%) and 26 degrees C (by 46.9%), but decreased at 2 0 degrees C (by 6.1%).