A composition is disclosed suitable for the prevention and/or treatment of muscular energetic deficiencies and states of asthenia for enhancing sport performances and for the treatment of states of heart fatigue, that may take the form of a dietary supplement, dietetic support or of an actual medicine, which comprises as characterizing active ingredients a combination of L-carnitine and/or at least one alkanoyl L-carnitine and creatinol-phosphate.