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G18R FREE COMMUNICATION/POSTER SKELETAL MUSCLE III

EFFECTS OF DIETARY MANIPULATION ON MUSCLE GLYCOGEN AND SARCOPLASMIC RETICULUM FUNCTION DURING PROLONGED EXERCISE

Kollias, H1; Duhamel, T1; Tupling, R1; Sandiford, S1; Schertzer, J1; Green, H1

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Medicine & Science in Sports & Exercise: May 2001 - Volume 33 - Issue 5 - p S297
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The purpose of this study was to investigate the hypothesis that exercise performed during low glycogen levels in associated with an increased depression in sarcoplasmic reticulum (SR) function. To investigate this hypothesis, untrained males (5) and females (5), with a peak aerobic power (VO2 peak) of 3.5 ± 0.1 and 2.4 ± 0.1 L/min, respectively ( ± SE), cycled (65% VO2 peak), both while on a low carbohydrate (LO CHO) (23 ± 0.5% of energy from CHO) and normal diet (Normal CHO) (53 ± 2.2% of energy from CHO) for 4 days following glycogen depleting exercise. Resting muscle glycogen contents in vastus lateralis (378 ± 12 vs 259 ± 8 glucosyl units kg dry wt−1) were higher (p < 0.05) and times to fatigue (110 ± 37 vs 85 ± 24 min) were longer with Normal CHO. Maximal Ca2+-ATPase activities in homogenates, although higher (P < 0.05) at rest in LO CHO (131 ± 6 vs 119 ± 5 μmol.min g protein −1) were not different at fatigue. Homogenate based Ca2+-uptake, (μmol.min−1-1.g protein) were similar between diets at rest (351 ± 44 vs 369 ± 49). but decreased more rapidly (P < 0.05) on LO CHO compared to Normal CHO (304 ± 44 vs 369 ± 169 ± 29). These results demonstrate that the effects of dietary manipulation on SR function is specific to both the property measured (Ca2+-ATPase activity vs Ca2+-uptake) and the condition (rest vs exercise). Supported by NSERC (Canada)

©2001The American College of Sports Medicine