title: Dietary carbohydrate, muscle glycogen, and power output during rowing training.
abstract: The belief that high-carbohydrate diets enhance training capacity (mean power output) has been extrapolated from studies that have varied dietary carbohydrate over a few days and measured muscle glycogen but did not assess power output during training. We hypothesized that a high-carbohydrate (HI) diet (10 g.kg body mass-1.day-1) would promote greater muscle glycogen content and greater mean power output during training than a moderate-carbohydrate (MOD) diet (5 g.kg body mass-1.day-1) over 4 wk of intense twice-daily rowing training. Dietary protein intake was 2 g.kg body mass-1.day-1, and fat intake was adjusted to maintain body mass. Twelve male and 10 female collegiate rowers were randomly assigned to the treatment groups. Training was 40 min at 70% peak O2 consumption (VO2) (A.M.) and either three 2,500-m time trials to assess power output or interval training at 70-90% peak VO2 (P.M.). Mean daily training was 65 min at 70% peak VO2 and 38 min at greater than or equal to 90% peak VO2. Mean muscle glycogen content increased 65% in the HI group (P less than 0.05) but remained constant at 119 mmol/kg in the MOD group over the 4 wk. Mean power output in time trials increased 10.7 and 1.6% after 4 wk in the HI and MOD groups, respectively (P less than 0.05). We conclude that a diet with 10 g carbohydrate.kg body mass-1.day-1 promotes greater muscle glycogen content and greater power output during training than a diet containing 5 g carbohydrate.kg body mass-1.day-1 over 4 wk of intense twice-daily rowing training.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Exercise Physiology Laboratory, School of Health, Physical Education, and Recreation, Ohio State University, Columbus 43210-1284.
authors.forename: J C
authors.initials: JC
authors.lastname: Simonsen
authors.forename: W M
authors.initials: WM
authors.lastname: Sherman
authors.forename: D R
authors.initials: DR
authors.lastname: Lamb
authors.forename: A R
authors.initials: AR
authors.lastname: Dernbach
authors.forename: J A
authors.initials: JA
authors.lastname: Doyle
authors.forename: R
authors.initials: R
authors.lastname: Strauss
mesh_terms: D000328:Adult; D001786:Blood Glucose / Q000378:metabolism; D004040:Dietary Carbohydrates / Q000008:administration & dosage*; D015444:Exercise / Q000502:physiology*; D005260:Female; D006003:Glycogen / Q000378:metabolism*; D006801:Humans; D008297:Male; D009132:Muscles / Q000378:metabolism*; D010101:Oxygen Consumption; D010806:Physical Education and Training
chemical_list: D001786:Blood Glucose; D004040:Dietary Carbohydrates; D006003:Glycogen