Eccentric muscle effort is known to induce delayed muscle soreness (DOMS) and muscle damage which are not responsive to medical treatment with the most common analgesic agents. The aim of the study was to investigate the effects of oral L-carnitine supplementation on pain (VAS scale), tenderness (pain thresholds) and CK release induced by a 20-min eccentric effort of the quadriceps muscle. A single-blind study was carried out on 6 untrained subjects (mean age: 26 +/- 3.8 yrs; mean height: 173 +/- 4.6 cm; mean body weight, 68.3 +/- 4.5 kg) over 7 weeks during which each subject: a) was given 3 g/day of placebo for 3 weeks and, after a week's interval, 3 g/day of L-carnitine for 3 weeks: b) performed 2 step tests on the first day of the 3rd and 7th week inverting the order of the exercising limb. In a separate set of experiments carried out 8 months later, the possible effects of training on pain parameters and CK levels were also investigated in the same subjects who performed 2 step tests at a 4-weeks' interval, without medication. L-carnitine significantly reduced pain, tenderness and CK release after the effort with respect to placebo. In contrast, no significant difference was found in the parameters measured between the two tests performed without medication. It is concluded that L-carnitine has a protective effect against pain and damage from eccentric effort. This effect is mainly attributed to the vasodilatation property of the compound, which both improves energetic metabolism of the hypoxic/damaged muscle and enhances wash-out of algogenic metabolites.