Purpose: We determined the effects of conjugated linoleic acid (CLA) supplementation during resistance training.
Methods: Seventy-six subjects were randomized to receive CLA (5 g·d−1) or placebo (PLA) for 7 wk while resistance training 3 d·wk−1. Seventeen subjects crossed over to the opposite group for an additional 7 wk. Measurements at baseline, 7 wk, and 14 wk (for subjects in the crossover study) included body composition, muscle thickness of the elbow flexors and knee extensors, resting metabolic rate (RMR), bench and leg press strength, knee extension torque, and urinary markers of myofibrillar degradation (3-methylhistidine (3MH) and bone resorption (cross-linked N-telopeptides (Ntx)).
Results: After 7 wk the CLA group had greater increases in lean tissue mass (LTM) (+1.4 vs +0.2 kg; P < 0.05), greater losses of fat mass (−0.8 vs +0.4 kg; P < 0.05), and a smaller increase in 3MH (−0.1 vs + 1.3 μmol·kg−1 LTM·d−1; P < 0.05) compared with PLA. Changes between groups were similar for all other measurements, except for a greater increase in bench press strength for males on CLA (P < 0.05). In the crossover study subjects had minimal changes in body composition, but smaller increases in 3MH (−1.2 vs +2.2 μmol·kg−1 LTM·d−1; P < 0.01) and NTx (−4.8 vs +7.3 nmol·kg−1 LTM·d−1; P < 0.01) while on CLA versus PLA.
Conclusions: Supplementation with CLA during resistance training results in relatively small changes in body composition accompanied by a lessening of the catabolic effect of training on muscle protein.
1College of Kinesiology, University of Saskatchewan, Saskatoon, CANADA; 2College of Pharmacy and Nutrition, University of Saskatchewan, Saskatoon, CANADA; and 3Department of Anatomy and Cell Biology, University of Saskatchewan, Saskatoon, CANADA
Address for correspondence: Philip D. Chilibeck, Ph.D., 87 Campus Drive, College of Kinesiology, University of Saskatchewan, Saskatoon, SK, Canada; E-mail: firstname.lastname@example.org.
Submitted for publication December 2004.
Accepted for publication August 2005.