EN
Beta-alanine (BA) supplementation increases muscle carnosine concentration resulting in better muscle performance. In vitro experiments on isolated muscles and single muscle fibers indicated that carnosine improved excitation-contraction coupling and slowed fatigue. We investigated effects of BA supplementation on muscle carnosine levels and in vivo motor units (MUs) contractile properties in rat medial gastrocnemius muscle (MG). Ten male Wistar rats were randomly assigned to control (n=5) or BA (supplemented with 1% BA in the drinking water for 10 weeks; n=5) groups. Contractions of 258 MUs were evoked by electrical stimulation of ventral root filaments. MUs were classified into fast fatigable (FF), fast resistant (FR) and slow (S) according to the standard criteria. Twitch force (TwF), maximum tetanic force (TetF) and force profile during the fatigue test were analyzed. BA supplementation enhanced carnosine levels in white and red portion of MG muscle by 94% and 56%, respectively. After BA supplementation TwF in FF and TetF in FR MUs increased, and force was better maintained from 20th to 130th s of the applied fatigue test in FR MUs. In conclusion, BA supplementation primarily improves contractile performance of FR MUs.