NUTRITION IN SPORT

(Martin Jones) #1

have failed to observe an increase in the serum
concentration of HGH following supplementa-
tion with these amino acids. Those studies which
have shown some anabolic effect of these amino
acid supplements are flawed. Suminski et al.
(1997) found that the ingestion of 1500 mg of argi-
nine and 1500 mg of lysine immediately before
resistance exercise did not alter exercise-induced
changes in the concentration of growth hormone
in weight-training males. When the same amino
acid mixture was ingested under basal condi-
tions, the secretion of growth hormone was
increased to levels which were higher than after
ingestion of a placebo, 60 min after amino acid
ingestion during resting conditions. Additional
research is required to evaluate claims for com-
mercial products.
A few studies have examined the effect of argi-
nine and/or ornithine supplementation on body
composition, measures of muscular strength or
power and reported significant increases in lean
body mass. Where increases in lean body mass
have been reported (Crist et al. 1988; Yarasheski
et al. 1992), the functional ability of the muscle
was not assessed. M.H. Williams (1993) empha-
sizes the flawed experimental methodology in
each study, thus questioning the interpretation of
the findings. Although statistical significance
was reported in two of the studies, a recalcula-
tion, using the appropriate statistical technique,
actually revealed no significant differences
between the supplement and the placebo. Other
studies have reported no significant effect of
arginine or a mixture of amino acids on measures
of strength, power or HGH in experienced
weightlifters (Hawkins et al. 1991; Warren et al.
1991). The use of both HGH and anabolic
steroids is contraindicated for athletes, since they
are both proscribed by the IOC and both carry
significant health risks (Lombardo et al. 1991;
M.H. Williams 1993).
The ergogenic effect of supplementing the diet
with low-dose oral amino acids has been ques-
tioned (Fogelholm et al. 1993; Fry et al. 1993;
Lambertet al. 1993). Fogelholm et al. (1993) found
no difference in the concentrations of serum
growth hormone or insulin of competitive


weightlifters following 4 days supplementation
withl-arginine, l-orthinine and l-lysine. This
result was consistent with the findings of
Lambertet al. (1993), who reported that serum
growth hormone concentrations were not ele-
vated in male bodybuilders after the ingestion
of commercial amino acid supplements in the
quantities specified by the manufacturers. The
supplements of amino acids comprised two
mixtures: 2.4 g of arginine and lysine, and 1.85 g
of ornithine and tyrosine.
Fry and colleagues monitored both hormonal
and performance responses to amino acid sup-
plementation in parallel with high-volume train-
ing. In this study, 28 elite junior weightlifters
were tested for strength before and after 7 days of
high-volume training sessions. During this 7-day
training period, the subjects’ diets were supple-
mented with capsules containing either amino
acids (protein group) or lactose (placebo group).
The protein group took 2.4 g of amino acids (con-
taining a mixture of all 20 amino acids) immedi-
ately prior to their three daily meals for 7 days,
as well as 2.1 g of branched-chain amino acids
(l-leucine,l-isoleucine,l-valine, supplemented
withl-glutamine and l-carnitine), prior to each
training session. It was concluded that hormonal
responses, both at rest and following training,
were unaltered.
It is important to recognize that brief periods
of high-intensity exercise significantly increase
the concentration of growth hormone. Growth
hormone increased and remained approximately
10 times the basal value in sprint-trained
athletes, 1 h after a maximal 30-s sprint on a
non-motorized treadmill (Nevill et al. 1996). The
growth hormone response was greater in sprint-
trained than endurance-trained athletes, and no
differences were found between males and
females. Peak power output and the magnitude
of metabolic response to the sprint accounted
for 82% of the variation in serum peak growth
hormone response. Thus, sprint training per seis
effective in increasing growth hormone. Whether
or not sprinting could promote increases in IGF1
and IGF2 is unknown, but repeated eccentric
contractions have been shown to increase the

sprinting 545

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