Can Branched Chain Amino Acids Supplementation Reduce Muscle Damage Induced by Neuromuscular Electrical Stimulation ? A Combined Functional and Metabolic Non-invasive Investigation in Healthy Humans.

Neuromuscular electrical stimulation (NMES) is commonly used in rehabilitation contexts in order to increase or restore muscle capacities of hypoactive patients or patients with articular trauma. Although this technique seems to be particularly adapted to muscle rehabilitation, growing evidence is emerging regarding potential damaging effects of electrically- induced isometric contractions in healthy humans. Recent studies have reported a 10 to 30-fold increase in creatine kinase (CK) activity coupled to significantly increased muscle soreness and impaired force production as a result of NMESs. On that basis, further studies should be conducted on these deleterious effects which might limit the clinical application of NMES. Over the last decade, many studies paid attention to branched-chain amino acids (BCAA) supplementation as a potential prophylactic/therapeutic approach. The rationale of this approach is that BCAA might increase protein synthesis and reduce protein breakdown through physiological mechanisms involving mTOR regulation pathway (mammalian Target of Rapamycin). Additionally, BCAA could also be used as energetic substrate during exercise when glycogen stores are depleted. Overall, previous results have supported the efficacy of BCAA supplementation in attenuating muscle damage. Nevertheless, comprehensive studies investigating the effect of amino acid supplementation on markers of muscle damage are still scarce. Magnetic resonance imaging (IRM) and phosphorus 31 magnetic resonance spectroscopy (31P-MRS) are powerful non invasive tools allowing the exploration of skeletal muscle structure and energy metabolism. This ambitious project is devoted to the anatomical, functional and metabolic characterization of BCAA supplementation after NMES using MRI and 31P-MRS. Various markers of muscle damage, including maximal voluntary force production, T2 values and apparent diffusion coefficient (obtained by MRI) and energy metabolism assessed at rest and during exercise (using 31P-MRS), will be obtained before and after NMES. This project is of utmost importance for improving our knowledge of anatomic, metabolic and functional events related to BCAA supplementation in the context of exercise-induced muscle damage