improve prolonged aerobic endurance capacity.
Additionally, by decreasing the ratio of acetyl-
coenzyme A (CoA) to CoA and hence stimulating
the activity of pyruvate dehydrogenase, l-
carnitine supplementation may be theorized to
facilitate the oxidation of pyruvate. Such an
effect could reduce lactic acid accumulation and
improve anaerobic endurance exercise perfor-
mance (Wagenmakers 1991). On the other hand,
the increased oxidation of glucose could lead to
an earlier depletion of muscle glycogen and
impair performance, an ergolytic effect
(Wagenmakers 1991).
efficacy
Although l-carnitine supplementation will
increase plasma levels of carnitine, it has not
been shown to consistently increase muscle car-
nitine levels, the site of its action relative to the
use of FFA for energy production during exercise
(Wagenmakers 1991; Williams 1995). The data
are equivocal relative to the effects of l-carnitine
supplementation on the use of FFA during exer-
cise and V
.
o2max., with some studies providing
evidence of enhanced FFA utilization and
increased V
.
o2max.and other studies showing no
effect on energy metabolism (Kanter & Williams
1995; Williams 1995; Heinonen 1996). On the
other hand, research data clearly indicate that l-
carnitine supplementation does not affect lactic
acid accumulation in a fashion that may be con-
sidered to be ergogenic (Kanter & Williams 1995;
Williams 1995). Also, in general, in those studies
that included physical performance measures, l-
carnitine supplementation has not been shown
to enhance either aerobic or anaerobic exercise
performance (Kanter & Williams 1995; Williams
1995). However, research is needed to investigate
the potential ergogenic effects of chronic l-
carnitine supplementation on prolonged aerobic
endurance exercise tasks, such as marathon
running, to test the possibility of muscle glyco-
gen sparing and subsequent improved perfor-
mance. Colambani and others (1996) found that
acute supplementation of l-carnitine (2 g · 2 h–1
before the events) had no significant effect on
performance in either a marathon or a 20-km run,
but this dose may have been insufficient com-
pared to chronic supplementation protocols.safety
l-Carnitine appears to be safe in dosages utilized
in these studies, although large doses may cause
diarrhoea. Individuals should not use supple-
ments containing d-carnitine. The d-carnitine
isomer may impair the synthesis of l-carnitine
in the body leading to symptoms of l-carnitine
deficiency, including myopathy and muscular
weakness.Coenzyme Q 10theory
Coenzyme Q 10 (CoQ 10 ), a non-essential nutrient,
is a lipid with characteristics common to vita-
mins. It is located primarily in the mitochondria
of the cells, such as heart and muscle cells, and is
involved in the processing of oxygen for the pro-
duction of cellular energy. Increased processing
of oxygen could increase sport performance
in aerobic endurance events. CoQ 10 is also
an antioxidant. CoQ 10 is also referred to as
ubiquinone, or ubiquinone-10.efficacy
Bucci (1993) cites six studies showing beneficial
effects of CoQ 10 supplementation to various
subject populations, but these studies appeared
in the proceedings of a conference and do not
appear to have been published in peer-reviewed
journals. Moreover, each study suffered one or
more experimental design flaws, e.g. no control
group (Williams 1999).
A recent review of six well-controlled scientific
studies involving CoQ 10 supplementation (ª
70–150 mg · day–1for 4–8 weeks) either adminis-
tered separately or in combination with other
putative ergogenic nutrients, indicated that
although blood levels of CoQ 10 may be increased,
there was no effect on lipid peroxidation, sub-