Effects of Caffeine, L-Carnitine and Their Combination on 400m Freestyle Performance in Adolescent Female Swimmers

The study aim was to examine the effect of caffeine, L-carnitine, and their combination on lactate blood level, and exercise time during a 400m freestyle swimming trial. In a double-blind randomly designed study, 16 Karaj female freestyle swimmers aged 13.87±1.14 yr, BMI 21.69±4.34 kg/m2, height 160.87±58.75cm, weight 56.31±1.31kg were recruited. The trial activities included completing maximal 400m freestyle. The activity was performed half an hour after taking caffeine (3 mg/kg body weight) or L-carnitine (1.5g), caffeine + L-carnitine (3 mg/kg + 1.5 g), or placebo on 4 similar separate occasions. Blood lactate was measured 1 and 10 min after exercise. Repeated measures ANOVA indicated that no significant difference was observed for performance in all groups (p≥0.05), whereas significant differences were observed in lactate accumulation in 1 min after trial (p<0.05). These findings showed that consuming caffeine, L-carnitine and their combination has no meaningful effect on performance. However, it seems that taking caffeine alone or with L-carnitine result would result in more lactate accumulation in 1 min after exercise.