title: Failure to repeatedly supercompensate muscle glycogen stores in highly trained men.
abstract: OBJECTIVE
  It is not known whether it is possible to repeatedly supercompensate muscle glycogen stores after exhaustive exercise bouts undertaken within several days.
  
  
  METHODS
  We evaluated the effect of repeated exercise-diet manipulation on muscle glycogen and triacylglycerol (IMTG) metabolism and exercise capacity in six well-trained subjects who completed an intermittent, exhaustive cycling protocol (EX) on three occasions separated by 48 h (i.e., days 1, 3, and 5) in a 5-d period. Twenty-four hours before day 1, subjects consumed a moderate (6 g.kg)-carbohydrate (CHO) diet, followed by 5 d of a high (12 g.kg.d)-CHO diet. Muscle biopsies were taken at rest, immediately post-EX on days 1, 3, and 5, and after 3 h of recovery on days 1 and 3.
  
  
  RESULTS
  Compared with day 1, resting muscle [glycogen] was elevated on day 3 but not day 5 (435+/-57 vs 713+/-60 vs 409+/-40 mmol.kg, P<0.001). [IMTG] was reduced by 28% (P<0.05) after EX on day 1, but post-EX levels on days 3 and 5 were similar to rest. EX was enhanced on days 3 and 5 compared with day 1 (31.9+/-2.5 and 35.4+/-3.8 vs 24.1+/-1.4 kJ.kg, P<0.05). Glycogen synthase activity at rest and immediately post-EX was similar between trials. Additionally, the rates of muscle glycogen accumulation were similar during the 3-h recovery period on days 1 and 3.
  
  
  CONCLUSIONS
  We show that well-trained men cannot repeatedly supercompensate muscle [glycogen] after glycogen-depleting exercise and 2 d of a high-CHO diet, suggesting that the mechanisms responsible for glycogen accumulation are attenuated as a consequence of successive days of glycogen-depleting exercise.
authors.affiliation: Exercise Metabolism Group, School of Medical Sciences, RMIT University, Victoria, AUSTRALIA.
authors.forename: Patrick
authors.initials: P
authors.lastname: McInerney
authors.forename: Sarah J
authors.initials: SJ
authors.lastname: Lessard
authors.forename: Louise M
authors.initials: LM
authors.lastname: Burke
authors.forename: Vernon G
authors.initials: VG
authors.lastname: Coffey
authors.forename: Sonia L
authors.initials: SL
authors.lastname: Lo Giudice
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Southgate
authors.forename: John A
authors.initials: JA
authors.lastname: Hawley
mesh_terms: D000328:Adult; D001642:Bicycling / Q000502:physiology; D001786:Blood Glucose / Q000378:metabolism; D004040:Dietary Carbohydrates / Q000378:metabolism; D002149:Energy Intake / Q000502:physiology; D015444:Exercise / Q000502:physiology*; D017079:Exercise Tolerance / Q000502:physiology*; D005230:Fatty Acids, Nonesterified / Q000097:blood; D006003:Glycogen / Q000378:metabolism*; D006006:Glycogen Synthase / Q000378:metabolism; D006801:Humans; D007328:Insulin / Q000097:blood; D008297:Male; D018482:Muscle, Skeletal / Q000378:metabolism*; D012146:Rest / Q000502:physiology; D013647:Task Performance and Analysis; D014280:Triglycerides / Q000378:metabolism
chemical_list: D001786:Blood Glucose; D004040:Dietary Carbohydrates; D005230:Fatty Acids, Nonesterified; D007328:Insulin; D014280:Triglycerides; D006003:Glycogen; D006006:Glycogen Synthase