Failure to repeatedly supercompensate muscle glycogen stores in highly trained men.
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.
McInerney
Patrick
P
Exercise Metabolism Group, School of Medical Sciences, RMIT University, Victoria, AUSTRALIA.
Lessard
Sarah J
SJ
Burke
Louise M
LM
Coffey
Vernon G
VG
Lo Giudice
Sonia L
SL
Southgate
Robert J
RJ
Hawley
John A
JA
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
D001786:Blood Glucose; D004040:Dietary Carbohydrates; D005230:Fatty Acids, Nonesterified; D007328:Insulin; D014280:Triglycerides; D006003:Glycogen; D006006:Glycogen Synthase