title: Human growth hormone responses to repeated bouts of sprint exercise with different recovery periods between bouts.
abstract: This study examined the growth hormone (GH) response to repeated bouts of sprint cycling. Eight healthy men completed three trials consisting of two 30-s sprints on a cycle ergometer separated by either 60 min (Trial A) or 240 min (Trial B) of recovery and a single 30-s sprint carried out the day after Trial B (Trial C). Trials A and B were separated by at least 7 days. Blood samples were obtained at rest and during recovery from each sprint. In Trial A, GH was elevated immediately before sprint 2, and there was no further increase in GH following the second sprint [area under the curve: 460 (SD 348) vs. 226 min.mug(-1).l(-1) (SD 182), P = 0.05]. Free insulin-like growth factor I tended to be lower immediately before sprint 2 than sprint 1 (P = 0.06). Serum free fatty acids were not different immediately before each of the sprints. In Trial B, there was a trend for a smaller GH response to the second sprint [GH area under the curve: 512 (SD 396) vs. 242 min.mug(-1).l(-1) (SD 190), P = 0.09]. Free insulin-like growth factor I tended to be lower (P = 0.06), and serum free fatty acids were higher (P = 0.01) immediately before sprint 2 than sprint 1. There was no difference in the GH response to sprinting on consecutive days (Trials B and C). In conclusion, repeated bouts of sprint cycling on the same day result in an attenuation or even ablation of the exercise-induced increase in GH, depending on the recovery interval between sprints.
authors.affiliation: Sport and Exercise Science Group, School for Health, University of Bath, UK. k.stokes@bath.ac.uk
authors.forename: Keith
authors.initials: K
authors.lastname: Stokes
authors.forename: Mary
authors.initials: M
authors.lastname: Nevill
authors.forename: Jan
authors.initials: J
authors.lastname: Frystyk
authors.forename: Henryk
authors.initials: H
authors.lastname: Lakomy
authors.forename: George
authors.initials: G
authors.lastname: Hall
mesh_terms: D000054:Acceleration; D000328:Adult; D001642:Bicycling / Q000502:physiology*; D001810:Blood Volume; D005230:Fatty Acids, Nonesterified / Q000097:blood; D019382:Human Growth Hormone / Q000097:blood*; D006801:Humans; D018970:Insulin-Like Growth Factor Binding Protein 1 / Q000378:metabolism; D007334:Insulin-Like Growth Factor I / Q000378:metabolism; D008297:Male; D012016:Reference Values; D012146:Rest; D013997:Time Factors
chemical_list: D005230:Fatty Acids, Nonesterified; D018970:Insulin-Like Growth Factor Binding Protein 1; D019382:Human Growth Hormone; D007334:Insulin-Like Growth Factor I