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Mitchell M. Kanter

Free radicals have been implicated in the development of diverse diseases such as cancer, diabetes, and cataracts, and recent epidemic-logical data suggest an inverse relationship between antioxidant intake and cardiovascular disease risk. Data also suggest that antioxidants may delay aging, Research has indicated that free radical production and subsequent lipid peroxidation are normal sequelae to the rise in oxygen consumption with exercise. Consequently, antioxidant supplementation may detoxify the peroxides produced during exercise and diminish muscle damage and soreness. Vitamin E, beta carotene, and vitamin C have shown promise as protective antioxidants. Other ingestible products with antioxidant properties include selenium and coenzyme Q10. The role (if any) that free radicals play in the development of exercise-induced tissue damage, or the protective role that antioxidants may play, remains to be elucidated. Current methods used to assess exercise-induced lipid peroxidation are not extremely specific or sensitive; research that utilizes more sophisticated methodologies should help to answer many questions regarding dietary antioxidants.

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Paul Grace

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Luciano A. Silva, Paulo C.L Silveira, Cléber A. Pinho, Talita Tuon, Felipe Dal Pizzol and Ricardo A. Pinho

The objective of the study was to verify the effect of N-acetylcysteine (NAC) supplementation on parameters of oxidative damage and inflammatory response after high-intensity eccentric exercise (EE). 29 participants with a mean age of 21.3 ± 4 yr, weight of 74.5 ± 7.7 kg, and height of 177.2 ± 6.9 cm were selected and divided randomly into 3 groups: placebo (21 days; n = 8), NAC (21 days; n = 9), and NAC plus placebo (14 days; n = 8). Four participants withdrew from the study for personal reasons. 14 days after starting supplementation, the participants performed EE: 3 sets until exhaustion (elbow flexion and extension on the Scott bench, 80% 1RM). Blood samples were collected before and on the 2nd, 4th, and 7th day after EE. Muscle soreness (MS), lipoperoxidation, protein carbonylation, tumor-necrosis factor-cc(TNF-(), and interleukin 10 (IL-10) were determined. Results showed a significant increase in MS in all the groups on the 2nd day after EE and a decrease in the following days. A significant increase was observed in malondialdehyde and carbonyl levels on the 4th and 7th days after EE in all groups. TNF-EEincreased significantly on the 2nd day after eccentric exercise and decreased in the following days irrespective of NAC supplementation; concentration of IL-10 increased significantly on the 4th day in all groups. Only the supplemented groups maintained high levels of IL-10 on the 7th day after EE. The results suggest that treatment with NAC represents an important factor in the defense against muscle soreness and has different effects on oxidative damage and pro- and anti-inflammatory cytokines.

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James N. Cobley, Chris McGlory, James P. Morton and Graeme L. Close

Production of reactive oxygen species (ROS) during muscle contractions is associated with muscle fatigue and damage in the short term and adaptive responses in the long term. When adaptation is inconsequential acute antioxidant supplementation may be able to attenuate muscle fatigue and damage to enhance performance. This study aimed to determine the effects of acute oral N-acetylcysteine (NAC) supplementation on Yo-Yo Intermittent Recovery Test Level 1 (YIRT-L1) performance after repeated bouts of damaging intermittent exercise. In a pair-matched design, 12 recreationally trained men engaged in 6 d of either NAC (n = 6) or placebo (n = 6) supplementation. After a treatment-loading day, participants completed 3 testing sessions, on alternating days, consisting of a preexercise isokinetic dynamometry (IKD) test, a damaging intermittent-exercise protocol, YIRT-L1, and a postexercise IKD test. Another IKD test was completed on the 2 intervening d. NAC treatment resulted in a significant preservation of YIRT-L1 performance (p ≤ .0005). IKD performance significantly deteriorated over time at all contraction speeds, and this deterioration was not influenced by treatment group. Plasma creatine kinase values increased significantly over time (p = .002) and were significantly greater in the NAC group than in the placebo group (p = .029). NAC induced mild gastrointestinal side effects. NAC supplementation may be a useful strategy to enhance performance during short-term competitive situations when adaption is inconsequential. Titration studies to elucidate a treatment dose that enhances performance without inducing side effects are now required.

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Robert R. Jenkins

Elemental and gaseous oxygen presents a conundrum in that it is simultaneously essential for and potentially destructive to human life. Traditionally the ability to consume large volumes of oxygen has been assumed to be totally beneficial to the organism. In the past 10 years it has become clear that oxygen radicals are generated even during normal resting metabolism Nevertheless, such radicals are usually of no appreciable threat since a wide array of protective biochemical systems exist. However, under certain circumstances aerobic exercise may increase free radical production to a level that overwhelms those defenses. A broad array of nutrients such as vitamin C, vitamin E, p-carotene, and so forth are known to suppress such radical events. This paper reviews the status of our knowledge relative to the potential benefits of nutritional modification in augmenting the organism's normal defense against harmful radical chemistry.

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Mitchell M. Kanter and Melvin H. Williams

Three nutritional products that have very different mechanisms of action are antioxidant vitamins, carnitine, and choline. Antioxidant vitamins do not appear to have a direct effect on physical performance in well-fed people but have been touted for their ability to detoxify potentially damaging free radicals produced during exercise. Carnitine purportedly enhances lipid oxidation, increases VO2max, and decreases plasma lactate accumulation during exercise. However, studies of carnitine do not generally support its use for ergogenic purposes. Choline supplements have been advocated as a means of preventing the decline in acetylcholine production purported to occur during exercise; this decline may reduce the transmission of contraction-generating impulses across the skeletal muscle, an effect that could impair one’s ability to perform muscular work. However, there are no definitive studies in humans that justify choline supplementation. Much of the scientific data regarding the aforementioned nutrients are equivocal and contradictory. Their potential efficacy for improving physical performance remains largely theoretical.

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Theodore Tsakiris, Panagoula Angelogianni, Christine Tesseromatis, Stylianos Tsakiris and Kleopatra H. Schulpis

Background:

Forced exercise is associated with oxidative stress, and L-cysteine (L-cys) administration reduces free-radical production.

Aim:

To investigate whether L-cys (5 mg/kg) intraperitoneal administration can ameliorate modulated total antioxidant status (TAS), protein concentration, and the activities of acetylcholinesterase (AChE), (Na+,K+)-ATPase, and Mg2+-ATPase in rat brain after 2 and 3 hr of forced swimming.

Methods:

TAS, protein, and enzyme activities were measured spectrophotometrically before and after 2 and 3 hr of exercise without or with L-cys administration.

Results:

TAS concentration (55.6 ± 1.5 vs. 42.1 ± 1.0 vs. 37.4 ± 1.2 μmol/L, p < .001), protein concentration (5.68 ± 0.36 vs. 5.40 ± 0.18 vs. 4.01 ± 0.16 mg/ml, p < .01), and AChE activity (0.89 ± 0.05 vs. 0.61 ± 0.04 vs. 0.48 ± 0.03 ΔOD/min × mg protein, p < .001) were significantly reduced, whereas Na+,K+-ATPase (6.00 ± 0.36 vs. 10.44 ± 1.04 vs. 11.90 ± 1.21 µmol phosphorus inorganic/hr × mg protein, p < .001) and Mg2+-ATPase activity (7.20 ± 0.65 vs. 10.88 ± 1.08 vs. 11.55 ± 1.22 µmol phosphorus inorganic/hr × mg protein, p < .001) were statistically significantly increased after 2 and 3 hr of forced exercise. Post-L-cys administration, AChE activity was decreased (0.90 ± 0.04 vs. 0.47 ± 0.02 ΔOD/min × mg protein, p < .001) and remained unaltered (0.64 ± 0.04 vs. 0.67 ± 0.04 ΔOD/min × mg protein, p > .05) 2 and 3 hr postexercise (0.47 ± 0.02 vs. 0.54 ± 0.02 ΔOD/min × mg protein, p > .05). Na+,K+-ATPase was decreased and remained unchanged (1.85 ± 0.17 vs. 1.77 ± 0.19 µmol phosphorus inorganic/hr × mg protein, p > .05) 2 and 3 hr postswimming (1.91 ± 0.19 vs. 2.06 ±0.17 µmol phosphorus inorganic/hr × mg protein, p > .05). Mg2+-ATPase activity was similar with L-cys supplementation pre- vs. postswimming.

Conclusions:

L-cys administration might ameliorate modulated rat brain enzyme activities induced by free-radical production during forced swimming.

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Gulshanara Begum, Adam Cunliffe and Michael Leveritt

High-intensity exercise leads to reductions in muscle substrates (ATP, PCr, and glycogen) and a subsequent accumulation of metabolites (ADP, Pi, H+, and Mg2+) with a possible increase in free radical production. These factors independently and collectively have deleterious effects on muscle, with significant repercussions on high-intensity performance or training sessions. The effect of carnosine on overcoming muscle fatigue appears to be related to its ability to buffer the increased H+ concentration following high-intensity work. Carnosine, however, has other roles such as an antioxidant, a metal chelator, a Ca2+ and enzyme regulator, an inhibitor of protein glycosylation and protein-protein cross-linking. To date, only 1 study has investigated the effects of carnosine supplementation (not in pure form) on exercise performance in human subjects and found no improvement in repetitive high-intensity work. Much data has come from in vitro work on animal skeletal muscle fibers or other components of muscle contractile mechanisms. Thus further research needs to be carried out on humans to provide additional understanding on the effects of carnosine in vivo.

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Kamal Azizbeigi, Mohammad Ali Azarbayjani, Maghsoud Peeri, Hamid Agha-alinejad and Stephen Stannard

This study was undertaken to investigate the effects of progressive resistance-training (PRT) on plasma oxidative stress and antioxidant enzyme activity in erythrocytes. Twenty male volunteers were randomly assigned to 2 groups: PRT and control. Blood samples were collected before and after 8 wk of PRT and analyzed for enzymatic activities of superoxide dismutase (SOD) and glutathione peroxidase (GPx) in erythrocytes, plasma total antioxidant capacity (TAC), and malondialdehyde concentration (MDA, an index of lipid per oxidation in plasma). Resistance training commenced with 8 exercises on nonconsecutive days for 8 wk at 50% of estimated 1-repetition maximum (E1RM) and reached 80% E1RM by Week 8. The results showed that PRT significantly increased erythrocyte SOD activity (1,323 ± 212.52 vs. 1,449.9 ± 173.8 U/g Hb, p = .014). Plasma concentration of MDA also decreased (5.39 ± 1.7 vs. 3.67.4 ± 0.7 nmol/ml, p = .030), although TAC (1.42 ± 0.21 vs. 1.61 ± 0.19 mmol/L, p = .1530) and GPx (39.87 ± 11.5 vs. 48.18 ± 14.48 U/g Hb, p = .883) activity did not undergo any considerable changes. Based on these data, the authors conclude that an 8-wk program of PRT strengthens the defensive system of erythrocytes against free-radical damage and therefore can be applied as a useful approach to alleviate oxidative stress.