Nutrients and Muscle Injury
525
age to cellular components related to muscle func-
free iron, which could have reacted with the vitamin
tion (e.g. structure proteins and contractile pro-
C to form the ascorbate radical and Fe
2+
, ultimately
teins).
[39]
In this study, individuals performed 15
reacting with hydrogen peroxide to form the highly
minutes of cyclic (i.e. 15 seconds on and 15 seconds
reactive hydroxyl radical. The hydroxyl radical is
off) isotonic plantar flexion exercise. DOMS was
known to react with membrane lipids, promoting the
measured using a 10cm visual analogue scale. Indi-
chain reaction sequence of lipid peroxidation, lead-
viduals recorded their muscle soreness before and
ing to impaired membrane integrity.
[40]
This may
for up to 96 hours post-exercise. DOMS was noted
help to explain the findings of increased enzyme
to be lower in the vitamin C group at the 48-, 58- and
release from within the muscle. Unlike the Kamin-
72-hour timepoints, with the greatest difference ob-
sky and Boal
[21]
study, the antioxidant treatment in
served at the 58-hour timepoint (e.g. individuals
this investigation was administered after the eccen-
receiving placebo reported a mean rating of 6.3/10
tric exercise. This suggests that prophylactic use of
while individuals receiving vitamin C reported a
vitamin C may have greater protective properties
mean rating of 3.5/10). While these findings were of
than intake following the insult. The timing of sup-
statistical significance, it should be noted that a high
plementation in relation to the exercise bout needs to
degree of variability existed among individuals with
be considered in future research.
regard to DOMS attenuation with vitamin C treat-
Neither of these investigations measured muscle
ment, indicating that some individuals were `re-
performance, which has been suggested to best re-
sponders' while others were `non-responders'.
present the extent of muscle damage following exer-
Therefore, caution is advised when interpreting
cise.
[41]
Therefore, it is presently unknown whether
these data.
or not vitamin C supplementation alone can
favourably alter muscle performance characteristics.
The findings of Kaminsky and Boal
[21]
differ
Whether moderate- to high-dose vitamin C would
from those of Childs et al.
[19]
In this investigation, 14
have a beneficial or detrimental use in a practical
untrained men ingested either a placebo drink mix or
setting, where muscle force decrements may be of
a drink mix containing 12.5mg of vitamin C and
greatest concern, remains to be determined.
10mg of the antioxidant N-acetyl-cysteine per kilo-
gram of body mass immediately after exercise and
Aside from vitamin C supplementation, other
each day following exercise for 7 days, in a double-
investigations have focused on the role of vitamin E
blind design. The dosage of vitamin C used was
in attenuating exercise-induced muscle injury. The
roughly one-third of the amount used in the Kamin-
proposed mechanism of action of vitamin E appears
sky and Boal
[21]
study. The exercise protocol includ-
to be sarcolemma stabilisation, while functioning as
ed three sets of ten repetitions performed at 80% of
a chain-breaking antioxidant to inhibit lipid perox-
the individuals' eccentric one-repetition maximum
idation owing to ROS generation. Beaton et al.
[16]
with the elbow flexors. While certain antioxidant
supplemented individuals with either placebo or
enzymes (e.g. superoxide dismutase and glutathione
1200 IU/day of vitamin E for 30 days prior to
peroxidase) were higher with the antioxidant treat-
performing 24 sets of ten repetitions of knee flexion/
ment, no difference was noted in DOMS between
extension exercise, in a double-blind manner. Both
conditions. Neither ROM nor IL-6 were affected by
direct and indirect markers of muscle damage were
the antioxidant treatment. The two most commonly
assessed before and through 7 days of exercise re-
used markers of sarcolemma integrity, CK and
covery. With the exception of a lower CK activity at
LDH, were higher in individuals in the antioxidant
3 days following exercise, vitamin E supplementa-
treatment group, suggesting that supplementation
tion had no effect on any measured variable, includ-
might have exacerbated the damage response.
ing the direct assessment of tissue damage, cytos-
keletal disruption. Moreover, vitamin E did not af-
It is possible that the damaging nature of the
fect muscle force. It is possible that the extreme
eccentric exercise could have led to an increase in
©
2007 Adis Data Information BV. All rights reserved.
Sports Med 2007; 37 (6)
Study 