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Op maandag 22 juni 2009 11:58 schreef leolinedance het volgende:[..]
Volgens verschillende tests die ik gelezen heb is het verschil in multivitaminen marginaal. Zeker wanneer je kijkt naar prijs-kwaliteit. Dit is dus niet gebaseerd op eigen kennis.
Waarom mag je geen multivitaminen slikken voor of na het sporten? Doe ik altijd wel...
Vitamins 'undo exercise efforts'
http://news.bbc.co.uk/2/hi/health/8043456.stmComplete studie hierzo >
Antioxidants prevent health-promoting effects
of physical exercise in humansVerder:
Moderate exercise is an antioxidant: upregulation of antioxidant genes by training.
Gomez-Cabrera MC, Domenech E, Viña J. Department of Physiology, Faculty of Medicine, University of Valencia, Blasco Ibañez, 15, 46010 Valencia, Spain.
Exercise causes oxidative stress only when exhaustive. Strenuous exercise causes oxidation of glutathione, release of cytosolic enzymes, and other signs of cell damage. However, there is increasing evidence that reactive oxygen species (ROS) not only are toxic but also play an important role in cell signaling and in the regulation of gene expression. Xanthine oxidase is involved in the generation of superoxide associated with exhaustive exercise. Allopurinol (an inhibitor of this enzyme) prevents muscle damage after exhaustive exercise, but also modifies cell signaling pathways associated with both moderate and exhaustive exercise in rats and humans. In gastrocnemius muscle from rats, exercise caused an activation of MAP kinases. This in turn activated the NF-kappaB pathway and consequently the expression of important enzymes associated with defense against ROS (superoxide dismutase) and adaptation to exercise (eNOS and iNOS). All these changes were abolished when ROS production was prevented by allopurinol. Thus ROS act as signals in exercise because decreasing their formation prevents activation of important signaling pathways that cause useful adaptations in cells. Because these signals result in an upregulation of powerful antioxidant enzymes, exercise itself can be considered an antioxidant. We have found that interfering with free radical metabolism with antioxidants may hamper useful adaptations to training.
Oral antioxidants and cardiovascular health in the exercise trained and untrained elderly: a radically different outcome.
Wray DW, Uberoi A, Lawrenson L, Bailey DM, Richardson RS. Both antioxidant supplementation and exercise training have been identified as interventions which may reduce oxidative stress and thus improve cardiovascular health, but the interaction of these interventions on arterial blood pressure and vascular function has not been studied in older humans. Thus, in six older (71 +/- 2 yrs) mildly hypertensive men, arterial blood pressure was evaluated non-invasively at rest and during small muscle mass (knee-extensor) exercise with and without a pharmacologic dose of oral antioxidants (Vitamins C, E, and alpha-lipoic acid). The efficacy of the antioxidant intervention to decrease plasma free radical concentration was verified via electron paramagnetic resonance (EPR) spectroscopy, while changes in endothelial function in response to exercise training and antioxidant administration were evaluated via flow-mediated vasodilation (FMD). Subjects were re-evaluated after a six-week aerobic exercise training program. Prior to training, acute antioxidant administration did not change resting arterial blood pressure or FMD. Six weeks of knee-extensor exercise training reduced systolic (from 150 +/- 8 to 138 +/- 3 mmHg, pre- vs. post-training) and diastolic (from 91 +/- 5 to 79 +/- 3 mmHg, pre- vs. post-training) blood pressure, and improved FMD (1.5 +/- 1% to 4.9 +/- 1%, pre- vs. post-training). However, antioxidant administration after exercise training negated these improvements, returning subjects to a hypertensive state and blunting training-induced improvements in FMD. The paradoxical effects of these interventions suggest a need for caution when exercise and acute antioxidant supplementation are combined in elderly, mildly hypertensive individuals.
Exercise-induced brachial artery vasodilation: role of free radicals.
Richardson RS, Donato AJ, Uberoi A, Wray DW, Lawrenson L, Nishiyama S, Bailey DM. Dept of Medicine, Physiology Division, Univ of California San Diego, La Jolla, CA 92093-0623, USA. rrichardson@ucsd.edu
Originally thought of as simply damaging or toxic "accidents" of in vivo chemistry, free radicals are becoming increasingly recognized as redox signaling molecules implicit in cellular homeostasis. Indeed, at the vascular level, it is plausible that oxidative stress plays a regulatory role in normal vascular function. Using electron paramagnetic resonance (EPR) spectroscopy, we sought to document the ability of an oral antioxidant cocktail (vitamins C, E, and alpha-lipoic acid) to reduce circulating free radicals, and we employed Doppler ultrasound to examine the consequence of an antioxidant-mediated reduction in oxidative stress on exercise-induced vasodilation. A total of 25 young (18-31 yr) healthy male subjects partook in these studies. EPR spectroscopy revealed a reduction in circulating free radicals following antioxidant administration at rest ( approximately 98%) and as a consequence of exercise ( approximately 85%). Plasma total antioxidant capacity and vitamin C both increased following the ingestion of the antioxidant cocktail, whereas vitamin E levels were not influenced by the ingestion of the antioxidants. Brachial artery vasodilation during submaximal forearm handgrip exercise was greater with the placebo (7.4 +/- 1.8%) than with the antioxidant cocktail (2.3 +/- 0.7%). These data document the efficacy of an oral antioxidant cocktail in reducing free radicals and suggest that, in a healthy state, the aggressive disruption of the delicate balance between pro- and antioxidant forces can negatively impact vascular function. These findings implicate an exercise-induced reliance upon pro-oxidant-stimulated vasodilation, thereby revealing an important and positive vascular role for free radicals.
Etc etc...
Ik pak dus geen extra anti-oxidanten op sportdagen. Het komt erop neer dat het bijslikken van extra anti-oxidanten de werking/respons van het eigen lichaam onderdrukt waardoor er een onderbreking van het herstelproces plaatsvindt. e.e.a. is natuurlijk niet 100% hard te maken. Maar verschillende studies wijzen erop dat dit effect wel degelijk optreedt.