Richard J. Bloomer

Acute exercise and oxidative stress: a 30 year history

The topic of exercise-induced oxidative stress has received considerable attention in recent years, with close to 300 original investigations published since the early work of Dillard and colleagues in 1978. Single bouts of aerobic and anaerobic exercise can induce an acute state of oxidative stress. This is indicated by an increased presence of oxidized molecules in a variety of tissues. Exercise mode, intensity, and duration, as well as the subject population tested, all can impact the extent of oxidation. Moreover, the use of antioxidant supplements can impact the findings. Although a single bout of exercise often leads to an acute oxidative stress, in accordance with the principle of hormesis, such an increase appears necessary to allow for an up-regulation in endogenous antioxidant defenses. This review presents a comprehensive summary of original investigations focused on exercise-induced oxidative stress. This should provide the reader with a well-documented account of the research done within this area of science over the past 30 years.

Effects of acute aerobic and anaerobic exercise on blood markers of oxidative stress

The purpose of this study was to compare oxidative modification of blood proteins, lipids, DNA, and glutathione in the 24 hours following aerobic and anaerobic exercise using similar muscle groups. Ten cross-trained men (24.3 ± 3.8 years, [mean ± SEM]) performed in random order 30 minutes of continuous cycling at 70% of VO2max and intermittent dumbbell squatting at 70% of 1 repetition maximum (1RM), separated by 1–2 weeks, in a crossover design. Blood samples taken before, and immediately, 1, 6, and 24 hours postexercise were analyzed for plasma protein carbonyls (PC), plasma malondialdehyde (MDA), and whole-blood total (TGSH), oxidized (GSSG), and reduced (GSH) glutathione. Blood samples taken before and 24 hours postexercise were analyzed for serum 8-hydroxy-29-deoxyguanosine (8-OHdG). PC values were greater at 6 and 24 hours postexercise compared with pre-exercise for squatting, with greater PC values at 24 hours postexercise for squatting compared with cycling (0.634 ± 0.053 vs. 0.359 ± 0.018 nM·mg protein-1). There was no significant interaction or main effects for MDA or 8-OHdG. GSSG experienced a shortlived increase and GSH a transient decrease immediately following both exercise modes. These data suggest that 30 minutes of aerobic and anaerobic exercise performed by young, cross-trained men (a) can increase certain biomarkers of oxidative stress in blood, (b) differentially affect oxidative stress biomarkers, and (c) result in a different magnitude of oxidation based on the macromolecule studied. Practical applications: While protein and glutathione oxidation was increased following acute exercise as performed in this study, future research may investigate methods of reducing macromolecule oxidation, possibly through the use of antioxidant therapy.

Impact of caloric and dietary restriction regimens on markers of health and longevity in humans and animals: a summary of available findings

Considerable interest has been shown in the ability of caloric restriction (CR) to improve multiple parameters of health and to extend lifespan. CR is the reduction of caloric intake - typically by 20 - 40% of ad libitum consumption - while maintaining adequate nutrient intake. Several alternatives to CR exist. CR combined with exercise (CE) consists of both decreased caloric intake and increased caloric expenditure. Alternate-day fasting (ADF) consists of two interchanging days; one day, subjects may consume food ad libitum (sometimes equaling twice the normal intake); on the other day, food is reduced or withheld altogether. Dietary restriction (DR) - restriction of one or more components of intake (typically macronutrients) with minimal to no reduction in total caloric intake - is another alternative to CR. Many religions incorporate one or more forms of food restriction. The following religious fasting periods are featured in this review: 1) Islamic Ramadan; 2) the three principal fasting periods of Greek Orthodox Christianity (Nativity, Lent, and the Assumption); and 3) the Biblical-based Daniel Fast. This review provides a summary of the current state of knowledge related to CR and DR. A specific section is provided that illustrates related work pertaining to religious forms of food restriction. Where available, studies involving both humans and animals are presented. The review includes suggestions for future research pertaining to the topics of discussion.

Blood Oxidative Stress Biomarkers : Influence of Sex, Exercise Training Status, and Dietary Intake

BACKGROUND Sex and lifestyle factors are known to influence the oxidation of protein, lipids, and DNA. Biomarkers such as protein carbonyls (PC), malondialdehyde (MDA), and 8-hydroxydeoxyguanosine (8-OHdG) have been commonly used in an attempt to characterize the oxidative status of human subjects. OBJECTIVE This study compared resting blood oxidative stress biomarkers, in relation to exercise training status and dietary intake, between men and women. METHODS Exercise-trained and sedentary men and women (with normal menstrual cycles; reporting during the early follicular phase) were recruited from the University of Memphis, Tennessee, campus and surrounding community via recruitment flyers and word of mouth. Participants were categorized by sex and current exercise training status (ie, trained or untrained). Each completed a detailed 5-day food record of all food and drink consumed. Diets were analyzed for kilocalories and macro- and micronutrient (vitamins C, E, A) intake. Venous blood samples were obtained at rest and analyzed for PC, MDA, and 8-OHdG. RESULTS In the 131 participants (89 men, of whom 74 were exercise trained and 15 untrained, and 42 women, of whom 22 were exercise trained and 20 untrained; mean [SD] age, 24 [4] years), PC did not differ significantly between trained men and women or between untrained men and women. However, trained participants had significantly lower plasma PC (measured in nmol . mg protein(-1)) (mean [SEM] 0.0966 [0.0055]) than did untrained participants (0.1036 [0.0098]) (P < 0.05). MDA levels (measured in micromol . L(-1)) were significantly lower in trained women (0.4264 [0.0559]) compared with trained men (0.6959 [0.0593]); in trained men and women combined (0.5621 [0.0566]) compared with untrained men and women combined (0.7397 [0.0718]); and in women combined (0.5665 [0.0611]) compared with men combined (0.7338 [0.0789]) (P < 0.05 for all comparisons). No significant differences were noted between any groups for 8-OHdG. Neither PC nor 8-OHdG were correlated to any dietary variable, with the exception of PC and percent of protein in untrained men (r = 0.552; P = 0.033). MDA was positively correlated to protein intake and negatively correlated to percent of carbohydrate and vitamin C intake, primarily in trained men (P < or = 0.03). CONCLUSIONS In this sample of young healthy adults, oxidative stress was lower in women than in men and in trained compared with untrained individuals, particularly regarding MDA. With the exception of MDA primarily in trained men, dietary intake did not appear to be correlated to biomarkers of oxidative stress.

Effect of exercise on oxidative stress biomarkers.

Acute bouts of aerobic and anaerobic exercise can induce a state of oxidative stress, as indicated by an increase in oxidized molecules in a variety of tissues and body fluids. The extent of oxidation is dependent on the exercise mode, intensity, and duration, and is specifically related to the degree of oxidant production. Findings of increased oxidative stress have been reported for both healthy and diseased subjects following single bouts of exercise. While acute exercise has the ability to induce an oxidative stress, this same exercise stimulus appears necessary to allow for an upregulation in endogenous antioxidant defenses. This chapter presents a summary of exercise-induced oxidative stress.

Effect of eicosapentaenoic and docosahexaenoic acid on resting and exercise-induced inflammatory and oxidative stress biomarkers: a randomized, placebo controlled, cross-over study.

BackgroundThe purpose of the present investigation was to determine the effects of EPA/DHA supplementation on resting and exercise-induced inflammation and oxidative stress in exercise-trained men. Fourteen men supplemented with 2224 mg EPA+2208 mg DHA and a placebo for 6 weeks in a random order, double blind cross-over design (with an 8 week washout) prior to performing a 60 minute treadmill climb using a weighted pack. Blood was collected pre and post exercise and analyzed for a variety of oxidative stress and inflammatory biomarkers. Blood lactate, muscle soreness, and creatine kinase activity were also measured.ResultsTreatment with EPA/DHA resulted in a significant increase in blood levels of both EPA (18 ± 2 μmol·L-1 vs. 143 ± 23 μmol·L-1; p < 0.0001) and DHA (67 ± 4 μmol·L-1 vs. 157 ± 13 μmol·L-1; p < 0.0001), while no differences were noted for placebo. Resting levels of CRP and TNF-α were lower with EPA/DHA compared to placebo (p < 0.05). Resting oxidative stress markers were not different (p > 0.05). There was a mild increase in oxidative stress in response to exercise (XO and H2O2) (p < 0.05). No interaction effects were noted. However, a condition effect was noted for CRP and TNF-α, with lower values with the EPA/DHA condition.ConclusionEPA/DHA supplementation increases blood levels of these fatty acids and results in decreased resting levels of inflammatory biomarkers in exercise-trained men, but does not appear necessary for exercise-induced attenuation in either inflammation or oxidative stress. This may be due to the finding that trained men exhibit a minimal increase in both inflammation and oxidative stress in response to moderate duration (60 minute) aerobic exercise.

Decreased blood antioxidant capacity and increased lipid peroxidation in young cigarette smokers compared to nonsmokers: Impact of dietary intake

BackgroundBlood of cigarette smokers routinely displays decreased antioxidant capacity and increased oxidized lipids compared to nonsmokers. This is thought to be due to both chronic exposure to cigarette smoke in addition to low intake of dietary antioxidants, and is a routine finding in veteran smokers. No study to date has determined the independent and combined impact of dietary intake and cigarette smoking on blood antioxidant capacity and oxidative stress in a sample of young, novice smokers.MethodsWe compared resting plasma antioxidant reducing capacity (ARC; expressed in uric acid equivalents), serum trolox-equivalent antioxidant capacity (TEAC), whole blood total glutathione, plasma malondialdehyde (MDA), and plasma oxidized low density lipoprotein (oxLDL) between 15 young (24 ± 4 years), novice smokers (pack-year history: 3 ± 2) and 13 nonsmokers of similar age (24 ± 5 years). Detailed dietary records were maintained during a seven-day period for analysis of total energy, macro- and micronutrient intake.ResultsARC (0.0676 ± 0.0352 vs. 0.1257 ± 0.0542 mmol·L-1; mean ± SD, p = 0.019), TEAC (0.721 ± 0.120 vs. 0.765 ± 0.130 mmol·L-1, p = 0.24) and glutathione (835 ± 143 vs. 898 ± 168 μmol·L-1, p = 0.28) were lower in smokers compared to nonsmokers, with only the former being statistically significant. MDA (0.919 ± 0.32 vs. 0.647 ± 0.16 μmol·L-1, p = 0.05) and oxLDL were both higher in smokers compared to nonsmokers (229 ± 94 vs. 110 ± 62 ng·mL-1, p = 0.12), although only the MDA comparison was of statistical significance. Interestingly, these findings existed despite no differences in dietary intake, including antioxidant micronutrient consumption, between both smokers and nonsmokers.ConclusionThese data, with specificity to young, novice cigarette smokers, underscore the importance of smoking abstinence. Future studies with larger sample sizes, inclusive of smokers of different ages and smoking histories, are needed to extend these findings.

Effects of Exercise and Weight Loss on Mental Stress–Induced Cardiovascular Responses in Individuals With High Blood Pressure

The purpose of this study was to determine the effects of exercise and weight loss on cardiovascular responses during mental stress in mildly to moderately overweight patients with elevated blood pressure. Ninety-nine men and women with high normal or unmedicated stage 1 to stage 2 hypertension (systolic blood pressure 130 to 179 mm Hg, diastolic blood pressure 85 to 109 mm Hg) underwent a battery of mental stress tests, including simulated public speaking, anger recall interview, mirror trace, and cold pressor, before and after a 6-month treatment program. Subjects were randomly assigned to 1 of 3 treatments: (1) aerobic exercise, (2) weight management combining aerobic exercise with a behavioral weight loss program, or (3) waiting list control group. After 6 months, compared with control subjects, participants in both active treatment groups had lower levels of systolic blood pressure, diastolic blood pressure, total peripheral resistance, and heart rate at rest and during mental stress. Compared with subjects in the control group, subjects in the exercise and weight management groups also had greater resting stroke volume and cardiac output. Diastolic blood pressure was lower for the weight management group than for the exercise-only group during all mental stress tasks. These results demonstrate that exercise, particularly when combined with a weight loss program, can lower both resting and stress-induced blood pressure levels and produce a favorable hemodynamic pattern resembling that targeted for antihypertensive therapy.

Comparison of coconut water and a carbohydrate-electrolyte sport drink on measures of hydration and physical performance in exercise-trained men

BackgroundSport drinks are ubiquitous within the recreational and competitive fitness and sporting world. Most are manufactured and artificially flavored carbohydrate-electrolyte beverages. Recently, attention has been given to coconut water, a natural alternative to manufactured sport drinks, with initial evidence indicating efficacy with regard to maintaining hydration. We compared coconut water and a carbohydrate-electrolyte sport drink on measures of hydration and physical performance in exercise-trained men.MethodsFollowing a 60-minute bout of dehydrating treadmill exercise, 12 exercise-trained men (26.6 ± 5.7 yrs) received bottled water (BW), pure coconut water (VitaCoco®: CW), coconut water from concentrate (CWC), or a carbohydrate-electrolyte sport drink (SD) [a fluid amount based on body mass loss during the dehydrating exercise] on four occasions (separated by at least 5 days) in a random order, single blind (subject and not investigators), cross-over design. Hydration status (body mass, fluid retention, plasma osmolality, urine specific gravity) and performance (treadmill time to exhaustion; assessed after rehydration) were determined during the recovery period. Subjective measures of thirst, bloatedness, refreshed, stomach upset, and tiredness were also determined using a 5-point visual analog scale.ResultsSubjects lost approximately 1.7 kg (~2% of body mass) during the dehydrating exercise and regained this amount in a relatively similar manner following consumption of all conditions. No differences were noted between coconut water (CW or CWC) and SD for any measures of fluid retention (p > 0.05). Regarding exercise performance, no significant difference (p > 0.05) was noted between BW (11.9 ± 5.9 min), CW (12.3 ± 5.8 min), CWC (11.9 ± 6.0 min), and SD (12.8 ± 4.9 min). In general, subjects reported feeling more bloated and experienced greater stomach upset with the CW and CWC conditions.ConclusionAll tested beverages are capable of promoting rehydration and supporting subsequent exercise. Little difference is noted between the four tested conditions with regard to markers of hydration or exercise performance in a sample of young, healthy men. Additional study inclusive of a more demanding dehydration protocol, as well as a time trial test as the measure of exercise performance, may more specifically determine the efficacy of these beverages on enhancing hydration and performance following dehydrating exercise.

The Role of Nutritional Supplements in the Prevention and Treatment of Resistance Exercise-Induced Skeletal Muscle Injury

The topic of exercise-induced skeletal muscle injury has received considerable attention in recent years. Likewise, strategies to minimise the injury resulting from heavy resistance exercise have been studied. Over the past 15 years, several investigations have been performed focused on the role of nutritional supplements to attenuate signs and symptoms of muscle injury. Of these, some have reported favourable results, while many others have reported no benefit of the selected nutrient. Despite these mixed findings, recommendations for the use of nutritional supplements for the purposes of attenuating muscle injury are rampant within the popular fitness media and athletic world, largely without scientific support. Those nutrients include the antioxidant vitamin C (ascorbic acid) and vitamin E (tocopherol), N-acetyl-cysteine, flavonoids, L-carnitine, astaxanthin, β-hydroxy-β-methylbutyrate, creatine monohydrate, essential fatty acids, branched-chain amino acids, bromelain, proteins and carbohydrates. A discussion of all published peer-reviewed articles in reference to these nutrients and their impact on resistance exercise-induced skeletal muscle injury is presented, in addition to a brief view into the potential mechanism of action for each nutrient.Based on the current state of knowledge, the following conclusions can be made with regard to nutritional supplements and their role in attenuating signs and symptoms of skeletal muscle injury occurring as a consequence of heavy resistance exercise: (i) there appears to be a potential role for certain supplements (vitamin C, vitamin E, flavonoids, and L-carnitine); (ii) these supplements cannot effectively eliminate muscle injury, only attenuate certain signs and symptoms; (iii) it is presently unclear what the optimal dosage of these nutrients is (whether used alone or in combination); (iv) it is unclear what the optimal pretreatment period is; and (v) the effectiveness is largely specific to non-resistance trained individuals.Ultimately, because so few studies have been conducted in this area, it is difficult to recommend with confidence the use of selected nutrients for the sole purpose of minimising signs and symptoms of resistance exercise-induced muscle injury, in particular with regard to resistance-trained individuals.