Leucine Supplementation

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Strength and body composition changes associated with leucine

supplementation and resistance training

T. Ispoglou & R. F. G. J. King Leeds Metropolitan University, UK

Evidence to support fue role of leucíne as an ergogenic aid and

supplement to enhance muscle growth during resistance training is

limited (Koopman et al., 2005: American Journal 01 Physiology:

Endocrinology and Metabolism, 288, E645 - E653). Leucine alone

can enhance protein synthesis ( et al., 2000: Joumal 01

Nutrition, 130, 2413-2419) while resistance exercise has been shown

to increase protein synthesis and breakdown (Biolo et al., 1995:

American Joumal 01 Physiology, 268, E514-E520). The

aim of this stUdy was to investigate the effects of combined daily

and post-exercise leucine supplementation on strength and body

composition during 12 weeks of training.

After approval was granted by the local ethics cornmittee, 26

untrained men were matched and allocated to one of two groups of

supplementation (placebo: n = 13, mean age 28.2 years, s = 7.3;

leucine, n= 13, mean age 28.5 years, s=O.O). Participants trained

twice per week in eight exercises and ingested daily either 4 g of

leucine or lactose. Five-repetition maximum strength (5-RM) was

assessed every 4 weeks. Fat-free mass was measured using dual-energy

X-ray absorptiometry, multi-frequency bioelectrical impedance, and

total body potassium.

There were increases in 5-RM strength ofleg press (P= 0.001), bench

press (P= 0.001), preacher curls (P= 0.000), and triceps press (P=

0.000) (two-way analysis ofvariance); total strength (sum of 5-RM in

eight exercises) gains in the leucine group were greater than those

in the placebo group (t12 = -2.508, two-tailed P=0.028). Total fat-

free mass was greater than pre-exercise values for both the placebo

(P= 0.005) and leucine (P= 0.002) groups.

There was an increase (P < 0.05) in fat-free mass of

the arms, legs, and trunk regions of the leucine group, and algo in

the arms and legs of the placebo group; the mean gains in trunk fat-

free mass were 0.3 kg (s=0.8) for the placebo group (P=0.176) and 0.8

kg (s= 1.1) for the leucine group (P=0.031).

Our results demonstrate that leucine supplementation improved

strength performance to a greater extent than placebo in specific

exercises; the total percentage gains were 31.2% (s=6.1) and 41%

(s=8.6) for the placebo and leucine groups respectively. Greater

gains in trunk fat-free mass accompanied the group with the highest

strength gains. The results suggest that leucine supplementation

combined with resistance training improves strength and fat-free mass.

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Carruthers

Wakefield, UK