catabolic, effect of HMB supplementation. In one
study, HMB supplementation (1.5 or 3.0 g ·
day–1), in a dose–response manner, induced sig-
nificant improvements in lean body mass and
muscle strength in untrained men over a 3-week
period (Nissen et al. 1996b). In two other studies,
HMB supplementation (3 g · day–1) increased
strength in physically active males in the 1-
repetition maximal bench press (Nissen et al.
1996b) and decreased body fat and increased
lean body mass and bench press strength in both
trained and untrained subjects over a 4-week
period of resistance training (Nissen et al.
1996a).
Although these preliminary findings are
impressive, replication from other laboratories
is needed. Additionally, each study included
several threats to internal validity, including the
use of unorthodox measures of muscle strength
or absence of a true placebo, and in tests of multi-
ple dependent variables, such as multiple meas-
ures of strength, HMB benefited performance in
some tests, but not all.
safety
Studies in humans at doses of 1.5–3.0 g · day–1for
several weeks have reported no acute adverse
effects. Chronic supplementation has not evi-
denced adverse effects in animals, but no data
appear to be available for humans.
Herbal products
theory
Numerous herbal products have been marketed
as potential ergogenics for physically active indi-
viduals. Three such products have been mar-
keted as bodybuilding supplements as a means
to enhance muscle size and strength: g-oryzanol,
a ferulic acid ester derived from rice bran
oil; yohimbine (yohimbe), a nitrogen-containing
alkaloid from the bark of the yohimbe tree; and
smilax, an extract of phytosterols from the dried
roots of Smilax officinalisor various forms of sar-
saparilla. Advertisers theorize that these herbal
products contain the male hormone testosterone
or stimulate its endogenous production, thus
inducing increases in muscle size and strength.efficacy
A scientific literature review revealed no research
to validate the claims made by the manufacturers
that g-oryzanol, smilax or yohimbine either
raise serum testosterone levels or induce gains in
muscle size or strength, confirming the findings
of previous scientific reviews (Wheeler & Garleb
1991; Grunewald & Bailey 1993). Wheeler and
Garleb (1991) speculated that g-oryzanol might
actually decrease serum testosterone. Well-
controlled research with these herbal products,
and other plant-derived purported ergogenics
such as dehydroepiandrosterone (DHEA), is
limited, but that which is available does not sub-
stantiate advertising claims. For example, Fry
and others (1997) recently reported that g-
oryzanol supplementation (500 mg · day–1for 9
weeks), in comparison to a placebo condition,
did not increase circulating concentrations of
testosterone or improve 1-repetition maximum
muscular strength in the bench press or squat
exercise.safety
Although herbal dietary supplements may be
safe, most lack appropriate safety data. Some
preparations have been reported to cause
various health problems, including anaphylactic
reactions.Aerobic endurance sport tasks
Phosphorus (phosphates)theory
Dietary phosphates, the source of the essential
nutrient phosphorus, are incorporated into
many compounds in the body that are involved
in energy metabolism, such as ATP as an energy
substrate, thiamin pyrophosphate as a vitamin
cofactor, sodium phosphate as a buffer, and 2,3-
diphosphoglycerate (2,3-DPG) for red blood cell