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·h−1) or GF (G = 60 g·h−1; F = 30 g·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·kg−1 dry muscle (dm) vs GF = 112 ± 16 mmol·kg−1 dm; P > 0.05). Total glycogen storage during the 4-h recovery period was 176 ± 33 and 155 ± 31 mmol·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·kg−1 dm·h−1 vs GF = 39 ± 8 mmol·kg−1 dm·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·L−1, P < 0.05).
Conclusions: Glucose and glucose/fructose (2:1 ratio) solutions, ingested at a rate of 90 g·h−1, are equally effective at restoring muscle glycogen in exercised muscles during the recovery from exhaustive exercise.
1School of Sport and Exercise Sciences, University of Birmingham, Birmingham, UNITED KINGDOM; 2Department of Fetal Medicine, Division of Reproduction and Child Health, Birmingham Women's Hospital, Birmingham, UNITED KINGDOM; and 3Department of Paediatrics, Birmingham Heartlands Hospital, Birmingham, UNITED KINGDOM
Address for correspondence: Asker E. Jeukendrup, Ph.D., School of Sport and Exercise Sciences, University of Birmingham, Birmingham, B15 2TT, United Kingdom; E-mail: A.E.Jeukendrup@bham.ac.uk.
Submitted for publication July 2007.
Accepted for publication April 2008.