Abstract
To assess the influence of exercise training on the growth hormone (GH) response to acute exercise, six untrained males completed a 20-min, high- intensity, constant-load exercise test prior to and after 3 and 6 wk of training (the absolute power output (PO) during each test remained constant, X̄ PO = 182.5 ± 29.5 W). Training increased (pre- vs post-training) oxygen uptake (V̇O2) at lactate threshold (1.57 ± 0.33 L·min-1 vs 1.97 ± 0.24 L·min-1, P ≤ 0.05), V̇O2 at 2.5 mM blood lactate concentration ([HLa]) (1.83 ± 0.38 L·min-1 vs 2.33 ± 0.38 L·min-1, P ≤ 0.05), and V̇O(2peak) (3.15 ± 0.54 L·min-1 vs 3.41 ± 0.47 L·min-1, P ≤ 0.05). Power output at the lactate threshold (PO-LT) increased with training from 103 ± 28 to 132 ± 23W (P ≤ 0.05). Integrated GH concentration (20 min exercise + 45 min recovery) (μg·L-1 X min) after 3 wk (138 ± 106) and 6 wk (130 ± 145) were significantly lower (P ≤ 0.05) than pre-training (238 ± 145). Plasma epinephrine and norepinephrine responses to training were similar to the GH response (EPI - pre-training = 2447 ± 1110; week 3 = 1046 ± 144; week 6 = 955 ± 322 pmol·L-1; P ≤ 0.05; NE - pre-training = 23.0 ± 5.2; week 3 = 13.4 ± 4.8; week 6 = 12.1 ± 6.8 nmol · L-1; P ≤ 0.05). These data indicate that the GH and catecholamine response to a constant-load exercise stimulus are reduced within the first 3 wk of exercise training and support the hypothesis that a critical threshold of exercise intensity must be reached to stimulate GH release.
Original language | English (US) |
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Pages (from-to) | 669-676 |
Number of pages | 8 |
Journal | Medicine and science in sports and exercise |
Volume | 29 |
Issue number | 5 |
DOIs | |
State | Published - May 1997 |
Externally published | Yes |
Keywords
- BLOOD LACTATE
- CATECHOLAMINES
- EXERCISE
- GROWTH HORMONE
- TRAINING
ASJC Scopus subject areas
- Orthopedics and Sports Medicine
- Physical Therapy, Sports Therapy and Rehabilitation