Effects Of Vitamin E (Palm Vitee) Supplementation On Exercise-Induced Lipid Peroxidation And Endurance Performance In The Heat
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Date
2005-01
Authors
CHEE KEONG
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Abstract
The increase in oxygen consumption during endurance exercise
leads to free radical (FR) production and subsequent lipid peroxidation (LlPOX).
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 LlPOX. It is however
unclear if vitamin E supplementation could decrease LlPOX and improve endurance
running performance of heat-adapted recreational athletes in the heat. PURPOSE:
The first phase of this study examined the effects of exercise in the heat (H) and
thermoneutral (N) environments on endurance running performance and exerciseinduced
LlPOX while the second phase investigated the effects of vitamin E (Palm
Vitee) supplementation on exercise-induced L1POX and endurance performance in the
heat. METHODS: First phase - 17 healthy, male recreational athletes (aged: 25.8 ±
1.8 yrs; body weight: 59.1 ± 1.6 kg; V02max: 57.6 ± 1.8 mL.kg-1.min-1
) completed two
endurance running trials until exhaustion on a motorised treadmill at - 70% of V02max
at environmental temperatures of 31°C (H) and 25°C (N) with a relative humidity (RH)
of - 70% on two separate occasions. Second phase - 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% 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% RH. During the trials, rectal temperature (Tree), skin
temperature (Tsk) , heart rate (HR) and ratings of perceived exertion (RPE) were
recorded at 10-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), cholesterol and vitamin E. RESULTS: First phase -
Compared to the N trial, time to exhaustion was significantly (p<0.001) shorter in the H
trial (68.8 ± 3.1 vs 91.8 ± 4.3 min). Tree, Tsk , mean exercise HR, RPE, during the
course of the trial were significantly higher in the H trial. Tree at exhaustion was
significantly higher in the H trial than in the N trial (39.3 ± 0.1°C vs 38.8 ± 0.1°C;
p<0.001). Plasma volume reductions, GLU, LAC and FFA concentrations, particularly
towards the latter half of the trials, were significantly higher in the H trial (p<0.01). No
significant differences in V02, TRI and TAS were observed between trials. Plasma
MDA was significantly higher (p<0.05) at exhaustion compared to the resting level in
the H trial but this significance was lost when the data were adjusted for changes in
plasma volume. Plasma CK activity only increased slightly at exhaustion in both the
trials but no statistically significant difference was evident between the two trials.
However, at 24 h post-exercise, CK activity was significantly (p<0.01) higher than the
resting values in both the trials. Second phase - No significant differences were
evident in Tree, Tsk, HR, RPE, V02 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 trial. Resting plasma MDA concentration in the E trial was significantly lower
than that in the P trial (0.38 vs 0.46 J.lmoI.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=O.090). CK activity at exhaustion, 1 hand 24 h post-exercise was not different
during the two trials but was significantly higher (p<O.001) than the corresponding
resting values in both trials. CONCLUSION: These results reveal that for a given
workload there was a greater thermoregulatory stress in the H trial. Endurance
performance in heat (31°C) was reduced by 25% when compared to performance in a
thermoneutral environment (25°C). As the levels of plasma MDA increased at
exhaustion compared to the corresponding resting values in both trials, there was a
possibility that FRs could have contributed to fatigue at the end of both endurance
running trials in the first phase. However, as the levels of MDA was not significantly
different between trials, the role of FRs during endurance exercise in the heat and
fatigue remains unclear and need further investigation. 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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Keywords
Effects Of Vitamin E (Palm Vitee) Supplementation On Exercise-Induced Lipid Peroxidation , And Endurance Performance In The Heat