The influence of muscle action on the acute growth hormone response to resistance exercise and short-term detraining

The effects of resistance training with concentric or concentric -eccentric muscle actions on the acute hormonal response to a resistance exercise pro tocol was investigated. Thirty-two men completed a 19 week lower-body resis tance training program (consisting of the leg press and leg extension exerc ises) in which they (1) performed concentric actions only (CON); (2) perfor med both concentric and eccentric actions (CON-ECC); (3) performed double c oncentric actions for each repetition (CON-CON); or (4) did not exercise. F ollowing training each subject performed two exercise tests consisting of t hree sets of 30 isokinetic concentric (day 1) and eccentric (day 2) knee ex tensions separated by 48 h. The exercise tests were repeated following 4 we eks of detraining. Blood samples were obtained before and after each exerci se test. Serum growth hormone (GH) was significantly (P < 0.05) greater for the concentric test in groups CON and CON-CON whereas GH was lower for the concentric test in CON-ECC compared with the eccentric test prior to detra ining. Following detraining, GH was greater during the concentric test in C ON-ECC than in the eccentric test, whereas no differences were observed bet ween the concentric and eccentric tests in CON and CON-CON and the acute GH response to resistance exercise was attenuated. These data indicate that G H is sensitive to muscle action type with differential responses observed w ith resistance exercise after short-term detraining. (C) 2001 Harcourt Publ ishers Ltd.