Nutrients and Muscle Injury
521
muscle injury are included. Therefore, readers are
the topic for a more detailed understanding of the
cautioned that the data presented apply specifically
processes involved.
[1-4,6]
to resistance exercise. It is possible that the positive
It is clear from the available evidence that strenu-
or negative findings for a given nutrient may have
ous, unaccustomed exercise, typically involving ec-
differing results when applied in the context of
centric actions in which the muscle is actively
aerobic exercise. However, a review of the literature
lengthened, damages muscle in a fibre-specific man-
on this topic concludes that results obtained from
ner (e.g. the actively engaged fibres are damaged,
studies using nutritional supplements (primarily an-
with selective sarcomeres being targets of dam-
tioxidants) to attenuate muscle injury resulting from
age
[4]
). While both type 1 (slow) and type 2 (fast)
aerobic exercise have been mixed, with potential
fibres experience injury, there appears to be a type 2
noted for vitamin E (tocopherol) to stabilise muscle
fibre bias, as demonstrated previously in animals.
[11]
cell membranes resulting in lower creatine kinase
It is believed that the eccentric muscle actions in-
(CK) release into the circulation.
[10]
Readers inter-
volve fewer motor units, less muscle fibre involve-
ested in the role of nutrients to minimise muscle
ment and greater force production. In this way, more
injury resulting from aerobic exercise are referred to
stress is placed on the engaged fibres, leading to
Goldfarb.
[10]
damage. Higher training intensity, an increase in
While aerobic exercise certainly has the ability to
angular velocity, longer duration of eccentric ac-
cause muscle damage (often measured by muscle
tions and longer fibre lengths as they are subjected
protein release into the blood), the extent of damage
to the stress
[12]
contribute to greater injury. It ap-
with lower intensity, longer duration aerobic exer-
pears that the initial mechanical insult produces
cise is often less than with higher intensity heavy
damage that occurs rapidly (i.e. within 15 min-
resistance exercise, as used in the studies presented
utes
[13]
) and sporadically throughout the fibre (i.e.
here. Including only those studies utilising heavy
focal injury). This initial mechanical trauma gives
resistance exercise allows for the study pool to re-
rise to a host of biochemical changes within the
main more homogeneous, without extrapolating
affected area, which may lead to increased genera-
findings from one form of exercise to another, per-
tion of inflammatory cytokines and reactive oxygen
haps allowing for more specific conclusions to be
species (ROS) that may further degrade muscle pro-
drawn. This article includes a brief discussion of the
teins and contribute to delayed injury.
proposed mechanism(s) of action of those nutrients
Both direct and indirect markers of muscle fibre
for which data are presently available in relation to
injury often accompany the damage. These include
attenuating muscle injury resulting from resistance
direct markers of tissue damage (e.g. cytoskeleton
exercise, in addition to the specific findings from
disruption and/or magnetic resonance imaging
peer-reviewed research articles. The review con-
[MRI] of the affected muscle), in addition to multi-
cludes with a synopsis of the current state of knowl-
ple indirect markers including: delayed-onset mus-
edge related to the role of nutritional supplements in
cle soreness (DOMS), decreased muscle force (both
attenuating resistance exercise-induced muscle inju-
isometric and dynamic) and decreased range of mo-
ry.
tion (ROM), increased muscle girth (probably medi-
ated by inflammation), increased urinary markers of
1. Skeletal Muscle Injury
protein degradation (e.g. 3-methylhistidine
[3-MH]), increased blood markers of muscle cell
In order to fully understand the methods of action
membrane disruption (CK and lactate
of the nutritional supplements in attenuating signs
dehydrogenase [LDH]) and increased inflammatory
and symptoms of muscle injury, as well as their
biomarkers (C-reactive protein and interleukin-6
limitations to do so, it is first necessary to briefly
[IL-6]). Related to these markers, the time course of
describe the process of skeletal muscle injury. Read-
peak change varies greatly from one to another.
ers are referred to the following excellent reviews on
©
2007 Adis Data Information BV. All rights reserved.
Sports Med 2007; 37 (6)
Study 