Increased dietary carbohydrate and endurance during single-leg cycling using a limb with normal muscle glycogen concentration.
The purpose of this study was to test the hypothesis that increased availability of blood-borne glucose would improve endurance after carbohydrate loading. A single-leg exercise model was employed, taking advantage of the fact that supercompensation of muscle glycogen occurs only in a previously exercised limb. Endurance time to exhaustion at 70% of maximal oxygen uptake (VO2 max) was determined for 11 males and three females who were then allocated to a control group or a high-carbohydrate (CHO) group. For 3 days following Test 1 the control group maintained a prescribed normal diet whilst the CHO group increased the proportion of energy derived from carbohydrate (62.1 +/- 4.3% cf. 43.9 +/- 2.0%, P less than 0.01). The endurance test was then repeated using the leg that was inactive during Test 1. Endurance time was increased on Test 2 (123.7 +/- 43.2 min cf. 98.5 +/- 21.9 min, P less than 0.05 one-tailed test) for the CHO group but not for the control group (101.8 +/- 21.7 min cf. 107.5 +/- 9.1 min, NS). There was no indication of enhanced carbohydrate metabolism during Test 2 for the CHO group but mean heart rate was lower during Test 2 than during Test 1 (145 +/- 14 beat min-1 cf. 152 +/- 12 beat min-1, P less than 0.05). These results suggest that the prior consumption of a high-carbohydrate diet improves endurance during high-intensity cycling with a limb with normal muscle glycogen concentration.
Hardman
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AE
Department of Physical Education and Sports Science, University of Technology, Loughborough, Leicestershire, UK.
Williams
C
C
D000328:Adult; D001642:Bicycling; D004040:Dietary Carbohydrates / Q000008:administration & dosage* / Q000378:metabolism; D005260:Female; D006003:Glycogen / Q000378:metabolism*; D006801:Humans; D008297:Male; D009132:Muscles / Q000378:metabolism*; D010807:Physical Endurance
D004040:Dietary Carbohydrates; D006003:Glycogen