[The response of the growth hormone to acute effort is a function of training]

The increase of the growth hormone (GH) during exercise is known although the relationship of this response with other hormones, the type and intensity of the exercise, nutritional state and with the degree of training are reasons for discussion. The aim of this investigation was to study the response of the HG on a group of young adults with different degrees of training, according to the maximum consumption of oxygen (VO2 max) achieved over a short period of time.

Thirty-nine healthy subjects who underwent maximum effort on the treadmill were grouped according to VO2 max reached (less than 3,000 ml/min; 3,000-4,500 ml/min and greater than 4,500 ml/min). Systolic blood pressure (SBP) and diastolic blood pressure (DBP), respiratory quotient (RQ), O2 pulse, cardiac frequency (CF) respiratory equivalence (RE), glycemia, plasma insulin (PI), C peptide, lactic acid, venous pH, plasma renin activity (PRA), plasma aldosterone, thyrotropine (TSH), triodothyronine (T3), thyroxine (T4), adrenocorticotropine (ACTH), cortisol and GH were measured basally and following achievement of VO2 max.

The GH was only increased in those subjects with a VO2 max higher than 3,000 ml/min with a significant positive correlation found between the GH and VO2 max and a significant negative correlation was found between the GH and lactic acid at the end of the test. The increase of glycemia at the end of the test correlated with the VO2 max. The PI and C peptide increased at the end of the test in the subjects with greater VO2 max capacity and correlated positively with the VO2 max and with the GH upon completion of the exercise.

These results suggest that the response of the growth hormone to exercise is a function of maximum oxygen consumption although this only explains 24% of the variants of the growth hormone. Despite important hormonal and metabolic mobilization during exercise, no model of multiple regression has been found which substantially improves the association found between the growth hormone and maximum oxygen consumption.