High-dose testosterone supplementation disturbs liver pro-oxidant/antioxidant balance and function in adolescent male Wistar rats undergoing moderate-intensity endurance training.

In some countries, anabolic-androgenic steroid abuse is rampant among adolescent boys and young men, including some of those seeking physical fitness and/or pleasing appearance through various exercise types. This tactic carries the risk of severe harmful health effects, including liver injury. Most anabolic-androgenic steroid stacking protocols employed are based on the use of the 'prototypic' anabolic-androgenic steroid testosterone and/or its esters. There is a vast body of data on the effects of anabolic-androgenic steroids' abuse combined with physical exercise training on the liver antioxidant barrier in adult subjects, whereas those concerning adolescents are scant. This study aimed to assess, in adolescent male Wistar rats undergoing a 6-week moderate-intensity endurance training (treadmill running), the influence of concurrent weekly supplementation with intramuscular testosterone enanthate (TE, 8 or 80 mg/kg body weight/week) on selected indices of liver status and oxidative stress. The rats were sacrificed, and their livers and blood samples were harvested two days after the last training session. High-dose TE treatment significantly reduced body and liver weight gains. Neither low-dose nor high-dose TE treatment affected liver α-tocopherol or γ-tocopherol content, whereas low-dose TE treatment significantly lowered hepatic reduced glutathione content. TE treatment significantly elevated liver thiobarbituric acid-reactive substances content and blood activities of alkaline phosphatase and γ-glutamyltransferase, but not of aspartate aminotransferase or alanine aminotransferase. Liver catalase activity was lowered by >50% in both TE-treated groups, while superoxide dismutase activity was significantly but slightly affected (-15%) only by the high-dose TE treatment. Glutathione peroxidase and glutathione reductase activities were not significantly altered. TE treatment significantly increased liver thiobarbituric acid-reactive substances content and lowered blood HDL-cholesterol, but did not significantly affect LDL-cholesterol or triglycerides level. In conclusion, high-dose TE treatment significantly disturbed liver antioxidant barrier and prooxidative-antioxidative balance and hence counteracted favorable effects of concurrent moderate-intensity endurance training in adolescent male rats.

Chest pain in an elite master ultra-marathon runner: a case report with a follow-up on his subsequent athletic activity.

Ultra-marathon running has enjoyed increasing popularity, with the number of master ultra-marathon runners growing annually. This study presents a case of a 51-year-old highly experienced long-distance runner (body mass: 65.1 kg, body height: 168 cm), who took part in a 48-h ultra-marathon race held in 2010, but dropped out of the competition due to acute cardiac problems manifested after 16 h of running and having completed a distance of 129 km. Two weeks following the race, intense cardiac examination was performed to explain the drop-out due to chest pain. A 12­lead electrocardiogram, a 2D transthoracic echocardiography in 3 apical projections of the left ventricle, a computed tomography of the chest, an invasive coronary angiography and a maximal oxygen uptake (VO2max) test were performed. The 12-lead ECG revealed a negative T wave in III and aVF without morphological abnormalities. The echocardiographic examinations presented a normal size and function of the heart chambers, and a normal valvar structure and function (only trivial mitral and tricuspid regurgitation was observed). The invasive coronary arteriography - due to an increased calcium score in the CT scan - showed only a non-significant systolic dynamic narrowing in the eighth segment of the left anterior descending artery due to a muscle bridge. The physical performance characteristics of the athlete and a follow-up history of his athletic activity showed that the cardiac problems he had experienced during the ultra-marathon race did not prevent him from being active in sport. Int J Occup Med Environ Health. 2020;33(4):523-34.

Effects of Six-Week Ginkgo biloba Supplementation on Aerobic Performance, Blood Pro/Antioxidant Balance, and Serum Brain-Derived Neurotrophic Factor in Physically Active Men.

Extracts of Ginkgo biloba leaves, a natural source of flavonoids and polyphenolic compounds, are commonly used as therapeutic agents for the improvement of both cognitive and physiological performance. The present study was aimed to test the effects of a six-week supplementation with 160 mg/day of a standardized extract of Ginkgo biloba or a matching placebo on aerobic performance, blood antioxidant capacity, and brain-derived neurotrophic factor (BDNF) level in healthy, physically active young men, randomly allocated to two groups (n = 9 each). At baseline, as well as on the day following the treatment, the participants performed an incremental cycling test for the assessment of maximal oxygen uptake. Venous blood samples taken at rest, then immediately post-test and following 1 h of recovery, were analyzed for activities of antioxidant enzymes and plasma concentrations of non-enzymatic antioxidants, total phenolics, uric acid, lipid peroxidation products, ferric reducing ability of plasma (FRAP), and serum brain-derived neurotrophic factor (BDNF). Our results show that six weeks' supplementation with Ginkgo biloba extract in physically active young men may provide some marginal improvements in their endurance performance expressed as VO2max and blood antioxidant capacity, as evidenced by specific biomarkers, and elicit somewhat better neuroprotection through increased exercise-induced production of BDNF.

High-dose testosterone enanthate supplementation boosts oxidative stress, but exerts little effect on the antioxidant barrier in sedentary adolescent male rat liver.

BACKGROUND: Anabolic-androgenic steroids abuse is on the rise among adolescent boys and young men, mostly in those seeking a 'shortcut' to an improved body image. This approach is associated with the risk of severe adverse health effects, some of which involve the liver and are linked to hepatic oxidative stress. Testosterone and its esters is a cornerstone of most anabolic-androgenic steroid stacking protocols. METHODS: We assessed and compared several hepatotoxicity and liver oxidative stress indices, as well as the contents of some components of the hepatic antioxidant barrier between sedentary adolescent male rats given a 6-week course of weekly im testosterone enanthate (TE, 8 or 80mg/kgBW/week) or vehicle (sesame oil) injections. Blood and livers for the assessments were harvested seven days after the last injection. RESULTS: TE supplementation dose-dependently elevated blood testosterone and significantly increased the liver content of thiobarbituric acid-reactive substances. Only the high-dose TE supplementation significantly slowed down body weight gain, reduced the liver weight/body weight ratio, increased liver heat shock protein 70/72 content and elevated blood enzyme markers of liver stress. There was no significant difference in reduced glutathione and α- or γ-tocopherol content between the TE-treated and control rats. Of the antioxidant enzymes studied (superoxide dismutase, catalase, glutathione peroxidase and glutathione reductase), only the dismutase activity was significantly while moderately elevated and only by the high-dose TE supplementation. CONCLUSION: (Sub)chronic supplementation of sedentary adolescent male rats with high TE doses does not exert a lasting major effect on the liver antioxidant barrier and redox homeostasis.

Associations of visceral fat area and physical activity levels with the risk of metabolic syndrome in postmenopausal women.

This study was aimed at the evaluation of relationship between visceral fat area (VFA) and physical activity (PA) with the metabolic syndrome (MetS) risk in the physically active postmenopausal women. A total of 85 attendants of the University of the Third Age (U3A) aged 62.8 ± 5.9 years (median time since menopause 11.8 y), participated in this study. VFA was assessed by bioimpedance method using InBody 720 analyzer. PA was assessed using the ActiGraph GT1 M accelerometer. Fasting levels of serum lipids (TG, HDL), serum glucose, waist circumference (WC) and blood pressure were measured to diagnose MetS according to NCEP-ATP III criteria. In 73 out of 85 participants the VFA exceeded the upper normal level of 100 cm2, however, in almost a half of this group (n = 36) with elevated VFA (139.5 ± 26.1 cm2 on average), only 2 out of 5 criteria for MetS diagnosis were met. Participants were physically active, making on average 10,919 ± 3435 steps/day. The risk of MetS occurrence in women with VFA > 100 cm2 was twelve times higher (OR 12.33; CI 95% [1.5; 99.8]) than in the group with VFA < 100 cm2. The participants from the group with the highest PA level (≥12,500 steps/day) were at almost 4 times lower risk for MetS, than their less active counterparts (OR 3.84; CI 95% [1.27;11.64]). Increased level of VFA is a strong risk factor for the MetS in postmenopausal women, however high level of regular PA above the threshold of 12,500 steps/day may substantially reduce it.

Physical activity, body composition and general health status of physically active students of the University of the Third Age (U3A).

OBJECTIVE: To evaluate general health status of a group of older adults, physically active students of the University of the Third Age (U3A), based on results of biochemical analyses of blood, assessment of their physical activity (PA) level, body composition and cognitive function with respect to age and sex. METHODS: A total of 104 students (85 women and 19 men, aged 63.7±6.6 y) of the U3A's located in the Upper Silesia region of Poland volunteered to participate in this study. A habitual PA level and body composition were objectively assessed by using ActiGraph GT1M and InBody 720, respectively. Serum lipid profile and glucose metabolism markers were measured for assessment of cardiovascular disease risk factors. Moreover, subjects' cognitive functions were tested. RESULTS: Most of the study participants reached the daily step goal of 10,000 steps and thus fulfilled the ACSM recommendations for the quantity and quality of cardiorespiratory exercise. Highly negative correlations between the number of steps per day and body adiposity markers, serum insulin and HOMA-IR confirmed that vigorous physical activity at the recommended level was associated with better body composition and lower levels of risk markers of coronary heart disease and diabetes. Most of the U3A students were characterized by a favorable lipid profile, prevalence of normal blood pressure, low rates of HOMA-estimated insulin resistance and normal cognitive function. CONCLUSION: Adherence to ACSM recommendations is associated with beneficial changes in risk factors related to cardiovascular disease.

Effects of Regular Recreational Exercise Training on Serum ANGPTL3-Like Protein and Lipid Profile in Young Healthy Adults.

Evidence of the role of ANGPTL3, a liver-secreted glycoprotein, in serum lipid turnover, led us to hypothesize that this protein may be involved in modification of the lipid profile induced by exercise-training. Given the lack of data regarding this issue, the main goal of the present study was to investigate the effects of regular participation in a recreational physical activity program on serum ANGPTL3 and selected lipid profile measures in young, apparently healthy female and male adults. We compared serum ANGPTL3, lipid profile measures, common lipid ratios, the Atherogenic Index of Plasma (AIP) and glucose in fasting blood samples derived from 22 active physical education students including active females (AF, N=6) and males (AM, N=16) with samples from 28 relatively sedentary age-matched peers, including female (SF, N=9) and male (SM, N=19) individuals not involved in any regular physical conditioning program. Despite high inter-individual variability of serum ANGPTL3, there was a general tendency toward higher serum ANGPTL3 and HDL-C in women compared to men, but without significant differences related to their physical activity status. Based on both routine lipid profile measures and lipid ratios, all participants had normal lipid profiles, normal glycemia, as well as favorable anthropometric indices not suggesting increased cardiometabolic risk. However, lower levels of the TG/HDL-C ratio and AIP in physically active compared to relatively sedentary participants, reflecting the predominance of large, buoyant LDL particles, strongly support the view of beneficial health-promoting effects of regular participation in recreational sport activities.

Ultramarathon run markedly reduces plasma sphingosine-1-phosphate concentration.

We have previously shown that acute exercise increases the level of sphingosine-1-phosphate (S1P) in plasma and ceramide in erythrocytes of untrained subjects. The aim of the current study was to examine the effect of ultramarathon run on the plasma and erythrocyte levels of the following bioactive sphingolipids: S1P, sphinganine-1-phosphate (SA1P), sphingosine, sphinganine, and ceramide. Blood samples were collected from seven male amateur runners participating in a 48-hr ultramarathon race before the run, after 24 and 48 hr of running, and following 24 and 48 hr of recovery. The sphingolipids were quantified by means of HPLC. Sustained running for 48 hr resulted in a progressive decline in plasma S1P to a level significantly lower than at prerace, and then remained stable over the next 48 hr of recovery. In erythrocytes, S1P content was stable until 24 hr of recovery, then rose abruptly to reach peak values after 48 hr of recovery. The plasma level of SA1P decreased progressively during the competition and remained unchanged over the recovery. In erythrocytes, the level of SA1P increased after 24 hr running and normalized thereafter. The level of ceramide, both in plasma and erythrocytes, was not significantly affected by the ultraendurance run. We speculate that reduction in plasma level of S1P during and after the run reduces its biological actions and might be responsible for some negative side-effects of the ultraendurance effort.

Metabolic responses to a 48-h ultra-marathon run in middle-aged male amateur runners.

PURPOSE: To evaluate ongoing metabolic changes during a 48-h competitive run and a 48-h recovery period, with focus on potential health risks exemplified by heart and skeletal muscle damage biomarkers and oxidative stress-related indices. METHODS: Blood samples were taken before the race, after 12, 24, and 48 h of running, and after 24 and 48 h of recovery from male amateur runners (N = 7, age 35-59 years, VO2max mean ± SD 57.0 ± 4.0 ml kg(-1) min(-1), total distance covered 183-320 km). The samples were analyzed for morphology, acid-base and electrolyte balance, iron status, lipid profile, interleukin-6, high-sensitivity C-reactive protein, N-terminal pro-brain-type natriuretic peptide, high-sensitivity cardiac troponin T, non-enzymatic antioxidants, activities of selected enzymes including antioxidant enzymes, and total antioxidant status. RESULTS: The sustained ultra-endurance run caused hypocapnic alkalosis with slight hyperkalemia and hypocalcemia, but no hyponatremia. Blood biochemistry showed severe muscle but not liver damage, and an acute inflammatory response. These effects were evidenced by leukocytosis, several fold rises in interleukin-6 and high sensitivity C-reactive protein, extreme elevations in serum levels of muscle enzymes, and marked increases in cardiac biomarker levels. Most of the changes dissolved during the 48 h post-race recovery. Neither the iron pool, nor erythropoiesis, nor pro-oxidant/antioxidant balance were substantially affected. CONCLUSIONS: The changes consequent on the ultra-endurance run do not pose a serious health risk in men who begin their endeavor with ultra-endurance running in mid-life. There is some circumstantial evidence that hyperventilatory hypocapnia may modulate inflammatory response by stimulating the release of interleukin-6 from working skeletal muscles.

Acute metabolic responses to a 24-h ultra-marathon race in male amateur runners.

The study was conducted to evaluate the metabolic responses to a 24 h ultra-endurance race in male runners. Paired venous and capillary blood samples from 14 athletes (mean age 43.0 ± 10.8 years, body weight 64.3 ± 7.2 kg, VO(2max) 57.8 ± 6.1 ml kg(-1) min(-1)), taken 3 h before the run, after completing the marathon distance (42.195 km), after 12 h, and at the finish of the race, were analyzed for blood morphology, acid-base balance and electrolytes, lipid profile, interleukin-6 (IL-6), high-sensitivity C-reactive protein (hsCRP), and serum enzyme activities. Mean distance covered during the race was 168.5 ± 23.1 km (range 125.2-218.5 km). Prolonged ultra-endurance exercise triggered immune and inflammatory responses, as evidenced by a twofold increase in total leukocyte count with neutrophils and monocytes as main contributors, nearly 30-fold increase in serum IL-6 and over 20-fold rise in hsCRP. A progressive exponential increase in mean creatine kinase activity up to the level 70-fold higher than the respective pre-race value, a several fold rise in serum activities of aspartate aminotransferase and alanine aminotransferase, and a fairly stable serum γ-glutamyl transferase level, were indicative of muscle, but not of liver damage. With duration of exercise, there was a progressive development of hyperventilation-induced hypocapnic alkalosis, and a marked alteration in substrate utilization towards fat oxidation to maintain blood glucose homeostasis. The results of this study may imply that progressive decline in partial CO(2) pressure (hypocapnia) that develops during prolonged exercise may contribute to increased interleukin-6 production.

High-dose testosterone propionate treatment reverses the effects of endurance training on myocardial antioxidant defenses in adolescent male rats.

This study was aimed at evaluation of changes in activities of selected antioxidant enzymes (superoxide dismutase, catalase, glutathione peroxidase, and glutathione reductase) and contents of key nonenzymatic antioxidants (glutathione, protein thiol groups, and α- and γ-tocopherols) in the left heart ventricle of young male Wistar rats subjected to endurance training (treadmill running, 1 h daily, 5 days a week, for 6 weeks) or/and testosterone propionate treatment (8 or 80 mg/kg body weight, intramuscularly, once a week, for 6 weeks) during adolescence. The training alone increased the activities of key antioxidant enzymes, but lowered the pool of nonenzymatic antioxidants and enhanced myocardial oxidative stress as evidenced by elevation of the lipid peroxidation biomarker malondialdehyde. The lower-dose testosterone treatment showed mixed effects on the individual components of the antioxidant defense system, but markedly enhanced lipid peroxidation. The higher-dose testosterone treatment decreased the activities of the antioxidant enzymes, lowered the contents of the nonenzymatic antioxidants, except for that of γ-tocopherol, reversed the effect of endurance training on the antioxidant enzymes activities, and enhanced lipid peroxidation more than the lower-dose treatment. These data demonstrate the potential risk to cardiac health from exogenous androgen use, either alone or in combination with endurance training, in adolescents.

Testosterone affects hormone-sensitive lipase (HSL) activity and lipid metabolism in the left ventricle.

Fatty acids, which are the major cardiac fuel, are derived from lipid droplets stored in cardiomyocytes, among other sources. The heart expresses hormone-sensitive lipase (HSL), which regulates triglycerides (TG) breakdown, and the enzyme is under hormonal control. Evidence obtained from adipose tissue suggests that testosterone regulates HSL activity. To test whether this is also true in the heart, we measured HSL activity in the left ventricle of sedentary male rats that had been treated with testosterone supplementation or orchidectomy with or without testosterone substitution. Left ventricle HSL activity against TG was significantly elevated in intact rats supplemented with testosterone. HSL activity against both TG and diacylglyceride was reduced by orchidectomy, whereas testosterone replacement fully reversed this effect. Moreover, testosterone increased left ventricle free fatty acid levels, caused an inhibitory effect on carbohydrate metabolism in the heart, and elevated left ventricular phosphocreatine and ATP levels as compared to control rats. These data indicate that testosterone is involved in cardiac HSL activity regulation which, in turn, may affect cardiac lipid and carbohydrate metabolism.

Short-term effects of electrically induced tachycardia on antioxidant defenses in the normal and hypertrophied rat left ventricle.

Increased oxidative stress resulting from enhanced production of reactive oxygen species and/or inadequate mechanisms of antioxidant defenses has been recognized as an important factor contributing to the initiation and progression of cardiac dysfunction under a wide variety of pathophysiological conditions. The main objective of this study was to examine the effect of electrically induced tachycardia on oxidative stress and the capacity of antioxidant defenses in the normal and hypertrophied left ventricle (LV) in the rat. Left ventricular hypertrophy (LVH) was produced by banding the descending abdominal aorta. The activities of antioxidant enzymes, concentrations of non-enzymatic antioxidants, and biomarkers of oxidative stress were measured in the LV of aortic-banded animals (LVH), untreated or banded rats subjected to short-term (45 min) atrial pacing [(CTR + S) and (LVH + S), respectively], and untreated (CTR) or sham-operated (SHAM) controls. The results indicate that the increase in heart rate in vivo as a result of atrial pacing to a maximum level, independent of sympathetic nerve activity, leads to a substantial increase in oxidative stress and a marked decline in the activities of antioxidant enzymes in both the normal and hypertrophied left ventricle of the rat. The accompanying increase in tissue content of alpha- and gamma-tocopherols seem to contribute to attenuation of the oxidant stress-related loss of thiol stores in the LV. Stable left ventricular hypertrophy induced by aortic banding for six weeks has a minor impact on the capacity of the endogenous antioxidant defense system in the LV, but significantly and negatively affects the ability of the heart LV to tolerate the stress of tachycardia.

Long-term consumption of a carbohydrate-restricted diet does not induce deleterious metabolic effects.

Carbohydrate (CHO)-restricted diets have been recommended for weight loss and to prevent obesity, but their long-term effects have not been fully elucidated. This study was designed to evaluate the effect of long-term (>1 year) consumption of a low-CHO high-fat diet ("The optimal diet," developed by Dr Kwasniewski referenced herein) on lipid profile, glycemic control, and cardiovascular disease risk factors in healthy subjects. Of 31 "optimal" dieters enrolled in the study (17 women and 14 men, aged 51.7+/-16.6 years), 22 declared adherence to the diet for more than 3 years. Average energy intake and principal nutrients consumed were assessed from 6-day dietary records provided by the participants. In most dieters, concentrations of beta-hydroxybutyrate, free fatty acids, total cholesterol, and low-density lipoprotein cholesterol exceeded the upper limits of the reference ranges for nonstarved subjects. The metabolic profiles of most subjects were positive for several indicators, including relatively low concentrations of triacylglycerols, high levels of high-density lipoprotein cholesterol (HDL-C), and normal ratios of low-density lipoprotein cholesterol/HDL-C and total cholesterol/HDL-C. In most subjects, plasma concentrations of glucose, insulin, glucagon, cortisol, homocysteine, glycerol, and C-reactive protein were within reference ranges. Notably, in all but one subject, the homeostasis model assessment index of insulin resistance remained below the threshold for diagnosis of insulin resistance. These results indicate that long-term (>1 year) compliance with a low-CHO high-fat "optimal diet" does not induce deleterious metabolic effects and does not increase the risk for cardiovascular disease, as evidenced by maintenance of adequate glycemic control and relatively low values for conventional cardiovascular risk factors.

Selenium levels in blood of upper Silesian population: evidence of suboptimal selenium status in a significant percentage of the population.

The selenium status and the relationship of whole-blood selenium and plasma homocysteine are reported for healthy human subjects living in Upper Silesia. A total of 1063 individuals (627 male and 436 female) examined for whole-blood selenium were subdivided into six groups according to age; the youngest included adolescents (n=143) aged 10-15 yr, and the oldest were centenarians (n=132). The mean Se content was relatively low (62.5+/-18.4 microg/L), and it tended to be higher in men (65.9+/-17.2 microg/L) than in women (57.5+/-18.9 microg/L). Selenium levels appeared to be age dependent, as the highest values were observed in young and middle-age adults (21-40 yr), whereas they were significantly lower in adolescents and in the elderly. In more than 40% of apparently healthy adults (aged 21-69 yr), the Se concentration was within the range 60-80 microg/L (i.e., below the lower limit of the nutritional adequacy range [80 microg/L]). A significant inverse correlation between whole-blood selenium and plasma total homocysteine was detected in a smaller population sample of middle-aged and elderly persons (n=204).

Antioxidant status in newborns and infants suffering from congenital heart defects.

There is a common view that free radicals may play an important role in tissue damage resulting from circulatory insufficiency, cardiosurgery etc. There are very few data concerning the involvement of free radical reactions in the newborns and infants suffering from congenital heart defects (CHD). Antioxidant status was evaluated in 41 newborns and infants under 1 year of age, among them 23 suffering from CHD (14 with left-to-right shunt and 9 with cyanotic heart defect) and 18 healthy controls. The study based on the assessment of activities of antioxidant enzymes in blood (superoxide dismutase, catalase and glutathione peroxidase), levels of low molecular weight antioxidants (vitamin E, uric acid and selenium) and the concentration of malondialdehyde (MDA) as a marker of lipid peroxidation. All subjects had low blood selenium concentration as compared to the level considered as being adequate. Infants suffering from CHD had lower, as compared to healthy controls, plasma vitamin E concentration. The difference was significant in the case of acyanotic ones. The activities of superoxide dismutase and catalase in infants with CHD were not significantly different from the respective values recorded in healthy controls. The activity of glutathione peroxidase in whole blood was the lowest in infants with cyanotic heart defect in whom lipid peroxidation, as evaluated by MDA level, was the most enhanced. Significantly higher plasma concentration of uric acid which may be interpreted as a positive mechanism enabling better protection of red blood cells from peroxidative damage was found in this group of infants. It is concluded that enhanced oxidative stress due to imbalance between prooxidant and antioxidant reactions appears to be associated with congenital heart defect pathology in infants.

Effects of a low carbohydrate diet and graded exercise during the follicular and luteal phases on the blood antioxidant status in healthy women.

The aim of this study was to examine the effect of a low-carbohydrate (L-CHO) diet and graded cycling exercise on the enzymatic and non-enzymatic blood antioxidant defence system in young eumenorrhoeic women. Seven healthy physical education students exercised incrementally until they were fatigued under four different phase-diet conditions of the menstrual cycle, i.e. twice either during the mid-follicular or the mid-luteal phase, in each case either after 3 days of eating a normal mixed diet (59% carbohydrate, 27% fat, 14% protein) or 3 days of eating an isoenergy L-CHO diet (5% carbohydrate, 52% fat, 43% protein). In venous blood samples obtained at rest, immediately post test and during recovery, the activity of antioxidant enzymes and concentrations of reduced glutathione and selenium were determined. Plasma samples were analysed for concentrations of malondialdehyde, vitamin E (alpha-tocopherol), uric acid and activity of creatine kinase. The 3 days of the L-CHO diet, which had been preceded by glycogen-depleting exercise, resulted in a stimulation of the blood antioxidant defence system in young eumenorrhoeic women both at rest and during the graded cycling exercise to maximal oxygen uptake. It seems justified to presume that higher daily doses of haem iron, selenium and alpha-tocopherol provided by the L-CHO diet contributed to the enhancement of catalase activity, the rise in plasma concentrations of alpha-tocopherol and selenium, which resulted in better protection of the cell membranes against damage from peroxides, as reflected by a limited release of creatine kinase into plasma. With the exception of the case of glutathione reductase, the phases of the menstrual cycle had only minor effects on the indices of the blood antioxidant defence system.