Androgenic responses to resistance exercise: effects of feeding and L-carnitine.
OBJECTIVE
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.


CONCLUSIONS
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.
Kraemer
William J
WJ
Human Performance Laboratory, Department of Kinesiology, University of Connecticut, Storrs, CT 06269-1110, USA. William.Kraemer@uconn.edu
Spiering
Barry A
BA
Volek
Jeff S
JS
Ratamess
Nicholas A
NA
Sharman
Matthew J
MJ
Rubin
Martyn R
MR
French
Duncan N
DN
Silvestre
Ricardo
R
Hatfield
Disa L
DL
Van Heest
Jaci L
JL
Vingren
Jakob L
JL
Judelson
Daniel A
DA
Deschenes
Michael R
MR
Maresh
Carl M
CM
D000328:Adult; D002331:Carnitine / Q000008:administration & dosage / Q000378:metabolism*; D018592:Cross-Over Studies; D019587:Dietary Supplements; D004311:Double-Blind Method; D006801:Humans; D007986:Luteinizing Hormone / Q000378:metabolism; D008297:Male; D010919:Placebos; D011944:Receptors, Androgen / Q000378:metabolism*; D014481:United States; D014803:Vitamin B Complex / Q000008:administration & dosage / Q000378:metabolism*; D014891:Weight Lifting / Q000502:physiology*
D010919:Placebos; D011944:Receptors, Androgen; D014803:Vitamin B Complex; D007986:Luteinizing Hormone; D002331:Carnitine