Determining factors of functioning in hemodialysis patients using the international classification of functioning, disability and health.

BACKGROUND: Hemodialysis (HD) treatment affects functioning, physical activity level, clinical biomarkers, and body composition. However, the association between these variables with functioning, considering International Classification of Functioning, Disability and Health (ICF) domains remains unclear. Thus, the aim of this study was to investigate the possible association between physical activity, biomarkers, and body composition with functioning in HD patients in reference to the ICF. METHODS: Eighty HD patients performed different tests grouped according to ICF domain: Body structure and function - handgrip strength (HS), 5-repetition sit-to-stand test, and 60-s sit-to-stand test (5-STS, 60-STS, respectively); Activity - short physical performance battery (SPPB); and Participation - participation scale questionnaire. Physical activity [Human Activity Profile questionnaire (HAP)], body composition (Dual-energy X-ray absorptiometry), Parathormone (PTH), and alkaline phosphatase were analyzed as possible variables associated with ICF domains. Data analyses were performed using simple and multiple regression models adjusted for age, duration of HD, and diuresis volume. RESULTS: In the body structure and function domain, appendicular lean mass, PTH level, and age were associated with HS (R2 = 0.558); HAP and PTH were associated with 5-STS (R2 = 0.263); and HAP, PTH, duration of HD, and age were associated with 60-STS (R2 = 0.337). In the activity domain, HAP, PTH, alkaline phosphatase, duration of HD, age, and body fat were associated with SPPB (R2 = 0.689). Finally, only HAP was associated with the participation scale (R2 = 0.067). CONCLUSION: Physical activity and PTH levels are determinant protagonists of functioning in all ICF domains in hemodialysis patients.

Fibromyalgia in social media: content and quality of the information analysis of videos on the YouTube platform.

To evaluate the fibromyalgia (FM) content in YouTube videos and verify if American College of Rheumatology (ACR) guidelines are being met. The videos were searched with the keyword "Fibromyalgia." Two independent researchers evaluated and coded specific characteristics of the videos. The popularity of the videos, the presentation properties, and content related to FM according to the ACR criteria were analyzed. Of the 200 videos included, the majority were presented by health professionals, 61.5%. Most videos covered more than one subject, 38.5%. The videos presented by health professionals were the most viewed. Following the ACR guidelines, 38% defined FM, 24% described the etiology, 19.5% described the diagnostic criteria and 52% presented recommended management strategies. The results indicate that users mainly watch videos published by health professionals. Most of the published videos do not follow the information recommended by the ACR guidelines. Therefore, videos should be interpreted with caution, not being the most appropriate resource for health education for patients with FM. Most of the videos published on YouTube about FM do not meet the ACR guidelines for FM.

Maximal inspiratory pressure is associated with health-related quality of life and is a reliable method for evaluation of patients on hemodialysis.

OBJECTIVE: To evaluate the association between Maximal Inspiratory Pressure (MIP) and health-related quality of life (HRQoL) and to verify the reliability of the MIP in patients on hemodialysis. METHODS: In a repeated-measures design, patients on hemodialysis performed MIP and specific HRQoL questionnaire (trial 1). The MIP was repeated after 6 to 8 weeks (trial 2) and reliability was assessed using Intra-class Correlation Coefficient. Standard Error of Measurement and Minimal Detectable Change scores were calculated. RESULTS: Sixty-one individuals (68.9% men) were evaluated in trial 1. MIP was associated with specific domains "Symptoms" (r = 0.45; R2 adjusted = 0.192) and the kidney disease component summary (r = 0.38; R2 adjusted = 0.138). Regarding generic domains, the MIP was associated with "Physical Functioning" (r = 0.57; R2 adjusted = 0.375) and Physical component summary (r = 0.47; R2 adjusted = 0.258). Thirty-three patients were randomly selected to perform a second MIP test (trial 2). The Intra-class Correlation Coefficient was 0.94 (95%CI 0.88-0.97). By Bland-Altman analysis, the bias was 3.2 cmH2O, which represents a difference of 3.7%. The Standard Error of Measurement and Minimal Detectable Change for MIP were 5.9 cmH2O and 13.8 cmH2O, respectively. CONCLUSION: The MIP is a reliable test, associated with physical domains of HRQoL in patients on hemodialysis. Thus, it is a useful method for respiratory evaluation in this population.

Effectiveness of conservative therapy on pain, disability and quality of life for low back pain in pregnancy: A systematic review of randomized controlled trials.

BACKGROUND: Efficacy of conservative therapy for low back pain in pregnancy (PLBP) is unclear. OBJECTIVE: To investigate the efficacy of conservative therapy on pain, disability, and quality of life in PLBP. METHODS: The protocol of this systematic review was prospectively registered at PROSPERO (CRD42020164640). Search strategy was conducted on six databases up to August 24 2020 without date or language restrictions. Minimal intervention (i.e., placebo, sham, waiting list or no intervention) was the comparator of interest. Selection of randomized controlled trials, data extraction and methodological quality assessment of included trials were conducted independently by two reviewers. The PEDro scale (0-10) was used to assess methodological quality. Effect sizes for specific therapies were pooled when possible, using random-effects models. The quality of the evidence was assessed using the Grading of Recommendations Assessment (GRADE) approach. RESULTS: Ten included trials provide uncertain evidence (low to very low quality) about the effects of auriculotherapy, education, exercise, exercise plus education, oil treatment, and osteopathy in pain, disability, and quality of life at short- and long-term. At short-term, mean differences (MDs) and 95% confidence intervals (CI) on a 0-10 points pain intensity scale were: for oil treatment, 2.8 points (2.6, 3.1) (n = one trial, 114 participants); for auriculotherapy, 1.6 points (1.2, 2.0) (n = one trial, 112 participants); for exercise, 2.2 points (-1.8, 6.2) (n = three trials, 297 participants). CONCLUSION: There is an urgent need for larger high-quality trials investigating effects of conservative therapy in pain, disability, and quality of life in this population.

Inflammatory and oxidative biomarkers as determinants of functional capacity in patients with COPD assessed by 6-min walk test-derived outcomes.

INTRODUCTION: Reduction in functional capacity is a negative clinical outcome of chronic obstructive pulmonary disease (COPD). Studies have shown association between inflammatory and oxidative stress biomarkers and functional capacity. However, it is unclear whether these biomarkers are associated with outcomes of functional capacity. Therefore, the aim of this study was to evaluate whether plasma biomarkers of inflammation and oxidative stress are predictors of the 6-min walking test (6MWT)-derived outcomes. METHODS: Twenty COPD patients were assessed on three consecutive days with different clinical measures, including functional capacity, and blood sampling. Plasma concentrations of IL-6, IL-8, TNF-ɑ, IL-10 and soluble TNF-ɑ receptors (sTNFR1 and sTNFR2) were determined by immunoassays. Oxidative stress was evaluated by determining lipid peroxidation products based on the enzymatic activity of superoxide dismutase (SOD) and catalase, and total antioxidant capacity of plasma. Functional capacity was assessed considering the six-minute walking distance (6MWD) and the estimate of six-minute walking work (6MWW). The association between biomarkers (i.e. inflammation and oxidative stress) and functional exercise capacity was investigated through the Pearson's correlation coefficient. To identify the determinants of the 6MWT, multiple linear stepwise regression analyses were performed with adjustment for age, sex and GOLD classification. RESULTS: Patients were predominantly male (65%), with mean age of 64 years and moderate airflow obstruction and impaired functional capacity. There were positive correlations between SOD activity and 6MWD (r = 0.520; p = 0.02) and 6MWW (r = 0.554; p = 0.01), as well as a negative correlation between sTNF-R1 and 6MWD (r = -0.437; p = 0.05). SOD was an independent determinant of the functional capacity, explaining 23% of the variability of 6MWD (p = 0.019) and 27% of the variability of 6MWW (p = 0.011). sTNF-R1 levels were associated with 6MWD and, together with SOD explained 40% of variability in 6MWD (p = 0.005). CONCLUSION: SOD activity was an independent determinant of performance in the 6MWT, and together with sTNFR1 explained 40% of the variations in walking distance in COPD patients. SOD activity and sTNFR1 levels might be seen as potential biomarkers of the functional capacity in patients with COPD.

Assessment of functional performance in Chagas heart disease by Human Activity Profile questionnaire.

PURPOSE: To verify the association between Human Activity Profile and functional capacity, functional class and systolic function of the patients with Chagas heart disease (CHD). METHODS: Sixty-two patients with CHD were evaluated by echocardiography, maximal exercise testing and Human Activity Profile questionnaire. The sample was stratified, according to the values of peak oxygen uptake (low or normal), functional class (symptomatic or asymptomatic), and left ventricular ejection fraction (preserved or systolic dysfunction). Linear regression and two-group comparisons analyses were used. Receiver-operating characteristic analysis was used to determine different cutoff values of the Human Activity Profile for low peak oxygen uptake prediction. RESULTS: Peak oxygen uptake was an independent predictor of Human Activity Profile (R2-adjusted = 0.27). Patients with low peak oxygen uptake had lower scores in Human Activity Profile [difference of 6.9 (95%CI 2.5-11.4)] than those with normal peak oxygen uptake. Symptomatic patients also showed lower scores when compared to the asymptomatic [difference of 6.2 (95%CI 1.7-10.8)]. There was no difference between left ventricular ejection fraction classes. The Human Activity Profile score of 76.5 was the optimal cut point value in predicting low peak oxygen uptake (sensitivity = 66.0% and specificity = 71.8%). CONCLUSION: The Human Activity Profile questionnaire is associated with functional capacity of patients with CHD and is able to identify individuals with low peak oxygen uptake.Implications for rehabilitationFunctional impairment is one of the most common clinical findings in all stages and is an important predictor of poor prognosis of the Chagas heart disease;A patient-derived measure of functional capacity is potentially useful in the setting of the Chagas heart disease;The Human Activity Profile questionnaire is effective in the identification of patients with Chagas heart disease with functional impairment and may be a valid method for functional evaluation.

Whole-Body Vibration Exercise in Different Postures on Handgrip Strength in Healthy Women: A Cross-Over Study.

OBJECTIVE: To compare the effect of Whole-Body Vibration Exercise (WBVE) applied in push-up modified and half-squat positions, on handgrip strength (HS) and on the electromyography registry (EMGrms) of the flexor digitorum superficialis muscle (FDSM) of the dominant hand. METHODS: Nineteen healthy women (age 23.40 ± 4.03 years, bodyweight: 58.89 ± 9.87 kg), performed in a randomized order five different tests: (S1) Control; (S2) Push-up modified; (S3) Push-up placebo; (S4); Half-squatting; (S5) Half-squatting placebo. The HS and the EMGrms were assessed at baseline and immediately after the tests. ANOVA two-way design mixed test, with Tukey post hoc, was used to evaluate the HS, EMGrms and the ratio between EMGrms and HS, i.e., neural ratio (NR). Thus, the lower NR represents the greater neuromuscular modifications. The statistical significance level was set up at p < 0.05. RESULTS: WBVE on S2 increased HS compared to the stimulus applied to the S4 (p = 0.0001). The increase in HS was associated with a reduction in the EMGrms of the FDSM (p < 0.001) and a lower NR (p < 0.0001), i.e., greater neuromuscular modifications, in the S2 compared to the S4 after the tests. CONCLUSION: The distance of the stimulus and the positioning on the vibratory platform influence the maximum muscular strength due to neuromuscular modifications of hands in healthy women.

Cardiorespiratory responses in different types of squats and frequencies of whole body vibration in patients with chronic obstructive pulmonary disease.

This study aims to investigate the cardiorespiratory responses to different vibration frequencies to characterize the intensity of exercise, as well as to compare the effect of two types of squatting exercises (static and dynamic) on the whole body vibration (WBV) exercise in individuals with chronic obstructive pulmonary disease (COPD). Twenty-six subjects were divided and paired into healthy and COPD groups that performed static squatting associated with WBV (frequencies: 30, 35, and 40 Hz; amplitude: 2 mm) and dynamic squatting associated with WBV (frequency: 35 Hz; amplitude 2 mm) on a vertical vibration platform. Oxygen consumption (V̇o2), heart rate (HR), minute ventilation (V̇e), ratio of minute ventilation to oxygen production (V̇e/V̇o2), ratio of minute ventilation to carbon dioxide production (V̇e/V̇co2), oxygen saturation (SpO2), and rating of perceived exertion were measured. For both groups, there was a decrease in V̇e/V̇o2 and V̇e/V̇co2 ratios during static and dynamic squats, as well as an increase in other cardiorespiratory parameters, and no significant difference existed between them. There was an effect of the type of squat on the HR variation; the values in the static squat were higher than those of the dynamic squat in both groups. There was a significant difference with a reduction in SpO2 at 40 Hz frequency when compared with 30 Hz in the COPD group. The other variables behaved similarly between the frequencies. The WBV exercise, regardless of the frequencies used, represented a mild effort that promoted cardiorespiratory response in COPD, with greater responses in the static squat and no adverse effect. NEW & NOTEWORTHY This study showed that an acute session of light exercise of whole body vibration (WBV) can increase the cardiorespiratory responses in patients with chronic obstructive pulmonary disease (COPD), reaching values similar to that of the control group. The results might contribute, therefore, to the elaboration of exercise protocols with WBV for the treatment of patients with COPD during rehabilitation. Thus, future studies referring to training on the vibratory platform could use these exercise parameters and demonstrate possible long-term benefits.

Acute Effects of Whole-Body Vibration on Inflammatory Markers in People with Chronic Obstructive Pulmonary Disease: A Pilot Study.

Whole-body vibration (WBV) has gained prominence in the rehabilitation of individuals with chronic obstructive pulmonary disease (COPD) because it is a safe and low intensity exercise that promises beneficial effects on physical performance and quality of life. However, its effects on plasma cytokine levels in COPD are still unclear. The aim of the current study was to investigate the acute effects of WBV on inflammatory biomarkers in people with COPD. Twenty-six participants, COPD people (n=13) and healthy controls (n=13), were included. Both groups performed WBV at amplitude of 2 mm and frequency of vibration of 35 Hz, during six series of 30 seconds. They were assessed for lung function, body composition, 6-minute walking test (6MWT), handgrip strength test, plasma concentrations of interleukin (IL), IL-6, IL-8, and IL-10, and soluble tumor necrosis factor alpha (TNF-α) receptors (sTNFR-1 and sTNFR-2). People with COPD had moderate disease [forced expiratory volume in the first second (FEV1) = 58.1%], as well as a worse performance in the 6MWT. The plasma cytokine profile at rest showed that participants with COPD had higher levels of IL-8 and lower levels of IL-10. After one session of WBV, we found an increased plasma IL-10 level in the COPD group, with similar levels for healthy controls. One session of WBV modified the plasma IL-10 level. No effects were found on the other investigated cytokines.

Whole body vibration training increases physical measures and quality of life without altering inflammatory-oxidative biomarkers in patients with moderate COPD.

Whole body vibration training (WBVT) has been identified as an alternative intervention to improve exercise capacity and quality of life of patients with chronic obstructive pulmonary disease (COPD). However, the effect of WBVT on inflammatory-oxidative biomarkers remains unknown. The aim of this trial was to investigate the effects of WBVT on quality of life and physical and inflammatory-oxidative parameters in patients with COPD. Twenty patients were equally divided into 1) an intervention group (IG) that performed the WBVT, and 2) a control group (CG) that did not receive any intervention. Intervention consisted in performing static squatting on a vibrating platform, in six series of 30 s, 3 days/wk, for 12 wk. Patients were evaluated for plasma levels of IL-6, IL-8, IFN-γ, soluble receptors of TNF-α; white cell count; plasma levels of oxidant and antioxidant markers; 6-min walking distance (6MWD); peak oxygen uptake (V̇o2peak); handgrip strength; quality of life; timed 5-chair sit-to-stand (5STS); and timed get-up and go test (TUG). After WBVT, patients from IG showed a significant increase in the 6MWD, V̇o2peak, and handgrip strength ( P < 0.05). Furthermore, patients from the IG reached minimal clinically important difference regarding quality of life. No significant differences were found in 5STS, TUG, inflammatory-oxidative biomarkers, and white cell count in the IG. The CG did not show significant improvement in all assessments ( P > 0.05). Taken together, our results demonstrated that the WBVT induced clinically significant benefits regarding exercise capacity, muscle strength, and quality of life in patients with COPD that were not related to inflammatory-oxidative biomarker changes. NEW & NOTEWORTHY Whole body vibration training is a new option for nonpharmacological treatment of chronic obstructive pulmonary disease (COPD). This study showed the potential of this training to improve exercise capacity, quality of life, and muscle strength in patients with COPD. Furthermore, to our knowledge this was the first study showing that vibration exercise does not modify the plasma levels of inflammatory-oxidative biomarkers, suggesting that the beneficial effects on physical measures and quality of life are independent of changes in biomarkers.

Effect of exercise on the plasma BDNF levels in elderly women with knee osteoarthritis.

Knee osteoarthritis is a common disease in the elderly population worldwide. The alleviation of the symptoms associated with this disease can be achieved with physical exercise that induces a cascade of molecular and cellular processes. Of the neurotrophins, brain-derived neurotrophic factor (BDNF) appears to be the most affected by physical activity. Moreover, BDNF seems to have a negative modulatory role in inflammation, and its production by skeletal muscle cells or by cells of the immune system drives the immunoprotective role of physical activity in situations of chronic inflammation. Therefore, the aim of this study was to evaluate plasma BDNF concentrations in elderly individuals presenting with knee osteoarthritis. To accomplish this, sixteen volunteers (mean age 67 ± 4.41 years) presenting with clinically and radiographically diagnosed knee osteoarthritis were evaluated during acute exercise (1 session of 20 min on a treadmill) and after chronic exercise (12 weeks of aerobic training, consisting of a 50-min walk 3 times per week). Additionally, both a functional assessment (during a 6-min walk) and a pain perception assessment were performed at the start and at the end of physical exercises (training). The plasma BDNF concentrations were measured by ELISA. For the population studied, acute exercise increased the levels of BDNF only before the 12-week training period (p < 0.001). Moreover, the training augmented the plasma concentrations of BDNF (p < 0.0001) and improved clinical parameters (functional p < 0.001; pain perception p < 0.01).

Influence of the knee flexion on muscle activation and transmissibility during whole body vibration.

The influence of the knee flexion on muscle activation and transmissibility during whole body vibration is controversially discussed in the literature. In this study, 34 individuals had electromyography activity (EMG) of the vastus lateralis and the acceleration assessed while squatting with 60° and 90° of knee flexion either with or without whole-body vibration (WBV). The conditions were maintained for 10s with 1min of rest between each condition. The main findings were (1) the larger the angle of knee flexion (90° vs. 60°), the greater the EMG (p<0.001), with no difference on acceleration transmissibility; (2) for both angles of knee flexion, the addition of WBV produced no significant difference in EMG and higher acceleration compared to without WBV (p<0.001). These results suggest that the larger the knee flexion angle (60° vs. 90°), the greater the muscle activation without acceleration modification. However, the addition of WBV increases the transmissibility of acceleration in the lower limbs without modification in EMG of vastus lateralis.

Central angiotensin AT1 receptors are involved in metabolic adjustments in response to graded exercise in rats.

To investigate the influence of central angiotensin AT1-receptors blockade on metabolic adjustments during graded exercise, Losartan (Los) was intracerebroventricularly injected in rats before running until fatigue. Oxygen consumption (VO2) was measured (n=6) and blood samples collected (n=7) to determine variations of glucose, lactate and free fatty acids (FFA). Los-rats exhibited a hyperglycemic response, already observed at 20% of maximal work, followed by a higher lactate levels and FFA mobilization from adipose tissue. Despite the reduced total time to fatigue and the higher VO2 associated with reduced mechanical efficiency, exercise led to the attainment of similar levels of effort in both groups. In summary, central AT1-receptor blockade during graded exercise induces hyperglycemia and higher FFA mobilization from adipose tissue at low exercise intensities in rats running at the same absolute exercise intensity. These data suggest that the central angiotensinergic system is involved in metabolic adjustments during exercise since central blockade of AT1-receptors shifts energy balance during graded exercise, similarly to situations of higher and premature sympathetic activation.

Carbohydrate ingestion during exercise does not delay the onset of fatigue during submaximal cycle exercise.

The objective of this study was to evaluate the effect of the ingestion of carbohydrate (CHO, in the form of maltodextrin) or placebo (PLAC, in the form of gelatin) on the physical performance of cyclists during submaximal exercise until fatigue on an ergometric cycle. Nine volunteers exercised on 2 separate occasions at least 2 days apart. On each occasion, after 48 hours of a balanced diet, they pedaled at approximately 66% Vo2peak until fatigue. Every 15 minutes, 150 mL of water and 18 capsules, containing either 0.5 g of CHO or PLAC (approximately 0.13 g x kg(-1) of body weight), were ingested in accordance with a double-blind, randomized protocol. The results show that after 40% of total exercise time, blood glucose levels in the CHO test returned to baseline levels. However, in the PLAC trial these levels failed to return to baseline levels, remaining lower than levels recorded in the CHO test after 60% of total exercise time. Despite these results, CHO ingestion failed to delay the onset of fatigue (CHO: 91.8 +/- 10.1 minutes vs. PLAC: 93.3 +/- 16.1 minutes; p = 0.87). In practical terms, coaches and trainers should consider that CHO ingestion in previously fed users does not delay the onset of fatigue during submaximal cycle exercise.

Sustained, prolonged exercise at stable heart rate defined by the deflection point identification method.

Gripp,The objectives of this study were to identify the heart rate deflection point (HRDP) assessed according to the Conconi test method, to evaluate the ability of trained cyclists to pedal for 90 minutes while remaining within a stable heart rate (HR) range determined by identifying the HRDP, and to discuss the motor and physiological parameters recorded during this long-duration exercise. Ten trained men cyclists (VO2max: 64.1 +/- 8.86 mlxkgxmin) had their HRDPs determined. One week later, they performed continuous exercise for 90 minutes on a cycle ergometer at a stable HR sustained within a range comprising the HRDP +/- 5 bpm. Subjects' HR and power output values were registered at each minute. Blood lactate, blood glucose, and body temperature were measured at rest and during exercise. All exercise was performed inside an environmental chamber (temperature of 22 degrees C, relative humidity of 60%). In the first 5 minutes, the participants increased power output to reach the HRDP, and adjustments were required in their physiological parameters to meet this exercise demand. Between the 5th and the 30th minutes, HRDP had already been reached by all participants; nevertheless, all the other physiological and motor parameters were adjusting to this exercise demand. After 30 minutes of exercise, the physiological and motor variables had already adjusted to the new demand and remained stable until the end of exercise (blood lactate was not significantly different from 4 mmolxL). These results suggest the efficacy of the HRDP as an auxiliary method for prescribing and controlling sport training: after the defined HRDP has been reached, the technique confirms maintenance of power output, as well as the other physiological parameters, at threshold levels until the end of exercise.

Central AT(1) receptor blockade increases metabolic cost during exercise reducing mechanical efficiency and running performance in rats.

The effect of central angiotensin AT(1) receptor blockade on metabolic rate and running performance in rats during exercise on a treadmill (18 m x min(-1), 5% inclination) was investigated. Oxygen consumption (VO(2)) was measured, using the indirect calorimetry system, while the animals were exercising until fatigue after injection of 2 microL of losartan (Los; 60 nmol, n=9), an angiotensin II AT(1) receptor antagonist, or 2 microL of 0.15 M NaCl (Sal, n=9) into the right lateral cerebral ventricle. Mechanical efficiency (ME) and workload (W) were calculated. The W performance by Los-treated animals was 29% lesser than in Sal-treated animals (p<0.02). During the first 10 min of exercise (dynamic state of exercise), there was a similar increase in VO(2), while ME remained the same in both groups. Thereafter (steady state of exercise), VO(2) remained stable in the Sal group but continued to increase and stabilized at a higher level in Los-treated animals until fatigue. During the steady state of exercise there was a sharper reduction in ME in Los-treated rats compared to Sal-treated animals (p<0.01) that was closely correlated to W (r=0.74; p<0.01). Our data showed that AT(1) receptor blockade increases metabolic cost during exercise, reducing mechanical efficiency. These results indicate that central angiotensinergic transmission modulates heat production, improving ME during the steady state of exercise.

Acute heat exposure increases high-intensity performance during sprint cycle exercise.

The purpose of this study was to investigate the effects of acute heat exposure at thermal balance on high-intensity performance during sprint cycle exercise. Nine healthy male subjects were tested in three different, well-controlled environments in an environmental chamber: T (22 degrees C, 65% RH), H1 (30 degrees C, 55% RH) and H2 (35 degrees C, 62% RH), each test being carried out on a different day following a randomized sequence. After 30 min of exposure to the set environment, subjects performed the 30-s sprint cycle exercise. Heart rate, rectal and skin temperatures were measured prior to exercise, at rest, before and after environmental exposure, and after exercise. There were no differences in subjects' core temperature or heart rate prior to exercise. However, skin temperature was significantly higher in hot trials compared with the control throughout the experimental session (P < 0.05). Peak power was significantly higher in the hot environments compared with the control. Mean power was higher only in H2 compared with T (P < 0.05). This difference in power output was the consequence of a faster pedaling cadence in the hot trials (P < 0.05). Plasma ammonia was higher in the hot trials versus control at 4 min post-sprint. No differences in blood lactate levels at 3 min post-sprint were observed between tests. The results of this study suggest that the exposure to hot environment caused an improvement in power output for a single 30-s sprint. This increase in power output was associated with an elevation in plasma ammonia suggestive of an increase in adenine nucleotide loss.

Central nitric oxide inhibition modifies metabolic adjustments induced by exercise in rats.

The influence of the central nervous system on metabolic function is of interest in situations deviating from basal states, such as during exercise. Our previous study in rats demonstrated that central nitric oxide (NO) blockade increases metabolic rate, reducing mechanical efficiency during exercise. To assess the role of brain nitric oxide in the plasma glucose, lactate and free fatty acids (FFAs) concentrations of rats submitted to an incremental exercise protocol on a treadmill until fatigue, 1.43 micromol (2 microl) of N(omega)-nitro-l-arginine methyl ester (L-NAME, n=6), a NO synthase inhibitor, or 2 microl of 0.15M NaCl (SAL, n=6) was injected into the lateral cerebral ventricle (icv) of male Wistar rats immediately before exercise (starting at 10 m/min, with increments of 1m/min every 3 min until fatigue, 10% inclination). Blood samples were collected through a chronic jugular catheter at rest and during exercise until fatigue. During exercise, the L-NAME-treated animals had the following metabolic response compared to controls: (1) an increased hyperglycemic response during the first 60% of time to fatigue; (2) higher plasma lactate levels; and (3) a significant transitory increase in plasma free fatty acids during the dynamic phase of exercise that returned to basal levels earlier than controls during the steady state phase of exercise. In addition L-NAME-treated rats fatigued earlier than controls. The data indicate that the inhibition of the brain nitrergic system induced by icv L-NAME treatment disrupted the accuracy of the neural mechanism that regulates plasma glucose and free fatty acids mobilization during exercise in rats.

Central angiotensin AT1-receptor blockade affects thermoregulation and running performance in rats.

The effect of central angiotensin AT1-receptor blockade on thermoregulation in rats during exercise on a treadmill (18 m/min, 5% inclination) was investigated. Core (Tb) and skin tail temperatures were measured in rats while they were exercising until fatigue after injection of 2 microl of losartan (Los; 20 nmol, n = 4; 30 nmol, n = 4; 60 nmol, n = 7), an angiotensin II AT1-receptor antagonist, or 2 microl of 0.15 mol/l NaCl (Sal; n = 15) into the right lateral cerebral ventricle. Body heat rate (BHR), heat storage rate, threshold Tb for tail vasodilation (TTbV), time to fatigue, and workload were calculated. During exercise, the BHR and heat storage rate of Los-treated animals were, respectively, 40 and 53% higher (P < 0.01) than in Sal-treated animals. Additionally, rats injected with Los showed an increased TTbV (38.59 +/- 0.19 degrees C for Los vs. 38.12 +/- 0.1 degrees C for Sal, P < 0.02), a higher Tb at fatigue point (39.07 +/- 0.14 degrees C Los vs. 38.66 +/- 0.07 degrees C Sal, P < 0.01), and a reduced running performance (27.29 +/- 4.48 min Los vs. 52.47 +/- 6.67 min Sal, P < 0.01), which was closely related to the increased BHR. Our data suggest that AT1-receptor blockade attenuates heat dissipation during exercise due to the higher TTbV, leading to a faster exercise-induced increase in Tb, thus decreasing running performance.

Evidence that brain nitric oxide inhibition increases metabolic cost of exercise, reducing running performance in rats.

To assess the role of nitric oxide (NO) in the metabolic rate and running performance of rats submitted to exercise on a treadmill, 1.43 micromol (2 microL) of Nomega-nitro-L-arginine methyl ester (L-NAME, n=6), a NO synthase inhibitor, or 2 microL of 0.15M NaCl (SAL, n=6) was injected into the lateral cerebral ventricle of male Wistar rats immediately before the animals started running (18m min(-1), 5% inclination). Oxygen consumption (VO2) was measured at rest, during the exercise until fatigue and thereafter during the 30 min of recovery using the indirect calorimetry system. Mechanical efficiency (ME) was also calculated during the running period. During the first 11 min of exercise, there was a similar increase in VO2 while ME remained the same in both groups. Thereafter, VO2 remained stable in the SAL group but continued to increase and remained higher in the L-NAME group until fatigue. The L-NAME-treated rats also showed a sharper decrease in ME than controls. In addition, there was a significant reduction in workload performance by L-NAME-treated animals compared to SAL-treated animals. This suggests that central blockage of nitric oxide increases metabolic cost during exercise, reduces mechanical efficiency and decreases running performance in rats.