007 THE ERGOGENIC EFFECTS OF EURYCOMA
LONGIFOLIA JACK: A PILOT STUDY
S. Hamzah, A. Yusof. Department of Exercise Physiology, Sports Centre,
University of Malaya, 50603 Kuala Lumpur, Malaysia

Eurycoma longifolia Jack (ELJ), which contains quassinoids such as
eurycomalacton, eurycomanon, and eurycomanol, has been reported
to have aphrodisiac properties and to increase testosterone levels in
men.1

Previous studies have established that the testosterone
supplementation increases fat free mass, muscle strength, and muscle
mass, which are important for physical function and athletic perform-
ance.2,3

Thus, the objective of this study was to investigate the effect of
the increase in testosterone levels, obtained by administration of ELJ,
on body composition and muscle strength and size in man. Fourteen
healthy men performed an intense strength training programme with
initial load of 60% RM (2 sets of 10 repetitions with 1 minute rest
between, for 10 stations) on alternate days for five weeks. Simultane-
ously, seven men were randomly selected to consume 100 mg/day
ELJ water soluble extract, and seven men received placebo. The inten-
sity of the exercise was increased by 10% RM/week. Body composi-
tion, arm circumference, one repetition maximum (1 RM), and surface
electromyography (sEMG) activity were measured and recorded one
day before and after the five weeks of supplementation and interven-
tion. The lean body mass of the treatment group showed a significant
increment, from 52.26 (7.18) kg to 54.39 (7.43) kg (p = 0.012), but
no significant changes in fat free mass were observed in the placebo
group. Percentage body fat was significantly decreased in the
treatment and placebo group, from 31.30 (5.48)% to 28.44 (6.43)%
(p = 0.01) and from 22.83 (2.43)% to 21.33 (2.35)% (p = 0.001)
respectively. The 1RM test showed a significant increase from 73.71
(16.63) to 78.71 (17.0) kg (p = 0.006) in the treatment group and
from 77.29 (8.9) to 79.43 (8.8) kg (p = 0.011) in the placebo group.
The increase in strength in the treatment group was larger than in the
placebo group (6.78% and 2.77% respectively). The mean frequency
of sEMG on the biceps in the treatment and placebo groups
decreased significantly, from 121.77 (40.0) to 90.47 (64.6) ?V (p =
0.012) and from 127.95 (30.9) to 98.8 (50.1) ?V (p = 0.036)
respectively. The treatment produced 2.92% greater reduction in elec-
trical activity of the muscle measured at the end of the experiment
compared with placebo. The mean arm circumference of the treatment
group increased significantly by 1.8 cm after the supplementation,
from 30.87 (1.88) to 32.67 (1.96) cm (p = 0.011), but there was no
significant increase in the placebo group. The results suggest that
water soluble extract of Eurycoma longifolia Jack increased fat free
mass, reduced body fat, and increased muscle strength and size, and
thus may have an ergogenic effect. Further investigations are
warranted.

1. Ismail MTM. Proceedings paper: Asian Congress of Sexology.
2002.
2. Bhasin S, Storer TW, Berman N, et al. The effects of
supraphysiologic doses of testosterone on muscle size and strength in
men. N Engl J Med 1996;335:1?7.
3. Brodsky IG, Balagopal P, Nair KS. Effects of testosterone replace-
ment on muscle mass and muscle protein synthesis in hypogonadal
men: a Clinical Research Center Study. J Clin Endocrinol Metab
1996;81:3469?75.