Androgenic Responses to Resistance Exercise: Effects of Feeding and L-carnitine

Med Sci Sports Exerc. 2006 Jul;38(7):1288-96. doi: 10.1249/01.mss.0000227314.85728.35.

Abstract

Purpose: The purpose of this investigation was to determine the effects of 3 wk of L-carnitine L-tartrate (LCLT) supplementation and post-resistance-exercise (RE) feeding on hormonal and androgen receptor (AR) responses.

Methods: Ten resistance-trained men (mean+/-SD: age, 22+/-1 yr; mass, 86.3+/-15.3 kg; height, 181+/-11 cm) supplemented with LCLT (equivalent to 2 g of L-carnitine per day) or placebo (PL) for 21 d, provided muscle biopsies for AR determinations, then performed two RE protocols: one followed by water intake, and one followed by feeding (8 kcal.kg body mass, consisting of 56% carbohydrate, 16% protein, and 28% fat). RE protocols were randomized and included serial blood draws and a 1-h post-RE biopsy. After a 7-d washout period, subjects crossed over, and all experimental procedures were repeated.

Results: LCLT supplementation upregulated (P<0.05) preexercise AR content compared with PL (12.9+/-5.9 vs 11.2+/-4.0 au, respectively). RE increased (P<0.05) AR content compared with pre-RE values in the PL trial only. Post-RE feeding significantly increased AR content compared with baseline and water trials for both LCLT and PL. Serum total testosterone concentrations were suppressed (P<0.05) during feeding trials with respect to corresponding water and pre-RE values. Luteinizing hormone demonstrated subtle, yet significant changes in response to feeding and LCLT.

Conclusion: In summary, these data demonstrated that: 1) feeding after RE increased AR content, which may result in increased testosterone uptake, and thus enhanced luteinizing hormone secretion via feedback mechanisms; and 2) LCLT supplementation upregulated AR content, which may promote recovery from RE.

Publication types

  • Randomized Controlled Trial

MeSH terms

  • Adult
  • Carnitine / administration & dosage
  • Carnitine / metabolism*
  • Cross-Over Studies
  • Dietary Supplements*
  • Double-Blind Method
  • Humans
  • Luteinizing Hormone / metabolism
  • Male
  • Placebos
  • Receptors, Androgen / metabolism*
  • United States
  • Vitamin B Complex / administration & dosage
  • Vitamin B Complex / metabolism*
  • Weight Lifting / physiology*

Substances

  • Placebos
  • Receptors, Androgen
  • Vitamin B Complex
  • Luteinizing Hormone
  • Carnitine