The purpose of this study was to investigate the effect of oral creatine supplementation on intramyocellular lipid content (IMCL) and muscle oxidative capacity during muscle disuse and subsequent training. A double-blind placebo-controlled trial was performed with 22 young healthy volunteers. The right leg was immobilized using a cast for two weeks, after which subjects participated in a 6-week rehabilitation training program. Half of the subjects received 15g creatine monohydrate during the immobilisation and 2.5g during rehabilitation training program (CR) and the others ingested placebo (PL; maltodextrin). Before and after immobilisation and retraining, needle biopsies were taken from the right and left vastus lateralis muscles. During immobilisation IMCL in type I fibres increased in the PL (~20%, p<0.05) but was constant in CR. Rehabilitation training returned IMCL content in type I fibres to baseline in PL, whereas in CR it dropped to ~40% below baseline (p<0.05). At the end of study type I fibre IMCL content on average was ~30% lower in CR than in PL (p<0.05). Immobilisation slightly increased IMCL content in type IIa fibres in both groups, but values returned to baseline during retraining. Immobilisation decreased succinate dehydrogenase (SDH) activity and muscle fatty acid translocase/CD36 protein content (p<0.05), yet values returned to baseline within the 6-week retraining period. Values were similar between PL and CR at any time. We conclude that oral creatine supplementation offsets the increase in IMCL content that occurs during immobilisation and in conjunction with exercise training it can significantly reduce IMCL content in humans.
