Singh, Harbindar Jeet
(2004)
The effects of tocotrienol supplementation on exercise-induced
lipid peroxidation and endurance performance in the heat.
Singh.
(Submitted)
Abstract
INTRODUCTION: The increase in oxygen consumption during endurance
exercise leads to free radical (FR) production and subsequent lipid peroxidation (LIPOX).
Raised body temperature has also been reported to increase the rate of FR production.
This oxidative stress may impair endurance performance since FRs can cause cell
damage and has been implicated in muscular fatigue. Vitamin E supplementation has
been shown to attenuate FR-induced LIPOX. It is however unclear if vitamin E
supplementation could decrease LIPOX and improve endurance running performance of
heat-adapted recreational athletes in the heat. PURPOSE: This study examined the
effects of tocotrienol (Palm Vitee) supplementation on exercise-induced LIPOX and
endurance performance in the heat. METHODS: 18 healthy, male recreational athletes
(aged: 24.9 ± 1.4 yrs; body weight: 59.6 ± 1.5 kg; V02max: 57.7 ± 1.5 ml.kg·1.min"1
)
completed two endurance running trials until exhaustion on a motorised treadmill at 70°/o
V02max on two separate occasions following a 6-week supplementation of either vitamin E
(E) or placebo (P). Both trials were conducted at an ambient temperature of 31°C and a
70°/o RH. During the trials, rectal temperature (T rec), skin temperature (Tsk). heart rate
(HR) and ratings of perceived exertion (RPE) were recorded at 1 0-min intervals while
oxygen uptake (V02) was recorded every 20 min. Blood samples were collected every
20 min during the running trials for the determination of plasma volume changes (PVC),
lactate (LAC), glucose (GLU), free fatty acid (FFA), triglyceride (TRI), malondialdehyde
(MDA), creatine kinase (CK), total antioxidant status (TAS) and vitamin E. RESULTS: No
significant differences were evident in T rec• T Skt HR. RPE, vo2 or in the time to exhaustion
between the E and P trials (81.1 ± 4.5 vs 76.9 ± 4.5 min respectively). Similarly, PVC,
CK, LAC, GLU, FFA, TRI and TAS were also not different between the two trials. Vitamin
E supplementation, however, resulted in a significantly higher (p<0.001) mean serum
vitamin E concentration at rest and during post-exercise compared to that in the placebo
tnal. Resting plasma MDA concentration in the E trial was significantly lower than that in
the P trial (0.38 vs 0.46 pmol.l" 1
; p<0.05). At exhaustion. plasma MDA was higher than
the resting values in both trials and it was higher in the P trial compared to the E trial
although the difference did not reach statistical significance (p=0.090). CK activity at
exhaustion, 1 h and 24 h post-exercise was not different during the two trials but was
significantly higher {p<0.001) than the corresponding resting values in both trials.
CONCLUSION: Vitamin E supplementation decreased lipid peroxidation at rest and, to
some extent, during exercise in the heat as evident from the lower MDA levels. It
however, does not enhance endurance running performance or prevent exercise-induced
muscle damage during exercise in the heat. In addition, vitamin E supplementation did
not influence the changes of some of the physiological parameters (e.g. PVC, LAC, GLU,
FFA, TRI, CK and TAS) that occurred during exercise in the heat.
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