and Sports Nutrition, Athletics, Endurance
effect of whey protein supplementation with and without creatine
monohydrate combined with resistance training on lean tissue mass
and muscle strength
Burke DG, Chilibeck PD, Davidson KS, Candow DG, Farthing
J, Smith-Palmer T. Department of Human Kinetics, St. Francis
Xavier University, Antigonish, Nova Scotia, B2G 2W5, Canada. [1:
Int J Sport Nutr Exerc Metab 2001 Sep;11(3):349-64] Males that
supplemented with whey protein while resistance training demonstrated
greater improvement in knee extension peak torque and lean tissue
mass than males engaged in training alone. Males that supplemented
with a combination of whey protein and creatine had greater increases
in lean tissue mass and bench press than those who supplemented
with only whey protein or placebo.
exercise intensity can be related to plasma glutathione levels
Gambelunghe C, Rossi R, Micheletti A, Mariucci G, Rufini S.
[J Physiol Biochem 2001 Mar;57(2):9-14] The aim of the present study
was to examine the effect of different kinds of physical exercise
on plasma glutathione levels. Our results suggest that GSH plays a
central antioxidant role in blood during intensive physical exercise
and that its modifications are closely related to exercise intensity.
antioxidant nutrients and the athlete
Packer L. [Department of Molecular and Cell Biology,
University of California, Berkeley 94720-3200, USA.] Strenuous
physical exercise induces oxidative stress. Severe or prolonged
exercise can overwhelm antioxidant defences, which include vitamins
E and C and thiol antioxidants, which are interlinked in an antioxidant
network, as well as antioxidant enzymes. Evidence for oxidative
stress and damage during exercise comes from direct measurement
of free radicals, from measurement of damage to lipids and DNA,
and from measurement of antioxidant redox status, especially glutathione.
There is little evidence that antioxidant supplementation can
improve performance, but a large body of work suggests that bolstering
antioxidant defences may ameliorate exercise-induced damage, suggesting
that the benefits of antioxidant intervention may be for the long
term rather than the short term.
and physical performance
Clarkson PM. Department of Exercise Science, University
of Massachusetts, Amherst 01003, USA.[Crit Rev Food Sci Nutr 1995
Jan;35(1-2):131-41] Performance of strenuous physical activity
can increase oxygen consumption by 10- to 15-fold over rest to
meet energy demands. The resulting elevated oxygen consumption
produces an "oxidative stress" that leads to the generation of
free radicals and lipid peroxidation. A defense system of free
radical scavengers minimizes these dangerous radicals. Changes
in antioxidant scavengers and associated enzymes (e.g., glutathione,
tocopherol, glutathione peroxidase) also provide clues about demands
on the defense system. Physical training has been shown to result
in an augmented antioxidant system and a reduction in lipid peroxidation.
Supplementation with antioxidants appears to reduce lipid peroxidation
but has not been shown to enhance exercise performance. The "weekend
athlete" may not have the augmented antioxidant defense system
produced through continued training. This may make them more susceptible
to oxidative stress. Whether athletes or recreational exercisers
should take antioxidant supplements remains controversial. However,
it is important that those who exercise regularly or occasionally
ingest foods rich in antioxidants.
changes in human muscle after prolonged exercise, endurance training
and selenium supplementation
Zamora AJ, Tessier F, Marconnet P, Margaritis I, Marini JF.
[Eur J Appl Physiol 1995;71(6):505-11] The functional and structural
responses to acute exercise (E) and training, (T) with or without
selenium supplementation (Sel), were investigated in a double-blind
study on 24 young male subjects. The results in Sel would seem to
suggest a dampening effect of the selenium on the mitochondria changes,
both in chronic and acute exercise. The mechanism of this action on
mitochondrial turnover is uncertain, but might be related to a higher
efficiency of the selenium-dependent enzyme glutathione peroxidase.
in blood glutamine concentration following intense exercise may contribute
to immune suppression in overtrained athletes
amino acid concentrations in the overtraining syndrome: Possible
effects on the immune system
Parry-Billings M, Budgett R, Koutedakis K et al
(1992). [Medicine and Science in Sports and Exercise 24,
1353-8] Overtraining and long-term exercise are associated
with an impairment of immune function. We provide evidence
in support of the hypothesis that the supply of glutamine,
a key fuel for cells of the immune system, is impaired in
these conditions and that this may contribute to immunosuppression.
Plasma glutamine concentration was decreased in overtrained
athletes and after long-term exercise (marathon race) and
was increased after short-term, high intensity exercise (sprinting).
Branched chain amino acid supplementation during long-term
exercise was shown to prevent this decrease in the plasma
glutamine level. Given the proposed importance of glutamine
for cells of the immune system, it is concluded that the decrease
in plasma glutamine concentration in overtraining and following
long-term exercise, and not an intrinsic defect in T lymphocyte
function, may contribute to the immune deficiency reported
in these conditions.
hazards from nutritional imbalance in athletes
Shephard RJ, Shek PN. [Exerc Immunol Rev 1998;4:22-48] This
review examines the influences of nutritional imbalance on immune
function of competitive athletes, who may adopt an unusual diet
in an attempt to enhance performance. Since endurance exercise
leads to protein catabolism, an athlete may need 2.0 g/kg protein
rather than the 0.7-1.0 g/kg recommended for a sedentary individual.
Both sustained exercise and overtraining reduce plasma glutamine
levels, which may contribute to suppressed immune function postexercise.
Vitamins are important to immune function because of their antioxidant
role. However, the clinical benefits of vitamin C supplementation
are not enhanced by the use of more complex vitamin mixtures,
and excessive vitamin E can have negative effects. Iron, selenium,
zinc, calcium, and magnesium ion all influence immune function.
Supplements may be required after heavy sweating, but an excessive
intake of iron facilitates bacterial growth.
exercise and immune function. Links and possible mechanisms
Walsh NP, Blannin AK, Robson PJ, Gleeson M. [Sports Med
1998 Sep;26(3):177-91] Glutamine is the most abundant free amino
acid in human muscle and plasma and is utilised at high rates
by rapidly dividing cells, including leucocytes, to provide energy
and optimal conditions for nucleotide biosynthesis. Falls in the
plasma glutamine level have been reported following endurance
events and prolonged exercise. These levels remain unchanged or
temporarily elevated after short term, high intensity exercise.
Plasma glutamine has also been reported to fall in patients with
untreated diabetes mellitus, in diet-induced metabolic acidosis
and in the recovery period following high intensity intermittent
exercise. Furthermore, athletes experiencing discomfort from the
overtraining syndrome exhibit lower resting levels of plasma glutamine
than active healthy controls. Therefore, physical activity directly
affects the availability of glutamine to the leucocytes and thus
may influence immune function.
endurance exercise impair glutamine metabolism?
Parry-Billings M, Blomstrand E, Leighton B et al (1990). Canadian
Journal of Sport Science 13, 13P (abstract)
glutamine changes after high intensity exercise in elite male
swimmers. Kargotich S, Rowbottom DG, Keast D et al (1996).
Medicine and Science in Sport and Exercise 28, S133 (abstract)
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