Submitted on January 5, 2009
Revised on March 3, 2009
Accepted on March 3, 2009
Reduced carbohydrate availability does not increase training induced stress protein adaptations but up-regulates oxidative enzyme activity in skeletal muscle
James P. Morton1*, Louise Croft1, Jonathan D. Bartlett1, Don PM MacLaren1, Thomas Reilly1, Louise Evans2, Anne McArdle3, and Barry Drust1
1 Liverpool John Moores University
2 Stepping Hill Hospital
3 University of Liverpool
* To whom correspondence should be addressed. E-mail: J.P.Morton{at}ljmu.ac.uk.
The present study aimed to test the hypothesis that training with reduced carbohydrate availability provides an enhanced stimulus for training-induced heat shock protein (HSP) and oxidative adaptations of skeletal muscle. Three groups of recreationally active males performed six weeks of high-intensity intermittent running four times per week. Group 1 (n=8; LOW+GLU) and 2 (n=7; LOW+PLA) trained twice per day, two days per week and consumed a 6.4% glucose or placebo solution, respectively, before every second training session and at regular intervals throughout exercise. Group 3 (n=8; NORM) trained once per day four days per week and consumed no beverage throughout training. Training-induced significant improvements in VO2max (P=0.001) and distance covered on a YoYo Intermittent Recovery Test 2 (P=0.001) in all groups, with no difference between conditions. Similarly, training resulted in significant increases HSP70, HSP60 and 
B-crystallin in the gastrocnemius (P=0.03, 0.02 and 0.01, respectively) and vastus lateralis (P=0.01, 0.02 and 0.003, respectively) muscles in all groups, with no difference between conditions. In contrast, training resulted in significant increases in succinate dehydrogenase (SDH) activity of the gastrocnemeius (LOW+CHO, LOW+PLA and NORM: 27, 76 and 53% increases, respectively; P=0.001) and vastus lateralis muscles (LOW+CHO, LOW+PLA and NORM: 17, 70 and 19% increases, respectively; P=0.001) where the magnitude of increase in SDH activity was significantly larger for both muscles (P=0.03 and 0.04 for gastrocnemius and vastus lateralis, respectively) for subjects training in the LOW+PLA condition. Data provide the first evidence that in whole body exercise conditions, carbohydrate availability appears to have no modulating effect on training-induced increases of the HSP content of skeletal muscle. In contrast, training under conditions of reduced carbohydrate availability from both endogenous and exogenous sources provides an enhanced stimulus for inducing oxidative enzyme adaptations of skeletal muscle although this does not translate to improved performance during high-intensity exercise.
