Physical training and fasting erythrocyte activities of free radical scavenging enzyme systems in sedentary men

Antioxidants Markers of Professional Soccer Players During the Season and their Relationship with Competitive Performance

The aim of this study was to assess antioxidant markers before and after a mid-season of professional soccer players from the 3^rd Spanish Division, and to correlate antioxidant markers with competitive performance. Sixty-five male players (age = 25.3 ± 4.2 yr, body mass = 73.2 ± 6.7 kg, body height = 177.8 ± 5.7 cm) from three soccer clubs from Cádiz (Spain) participated in the study. Body composition, maximal aerobic capacity (VO_2max), and baseline antioxidant blood markers (Total Antioxidant Status (TAS) and Reduced glutathione/Oxidized glutathione ratio) were assessed in the first week of the championship season (pre-test) and after 18 weeks in the mid-season (post-test). Soccer performance was registered according to the official classification ranking at both the mid-season and at the end of the season; ranking positions for Team A were 2^nd and 1^st, for Team B were 5^th and 5^th, while for Team C were 12^th and 14^th, respectively. Regression analyses showed that TAS and VO_2max were able to independently predict (p < 0.05) performance in our participants. Moreover, antioxidant levels showed significant main effects on performance (p < 0.001); where a higher antioxidant capacity was observed in the best performance soccer team, both before and after the mid-season. Notwithstanding, the competitive period compromised the antioxidant status since TAS levels significantly decreased after the 18-week training program and competition compared with baseline values in all soccer teams (p < 0.001). These results suggest the need of monitoring antioxidants in soccer players to prevent excessive oxidative stress and cellular damage which could compromise success in competition, by adjusting the training loads, diet or ergogenic aids, if needed.

The Effect of a Single Bout of Exercise on Vitamin B2 Status Is Not Different between High- and Low-Fit Females

High-fitness individuals have been suggested to be at risk of a poor vitamin B2 (riboflavin) status due to a potentially higher vitamin B2 demand, as measured by the erythrocyte glutathione reductase (EGR) activation coefficient (EGRAC). Longer-term exercise interventions have been shown to result in a lower vitamin B2 status, but studies are contradictory. Short-term exercise effects potentially contribute to discrepancies between studies but have only been tested in limited study populations. This study investigated if vitamin B2 status, measured by EGRAC, is affected by a single exercise bout in females who differ in fitness levels, and that represents long-term physical activity. At baseline and overnight after a 60-min cycling bout at 70% V·O₂peak, EGR activity and EGRAC were measured in 31 young female adults, divided into a high-fit (V·O₂peak ≥ 47 mL/kg/min, N = 15) and low-fit (V·O₂peak ≤ 37 mL/kg/min, N = 16) group. A single exercise bout significantly increased EGR activity in high-fit and low-fit females (P_time = 0.006). This response was not affected by fitness level (P_time*group = 0.256). The effect of exercise on EGRAC was not significant (P_time = 0.079) and not influenced by EGR activity. The exercise response of EGRAC was not significantly different between high-fit and low-fit females (P_time*group = 0.141). Thus, a single exercise bout increased EGR activity, but did not affect EGRAC, indicating that vitamin B2 status was not affected. The exercise response on EGRAC and EGR did not differ between high-fit and low-fit females.

General, 21-Day Postoperative Rehabilitation Program Has Beneficial Effect on Oxidative Stress Markers in Patients after Total Hip or Knee Replacement

Imbalance in prooxidant-antioxidant equilibrium plays an important role in the progression of osteoarthritis (OA). Postoperative rehabilitation significantly improves the functional activity of patients with OA. We aimed to assess the effect of the general 21-day postoperative rehabilitation on the oxidative stress markers in patients after total hip arthroplasty or knee replacement. Patients (n =41) started individually designed postoperative rehabilitation ca. 90 days after endoprosthesis implantation. We used the six-minute walk test (6MWT) to quantify the changes in their exercise capacity. We analyzed the oxidative stress markers: total antioxidant capacity (TAC), total superoxide dismutase (SOD), Cu-Zn-superoxide dismutase (CuZnSOD) and ceruloplasmin (Cp) activity, malondialdehyde (MDA) and lipofuscin (LPS) concentration in patients serum to asses changes in the oxidative stress intensity. We found that after 21-days postoperative rehabilitation program: the average distance walked by patients increased by 69 m; TAC increased by 0.20 ± 0.14 mmol/l; both SOD isoforms activities increased by 1.6 (±1.7) and 1.72 (±1.5) NU/ml, respectively; but Cp activity decreased by 1.8 (0.7-3.7) mg/dl. Also, we observed lower concentrations of lipid peroxidation markers: by 19.6 ± 24.4 μmol/l for MDA and by 0.4 ± 0.5 RF for LPS. A 21-day postoperative rehabilitation program effectively reduces oxidative processes, which helps the patients after total hip or knee replacement in a successful recovery.

Effect of physical activity on severity of primary angle closure glaucoma

Objective:

To determine the association between physical activity and severity of primary angle closure glaucoma in Malay patients.

Methods:

A cross-sectional study was conducted involving 150 primary angle closure glaucoma patients between April 2014 and August 2016. Using the International Physical Activity Questionnaire, the physical activity status was assessed and divided into three categories: mild, moderate and heavy physical activity. The duration of physical activity and corresponding minimum energy requirements were calculated. Ocular examination was performed including Humphrey visual field 24-2 analysis assessment. Based on two consecutive reliable Humphrey visual fields, the severity of glaucoma was scored according to modified Advanced Glaucoma Intervention Study and classified as mild (0–5), moderate (6–11) and severe (12–20). Association between physical activity and Advanced Glaucoma Intervention Study score was determined with multiple linear regression analysis.

Results:

A total of 150 Malay patients with primary angle closure glaucoma were included (50 patients with mild, 50 with moderate and 50 with severe glaucoma). Physical activity showed inverse association with the severity of primary angle closure glaucoma. After calculating adjustments for age, sex, duration of glaucoma, body mass index, systemic co-morbidities, family history of glaucoma, myopia and educational status [adjusted b –3.41, 95% confidence interval (–5.23, –1.59), p < 0.001], there was also an inverse relationship with Advanced Glaucoma Intervention Study score. Every increase in physical activity level reduces the Advanced Glaucoma Intervention Study score by 3.4 point.

Conclusion:

Physical activity is the potential modifiable risk factor in reducing the severity of glaucoma among primary angle closure glaucoma patients. However, there is possibility of the severity of glaucoma restricted the physical activity of primary angle closure glaucoma patients.

Enhanced erythrocyte antioxidant status following an 8-week aerobic exercise training program in heavy drinkers

Alcohol-induced oxidative stress is involved in the development and progression of various pathological conditions and diseases. On the other hand, exercise training has been shown to improve redox status, thus attenuating oxidative stress-associated disease processes. The purpose of the present study was to evaluate the effect of an exercise training program that has been previously reported to decrease alcohol consumption on blood redox status in heavy drinkers. In a non-randomized within-subject design, 11 sedentary, heavily drinking men (age: 30.3 ± 3.5 years; BMI: 28.4 ± 0.86 kg/m²) participated first in a control condition for 4 weeks, and then in an intervention where they completed an 8-week supervised aerobic training program of moderate intensity (50-60% of the heart rate reserve). Blood samples were collected in the control condition (pre-, post-control) as well as before, during (week 4 of the training program), and after intervention (week 8 of the training program). Samples were analyzed for total antioxidant capacity (TAC), thiobarbituric acid reactive substances (TBARS), protein carbonyls (PC), uric acid (UA), bilirubin, reduced glutathione (GSH), and catalase activity. No significant change in indices of redox status in the pre- and post-control was observed. Catalase activity increased (p < 0.05) after 8 weeks of intervention compared to week 4. GSH increased (p < 0.05) after 8 weeks of intervention compared to the control condition and to week 4 of intervention. TAC, UA, bilirubin, TBARS, and PC did not significantly change at any time point. Moreover, concentrations of GSH, TBARS, and catalase activity negatively correlated with alcohol consumption. In conclusion, an 8-week aerobic training program enhanced erythrocyte antioxidant status in heavy drinkers, indicating that aerobic training may attenuate pathological processes caused by alcohol-induced oxidative stress.

Beneficial effects of an intradialytic cycling training program in patients with end-stage kidney disease

In chronic kidney disease (CKD), oxidative stress (OS) plays a central role in the development of cardiovascular diseases. This pilot program aimed to determine whether an intradialytic aerobic cycling training protocol, by increasing physical fitness, could reduce OS and improve other CKD-related disorders such as altered body composition and lipid profile. Eighteen hemodialysis patients were randomly assigned to either an intradialytic training (cycling: 30 min, 55%–60% peak power, 3 days/week) group (EX; n = 8) or a control group (CON; n = 10) for 3 months. Body composition (from dual-energy X-ray absorptiometry), physical fitness (peak oxygen uptake and the 6-minute walk test (6MWT)), lipid profile (triglycerides (TG), total cholesterol, high-density lipoprotein, and low-density lipoprotein (LDL)), and pro/antioxidant status (15-F2α-isoprostanes (F2-IsoP) and oxidized LDL in plasma; superoxide dismutase, glutathione peroxidase, and reduced/oxidized glutathione in erythrocytes) were determined at baseline and 3 months later. The intradialytic training protocol did not modify body composition but had significant effects on physical fitness, lipid profile, and pro/antioxidant status. Indeed, at 3 months: (i) performance on the 6MWT was increased in EX (+23.4%, p < 0.001) but did not change in CON, (ii) plasma TG were reduced in EX (–23%, p < 0.03) but were not modified in CON, and (iii) plasma F2-IsoP concentrations were lower in EX than in CON (–35.7%, p = 0.02). In conclusion, our results show that 30 min of intradialytic training, 3 times per week for 3 months, are enough to exert beneficial effects on the most sensitive and reliable marker of lipid peroxidation (IsoP) while improving CKD-associated disorders (lipid profile and physical fitness). Intradialytic aerobic cycling training represents a useful and easy strategy to reduce CKD-associated disorders. These results need to be confirmed with a larger randomized study.

Age-related responses in circulating markers of redox status in healthy adolescents and adults during the course of a training macrocycle

Redox status changes during an annual training cycle in young and adult track and field athletes and possible differences between the two age groups were assessed. Forty-six individuals (24 children and 22 adults) were assigned to four groups: trained adolescents, (TAD, N = 13), untrained adolescents (UAD, N = 11), trained adults (TA, N = 12), and untrained adults (UA, N = 10). Aerobic capacity and redox status related variables [total antioxidant capacity (TAC), glutathione (GSH), catalase activity, TBARS, protein carbonyls (PC), uric acid, and bilirubin] were assessed at rest and in response to a time-trial bout before training, at mid- and posttraining. TAC, catalase activity, TBARS, PC, uric acid, and bilirubin increased and GSH declined in all groups in response to acute exercise independent of training status and age. Training improved aerobic capacity, TAC, and GSH at rest and in response to exercise. Age affected basal and exercise-induced responses since adults demonstrated a greater TAC and GSH levels at rest and a greater rise of TBARS, protein carbonyls, and TAC and decline of GSH in response to exercise. Catalase activity, uric acid, and bilirubin responses were comparable among groups. These results suggest that acute exercise, age, and training modulate the antioxidant reserves of the body.

Moderate exercise blunts oxidative stress induced by normobaric hypoxic confinement

PURPOSE

Both acute hypoxia and physical exercise are known to increase oxidative stress. This randomized prospective trial investigated whether the addition of moderate exercise can alter oxidative stress induced by continuous hypoxic exposure.

METHODS

Fourteen male participants were confined to 10-d continuous normobaric hypoxia (FIO2 = 0.139 ± 0.003, PIO2 = 88.2 ± 0.6 mm Hg, ∼4000-m simulated altitude) either with (HCE, n = 8, two training sessions per day at 50% of hypoxic maximal aerobic power) or without exercise (HCS, n = 6). Plasma levels of oxidative stress markers (advanced oxidation protein products [AOPP], nitrotyrosine, and malondialdehyde), antioxidant markers (ferric-reducing antioxidant power, superoxide dismutase, glutathione peroxidase, and catalase), nitric oxide end-products, and erythropoietin were measured before the exposure (Pre), after the first 24 h of exposure (D1), after the exposure (Post) and after the 24-h reoxygenation (Post + 1). In addition, graded exercise test in hypoxia was performed before and after the protocol.

RESULTS

Maximal aerobic power increased after the protocol in HCE only (+6.8%, P < 0.05). Compared with baseline, AOPP was higher at Post + 1 (+28%, P < 0.05) and nitrotyrosine at Post (+81%, P < 0.05) in HCS only. Superoxide dismutase (+30%, P < 0.05) and catalase (+53%, P < 0.05) increased at Post in HCE only. Higher levels of ferric-reducing antioxidant power (+41%, P < 0.05) at Post and lower levels of AOPP (-47%, P < 0.01) at Post + 1 were measured in HCE versus HCS. Glutathione peroxidase (+31%, P < 0.01) increased in both groups at Post + 1. Similar erythropoietin kinetics was noted in both groups with an increase at D1 (+143%, P < 0.01), a return to baseline at Post, and a decrease at Post + 1 (-56%, P < 0.05).

CONCLUSIONS

These data provide evidence that 2 h of moderate daily exercise training can attenuate the oxidative stress induced by continuous hypoxic exposure.

Exercise is the real polypill

The concept of a "polypill" is receiving growing attention to prevent cardiovascular disease. Yet similar if not overall higher benefits are achievable with regular exercise, a drug-free intervention for which our genome has been haped over evolution. Compared with drugs, exercise is available at low cost and relatively free of adverse effects. We summarize epidemiological evidence on the preventive/therapeutic benefits of exercise and on the main biological mediators involved.

Nitric oxide and reactive oxygen species in limb vascular function: what is the effect of physical activity?

Nitric oxide (NO) is known to be one of the most important regulatory compounds within the cardiovascular system where it is central for functions such as regulation of blood pressure, blood flow, and vascular growth. The bioavailability of NO is determined by a balance between, on one hand, the extent of enzymatic and non-enzymatic formation of NO and on the other hand, removal of NO, which in part is dependent on the reaction of NO with reactive oxygen species (ROS). The presence of ROS is dependent on the extent of ROS formation via mitochondria and/or enzymes such as NAD(P)H oxidase (NOX) and xanthine oxidase (XO) and the degree of ROS removal through the antioxidant defense system or other reactions. The development of cardiovascular disease has been proposed to be closely related to a reduced bioavailability of NO in parallel with an increased presence of ROS. Excessive levels of ROS not only lower the bioavailability of NO but may also cause cellular damage in the cardiovascular system. Physical activity has been shown to greatly improve cardiovascular function, in part through improved bioavailability of NO, enhanced endogenous antioxidant defense and a lowering of the expression of ROS-forming enzymes. Regular physical activity is therefore likely to be a highly useful tool in the treatment of cardiovascular disease. Future studies should focus on which form of exercise may be most optimal for enhancing NO bioavailability and improving cardiovascular health.

You are what you eat: within-subject increases in fruit and vegetable consumption confer beneficial skin-color changes

BACKGROUND

Fruit and vegetable consumption and ingestion of carotenoids have been found to be associated with human skin-color (yellowness) in a recent cross-sectional study. This carotenoid-based coloration contributes beneficially to the appearance of health in humans and is held to be a sexually selected cue of condition in other species.

METHODOLOGY AND PRINCIPAL FINDINGS

Here we investigate the effects of fruit and vegetable consumption on skin-color longitudinally to determine the magnitude and duration of diet change required to change skin-color perceptibly. Diet and skin-color were recorded at baseline and after three and six weeks, in a group of 35 individuals who were without makeup, self-tanning agents and/or recent intensive UV exposure. Six-week changes in fruit and vegetable consumption were significantly correlated with changes in skin redness and yellowness over this period, and diet-linked skin reflectance changes were significantly associated with the spectral absorption of carotenoids and not melanin. We also used psychophysical methods to investigate the minimum color change required to confer perceptibly healthier and more attractive skin-coloration. Modest dietary changes are required to enhance apparent health (2.91 portions per day) and attractiveness (3.30 portions).

CONCLUSIONS

Increased fruit and vegetable consumption confers measurable and perceptibly beneficial effects on Caucasian skin appearance within six weeks. This effect could potentially be used as a motivational tool in dietary intervention.

Effects of grape seed extract supplementation on exercise-induced oxidative stress in rats

The aim of the present study was to investigate the effects of grape seed extract (GSE) supplementation on exercise performance and oxidative stress in acutely and chronically exercised rats. A total of sixty-four male rats were used in the study. Rats were divided into six groups: control, chronic exercise control, acute exercise control (AEC), GSE-supplemented control, GSE-supplemented chronic exercise and GSE-supplemented acute exercise groups. Chronic exercise consisted of treadmill running at 25 m/min, 45 min/d, 5 d a week for 6 weeks. Rats in the acute exercise groups were run on the treadmill at 30 m/min until exhaustion. GSE were given at 100 mg/kg of body weight with drinking water for 6 weeks. Plasma was separated from blood samples for the analysis of oxidative stress markers. There was no significant difference in time of exhaustion between the acute exercise groups. Plasma malondialdehyde (MDA) levels were higher in the acute exercise groups and lower in the chronic exercise groups. GSE supplementation decreased MDA levels. Xanthine oxidase and adenosine deaminase activities were higher in the AEC group compared to all the other groups. NO levels were increased with both chronic exercise and GSE supplementation. Superoxide dismutase and glutathione peroxidase activities were lower in the acute exercised groups and higher in the chronic exercised groups. GSE supplementation caused an increase in antioxidant enzyme activities. In conclusion, GSE supplementation prevents exercise-induced oxidative stress by preventing lipid peroxidation and increasing antioxidant enzyme activities.

Effect of selenium supplementation on lipid peroxidation, antioxidant enzymes, and lactate levels in rats immediately after acute swimming exercise

The present study aims to evaluate the effect of selenium supplementation on lipid peroxidation and lactate levels in rats subjected to acute swimming exercise. Thirty-two adult male rats of Sprague-Dawley type were divided into four groups. Group 1, control; group 2, selenium-supplemented; group 3, swimming control; group 4, selenium-supplemented swimming group. The animals in groups 2 and 4 were supplemented with (i.p.) 6 mg/kg/day sodium selenite for 4 weeks. The blood samples taken from the animals by decapitation method were analyzed in terms of erythrocyte-reduced glutathione (GSH), serum glutathione peroxidase (GPx) and superoxide dismutase (SOD), and plasma malondialdehyde (MDA) and lactate using the colorimetric method, and serum selenium values using an atomic emission device. In the study, the highest MDA and lactate values were found in group 3, while the highest GSH, GPx and SOD values were obtained in group 4 (p < 0,001). Group 2 had the highest and group 3 had the lowest selenium levels (p < 0,001). Results of the study indicate that the increase in free radical production and lactate levels due to acute swimming exercise in rats might be offset by selenium supplementation. Selenium supplementation may be important in that it supports the antioxidant system in physical activity.

[Physical activity and endothelial dysfunction in type 2 diabetic patients: the role of nitric oxide and oxidative stress]

Type 2 diabetic patients have an increased level of systemic free radicals, which severely restrict the bioavailability of endothelium-derived nitric oxide (NO) and thus contribute to the development of an endothelial dysfunction. This review analyses the influence of physical training on molecular development mechanisms of the endothelial dysfunction and determines the significance of regular physical exercise for the endothelial function in type 2 diabetic patients. Systematic training reinforces the endogenic antioxidative capacity and results in a reduction in oxidative stress. Training - also combined with a change in diet - furthermore reduces hyperglycaemic blood sugar levels, thus curbing a major source of free radicals in diabetes. Moreover, physical exercise enhances vascular NO synthesis through an increased availability/activity of endothelial NO synthases (eNOS). Endurance, as well as resistance training with submaximal intensity or a combination of both forms of training is suitable to effectively improve the endothelial function in type 2 diabetic patients in the long term.

Impact of exercise training on oxidative stress in individuals with a spinal cord injury

Individuals with a spinal cord injury (SCI) have an increased cardiovascular risk. We hypothesize that (anti)oxidative imbalance is associated with the increased cardiovascular risk in SCI, while exercise can reverse this status. The aim of the study is to compare baseline levels of oxidative stress and antioxidative capacity between individuals with SCI and able-bodied (AB) subjects, and to assess acute and long-term effects of functional electrical stimulation (FES) exercise on oxidative stress and antioxidative capacity in SCI. Venous blood was taken from subjects with an SCI (n = 9) and age- and gender-matched AB subjects (n = 9) to examine oxidative stress through malondialdehyde (MDA) levels, while superoxide dismutase (SOD) and glutathione peroxidase (GPx) enzyme levels represented anti-oxidative capacity. Subsequently, subjects with an SCI performed an 8-week FES exercise training period. Blood was taken before and after the first exercise bout and after the last FES session to examine the acute and chronic effect of FES exercise, respectively. Baseline levels of MDA, SOD and GPx were not different between individuals with SCI and AB subjects. SCI demonstrated a correlation between initial fitness level and MDA (R = -0.83, P = 0.05). MDA, SOD and GPx levels were neither altered by a single FES exercise bout nor by 8 weeks FES training. In conclusion, although individuals with an SCI demonstrate a preserved (anti)oxidative status, the correlation between fitness level and (anti)oxidative balance suggests that higher fitness levels are related to improved (anti)oxidative status in SCI. Nonetheless, the FES exercise stimulus was insufficient to acutely or chronically change (anti)oxidative status in individuals with an SCI.

Blood as a reactive species generator and redox status regulator during exercise

The exact origin of reactive species and oxidative damage detected in blood is largely unknown. Blood interacts with all organs and tissues and, consequently, with many possible sources of reactive species. In addition, a multitude of oxidizable substrates are already in blood. A muscle-centric approach is frequently adopted to explain reactive species generation, which obscures the possibility that sources of reactive species and oxidative damage other than skeletal muscle may be also at work during exercise. Plasma and blood cells can autonomously produce significant amounts of reactive species at rest and during exercise. The major reactive species generators located in blood during exercise may be erythrocytes (mainly due to their quantity) and leukocytes (mainly due to their drastic activation during exercise). Therefore, it is plausible to assume that oxidative stress/damage measured frequently in blood after exercise or any other experimental intervention derives, at least in part, from the blood.

Antioxidant and redox status after maximal aerobic exercise at high altitude in acclimatized lowlanders and native highlanders

Exercise-induced increase in oxygen consumption leads to oxidative stress. On the contrary, hypoxia triggers oxidative stress despite decreased oxygen flux. Therefore, exercise under hypoxia may aggravate oxidative damage. Highlanders are expected to have better antioxidant capacity than lowlanders as a result of adaptation to hypoxia. The present study was undertaken to investigate the effect of exercise on antioxidant system in lowlanders and highlanders at high altitudes (HA). This study was conducted on active male volunteers, randomly selected and categorized into three groups, i.e., lowlanders tested at sea level (LL-SL, n = 35), lowlanders tested at altitude of 4560 m (LL-HA, n = 35) and native highlanders tested (HAN, n = 20) at the same height. Volunteers performed maximal exercise until exhaustion. Blood samples were collected before and after exercise. Both LL-SL and HAN had shown similar VO2max, which was significantly higher than LL-HA. GSH/GSSG ratio significantly increased in LL-SL and decreased in HAN after exercise. With exercise there were a decrease in superoxide dismutase and increase in glutathione peroxidase and catalase activities in HAN. Therefore, the results have suggested that HAN are more susceptible to oxidative stress when subjected to high-intensity exercise than lowlanders. The cumulative effect of higher VO2max and longer duration of exercise in hypoxia may be the reason of higher level of oxidative insult among HAN. Comparatively better management of antioxidant system observed in lowlanders at HA may be explained by the lower VO2max and shorter duration of exercise in hypoxia.

The role of exercise in minimizing postprandial oxidative stress in cigarette smokers

Cigarette smoking continues to pose a significant health burden on society. Two well-described mechanistic links associating smoking with morbidity and mortality include elevated blood lipids and increased oxidative stress. These variables have traditionally been measured while an individual is fasting, but evidence suggests that postprandial lipemia and oxidative stress provide more important information concerning susceptibility to disease, in particular cardiovascular disease. Cigarette smokers have elevated levels of biomarkers of oxidative stress at rest and experience impaired postprandial lipid and glucose metabolism. We have confirmed these findings while noting an exaggerated oxidative stress response to high-fat feeding. Smoking cessation is without question the best approach to minimizing smoking-induced ill health and disease, but success rates among those who attempt to quit are dismal. Other means to decrease a smoker's susceptibility to oxidative stress-related disease are needed. We propose that exercise may aid in attenuating postprandial oxidative stress, and we do so in 3 distinct ways. First, exercise stimulates an increase in endogenous antioxidant enzyme activity. Second, exercise improves blood triglyceride clearance via a reduced chylomicron-triglyceride half-life and an enhanced lipoprotein lipase activity. Third, exercise improves blood glucose clearance via an enhanced glucose 4 transport protein translocation and protein content, as well as insulin-insulin receptor binding and postreceptor signaling. Improvements in antioxidant status, as well as lipid and glucose processing, may aid greatly in minimizing feeding-induced oxidative stress in smokers. If so, and in accordance with the recent joint initiative of the American College of Sports Medicine and the American Medical Association, exercise may be viewed as a "medicine" for cigarette smokers at increased risk for postprandial oxidative stress. Research into this area may provide insight into the potential benefits of exercise for this purpose.

Thirteen days of "live high-train low" does not affect prooxidant/antioxidant balance in elite swimmers

We investigated the impact of 13 days of "living high-training low" (LHTL) on the antioxidant/prooxidant balance in elite endurance swimmers. Eighteen elite swimmers from the French Swimming Federation were submitted to a 13-day endurance training and divided into two groups: one group trained at 1,200 m and lived in hypoxia (2,500-3,000 m simulated altitude) and the second group trained and lived at 1,200 m. The subjects performed an acute hypoxic test (10 min at 4,800 m) before and 1 day after the training period. Plasma levels of advanced oxidation protein products (AOPP), malondialdehydes (MDA), ferric reducing antioxidant power (FRAP), and lipid-soluble antioxidants were measured before and after the 4,800 m tests. After the training, MDA and AOPP responses to the 4,800 m test were lower than before training for both groups (+10 vs. +2%; P = 0.01 for MDA and +80 vs. +14%; P = 0.01 for AOPP). Thirteen days of LHTL did not modify antioxidant status (FRAP and lipid-soluble antioxidants) despite intakes in vitamins A and E below the recommended daily allowances. The LHTL did not affect the antioxidant status in elite swimmers; however, the normoxic endurance training induced preconditioning mechanisms in response to the 4,800 m test.

Blood glutathione status and activity of glutathione-metabolizing antioxidant enzymes in erythrocytes of young trotters in basic training

The aim of this study was to evaluate response of blood glutathione status and activity of glutathione-metabolizing antioxidant enzymes in erythrocytes of young trotters in basic training. Nine untrained trotters (aged 16-20 months) were exposed to a 4-month training program based on exercises at low-to-moderate intensity. The conditioning consisted of breaking the horses and running them on distances varying from 4 to 40 km a week. The workloads were increased on a 3-week basis. Exercise intensity was monitored by measuring heart rate and blood lactate. Blood samples were collected at rest, before (RES0) and after (RESt) the conditioning period; moreover, on the latter occasion (on day 112 of training), the blood was also taken immediately after the routine exercise (EXE0) and 60 min thereafter (EXE60). The whole blood samples were analysed for the concentration of reduced, oxidized and total glutathione (GSH, GSSG and TGSH, respectively), while the activities of glutathione peroxidase (GPX) and glutathione-disulfide reductase (GR) were determined in haemolysates. Additionally, the erythrocytic concentrations of oxidized nicotinamide adenine dinucleotide (NAD(+)) and its phosphate (NADP(+)) were measured. All investigated parameters except NAD(+) and reduced/oxidized glutathione ratio (GSH/GSSG) changed during the training period. Following the effortm GPX, NADP(+) and GSH/GSSG were significantly lower (p < 0.05, p < 0.01, p < 0.001, respectively) while GSSG was markedly higher than at rest (RESt). The drop in NADP(+), low GSH/GSSG and high GSSG concentration were sustained at EXE60. Glutathione-disulfide reductase activity was higher after the workout but only at EXE60 the increase in activity was significant. Despite the activities of the GSH-GSSG cycle, enzymes were considerably higher after the training period, the elevated concentration of GSSG and significantly lower GSH/GSSG ratio in the post-exercise measurements suggest that production of reactive oxygen species possibly exceeds the capacity of antioxidative defenses of immature trotters. A more balanced diet with additional antioxidant supplementation and a revision of the basic training protocol used herein are advised.

Effects of the 'live high-train low' method on prooxidant/antioxidant balance on elite athletes

BACKGROUND/OBJECTIVES

We previously demonstrated that acute exposure to hypoxia (3 h at 3000 m) increased oxidative stress markers. Thus, by using the 'living high-training low' (LHTL) method, we further hypothesized that intermittent hypoxia associated with endurance training alters the prooxidant/antioxidant balance.

SUBJECTS/METHODS

Twelve elite athletes from the Athletic French Federation were subjected to 18-day endurance training. They were divided into two groups: one group (control group) trained at 1200 m and lived in hypoxia (2500-3000 m simulated altitude) and the second group trained and lived at 1200 m. The subjects performed an acute hypoxic test (10 min at 4800 m) before and immediately after the training. Plasma levels of advanced oxidation protein products (AOPP), malondialdehydes (MDA), ferric-reducing antioxidant power (FRAP), lipid-soluble antioxidants normalized for triacylglycerols, and cholesterol and retinol were measured before and after the 4800 m tests.

RESULTS

After the training, MDA and AOPP concentrations were decreased in response to the 4800 m test only for the control group. Eighteen days of LHTL induced a significant decrease of all antioxidant markers (FRAP, P=0.01; alpha-tocopherol, P=0.04; beta-carotene, P=0.01 and lycopene, P=0.02) for the runners. This imbalance between antioxidant and prooxidant might result from insufficient intakes in vitamins A and E.

CONCLUSIONS

The LHTL model characterized by the association of aerobic exercises and intermittent resting hypoxia exposures decreased the antioxidant status whereas the normoxic endurance training induced preconditioning mechanisms in response to the 4800 m test.

Oxidative stress : relationship with exercise and training

Free radicals are reactive compounds that are naturally produced in the human body. They can exert positive effects (e.g. on the immune system) or negative effects (e.g. lipids, proteins or DNA oxidation). To limit these harmful effects, an organism requires complex protection - the antioxidant system. This system consists of antioxidant enzymes (catalase, glutathione peroxidase, superoxide dismutase) and non-enzymatic antioxidants (e.g. vitamin E [tocopherol], vitamin A [retinol], vitamin C [ascorbic acid], glutathione and uric acid). An imbalance between free radical production and antioxidant defence leads to an oxidative stress state, which may be involved in aging processes and even in some pathology (e.g. cancer and Parkinson's disease). Physical exercise also increases oxidative stress and causes disruptions of the homeostasis. Training can have positive or negative effects on oxidative stress depending on training load, training specificity and the basal level of training. Moreover, oxidative stress seems to be involved in muscular fatigue and may lead to overtraining.

Effects of exercise and training in hypoxia on antioxidant/pro-oxidant balance

OBJECTIVE

The aim was to investigate the effects of acute exercise under hypoxic condition and the repetition of such exercise in a 'living low-training high' training on the antioxidant/prooxidant balance.

DESIGN

Randomized, repeated measures design.

SETTING

Faculté de Médecine, Clermont-Ferrand, France.

SUBJECTS

Fourteen runners were randomly divided into two groups. A 6-week endurance training protocol integrated two running sessions per week at the second ventilatory threshold into the usual training.

INTERVENTION

A 6-week endurance training protocol integrated two running sessions per week at the second ventilatory threshold into the usual training. The first hypoxic group (HG, n=8) carried out these sessions under hypoxia (3000 m simulated altitude) and the second normoxic group (NG, n=6) in normoxia. In control period, the runners were submitted to two incremental cycling tests performed in normoxia and under hypoxia (simulated altitude of 3000 m). Plasma levels of advanced oxidation protein products (AOPP), malondialdehydes (MDA) and lipid oxidizability, ferric-reducing antioxidant power (FRAP), lipid-soluble antioxidants (alpha-tocopherol and beta-carotene) normalized for triacyglycerols and cholesterol were measured before and after the two incremental tests and at rest before and after training.

RESULTS

No significant changes of MDA and AOPP level were observed after normoxic exercise, whereas hypoxic exercise induced a 56% rise of MDA and a 44% rise of AOPP. Plasma level of MDA and arterial oxygen hemoglobin desaturations after the acute both exercises were highly correlated (r=0.73). alpha-Tocopherol normalized for cholesterol and triacyglycerols increased only after hypoxic exercise (10-12%, P<0.01). After training, FRAP resting values (-21%, P<0.05) and alpha-tocopherol/triacyglycerols ratio (-24%, P<0.05) were diminished for HG, whereas NG values remained unchanged.

CONCLUSIONS

Intense exercise and hypoxia exposure may have a cumulative effect on oxidative stress. As a consequence, the repetition of such exercise characterizing the 'living low-training high' model has weakened the antioxidant capacities of the athletes.

SPONSORSHIP

International Olympic Committee and the Direction Régionale de la Jeunesse et des Sports de la Région Auvergne.

Response of blood cell antioxidant enzyme defences to antioxidant diet supplementation and to intense exercise

BACKGROUND

Exhaustive exercise induces oxidative stress. The cellular antioxidant defence systems have demonstrated great adaptation to chronic exercise.

AIM

To establish the influence of the antioxidant diet supplementation on the erythrocyte and lymphocyte antioxidant enzyme activities in athletes at basal and post-exercise levels.

METHODS

Fifteen amateur trained male athletes were randomly distributed in two groups: control and antioxidant supplemented (90 days' diet supplementation with 500 mg/day vitamin E and 30 mg/day beta-carotene, and the last 15 days also with 1 g/day vitamin C). The study was double blind. Maximal and submaximal exercise tests were performed after three months of diet supplementation. The study was developed during the training and competition season.

RESULTS

The sportsmen of the supplemented group presented significantly higher plasmatic final levels of vitamin C, vitamin E and beta-carotene. Erythrocyte glutathione reductase activity significantly decreased in the placebo group but was maintained in the supplemented group after the three months studied. The erythrocyte superoxide dismutase activity increased after the training/competition period in the placebo group. Lymphocyte catalase and glutathione peroxidase activities increased significantly in the supplemented group after the supplementation period but were maintained in the placebo group. No effects of the antioxidant supplementation were observed in the erythrocyte antioxidant enzyme response to the exercise tests. The antioxidant supplementation induced a better adaptation of lymphocyte catalase after submaximal test.

CONCLUSIONS

Lymphocytes showed higher sensibility to antioxidant supplementation, improving the response of antioxidant enzymes to training and to acute exercise. In erythrocytes the training adaptations were more important than the antioxidant supplementation effects.

Molecular Epidemiology of Physical Activity and Cancer

As in other areas of epidemiology, researchers studying physical activity and cancer have begun to include laboratory analyses of biological specimens in their studies. The incorporation of these “biomarkers” into epidemiology has been termed molecular epidemiology and is an approach primarily developed to study chemical carcinogens. Thus far, there has been no discussion in the field on how the established molecular epidemiologic framework might be adapted for research into physical activity, what methodologic needs exist, what the goals of such an approach might be, and what limitations exist. This article relates the literature on molecular epidemiology to the needs of physical activity research and tries to set research priorities for the field as it moves in this new direction. Although this approach will be very useful for investigating the mechanisms through which physical activity exerts effects, there are several challenges for physical activity epidemiologists in adapting molecular epidemiologic approaches. Primarily, there are currently no available biomarkers that might be considered measures of exposure or biologically effective dose. In addition, most available biomarkers of intermediate effects have been tested in training studies at activity levels much higher than those seen in population-based epidemiologic studies. Thus, it is not clear whether these biomarkers are valid at lower activity levels. Furthermore, the nature of the relationship between activity and many available biomarkers depends very much on the context of the activity. Addressing these issues should be a priority if we are to develop a molecular epidemiologic paradigm for studying physical activity.

Increase in selenium requirements with physical activity loads in well-trained athletes is not linear

Selenium requirements in athletes are supposed to be increased with energy expenditure (EE) to preserve selenium status and an optimal antioxidant balance. The question of whether selenium intakes are related to EE and whether plasma selenium status induces up-regulation in erythrocyte endogenous antioxidant defense and decreases plasma oxidative damage markers in athletes was addressed. 118 well-trained athletes completed 7 d food and activities records in a cross-sectional study. Blood was sampled on day 8. Among the athletes, 23% of the males and 66% of the females had selenium intakes below two-third of the French RDA. Plasma selenium concentrations in most of less trained athletes were lower than the postulated concentration to be required to maximize erythrocyte GSH-Px activity. Athletes with the highest daily EE had the highest selenium intakes, percentage of vegetal protein intakes and plasma selenium concentrations. Only 2.6% of the athletes exhibited low plasma selenium concentrations (< 0.75 micromol/l). The relation between plasma selenium and EE was polynomial (r = 0.50; P < 0.005). Erythrocyte GSH-Px activity in athletes was not linked to selenium status. Selenium requirements are increased in athletes without being linearly related to EE.

Antioxidant response to oxidative stress induced by exhaustive exercise

The aim of this work was to demonstrate the occurrence of oxidative stress during exhaustive exercise and to determine the antioxidant response. Eight voluntary male subjects participated in this study. The exercise was a cycling mountain stage (171 km) and the cyclists took a mean+/-S.E.M. time of 270+/-12 min to complete it. Blood samples were taken before the cycling stage, immediately after the stage, 3 h after finishing the stage and on the morning of the following day. We determined the activities of erythrocyte antioxidant enzymes, blood levels of oxidised glutathione, plasma levels of antioxidant vitamins and carotenoids, and the serum lipid and cholesterol profile. The mountain cycling stage induced significant increases in catalase and glutathione reductase activities. Significant decreases in glutathione peroxidase activity, both determined with hydrogen peroxide and with cumene hydroperoxide as substrates, were observed. Blood oxidised glutathione and serum uric acid rose after the stage. Plasma vitamin E increased after the stage but dropped to below basal values after 3 h of recovery. Triglycerides and VLDL-cholesterol increased significantly after the stage and remained high 3 h after the cycling stage. The mountain cycling stage induced oxidative stress, as was evidenced by the increases in blood GSSG and in serum urate concentrations and by the pattern of change of erythrocyte antioxidant enzyme activities. A specific utilisation of alpha-tocopherol against oxidative stress during recovery was evidenced.

Oxidative stress, exercise, and antioxidant supplementation

Cells continuously produce free radicals and reactive oxygen species (ROS) as part of metabolic processes. These free radicals are neutralized by an elaborate antioxidant defense system consisting of enzymes such as catalase, superoxide dismutase, glutathione peroxidase, and numerous non-enzymatic antioxidants, including vitamins A, E and C, glutathione, ubiquinone, and flavonoids. Exercise can produce an imbalance between ROS and antioxidants, which is referred to as oxidative stress. Dietary antioxidant supplements are marketed to and used by athletes as a means to counteract the oxidative stress of exercise. Whether strenuous exercise does, in fact, increase the need for additional antioxidants in the diet is not clear. This review examines the markers used to determine oxidative stress in blood and muscle samples (e.g. lipid peroxidation, expired pentane, malondialdehyde (MDA), F2-isoprostanes, congugated dienes, and 8-hydroxy-2'-deoxyguanosine (8-OhdG)), the changes in oxidative stress markers induced by exercise, and whether athletes require antioxidant supplements.

Plasma glutathione peroxidase in healthy young adults: influence of gender and physical activity

OBJECTIVES

Oxidative stress is implicated in the pathophysiology of many cardiovascular diseases. Plasma glutathione peroxidase (pl x GPx, GPx3) is an antioxidant enzyme found in the extracellular fluid. This study aimed to determine reference values for serum GPx3 concentration and GPx activity in young healthy males and females of similar aerobic fitness and to determine the impact of acute physical activity on serum GPx.

DESIGN AND METHODS

52 young, healthy but not physically trained subjects (24 male, 28 female; age = 20.4 +/- 0.7 yr, cycling VO(2 max) = 39.2 +/- 1.6 mL/kg/min; mean +/- SE) participated in this study. An independent group of 18 subjects participated in an acute, 90 min bout of 50% VO(2 max) cycling exercise. Serum GPx activity and GPx3 protein levels, as well as estradiol and 8-iso- prostaglandin F(2alpha) (8-iso-PGF(2alpha;) an index of lipid peroxidation) were determined.

RESULTS

Females had significantly higher serum GPx3 concentration (29.1 +/- 1.6 vs. 24.2 +/- 1.3 mg/L, p < 0.01) and serum GPx activity (256.4 +/- 10.4 vs. 222.8 +/- 15.6 U/L, p < 0.05) than males; specific activity (U/mg) was not different between genders. There was no significant gender difference in 8-iso-PGF(2alpha). No significant correlation was found between either GPx activity or GPx3 concentration and serum estradiol or VO(2)(max). The acute, prolonged, mild intensity exercise did not affect serum GPx activity or 8-iso-PGF(2a) levels in males or females.

CONCLUSIONS

The results of this study suggest that in a young, healthy but not physically well-trained population females are endowed with slightly higher serum GPx3 concentrations and GPx activities than males, but the functional significance of this has not been established. Furthermore, the results indicate that serum GPx levels are not associated with aerobic fitness level, or serum estradiol concentration and that acute, prolonged, mild exercise does not affect the activity of serum GPx in this population.

Teorias biológicas do envelhecimento: do genético ao estocástico

As teorias biológicas do envelhecimento examinam o assunto sob a ótica da degeneração da função e estrutura dos sistemas orgânicos e células. De forma geral, podem ser classificadas em duas categorias: as de natureza genético-desenvolvimentistae as de natureza estocástica. As primeiras entendem o envelhecimento no contexto de um continuum controlado geneticamente, enquanto as últimas trabalham com a hipótese de que o processo dependeria, principalmente, do acúmulo de agressões ambientais. Por outro lado, são freqüentes as alusões ao exercício físico como estratégia de intervenção que poderia ter influências positivas no processo de envelhecimento, retardando algumas das disfunções comuns na idade avançada. O presente estudo apresenta os princípios gerais de algumas das correntes teóricas mais aceitas, quais sejam: a) teorias com base genética; b) teorias com base em danos de origem química; c) teorias com base no desequilíbrio gradual; d) teorias com base em restrição calórica. São feitas considerações sobre seus pontos consensuais e duvidosos e, quando possível, analisando a possibilidade de o exercício influenciar em seu desenvolvimento. Conclui-se que as teorias afeitas a ambas as abordagens carecem de comprovação definitiva, existindo dúvidas sobre sua influência e as formas pelas quais interagiriam. Igualmente, considerando a natureza dos processos descritos nas diferentes propostas teóricas, o papel do exercício como estratégia de prevenção do envelhecimento parece, no mínimo, incerto.

Antioxidants: what role do they play in physical activity and health?

Exercise appears to increase reactive oxygen species, which can result in damage to cells. Exercise results in increased amounts of malondialdehyde in blood and pentane in breath; both serve as indirect indicators of lipid peroxidation. However, not all studies report increases; these equivocal results may be due to the large intersubject variability in response or the nonspecificity of the assays. Some studies have reported that supplementation with vitamins C and E, other antioxidants, or antioxidant mixtures can reduce symptoms or indicators of oxidative stress as a result of exercise. However, these supplements appear to have no beneficial effect on performance. Exercise training seems to reduce the oxidative stress of exercise, such that trained athletes show less evidence of lipid peroxidation for a given bout of exercise and an enhanced defense system in relation to untrained subjects. Whether the body's natural antioxidant defense system is sufficient to counteract the increase in reactive oxygen species with exercise or whether additional exogenous supplements are needed is not known, although trained athletes who received antioxidant supplements show evidence of reduced oxidative stress. Until research fully substantiates that the long-term use of antioxidants is safe and effective, the prudent recommendation for physically active individuals is to ingest a diet rich in antioxidants.

Physical activity, aerobic capacity and selected markers of oxidative stress and the anti-oxidant defence system in healthy active elderly men

The relationship of oxidative stress and the anti-oxidant defence system to maximal oxygen consumption (VO2max) and habitual physical activity was assessed in 26 elderly men (71.0 +/- 4.2 years) and compared to that of 12 young men (22.1 +/- 5.1 years). Physical activity was assessed by a questionnaire. Malondialdehyde (MDA), plasma total anti-oxidant status (TAS), the levels of red blood cell (RBC) superoxide dismutase (SOD) and glutathione peroxidase (GPX), as well as serum GPX activities were determined under resting conditions. The older and young men had similar TAS and RBC SOD, while MDA, RBC GPX and plasma GPX were higher, and RBC SOD/GPX ratio was significantly lower in the older men. Neither MDA nor anti-oxidants were associated with any of the physical activity/aerobic capacity measures in the elderly men. We conclude that in healthy elderly men with a good nutritional status, indicators of the anti-oxidant defence system are not lower in comparison with young men. Increased RBC and plasma GPX coupled with a high level of lipid peroxidation marker may indicate an adaptation of anti-oxidant defences to sustained oxidative stress. Furthermore, the results of the present study suggest that the level of habitual physical activity and aerobic capacity have no major influence on the resting balance between radical generation and blood anti-oxidant potential in healthy older men.

Nutrition in the exercising elderly

When making nutrition recommendations to the exercising elderly population, four important areas should be taken into consideration: (1) the changing needs that occur with age; (2) the changing needs that occur with exercise; (3) the presence of any chronic illnesses or diseases; and (4) whether one is exercising for fitness, recreation, or competition. For the most part, these four areas have been researched separately, and recommendations for elderly athletes need to be synthesized from this information. The nutrients for which food consumption is often inadequate and has the largest impact on the exercising elderly population include vitamin B6, vitamin B12, calcium, and vitamin D. The exercising elderly population needs to be aware of their bodies changing needs with exercise and should focus on maintaining energy balance while selecting a wide variety of foods high in complex carbohydrates. When adequate dietary intakes cannot be obtained, supplementation with a multivitamin of no more than 100% of the RDA is recommended.

Toxicokinetics of organic solvents: a review of modifying factors

This article reviews, with an emphasis on human experimental data, factors known or suspected to cause changes in the toxicokinetics of organic solvents. Such changes in the toxicokinetic pattern alters the relation between external exposure and target dose and thus may explain some of the observed individual variability in susceptibility to toxic effects. Factors shown to modify the uptake, distribution, biotransformation, or excretion of solvent include physical activity (work load), body composition, age, sex, genetic polymorphism of the biotransformation, ethnicity, diet, smoking, drug treatment, and coexposure to ethanol and other solvents. A better understanding of modifying factors is needed for several reasons. First, it may help in identifying important potential confounders and eliminating negligible ones. Second, the risk assessment process may be improved if different sources of variability between external exposures and target doses can be quantitatively assessed. Third, biological exposure monitoring may be also improved for the same reason.

Effects of hypobaric hypoxia on antioxidant enzymes in rats

1. The present study was undertaken to investigate the effects of hypobaric hypoxia, equivalent to an altitude of 5500 m, on antioxidant enzymes in rats. 2. Malondialdehyde levels in serum, heart, lung, liver and kidney of hypobaric-hypoxic rats were all significantly higher than in control rats by day 21 of exposure (P < 0.05), indicating increased oxidative stress. 3. Superoxide dismutase (SOD) catalyses the conversion of the superoxide anion to H2O2 and O2. The concentration of immunoreactive Mn-SOD in the serum of hypobaric-hypoxic rats was raised significantly from day 5 onwards, whereas in liver and lung, it had decreased significantly by day 21 (P < 0.05). 4. Glutathione peroxidase (GSH-Px) catalyses H2O2 and certain lipid peroxides. By day 21, GSH-Px activity had increased significantly in the heart and lungs, but decreased significantly in the liver (P < 0.05). 5. Catalase catalyses H2O2. Catalase activity in the liver and kidney of hypobaric-hypoxic rats was significantly decreased on day 1 (P < 0.05) though levels then recovered. 6. Mn-SOD mRNA in the liver of hypobaric-hypoxic rats was induced during the experiment, the effect being exceptionally marked, especially during the first 3 days of exposure to hypobaric hypoxia. 7. These results suggest that the liver may be more vulnerable than the other organs tested to oxidative stress under hypobaric hypoxia.

Micronutrients and exercise: anti-oxidants and minerals

Exercise has been shown to increase indirect measures of lipid peroxidation. However, exercise and training appear to augment the body's anti-oxidant defence system. Whether this augmented defence system can keep up with the increase in lipid peroxidation with exercise is not known. Iron depletion is experienced by many athletes, especially female endurance athletes and adolescents, but iron deficiency anaemia is rare. Iron depletion could affect the ability to train and recover from strenuous exercise, but this has not been examined. There is a concern that female athletes, especially adolescents, are not ingesting sufficient calcium, and this may affect the development of peak bone mass and increase the risk of bone fractures. Further research is needed on mineral and trace mineral intake and loss in athletes. It appears that most athletes have adequate status of chromium, zinc, phosphate and magnesium. Athletes who are restricting energy intake to achieve a low body mass (for example, endurance runners), may not have adequate vitamin or mineral status. More data are needed on vitamin/mineral status of athletes from underdeveloped countries. The general recommendation for athletes is that foods rich in anti-oxidants and minerals should be ingested rather than supplements.

Exercise, training and red blood cell turnover

Endurance training can lead to what has been termed 'sports anaemia'. Although under normal conditions, red blood cells (RBCs) have a lifespan of about 120 days, the rate of aging may increase during intensive training. However, RBC deficiency is rare in athletes, and sports anaemia is probably due to an expanded plasma volume. Cycling, running and swimming have been shown to cause RBC damage. While most investigators measure indices of haemolysis (for example, plasma haemoglobin or haptoglobin), RBC removal is normally an extravascular process that does not involve haemolysis. Attention is now turning to cellular indices (such as antioxidant depletion, or protein or lipid damage) that may be more indicative of exercise-induced damage. RBCs are vulnerable to oxidative damage because of their continuous exposure to oxygen and their high concentrations of polyunsaturated fatty acids and haem iron. As oxidative stress may be proportional to oxygen uptake, it is not surprising that antioxidants in muscle, liver and RBCs can be depleted during exercise. Oxidative damage to RBCs can also perturb ionic homeostasis and facilitate cellular dehydration. These changes impair RBC deformability which can, in turn, impede the passage of RBCs through the microcirculation. This may lead to hypoxia in working muscle during single episodes of exercise and possibly an increased rate of RBC destruction with long term exercise. Providing RBC destruction does not exceed the rate of RBC production, no detrimental effect to athletic performance should occur. An increased rate of RBC turnover may be advantageous because young cells are more efficient in transporting oxygen. Because most techniques examine the RBC population as a whole, more sophisticated methods which analyse cells individually are required to determine the mechanisms involved in exercise-induced damage of RBCs.

Antioxidants and physical performance

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. Indirect measurements of free radicals generated during exercise include assessing products of lipid peroxidation that appear in the blood (e.g., malondialdehyde and conjugated dienes) or expired in the breath (pentane). 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 the susceptibility of red blood cells to oxidative and osmotic stress following submaximal exercise

Red blood cell (RBC) susceptibility to oxidative and osmotic stress in vitro was investigated in cells from trained and untrained men before and after submaximal exercise. Whilst no significant change in peroxidative haemolysis occurred immediately after 1 h of cycling at 60% of maximal aerobic capacity (VO2max), a 20% increase was found 6h later in both groups (P < 0.05). The RBC osmotic fragility decreased by 15% immediately after exercise (P < 0.001) and this was maintained for 6h (P < 0.001). There was an associated decrease in mean cell volume (P < 0.05). Training decreased RBC susceptibility to peroxidative haemolysis (P < 0.025) but it did not influence any other parameter. These exercise-induced changes were smaller in magnitude but qualitatively similar to those found in haemopathological states involving haem-iron incorporation into membrane lipids and the short-circuiting of antioxidant protection. To explore this similarity, a more strenuous and mechanically stressful exercise test was used. Running at 75% VO2max for 45 min reduced the induction time of O2 uptake (peroxidation), consistent with reduced antioxidation capacity, and increased the maximal rate of O2 uptake in RBC challenged with cumene hydroperoxide (P < 0.001). The proportion of high-density RBC increased by 10% immediately after running (P < 0.001) but no change in membrane-incorporated haem-iron occurred. In contrast, treatment of RBC with oxidants (20-50 mumol.l-1) in vitro increased cell density and membrane incorporation of haem-iron substantially. These results showed that single episodes of submaximal exercise caused significant changes in RBC susceptibility to oxidative and osmotic stress. Such responses may account for the increase in RBC turnover found in athletes undertaking strenuous endurance training.

Control of physical exercise of rats in a swimming basin

To study the mutual interaction between physical exercise and antioxidant systems in rats, we selected swimming as a model for exercise performance. Swimming belongs to the natural behavior of a rat, which under proper experimental conditions, primarily involves physical exercise with little emotional arousal. Therefore, we developed a swimming basin in which the intensity of exercise was manipulated by swimming speed and swimming duration. A laser beam interruption system enables recording of swimming patterns. For comparison we also used the basin to induce emotional arousal. Hereto the basin was transformed into a maze, in which unexpected blockade of a learned swimming route induced a panic-like emotional reaction. The antioxidant enzyme superoxide dismutase decreased in rat plasma after emotional arousal, not after physical exercise. Depletion of the antioxidant glutathione in the liver by diethyl maleate led to decrease of swimming performance. Noradrenaline but not adrenaline plasma levels increased in response to physical exercise. After emotional arousal the ratio noradrenaline/adrenaline did not change. In contrast, lactate only increased in response to emotional arousal. Plasma levels of glucose increased after both stress situations. Beta-adrenoceptor function, determined in the heart and in erythrocytes, only changed after physical exercise. The sensitivity to the beta-agonist (-)isoprenaline in the right atrium decreased and a downregulation of the beta-adrenoceptor density was observed in the erythrocyte.

Changes in blood glutathione concentrations, and in erythrocyte glutathione reductase and glutathione S-transferase activity after running training and after participation in contests

Previously sedentary men (n = 23) and women (n = 18) were trained to run a half marathon contest after 40 weeks. Total blood glutathione had increased by 20 weeks of training and had returned to normal after 40 weeks. Erythrocyte glutathione reductase activity had increased by 20 weeks and remained elevated after 40 weeks. This effect was accompanied by decreases in glutathione reductase coefficients, which indicated that increases in the presence of riboflavin may have been responsible for the changes in reductase activity. Erythrocyte glutathione S-transferase activity had increased slightly after 20 weeks of training and a much more marked increase was found after 40 weeks. This may have been indicative of the occurrence of lipid peroxidation in this phase of training. The participants ran a 15-km race after the first 20 weeks of training and a half marathon after 40 weeks. Blood glutathione tended to decrease after the 15-km race and increased after the half marathon. In both cases it had returned to normal values 5 days after the race. Erythrocyte glutathione reductase was elevated 1 day after the races, and had returned to normal after 5 days. This could also have been explained from concurrent changes in the riboflavin content of the erythrocytes. Erythrocyte glutathione S-transferase activity decreased after both races, but was restored 5 days after the half marathon while such was not the case after the 15-km race.

Vitamin supplementation and physical exercise performance

Vitamins, just as minerals and trace elements, meet with great interest in the world of sports because of their supposed role in enhancing physical performance. Of the 13 compounds now considered as vitamins, most water-soluble vitamins and vitamin E are involved in mitochondrial energy metabolism. The influence of vitamin supplementation on mitochondrial metabolism is largely unknown. The principal argument for vitamin supplementation is the assumed increased vitamin requirement of athletes. Theoretically, an increased requirement can be caused by decreased absorption by the gastrointestinal tract, increased excretion in sweat, urine and faeces, increased turnover, as well as biochemical adaptation to training. Of course, a marginal low vitamin status can simply be the consequence of a long-term inadequate intake. However, considering the RDAs there are no indications that long-term vitamin intake among athletes is insufficient. Neither are there indications that vitamin excretion or turnover is increased in athletes. However, it is very likely that the (apparently) increased requirement is the consequence of biochemical adaptation to training and does not indicate a decreased intake. Although a marginal vitamin status, induced by inadequate vitamin intake, may have a negative effect on performance, there is no evidence to support the view that this occurs in trained athletes. Moreover, vitamin supplementation in athletes with an adequate vitamin status has no effect on physical working capacity. Possibly, exceptions have to be made for the use of vitamin E at high altitudes and for the use of vitamin C and multiple B-vitamin supplements in hot climates.

The red blood cell glutathione reductase activity in anaemic rats

The enzyme activity of glutathione reductase (GR, EC 1.6.4.2) was measured in rat red blood cells separated centrifugally in a density gradient of Percoll. The animals were divided into three groups: Groups IPHH, anaemia was induced by administration of phenylhydrazine hydrochloride; Group IITr, anaemia was induced by intense physical training; and Group C, control group. The activity of active and inactive forms of GR were higher in erythrocytes of animals from groups IPHH and IITr, both in young and old forms of cells, than in red cells of control rats, the degree of decrease in activity of both forms of GR in senescent red cells is similar in different kinds of anaemia.