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Effects of rapid weight loss and wrestling on muscle glycogen concentration
M A Tarnopolsky1, N Cipriano, C Woodcroft
1Department of Kinesiology, McMaster University, Hamilton, Ontario, Canada.
Objective:
To examine the effect of energy restriction and wrestling on muscle glycogen content in highly-trained male wrestlers.
Design:
Randomized, unblinded intervention trial.
Setting:
McMaster University Nutrition and Metabolism Research Laboratory.
Participants:
Twelve highly trained male wrestlers volunteered as subjects and were randomly assigned to one of two groups (Group A, n = 6; Group B, n = 6) as defined below.
Assessment Of Risk Factors:
All subjects were free of medical conditions that would preclude participation in the study and all had performed rapid weight loss at least three times/year with no medical complications.
Interventions:
Group A: simulated wrestling tournament, four 5-min wrestling bouts ( > 7 h) following a 5% body weight loss and 17 h repletion period; Group B: 5% weight loss through energy restriction (1,141 kcal/day), exercise, fluid restriction, and dehydration methods (sauna) > 72 h.
Main Outcome Measures:
Group A: muscle glycogen content before and after wrestling tournament and plasma lactate after each bout; Group B: muscle glycogen before and after weight loss.
Results:
Group A: no significant effect on muscle glycogen concentration, yet large increases were observed in blood lactate concentrations (up to 14.7 mmol/L); Group B: weight loss resulted in a 54% (p < 0.018) reduction in muscle glycogen concentration.
Conclusions:
The weight loss methods commonly performed by wrestlers resulted in large decreases in muscle glycogen concentration that were largely reversed during the 17-h repletion period between weigh-in and the start of the competition; participation in a wrestling tournament did not have a significant impact upon biceps brachii glycogen concentration when ad libitum feeding is allowed between matches.