The effects of L-carnitine L-tartrate supplementation on hormonal responses to resistance exercise and recovery.

The purpose of this investigation was to examine the influence of L-carnitine L-tartrate (LCLT) supplementation using a balanced, cross-over, placebo-controlled research design on the anabolic hormone response (i.e., testosterone [T], insulin-like growth factor-I, insulin-like growth factor-binding protein-3 [IGFBP-3], and immunofunctional and immunoreactive growth hormone [GHif and GHir]) to acute resistance exercise. Ten healthy, recreationally weight-trained men (mean +/- SD age 23.7 +/- 2.3 years, weight 78.7 +/- 8.5 kg, and height 179.2 +/- 4.6 cm) volunteered and were matched, and after 3 weeks of supplementation (2 g LCLT per day), fasting morning blood samples were obtained on six consecutive days (D1-D6). Subjects performed a squat protocol (5 sets of 15-20 repetitions) on D2. During the squat protocol, blood samples were obtained before exercise and 0, 15, 30, 120, and 180 minutes postexercise. After a 1-week washout period, subjects consumed the other supplement for a 3-week period, and the same experimental protocol was repeated using the exact same procedures. Expected exercise-induced increases in all of the hormones were observed for GHir, GHif, IGFBP-3, and T. Over the recovery period, LCLT reduced the amount of exercise-induced muscle tissue damage, which was assessed via magnetic resonance imaging scans of the thigh. LCLT supplementation significantly (p < 0.05) increased IGFBP-3 concentrations prior to and at 30, 120, and 180 minutes after acute exercise. No other direct effects of LCLT supplementation were observed on the absolute concentrations of the hormones examined, but with more undamaged tissue, a greater number of intact receptors would be available for hormonal interactions. These data support the use of LCLT as a recovery supplement for hypoxic exercise and lend further insights into the hormonal mechanisms that may help to mediate quicker recovery.