Effects ofl-carnitine loading on the aerobic and anaerobic performance of endurance athletes

L-Carnitine (l-c), a well known physiological carrier across the inner mitochondrial membrane of activated long chain fatty acids and acceptor of acyl groups from acyl-CoA, has been recently synthesised industrially. This has made it possible to study the effects ofl-c loading (4 g·d⁻¹ by mouth over a period of 2 weeks) on the aerobic and anaerobic performance of 6 long distance competitive walkers. As a result of the treatment: 1) mean total, free and esterified seruml-c both at rest and shortly after completing a 120 min walk at about 65% of the individual maximal aerobic power \((\dot V_{O_{2\max } } )\) were significantly increased; 2) \(V_{O_{2\max } } \) increased 6%, from 54.5±3.7 (S.D.) to 57.8±47 mlO₂·kg⁻¹·min⁻¹ (P<0.02); 3) blood lactate concentration (La _b ) as a consequence of short bouts of repeated exercise (series of 10, 15 and 20 jumps off both feet on a force platform) was unchanged; 4) heart rate, pulmonary ventilation, oxygen consumption, and respiratory quotient in the same conditions as for 1) were unchanged. It is concluded that, in trained athletes, as a consequence ofl-c loading \(\dot V_{O_{2\max } } \) is slightly but significantly raised, probably as a result of an activation of substrate flow through the TCA cycle, whereas the lipid contribution to metabolism in prolonged submaximal exercise remains unchanged.