Postexercise Muscle Glycogen Synthesis with Combined Glucose and Fructose Ingestion.
WALLIS, GARETH A. 1; HULSTON, CARL J. 1; MANN, CHRISTOPHER H. 2; ROPER, HELEN P. 3; TIPTON, KEVIN D. 1; JEUKENDRUP, ASKER E. 1
Medicine & Science in Sports & Exercise.
40(10):1789-1794, October 2008.
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Purpose: To evaluate the efficacy of using combined glucose and fructose (GF) ingestion as a means to stimulate short-term (4 h) postexercise muscle glycogen synthesis compared to glucose only (G).
Methods: On two separate occasions, six endurance-trained men performed an exhaustive glycogen-depleting exercise bout followed by a 4-h recovery period. Muscle biopsy samples were obtained from the vastus lateralis muscle at 0, 1, and 4 h after exercise. Subjects ingested carbohydrate solutions containing G (90 g[middle dot]h-1) or GF (G = 60 g[middle dot]h-1; F = 30 g[middle dot]h-1) commencing immediately after exercise and every 30 min thereafter.
Results: Immediate postexercise muscle glycogen concentrations were similar in both trials (G = 128 /- 25 mmol[middle dot]kg-1 dry muscle (dm) vs GF = 112 /- 16 mmol[middle dot]kg-1 dm; P > 0.05). Total glycogen storage during the 4-h recovery period was 176 /- 33 and 155 /- 31 mmol[middle dot]kg-1 dm for G and GF, respectively (G vs GF, P > 0.05). Hence, mean muscle glycogen synthesis rates during the 4-h recovery period did not differ between the two conditions (G = 44 /- 8 mmol[middle dot]kg-1 dm[middle dot]h-1 vs GF = 39 /- 8 mmol[middle dot]kg-1 dm[middle dot]h-1, P > 0.05). Plasma glucose and serum insulin responses during the recovery period were similar in both conditions, although plasma lactate concentrations were significantly elevated during GF compared to G (by ~0.8 mmol[middle dot]L-1, P < 0.05).
Conclusions: Glucose and glucose/fructose (2:1 ratio) solutions, ingested at a rate of 90 g[middle dot]h-1, are equally effective at restoring muscle glycogen in exercised muscles during the recovery from exhaustive exercise.
(C)2008The American College of Sports Medicine