Glycogen synthesis during exercise and rest with carbohydrate feeding in males and females.
Since it has been demonstrated that endurance-trained cyclists are able to synthesize glycogen during mild exercise, glycogen synthesis was investigated in non-endurance-trained males and females as well. Seven males and nine females exercised on a cycle ergometer to deplete muscle glycogen. After the exhaustive exercise and taking a muscle biopsy, the males either exercised 2.5 h at 40% of maximal work load (trial A) or rested for 2.5 h (trial B). In both trials the subjects drank a 25% maltodextrin-fructose solution. After 2.5 h of exercise or rest, a second muscle biopsy was taken for determination of glycogen and for histochemistry (ATPase and PAS). In the females glycogen synthesis was only studied during 2.5 h rest, after prior glycogen depletion. In the male subjects, during mild exercise with carbohydrate feeding muscle glycogen did not increase. During rest muscle glycogen increased in the males from 123 +/- 49 mmol/kg DW at exhaustion to 229 +/- 70 mmol/kg DW (P less than 0.001), resulting in a net increase of 42 mmol/kg DW/h. Glycogen synthesis during rest occurred both in type I and type II fibers. In the females, during 2.5 h of rest, muscle glycogen increased from 130 +/- 56 mmol/kg DW at exhaustion to 224 +/- 51 mmol/kg DW, resulting in a net increase of 37 mmol/kg DW/h. The results demonstrate that glycogen synthesis during mild exercise does not occur in non-endurance-trained athletes, whereas in the resting state glycogen synthesis in non-endurance-trained males is not different from endurance-trained cyclists. In addition, glycogen synthesis during rest is similar in males and females.
Kuipers
H
H
Dept. Physiology, University of Limburg, Maastricht, The Netherlands.
Saris
W H
WH
Brouns
F
F
Keizer
H A
HA
ten Bosch
C
C
D000328:Adult; D004040:Dietary Carbohydrates / Q000378:metabolism*; D015444:Exercise; D005260:Female; D006003:Glycogen / Q000096:biosynthesis*; D006801:Humans; D008297:Male; D009132:Muscles / Q000378:metabolism; D012146:Rest; D012737:Sex Factors
D004040:Dietary Carbohydrates; D006003:Glycogen