Impaired baroreflex sensitivity and increased systolic blood pressure variability in chronic post-ischemic stroke

OBJECTIVES

Acute post-stroke patients present cardiovascular autonomic dysfunction, which manifests as lower heart rate variability and impaired baroreflex sensitivity. However, few studies performed to date have evaluated cardiovascular autonomic function in chronic post-stroke patients. The aim of this study was to evaluate cardiovascular autonomic modulation in chronic post-ischemic stroke patients.

METHODS

The seventeen enrolled subjects were divided into a stroke group (SG, n=10, 5±1 years after stroke) and a control group (CG, n=7). Non-invasive curves for blood pressure were continuously recorded (Finometer®) for 15 minutes while the subject was in a supine position. Heart rate variability and blood pressure variability were analyzed in the time and frequency domains.

RESULTS

No differences were observed in systolic and diastolic pressure and heart rate between post-stroke patients and healthy individuals. The SG group had lower indexes for heart rate variability in the time domain (standard deviation of normal to normal R-R intervals, SDNN; variance of normal to normal R-R intervals, VarNN; and root mean square differences of successive R-R intervals, RMSSD) and a lower high-frequency band for heart rate variability than was observed in the CG. Systolic blood pressure variability and the low-frequency band for systolic pressure were higher in post-stroke patients, while the alpha index was lower in the SG than in the CG.

CONCLUSION

After ischemic stroke, affected patients present chronically reduced heart rate variability, impaired cardiac vagal modulation, increased systolic blood pressure variability and higher sympathetic vascular modulation along with impaired baroreflex sensitivity, which can increase the risk of cardiovascular events, despite adequate blood pressure control.

Combined aerobic and resistance exercise training attenuates cardiac dysfunctions in a model of diabetes and menopause

The study aimed at evaluating the effects of combined aerobic and resistance exercise training on cardiac morphometry and function, oxidative stress and inflammatory parameters in diabetic ovariectomized rats. For this, female Wistar rats (10 weeks-old) were divided into 4 groups (n = 8): euglycemic (E), diabetic (streptozotocin, 50 mg/kg, iv) (D), diabetic ovariectomized (DO) and trained diabetic ovariectomized (TDO). The combined exercise training was performed on a treadmill and in a ladder adapted to rats (8 weeks, at 40-60% of maximal capacity). The left ventricle (LV) morphometry and function were evaluated by echocardiography. Oxidative stress and inflammatory markers were measured on ventricles tissue. The sedentary diabetic animals (D and DO) showed impaired systolic and diastolic functions, as well as increased cardiac overload, evaluated by myocardial performance index (MPI- D: 0.32 ± 0.05; DO: 0.39 ± 0.13 vs. E: 0.25 ± 0.07), in relation to E group. Systolic and MPI dysfunctions were exacerbated in DO when compared to D group. The DO group presented higher protein oxidation and TNF-α/IL-10 ratio than D groups. Glutathione redox ratio (GSH/GSSG) and IL-10 were decreased in both D and DO groups when compared to E group. Exercise training improved exercise capacity, systolic and diastolic functions and MPI (0.18±0.11). The TDO group showed reduced protein oxidation and TNF-α/IL-10 ratio and increased GSH/GSSG and IL-10 in relation to the DO group. These results showed that combined exercise training was able to attenuate the cardiac dysfunctions, probably by reducing inflammation and oxidative stress in an experimental model of diabetes and menopause.

The impact of sedentarism on heart rate variability (HRV) at rest and in response to mental stress in young women

Sedentarism is one of the main risk factors for the onset of cardiometabolic diseases. Some biomarkers, such as heart rate variability (HRV), have been largely studied and found to be involved in the genesis of the dysfunctions associated with sedentary behavior. However, comparatively few studies have focused on the female sex. The objective of this study was to analyze the hemodynamic, autonomic and quality of life parameters at rest and in response to mental stress of sedentary and physically active young women. A total of 96 women, 18-30 years of age, were divided into sedentary (SW = 48) and active (AW = 48) groups. Anthropometric, hemodynamic and quality of life parameters were evaluated and the R-R interval was recorded to quantify the cardiac autonomic modulation at rest and in response to the Stroop Color Test. The groups were similar in age, weight, height, body mass index, fat percentage, systolic and diastolic blood pressure values and glycemia. The physical health domain of quality of life was compromised in the SW group. The SW group presented higher heart rate, lower variance of RR interval and RMSSD and higher cardiac sympathovagal balance (LF/HF) both at rest and in response to the mental stress test. We concluded that sedentary lifestyle in women induces impairment in autonomic cardiac modulation at rest and in response to physiological stress, compromising the quality of life, even before altering any cardiovascular or metabolic clinical parameters, reinforcing the potential role of HRV as early marker of cardiovascular risk in this population.

ACE gene dosage determines additional autonomic dysfunction and increases renal angiotensin II levels in diabetic mice

OBJECTIVES

The present study aimed to investigate cardiovascular autonomic modulation and angiotensin II (Ang II) activity in diabetic mice that were genetically engineered to harbor two or three copies of the angiotensin-converting enzyme gene.

METHODS

Diabetic and non-diabetic mice harboring 2 or 3 copies of the angiotensin-converting enzyme gene were used in the present study. Animals were divided into 4 groups: diabetic groups with two and three copies of the angiotensin-converting enzyme gene (2CD and 3CD) and the respective age-matched non-diabetic groups (2C and 3C). Hemodynamic, cardiovascular, and autonomic parameters as well as renal Ang II expression were evaluated.

RESULTS

Heart rate was lower in diabetic animals than in non-diabetic animals. Autonomic modulation analysis indicated that the 3CD group showed increased sympathetic modulation and decreased vagal modulation of heart rate variability, eliciting increased cardiac sympathovagal balance, compared with all the other groups. Concurrent diabetes and either angiotensin-converting enzyme polymorphism resulted in a significant increase in Ang II expression in the renal cortex.

CONCLUSION

Data indicates that a small increase in angiotensin-converting enzyme activity in diabetic animals leads to greater impairment of autonomic function, as demonstrated by increased sympathetic modulation and reduced cardiac vagal modulation along with increased renal expression of Ang II.

Aerobic Exercise Protects from Pseudomonas aeruginosa-Induced Pneumonia in Elderly Mice

BACKGROUND

Pseudomonas aeruginosa (PS) infection results in severe morbidity and mortality, especially in immune-deficient populations. Aerobic exercise (AE) modulates the immune system, but its effects on the outcomes of pulmonary PS infection in elderly mice are unknown.

METHODS

BALB/c mice (24 weeks old) were randomized to sedentary, exercise (EX), PS, and PS + EX groups for the acute experimental setting, and PS and PS + EX groups for the chronic setting. Low-intensity AE was performed for 5 weeks, 60 min/day; 24 h after the final AE session, mice were inoculated with 5 × 104 colony-forming units (CFU) of PS, and 24 h and 14 days after PS inoculation, mice were studied.

RESULTS

AE inhibited PS colonization (p < 0.001) and lung inflammation (total cells, neutrophils, lymphocytes [p < 0.01] in bronchoalveolar lavage [BAL]), with significant differences in BAL levels of IL-1β (p < 0.001), IL-6 (p < 0.01), CXCL1 (p < 0.001), and TNF-α (p < 0.001), as well as parenchymal neutrophils (p < 0.001). AE increased BAL levels of IL-10 and parenchymal (p < 0.001) and epithelial (p < 0.001) IL-10 expression, while epithelial (p < 0.001) and parenchymal (p < 0.001) NF-κB expression was decreased. AE diminished pulmonary lipid peroxidation (p < 0.001) and increased glutathione peroxidase (p < 0.01). Pre-incubation of BEAS-2B with IL-10 inhibited PS-induced epithelial cell expression of TNF-α (p < 0.05), CD40 (p < 0.01), and dichlorodihydrofluorescein diacetate (p < 0.05).

CONCLUSIONS

AE inhibits PS-induced lung inflammation and bacterial colonization in elderly mice, involving IL-10/NF-κB, and redox signaling.

Measurement of Mouse Heart Rate Variability using Echocardiographic System

Aim:

We employed an echocardiographic (ECHO) system as the backbone for the collection of electrocardiogram (ECG) and heart rate variability (HRV) data. The system was tested using an exercise model in which C57 male mice were exposed to sham or forced wheel running.

Methods:

Peak/peak (RR) interval was recorded over a 3 min period using the ECG platform of the ECHO system. Isoflurane-anesthetized male mice were divided into two groups (n = 8/group): sedentary (S) and forced wheel trained (T). HRV was analyzed in time and frequency domains (Fast Fourier Transform). Exercise training (T) was performed on a motorized wheel at low intensity 1 h/day, 5 days/week, 8 weeks duration. Cardiac morphometry and function were analyzed using ECHO while ECG was the basis to measure HRV. The sampling rate was 8000 Hz. Results show that the trained mice presented a reduction in heart rate as compared to the sedentary group. This was associated with lower cardiac sympathetic and higher parasympathetic modulation leading to an improved sympathetic/parasympathetic ratio (low-frequency band/high-frequency band). The trained group showed a reduction in isovolumetric relaxation time, reduced myocardial performance index, increased relative wall thickness, and left ventricle mass when compared to the sedentary group.

Conclusion:

Results document the utility of combining the ECHO and the ECG platform, allowing for the dual measurement of autonomic and cardiac function in mice.

Hypertension induces additional cardiometabolic impairments and attenuates aerobic exercise training adaptations in fructose-fed ovariectomized rats

We tested whether hypertension favors the development of additional cardiometabolic changes in fructose-fed ovariectomized rats and how it affects aerobic exercise training (ET) effects. All rats received fructose in drinking water (10%) beginning at weaning, were ovariectomized at 10 weeks of age and divided into the normotensive sedentary (NFOS) and trained (NFOT) and hypertensive sedentary (HFOS) and trained (HFOT) groups. ET was performed on a treadmill. Arterial pressure (AP) was directly recorded; heart rate and AP variabilities were analyzed. Lipoperoxidation (LPO) and antioxidant enzyme levels were measured in the left ventricle. In addition to increased AP levels, when compared with the NFOS group, the hypertensive groups had resting tachycardia, a reduction of 29% in the pulse interval variance (VAR-PI), 19% in RMSSD (root mean square of successive differences, a cardiac parasympathetic index) and 53% in the α-index (spontaneous baroreflex), while the systolic AP variance (VAR-SAP) and its low-frequency band (LF-SAP) were sharply increased. ET did not alter AP levels. Even in the presence of hypertension, ET induced resting bradycardia, decreases of 33% in VAR-SAP and 49% in LF-SAP, and an increase of more than 60% in VAR-PI and the α-index. However, some of these parameters were still impaired relative to those of normotensive rats. LPO was reduced and catalase was increased in both trained groups, with no difference between the normotensive and hypertensive groups. Negative correlations were obtained between LPO and RMSSD (r=-0.60, P<0.05) and α-index (r=-0.63, P<0.05). In conclusion, hypertension augmented the dysfunctions in fructose-fed ovariectomized rats and attenuated metabolic aerobic ET benefits. These changes may be related to cardiovascular autonomic and oxidative stress alterations.

Association between Diastolic Dysfunction with Inflammation and Oxidative Stress in Females ob/ob Mice

Objective: To evaluate autonomic and cardiovascular function, as well as inflammatory and oxidative stress markers in ob/ob female mice.

Methods: Metabolic parameters, cardiac function, arterial pressure (AP), autonomic, hormonal, inflammatory, and oxidative stress markers were evaluated in 12-weeks female wild-type (WT group) and ob/ob mice (OB group).

Results: OB animals showed increased body weight, blood glucose, and triglyceride levels, along with glucose intolerance, when compared to WT animals. Ejection fraction (EF) and AP were similar between groups; however, the OB group presented diastolic dysfunction, as well as an impairment on myocardial performance index. Moreover, the OB group exhibited important autonomic dysfunction and baroreflex sensitivity impairment, when compared to WT group. OB group showed increased Angiotensin II levels in heart and renal tissues; decreased adiponectin and increased inflammatory markers in adipose tissue and spleen. Additionally, OB mice presented a higher damage to proteins and lipoperoxidation and lower activity of antioxidant enzymes in kidney and heart. Correlations were found between autonomic dysfunction with angiotensin II and inflammatory mediators, as well as between inflammation and oxidative stress.

Conclusions: Our results showed that female adult ob/ob mice presented discrete diastolic dysfunction accompanied by autonomic disorder, which is associated with inflammation and oxidative stress in these animals.

UMA SESSÃO DE EXERCÍCIO RESISTIDO DINÂMICO NÃO INDUZ HIPOTENSÃO PÓS-EXERCÍCIO EM RATAS SHR

RESUMO Introdução: O exercício resistido dinâmico tem sido recomendado como complemento do aeróbico em indivíduos hipertensos. No entanto, poucos estudos avaliaram os efeitos do exercício resistido nessa população, principalmente em mulheres. Objetivo: Avaliar os efeitos de uma sessão de exercício resistido dinâmico sobre a pressão arterial, a frequência cardíaca e sobre o duplo produto em ratas SHR com hipertensão espontânea. Métodos: Foram utilizadas oito ratas SHR em fase não ovulatória do ciclo estral. Dois dias depois da canulação de artéria carótida, a pressão arterial foi diretamente registrada por 20 minutos no período basal e durante 60 minutos (5 min., 15-30 min., 30-45 min. e 45-60min.) após uma sessão de exercício resistido dinâmico em escada (20%-40% da carga máxima). Resultados: Não foram observadas mudanças na pressão arterial sistólica (basal 191 ± 6,1 vs. recuperação 45-60 min. 191 ± 7,8 mmHg), diastólica (basal 157 ± 2,6 vs. recuperação 45-60 min. 156 ± 3,7 mmHg) e média (basal 174 ± 2,5 vs. recuperação 45-60 min. 173 ± 4,9 mmHg) durante os 60 minutos pós-exercício. No entanto, houve redução da frequência cardíaca (45-60 min. 330 ± 10 vs. 379 ± 15 bpm) e normalização do duplo produto (64390 ± 3529 mmHg.bpm) no período de recuperação com relação ao período basal. Conclusão: Os resultados do presente estudo demonstram que o exercício resistido dinâmico de moderada intensidade induz redução da frequência cardíaca associada à normalização do duplo produto em ratas SHR apesar de não ter sido observada hipotensão pós-exercício. Tais resultados sugerem um bom controle do risco cardiovascular depois uma sessão de exercício resistido dinâmico de moderada intensidade em pacientes hipertensos.

Interval and continuous aerobic exercise training similarly increase cardiac function and autonomic modulation in infarcted mice

The present study aimed to compare the effects of moderate-intensity continuous and high-intensity interval exercise training (ET) on exercise tolerance, cardiac morphometry and function, hemodynamic, and cardiac autonomic modulation in myocardial infarcted mice. Wild-type mice (WT) were divided into four groups: sedentary WT (S); WT myocardium infarction sedentary (IS); WT myocardium infarction underwent to moderate-intensity continuous ET (MICT), and WT myocardium infarction underwent to high-intensity interval ET (MIIT). After 60 days of descending coronary artery ligation, moderate-intensity continuous ET consisted of running at 60% of maximum, while the high-intensity interval training consisted of eight sprints of 4 min at 80% of maximum and a 4-min recovery at 40% of maximum. Both exercises were performed 1 hr a day, 5 days a week, during 8 weeks. Results demonstrated that IS showed elevated exercise tolerance, as well as decreased hemodynamic and heart function, and autonomic control. On the other hand, both programs of ET were equally effective to increase all parameters, without further differences between the groups. In conclusion, the results of the present study showed that myocardial infarction leads to damage in both investigated strains and the two types of physical exercise attenuated the major impairments provoked by myocardial infarction in exercise tolerance, cardiac structure, cardiac function, hemodynamic and cardiac autonomic modulation.

Influence of Estimated Training Status on Anti and Pro-Oxidant Activity, Nitrite Concentration, and Blood Pressure in Middle-Aged and Older Women

The purpose of this study was to compare the association between anti and pro-oxidant activity, nitrite concentration, and blood pressure (BP) in middle-aged and older women with different levels of estimated training status (TS). The sample consisted of 155 females (50-84 years) who were submitted to a physical examination to evaluate estimated TS through the "Functional Fitness Battery Test," BP measurements, and plasma blood samples to evaluate pro-oxidant and antioxidant activity and nitrite concentrations. Participants were separated by age into a middle-aged group (<65 years) and an older (≥65 years) group and then subdivided in each group according to TS. Blood biochemistry was similar between groups. On the other hand, protein oxidation was lower in participants with higher TS, independent of age. Older females with higher TS presented higher nitrite concentrations, lower lipoperoxidation, and lower values of BP compared with those with lower TS. Lower GPx activity was observed in participants with higher TS compared with middle-aged with lower TS. Thus, our results suggest that good levels of TS may be associated with lower oxidative stress and higher nitrite concentration and may contribute to maintain normal or reduced blood pressure values.

Exercise Training Prevents Cardiovascular Derangements Induced by Fructose Overload in Developing Rats

The risks of chronic diseases associated with the increasing consumption of fructose-laden foods are amplified by the lack of regular physical activity and have become a serious public health issue worldwide. Moreover, childhood eating habits are strongly related to metabolic syndrome in adults. Thus, we aimed to investigate the preventive role of exercise training undertaken concurrently with a high fructose diet on cardiac function, hemodynamics, cardiovascular autonomic modulation and oxidative stress in male rats after weaning. Male Wistar rats were divided into 4 groups (n = 8/group): Sedentary control (SC), Trained control (TC), Sedentary Fructose (SF) and Trained Fructose (TF). Training was performed on a treadmill (8 weeks, 40–60% of maximum exercise test). Evaluations of cardiac function, hemodynamics, cardiovascular autonomic modulation and oxidative stress in plasma and in left ventricle (LV) were performed. Chronic fructose overload induced glucose intolerance and an increase in white adipose tissue (WAT) weight, in myocardial performance index (MPI) (SF:0.42±0.04 vs. SC:0.24±0.05) and in arterial pressure (SF:122±3 vs. SC:113±1 mmHg) associated with increased cardiac and vascular sympathetic modulation. Fructose also induced unfavorable changes in oxidative stress profile (plasmatic protein oxidation- SF:3.30±0.09 vs. SC:1.45±0.08 nmol/mg prot; and LV total antioxidant capacity (TRAP)- SF: 2.5±0.5 vs. SC:12.7±1.7 uM trolox). The TF group showed reduced WAT, glucose intolerance, MPI (0.35±0.04), arterial pressure (118±2mmHg), sympathetic modulation, plasmatic protein oxidation and increased TRAP when compared to SF group. Therefore, our findings indicate that cardiometabolic dysfunctions induced by fructose overload early in life may be prevented by moderate aerobic exercise training.

Abstract P167: Combined Exercise Training is Better than Isolated Aerobic and Resistance Exercise Training for an Experimental Model of Metabolic Syndrome and Menopausal Rats

The aim of this study was to verify the effects of three different moderate exercise training protocols (aerobic, resistance and combined (aerobic + resistance)) in a model of metabolic syndrome and menopause on a cardiovascular parameter and oxidative stress. Female SHR rats were divided into (n=8): hypertensive (H), hypertensive ovariectomized submitted to fructose overload (100g/L in drinking water) (HFO), aerobic trained hypertensive ovariectomized submitted to fructose overload (AHOF), resistance trained hypertensive ovariectomized submitted to fructose overload (RHOF) and combined trained hypertensive ovariectomized submitted to fructose overload (CHOF). Arterial pressure (AP) signals were directly recorded. Vascular autonomic modulation was evaluated by spectral analysis. The cardiac oxidative stress was evaluated by lipoperoxidation (LPO) determination. The association of fructose overload and hormone deprivation promoted an increase in AP (HOF: 174±4 vs. H: 146±4 mmHg), heart rate (HOF: 393±10 vs. H: 352±13 bpm), VAR-SAP (HOF: 77.8±11.9 vs H: 31.1±2.6 mmHg2), LF-SAP (HOF: 10.6±2.3 vs H: 5.0±0.9 mmHg2) and LPO, and reduced baroreflex sensitivity (tachycardia response: HOF: 1.06±0.06 vs. H: 1.91±0.17 bpm/mmHg). All exercise training protocols were able to reduce LPO and LF-SAP. It was noted that only the combined exercise training was able in reducing AP (CHOF: 158±4 mm Hg) and heart rate (CHOF: 303±5 bpm). The AP reduction noted only in the CHOF group may be associated with an improve in baroreflex sensitivity, represented by an increase of tachycardic response observed only in the CHOF (1.62±0.1 bpm/mmHg) and in the AHOF (1.54 ±0.07 bpm/mmHg) groups and a reduction of VAR-PAS observed only in the CHOF (30.31±3.85 mmHg 2 ) and in the RHOF (31±2.65 mmHg 2 ) groups. In conclusion, fructose overload induced impairment in hemodynamic, vascular autonomic control and increased oxidative stress in hypertensive rats submitted to ovarian hormones deprivation. However, all exercise training protocols showed a beneficial role. Moreover, the combined exercise training showed additional improvement, suggesting that this could be a better approach than isolated aerobic and resistance training.

Hypertension, Blood Pressure Variability, and Target Organ Lesion

Hypertensive patients have a higher risk of developing health complications, particularly cardiovascular (CV) events, than individuals with normal blood pressure (BP). Severity of complications depends on the magnitude of BP elevation and other CV risk factors associated with the target organ damage. Therefore, BP control and management of organ damage may contribute to reduce this risk. BP variability (BPV) has been considered a physiological marker of autonomic nervous system control and may be implicated in increased CV risk in hypertension. This review will present some evidence relating BPV and target organ damage in hypertension in clinical and experimental settings.

Resistance or aerobic training decreases blood pressure and improves cardiovascular autonomic control and oxidative stress in hypertensive menopausal rats

We investigated whether resistance training (RT) vs. aerobic training (AT) differentially impacts on arterial pressure and related mechanisms in ovariectomized spontaneously hypertensive rats (SHRs). Female SHRs were ovariectomized and assigned to one of the following groups: sedentary, AT, or RT; sham sedentary SHR were used as control group. AT was performed on a treadmill, whereas RT was performed on a vertical ladder. Both exercise protocols were performed for 8 wk, 5 days/wk. Arterial pressure, baroreflex sensitivity, autonomic modulation, and cardiac oxidative stress parameters (lipid peroxidation, protein oxidation, redox balance, NADPH oxidase, and antioxidant enzymes activities) were analyzed. Ovariectomy increased mean arterial pressure (∼9 mmHg), sympathetic modulation (∼40%), and oxidative stress in sedentary rats. Both RT and AT reduced mean arterial pressure (∼20 and ∼8 mmHg, respectively) and improved baroreflex sensitivity compared with sedentary ovariectomized rats. However, RT-induced arterial pressure decrease was significantly less pronounced than AT. Lipid peroxidation and protein oxidation were decreased while antioxidant enzymes were increased in both trained groups vs. sedentaries. The reduced gluthatione was higher after AT vs. other groups, whereas oxidized gluthatione was lower after RT vs. AT. Moreover, sympathetic and parasympathetic modulations were highly correlated with cardiac oxidative stress parameters. In conclusion, both RT and AT can decrease arterial pressure in a model of hypertension and menopause; although, at different magnitudes this decrease was related to attenuated autonomic dysfunction in association with cardiac oxidative stress improvement in both exercise protocols.

Red and Infrared Low-Level Laser Therapy Prior to Injury with or without Administration after Injury Modulate Oxidative Stress during the Muscle Repair Process

INTRODUCTION

Muscle injury is common among athletes and amateur practitioners of sports. Following an injury, the production of reactive oxygen species (ROS) occurs, which can harm healthy muscle fibers (secondary damage) and delay the repair process. Low-level laser therapy (LLLT) administered prior to or following an injury has demonstrated positive and protective effects on muscle repair, but the combination of both administration times together has not been clarified.

AIM

To evaluate the effect of LLLT (660 nm and 780 nm, 10 J/cm², 40 mW, 3.2 J) prior to injury with or without the administration after injury on oxidative stress during the muscle repair process.

METHODS

Wistar rats were divided into following groups: control; muscle injury alone; LLLT 660 nm + injury; LLLT 780 nm + injury; LLLT 660 nm before and after injury; and LLLT 780 nm before and after injury. The rats were euthanized on days 1, 3 and 7 following cryoinjury of the tibialis anterior (TA) muscle, which was then removed for analysis.

RESULTS

Lipid peroxidation decreased in the 660+injury group after one day. Moreover, red and infrared LLLT employed at both administration times induced a decrease in lipid peroxidation after seven days. CAT activity was altered by LLLT in all periods evaluated, with a decrease after one day in the 780+injury+780 group and after seven days in the 780+injury group as well as an increase in the 780+injury and 780+injury+780 groups after three days. Furthermore, increases in GPx and SOD activity were found after seven days in the 780+injury+780 group.

CONCLUSION

The administration of red and infrared laser therapy at different times positively modulates the activity of antioxidant enzymes and reduces stress markers during the muscle repair process.