Growth Hormone Response to High Intensity Upper Body Exercise.

Growth hormone (GH) increases after exercise with a dose(intensity)-response pattern. Most studies have analyzed the GH response to lower or total body exercises, but, to our knowledge, no studies have been carried out on upper body high intensity (higher than oxygen uptake peak – V’O2peak) exercise (UBHIE). PURPOSE: To study the relationship between GH response to exercise and UBHIE. We hypothesized that the GH response to UBHIE is associated with upper body physical fitness. METHODS: Sixteen male subjects with age ranging from 21 to 37 years old were recruited for this study after a screening to have a group of healthy individuals with a wide range of aerobic fitness and body composition. Based on skin-fold measurements, subjects had a fat mass ranging from 21 to 3.6 kg, corresponding to 22% and 5.5% of total body mass, respectively. Based on an arm cranking ergometer (ACE) incremental continuous maximal exercise test, subjects had a V’O2peak ranging from 2.14 to 4.01 l min-1 (25 to 55 ml kg-1 min-1). Based on V’O2peak results and using the same ACE, all subjects underwent a constant power UBHIE at an intensity corresponding to their 150%V’O2peak. The UBHIE was carried out up to exhaustion under metabolic (V’O2) and cardiac (ECG) monitoring. Blood samples were collected before and after (for 90 minutes) the test to assess lactate and GH concentration. Correlation analysis between variables of interests were carried out. P < 0.05 was considered significant. RESULTS: UBHIE was carried out at a mechanical power equal to 278±57.9 watt and lasted 91±19.5 seconds. Total mechanical work ranged from 16.04 to 39.48 kJ (25.2±7.3 kJ). V’O2 top values at the UBHIE were equal to 2.56±0.418 l min-1 (32±4.9 ml kg-1min-1). Lactate peak, reached 5.8±1.95 min after UBHIE, ranged from 9.1 to 14.8 mM. GH peak, reached 27.2±11.2 min after UBHIE, ranged from 1.78 to 15.2 μg l-1, corresponding to an increment of 113±91 times and a total production of 404±230 μg l-1 min. GH production correlated significantly with absolute (r=0.62) and relative (r=0.54) V’O2peak of the maximal aerobic power test and with peak power (r=0.6) at the UBHIE. CONCLUSIONS: The GH response to a short term high intensity upper body exercise is associated with aerobic fitness. Anaerobic fitness (lactate peak and total mechanical work) does not seem related to GH response to UBHIE.