Intramyocellular lipid utilisation in the highly trained athlete: Performance following CHO- and placebo-loading

• Published in: Journal of science and medicine in sport 2002-12, Vol.5 (4), p.130-130
• Main Authors: Johnson, NA, Stannard, SR, Mehalski, K, Trenell, MI, Sachinwalla, T, Thompson, CH, Thompson, M W
• Format: Article
• Language: English
• ISSN: 1440-2440; 1878-1861
• DOI: 10.1016/S1440-2440(02)80273-0

Self-paced endurance cycling performance following carbohydrate-loaded (C) and carbohydrate-lowered (P) diets was compared in eight highly trained male cyclists (VO sub(2)max 72.0 plus or minus 6.2 mlkg super(-1) min super(-1); body mass 73.8 plus or minus 6.9 kg; age 33 plus or minus 6yrs), in a double-blinded randomised crossover design. In both conditions subjects believed they were CHO-loaded. Vastus lateralis intramyocellular lipid (IMCL) was assessed by super(1)H-magnetic resonance spectroscopy. The role of this substrate in exercise is not well understood. Average performance time was significantly shorter in the C (174.47 plus or minus 10.95min) versus P (193.80 plus or minus 21.75min) condition, with large individual differences evident. The small ( similar to 4%) improvement in 5 subjects following (C) demonstrates the ability of some highly trained individuals to function near-optimally with minimal dietary carbohydrate. Resting [IMCL] was 128% higher in P than C and not significantly different between conditions post-exercise. This suggests that intramyocellular lipid stores may have contributed significantly to the substantially higher rates of whole body lipid metabolism in P. Three subjects displayed reductions of IMCL between 88-92%. To our knowledge this is the first study to report near depletion of intramyocellular lipid during exercise and suggests that the net breakdown of IMCL during exercise is a function of exercise dose and IMCL availability.