Testosterone And Androgen Receptor Responses To Resistance Exercise: Effects Of L-carnitine Supplementation:
1245 Board #100 3:30 PM - 5:00 PM
Spiering, Barry A.; Kraemer, William J. FACSM; Volek, Jeff S.; Ratamess, Nicholas A.; VanHeest, Jaci L.; Sharman, Matthew J.; Rubin, Martyn R.; French, Duncan N.; Judelson, Daniel A.; Maresh, Carl M. FACSM
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University of Connecticut, Storrs, CT.

(Sponsor: William J. Kraemer, FACSM)

Email: Barry.Spiering@uconn.edu

Supported in part by a grant from Lonza, Inc. (Fair Lawn, NJ 07410)

L-carnitine supplementation has been shown to affect androgenic hormonal responses to chronic exercise stress in animal studies. In humans, resistance exercise-induced muscle damage and soreness decreased following L-carnitine supplementation. This response was potentially due to enhanced hormonal receptor availability for binding interactions; however, this hypothesis has not been directly tested.


To examine the effects of L-carnitine supplementation on testosterone (T) and androgen receptor (AR) responses to resistance exercise.


Ten recreationally weight-trained men (mean±SD age: 22±1 y, mass: 86.3±15.3 kg, height: 181±11 cm) supplemented with L-carnitine (2g d−1) or placebo for 21-d followed by an acute heavy resistance exercise challenge (4 sets of 10 repetitions each of back squat, bench press, bent over row, and shoulder press exercises) in a randomized, balanced, repeated measures design. T concentrations were determined from blood samples obtained preexercise, immediately post-exercise, and serially every 10-min for 60-min thereafter. AR content was evaluated from skeletal muscle biopsies of the vastus lateralis obtained 48 to 72-h pre- and 1-h post-resistance exercise.


L-carnitine supplementation significantly (p < 0.05) increased T concentrations pre-exercise, at 0-, 30-, 40-, 50-, and 60-min post-exercise, and T integrated area under the curve. L- carnitine supplementation significantly increased pre-exercise AR content (12.9±5.9au for L-carnitine vs. 11.2±4.0au for placebo; p < 0.05). Post-exercise AR content was significantly greater than baseline during the placebo trial only (11.2±4.0au preexercise vs. 12.9±6.3au post-exercise; p < 0.05); however, post-exercise AR content was not different between L-carnitine and placebo (11.8±3.8au vs. 12.9±6.3au, respectively; p > 0.05).


L-carnitine supplementation up-regulated AR content per-exercise and increased T concentrations post-exercise. These responses may support T and AR interactions and promote recovery from resistance exercise.