A canine model to evaluate the effect of exercise intensity and duration on olfactory detection limits: the running nose.

Detection canines serve critical roles to support the military, homeland security and border protection. Some explosive detection tasks are physically demanding for dogs, and prior research suggests this can lead to a reduction in olfactory detection sensitivity. To further evaluate the effect of exercise intensity on olfactory sensitivity, we developed a novel olfactory paradigm that allowed us to measure olfactory detection thresholds while dogs exercised on a treadmill at two different exercise intensities. Dogs (n = 3) showed a decrement in olfactory detection for 1-bromooctane at 10-3 (v/v) dilutions and lower under greater exercise intensity. Dogs' hit rate for the lowest concentration dropped from 0.87 ± 0.04 when walking at low intensity to below 0.45 ± 0.06 when trotting at moderate intensity. This decline had an interaction with the duration of the session in moderate intensity exercise, whereby dogs performed near 100% detection in the first 10 min of the 8 km/h session, but showed 0% detection after 20 min. Hit rates for high odor concentrations (10-2) were relatively stable at both low (1 ± 0.00) and moderate (0.91 ± 0.04) exercise intensities. The paradigm and apparatus developed here may be useful to help further understand causes of operationally relevant olfactory detection threshold decline in dogs.

Effects of different exercise intensities or durations on salivary IgA secretion.

PURPOSE: This study aimed to examine changes in salivary immunoglobulin A (s-IgA) secretion at different intensities or durations of acute exercise. METHODS: Twelve healthy untrained young males were included in randomized crossover trials in Experiment 1 (cycling exercise for 30 min at a work rate equivalent to 35%, 55%, and 75% maximal oxygen uptake [ V ˙ O2max]) and Experiment 2 (cycling exercise at 55% V ˙ O2max intensity for 30, 60, and 90 min). Saliva samples were collected at baseline, immediately after, and 60 min after each exercise. RESULTS: Experiment 1: The percentage change in the s-IgA secretion rate in the 75% V ˙ O2max trial was significantly lower than that in the 55% V ˙ O2max trial immediately after exercise (- 45.7%). The percentage change in the salivary concentration of cortisol, an s-IgA regulating factor, immediately after exercise significantly increased compared to that at baseline in the 75% V ˙ O2max trial (+ 107.6%). A significant negative correlation was observed between the percentage changes in saliva flow rate and salivary cortisol concentration (r = - 0.52, P < 0.01). Experiment 2: The percentage change in the s-IgA secretion rate in the 90-min trial was significantly lower than that in the 30-min trial immediately after exercise (-37.0%). However, the percentage change in salivary cortisol concentration remained the same. CONCLUSION: Our findings suggest that a reduction in s-IgA secretion is induced by exercise intensity of greater than or equal to 75% V ˙ O2max for 30 min or exercise duration of greater than or equal to 90 min at 55% V ˙ O2max in healthy untrained young men.

The effects of daily dose of intense exercise on cardiac responses and atrial fibrillation.

Atrial fibrillation (AF) is a supraventricular tachyarrhythmia that is strongly associated with cardiovascular (CV) disease and sedentary lifestyles. Despite the benefits of exercise on overall health, AF incidence in high-level endurance athletes rivals that of CV disease patients, suggesting a J-shaped relationship with AF. To investigate the dependence of AF vulnerability on exercise, we varied daily swim durations (120, 180 or 240 min day-1 ) in 7-week-old male CD1 mice. We assessed mice after performing equivalent amounts of cumulative work during swimming (i.e. ∼700 L O2  kg-1 ), as determined from O2 consumption rates ( V ̇ O 2 ${\dot V_{{{\mathrm{O}}_2}}}$ ). The mean V ̇ O 2 ${\dot V_{{{\mathrm{O}}_2}}}$ during exercise increased progressively throughout the training period and was indistinguishable between the swim groups. Consistent with similar improvements in aerobic conditioning induced by swimming, skeletal muscle mitochondria content increased (P = 0.027) indistinguishably between exercise groups. Physiological ventricular remodelling, characterized by mild hypertrophy and left ventricular dilatation, was also similar between exercised mice without evidence of ventricular arrhythmia inducibility. By contrast, prolongation of daily swim durations caused progressive and vagal-dependent heart rate reductions (P = 0.008), as well as increased (P = 0.005) AF vulnerability. As expected, vagal inhibition prolonged (P = 0.013) atrial refractoriness, leading to reduced AF vulnerability, although still inducible in the 180 and 240 min swim groups. Accordingly, daily swim dose progressively increased atrial hypertrophy (P = 0.003), fibrosis (P < 0.001) and macrophage accumulation (P = 0.006) without differentially affecting the ventricular tissue properties. Thus, increasing daily exercise duration drives progressively adverse atrial-specific remodelling and vagal-dependent AF vulnerability despite robust and beneficial aerobic conditioning and physiological remodelling of ventricles and skeletal muscle. KEY POINTS: Previous studies have suggested that a J-shaped dose-response relationship exists between physical activity and cardiovascular health outcomes, with moderate exercise providing protection against many cardiovascular disease conditions, whereas chronic endurance exercise can promote atrial fibrillation (AF). We found that AF vulnerability increased alongside elevated atrial hypertrophy, fibrosis and inflammation as daily swim exercise durations in mice were prolonged (i.e. ≥180 min day-1 for 6 weeks). The MET-h week-1 (based on O2  measurements during swimming) needed to induce increased AF vulnerability mirrored the levels linked to AF in athletes. These adverse atria effects associated with excessive daily exercise occurred despite improved aerobic conditioning, skeletal muscle adaptation and physiological ventricular remodelling. We suggest that atrial-specific changes observed with exercise arise from excessive elevations in venous filling pressures during prolonged exercise bouts, which we argue has implications for all AF patients because elevated atrial pressures occur in most cardiovascular disease conditions as well as ageing which are linked to AF.

Effects of Physical Exercise on Executive Functions among College Students in China: Exploring the Influence of Exercise Intensity and Duration.

BACKGROUND: This study investigates the effects of exercise intensity and duration on executive functions among college students in China. METHOD: Participants in this study were Chinese college students divided into four groups based on exercise duration and intensity. Each group engaged in physical exercise twice a week for six weeks. Group 1 performed low-intensity exercises for 10 min per session; Group 2 performed low-intensity exercises for 20 min per session; Group 3 performed high-intensity exercises for 10 min per session; and Group 4 performed high-intensity exercise for 20 min per session. Executive functions were assessed in all subjects before the experiment (time 1), after one exercise session (time 2), at the end of the exercise program (time 3), and six weeks after the exercise program (time 4). A mixed ANOVA with a 2 (exercise intensity: low/high) × 2 (duration: short/long) × 4 (time of measurement: time 1/time 2/time 3/time 4) design was employed, with exercise intensity and exercise duration as independent variables and executive functions as the dependent variable. RESULTS: Mixed ANOVA showed that the results revealed a significant main effect of measurement time on working memory accuracy (p < 0.001) and reaction time (p < 0.001); inhibition control accuracy (p < 0.001) and reaction time (p < 0.001); cognitive flexibility accuracy (p < 0.001) and reaction time (p < 0.001). A single session of high-intensity exercise significantly improved executive functions in college students. Both low-intensity and high-intensity exercise were effective in enhancing executive functions, with high-intensity exercise demonstrating better maintenance of the effect. CONCLUSION: Both exercise intensity and exercise duration were found to enhance executive functions in college students, with exercise intensity showing greater effectiveness than exercise duration.

An evaluation of the role of the exercise training dose for changes in exercise capacity following a standard cardiac rehabilitation program.

BACKGROUND: To retrospectively characterize and compare the dose of exercise training (ET) within a large cohort of patients demonstrating different levels of improvement in exercise capacity following a cardiac rehabilitation (CR) program. METHODS: A total of 2310 patients who completed a 12-week, center-based, guidelines-informed CR program between January 2018 and December 2019 were included in the analysis. Peak metabolic equivalents (METpeak) were determined pre- and post-CR during which total duration (ET time) and intensity [percent of heart rate peak (%HRpeak)] of supervised ET were also obtained. Training responsiveness was quantified on the basis of changes in METpeak from pre- to post-CR. A cluster analysis was performed to identity clusters demonstrating discrete levels of responsiveness (i.e., negative, low, moderate, high, and very-high). These were compared for several baseline and ET-derived variables which were also included in a multivariable linear regression model. RESULTS: At pre-CR, baseline METpeak was progressively lower with greater training responsiveness (F(4,2305) = 44.2, P < 0.01, η2p = 0.71). Likewise, average training duration (F(4,2305) = 10.7 P < 0.01, η2p = 0.02) and %HRpeak (F(4,2305) = 25.1 P < 0.01, η2p = 0.042) quantified during onsite ET sessions were progressively greater with greater training responsiveness. The multivariable linear regression model confirmed that baseline METpeak, training duration and intensity during ET, BMI, and age (P < 0.001) were significant predictors of METpeak post-CR. CONCLUSIONS: Along with baseline METpeak, delta BMI, and age, the dose of ET (i.e., training duration and intensity) predicts METpeak at the conclusion of CR. A re-evaluation of current approaches for exercise intensity prescription is recommended to extend the benefits of completing CR to all patients.

The Effect of Exercise Prescription on the Human Gut Microbiota and Comparison between Clinical and Apparently Healthy Populations: A Systematic Review.

This study systematically reviewed all human longitudinal exercise interventions that reported changes in the gut microbiota; frequency, intensity, duration and type of exercise were assessed to determine the influence of these variables on changes to the gut microbiota in both healthy individuals and clinical populations (PROPERO registration: CRD42022309854). Using PRISMA guidelines, trials analysing gut microbiota change with exercise interventions were included independent of trial randomisation, population, trial duration or analysis technique. Studies were excluded when microbiota abundance was not reported or when exercise was combined with other interventions. Twenty-eight trials were included, of which twelve involved healthy populations only and sixteen involved mixed or clinical-only populations. The findings show that participation in exercise of moderate to high-intensity for 30-90 min ≥3 times per week (or between 150-270 min per week) for ≥8 weeks is likely to produce changes in the gut microbiota. Exercise appears to be effective in modifying the gut microbiota in both clinical and healthy populations. A more robust methodology is needed in future studies to improve the certainty of the evidence.

Longer physical exercise duration prevents abnormal fasting plasma glucose occurrences in the third trimester: Findings from a cohort of women with gestational diabetes mellitus in Shanghai.

Objective: This study aims to investigate the relationship between daily physical exercise (PE) duration and frequency of abnormal plasma glucose (PG) times both during fasting and 2 h after a standard diet in women with gestational diabetes mellitus (GDM). Methods: We established a cohort involving 878 GDM women. GDM was confirmed by a diagnostic 75-g oral glucose tolerance test. Information was extracted from the delivery records and antenatal checkup forms. Physical exercise information was collected through a questionnaire. Results: Over 80% of GDM women were under 35 years old. An abnormal fasting PG with ≥1 occurrence presented in 742/878 (84.51%), and the abnormal PG 2 h after standard diet with ≥1 occurrence presented in 634/878 (72.21%). Compared to GDM women with ≥4 occurrences of abnormal fasting PG, GDM women with 0 occurrences (odds ratio (OR) = 2.56), one occurrence (OR = 1.94), two occurrences (OR = 2.29), and three occurrences (OR = 2.16) had a higher proportion of PE duration being in the 45-60-min/day group than those in the <45-min/day group, and GDM women also had a higher proportion of PE during being in the 61-90- and >90-min/day group than those in the <45-min/day group. However, the duration of PE was not associated to the number of abnormal PG occurrences 2-h after the standard diet. Conclusion: Moderate-intensity PE duration in GDM women was negatively associated with the number of abnormal fasting PG occurrences but not with the number of PG occurrences 2 h after the standard diet.

Effect of wearing medical protective masks on treadmill running performance in the postpandemic era: a randomised trial.

BACKGROUND: In the postpandemic era, wearing protective masks in public places will still be an important means of blocking popular viruses in the future. The purpose of this study was to explore whether sports performance was affected by mask wearing and exercise duration during 15-min treadmill running at a speed of 75% maximal aerobic speed. METHODS: Thirty-six males were randomly divided into mask and nonmask groups. The kinematic and kinetic data were obtained at four time points (RN0-1 min, RN5-6 min, RN9-10 min, and RN14-15 min) during running. Two-way mixed ANOVA was applied to examine the effects between groups and times with Bonferroni post hoc comparison and independent samples t-test. RESULTS: The results showed that there was no difference between mask and nonmask group during running (p > 0.05). As running time increased, hip joint ROM, hip joint flexion/extension max, and ankle joint plantarflexion max angles increased; knee joint flexion min and ankle joint dorsiflexion max angles decreased; average peak vertical ground reaction forces (PVGRF) increased after 9 min-running (p < 0.05). CONCLUSIONS: Wearing a medical protective mask does not affect the joint angle and touchdown PVGRF of lower extremities during treadmill running while affected by running time and changed after 9 min-treadmill running. Future studies will examine the effects of wearing masks during the pandemic on muscle activation and blood biochemical values during exercise. TRIAL REGISTRATION NO: ChiCTR2000040535 (date of registration on December 1, 2020). Prospectively registered in the Chinese Clinical Trial Registry.

Exposures to Elevated Core Temperatures during Football Training: The Impact on Autonomic Nervous System Recovery and Function.

Exercising with elevated core temperatures may negatively affect autonomic nervous system (ANS) function. Additionally, longer training duration under higher core temperatures may augment these negative effects. This study evaluated the relationship between exercise training duration and 24 h ANS recovery and function at ≥37 °C, ≥38 °C and ≥39 °C core temperature thresholds in a sample of male Division I (D1) collegiate American football athletes. Fifty athletes were followed over their 25-week season. Using armband monitors (Warfighter MonitorTM, Tiger Tech Solutions, Inc., Miami, FL, USA), core temperature (°C) and 24 h post-exercise baseline heart rate (HR), HR recovery and heart rate variability (HRV) were measured. For HRV, two time-domain indices were measured: the root mean square of the standard deviation of the NN interval (rMSSD) and the standard deviation of the NN interval (SDNN). Linear regression models were performed to evaluate the associations between exercise training duration and ANS recovery (baseline HR and HRV) and function (HR recovery) at ≥37 °C, ≥38 °C and ≥39 °C core temperature thresholds. On average, the athletes were 21.3 (± 1.4) years old, weighed 103.0 (±20.2) kg and had a body fat percentage of 15.4% (±7.8%, 3.0% to 36.0%). The duration of training sessions was, on average, 161.1 (±40.6) min and they ranged from 90.1 to 339.6 min. Statistically significant associations between training duration and 24 h ANS recovery and function were observed at both the ≥38.0 °C (baseline HR: ß = 0.10 ± 0.02, R2 = 0.26, p < 0.0000; HR recovery: ß = -0.06 ± 0.02, R2 = 0.21, p = 0.0002; rMSSD: ß = -0.11 ± 0.02, R2 = 0.24, p < 0.0000; and SDNN: ß = -0.16 ± 0.04, R2 = 0.22, p < 0.0000) and ≥39.0 °C thresholds (ß = 0.39 ± 0.05, R2 = 0.62, p < 0.0000; HR recovery: ß = -0.26 ± 0.04, R2 = 0.52, p < 0.0000; rMSSD: ß = -0.37 ± 0.05, R2 = 0.58, p < 0.0000; and SDNN: ß = -0.67 ± 0.09, R2 = 0.59, p < 0.0000). With increasing core temperatures, increases in slope steepness and strengths of the associations were observed, indicating accelerated ANS deterioration. These findings demonstrate that exercise training under elevated core temperatures (≥38 °C) may negatively influence ANS recovery and function 24 h post exercise and progressively worsen.

Modeling Professional Rugby Union Peak Intensity-Duration Relationships Using a Power Law.

PURPOSE: Can power law models accurately predict the peak intensities of rugby competition as a function of time? METHODS: Match movement data were collected from 30 elite and 30 subelite rugby union athletes across competitive seasons, using wearable Global Navigation Satellite Systems and accelerometers. Each athlete's peak rolling mean value of each measure (mean speed, metabolic power, and PlayerLoad™) for 8 durations between 5 seconds and 10 minutes was predicted by the duration with 4 power law (log-log) models, one for forwards and backs in each half of a typical match. RESULTS: The log of peak exercise intensity and exercise duration (5-600 s) displayed strong linear relationships (R2 = .967-.993) across all 3 measures. Rugby backs had greater predicted intensities for shorter durations than forwards, but their intensities declined at a steeper rate as duration increased. Random prediction errors for mean speed, metabolic power, and PlayerLoad were 5% to 6%, 7% to 9%, and 8% to 10% (moderate to large), respectively, for elite players. Systematic prediction errors across the range of durations were trivial to small for elite players, underestimating intensities for shorter (5-10 s) and longer (300-600 s) durations by 2% to 4% and overestimating 20- to 120-second intensities by 2% to 3%. Random and systematic errors were slightly greater for subelites compared to elites, with ranges of 4% to 12% and 2% to 5%, respectively. CONCLUSIONS: Peak intensities of professional rugby union matches can be predicted with adequate precision (trivial to small errors) for prescribing training drills of a given duration, irrespective of playing position, match half, level of competition, or measure of exercise intensity. However, practitioners should be aware of the substantial (moderate to large) prediction errors at the level of the individual player.

Exercise duration: Independent effects on acute physiologic responses and the need for an individualized prescription.

An individualization of exercise prescription is implemented mainly in terms of intensity but not for duration. To survey the need for an individualized exercise duration prescription, we investigated acute physiologic responses during constant-load exercise of maximal duration (tmax ) and determined so-called duration thresholds. Differences between absolute (min) and relative terms (% tmax ) of exercise duration were analyzed. Healthy young and trained male and female participants (n = 11) performed an incremental exercise test and one tmax constant-load exercise test at a target intensity of 10% of maximal power output below the second lactate turn point (LTP2 ). Blood lactate, heart rate, and spirometric data were measured during all tests. tmax was markedly different across subjects (69.6 ± 14.8 min; range: 40-90 min). However, distinct duration phases separated by duration thresholds (DTh) were found in most measured variables. These duration thresholds (except DTh1) were significantly related to tmax (DTh2: r2  = 0.90, p < 0.0001; DTh3: r2  = 0.98, p < 0.0001) and showed substantial interindividual differences if expressed in absolute terms (DTh2: 24.8 ± 6.0 min; DTh3: 47.4 ± 10.6 min) but not in relative terms (DTh2: 35.4 ± 2.7% tmax ; DTh3: 67.9 ± 2.4% tmax ). Our data showed that (1) maximal duration was individually different despite the same relative intensity, (2) duration thresholds that were related to tmax could be determined in most measured variables, and (3) duration thresholds were comparable between subjects if expressed in relative terms. We therefore conclude that duration needs to be concerned as an independent variable of exercise prescription.

Duration of an acute moderate-intensity exercise session affects approach bias toward high-calorie food among individuals with obesity.

Obesity is partly driven by unhealthy eating behaviors underpinned by an approach bias toward high-calorie food. Although exercise is a useful strategy for weight loss among individuals with obesity, whether exercise modulates this approach bias is unclear. This study assessed whether the duration of an acute moderate-intensity exercise altered the approach bias toward high-calorie food among individuals with obesity. In total, 24 individuals with obesity were included in this study with a randomized, counterbalanced, crossover design. Participants completed three sessions of 30, 45, or 60 min of moderate-intensity exercise (40%-59% of heart rate reserve) on an elliptical trainer or completed a control rest session for 55 min. Food approach bias was evaluated using a joystick-based approach-avoidance task immediately before and after each session. Two-way repeated-measures analysis of variance was used to analyze the data. We found that compared with that before exercise, the approach bias score toward high-calorie food was significantly decreased only in the 45-min exercise session (p = .015) and that this score was also significantly lower than that after both the 60-min exercise session (p = .002) and the control session (p = .024). These findings suggest a dose-response relationship between exercise duration and approach bias, with 45 min of moderate-intensity exercise being an effective strategy for decreasing the approach bias toward high-calorie food among individuals with obesity.

Effect of training on skeletal muscle bioenergetic system in patients with mitochondrial myopathies: A computational study.

A computer model of the skeletal muscle bioenergetic system, involving the "Pi double-threshold" mechanism of muscle fatigue, was used to investigate the effect of muscle training on system kinetic properties in mitochondrial myopathies (MM) patients with inborn OXPHOS deficiencies. An increase in OXPHOS activity and decrease in peak Pi can account for the training-induced increase in V̇O2max, acceleration of the primary phase II of the V̇O2 on-kinetics, delay of muscle fatigue and prolongation of exercise at a given work intensity encountered in experimental studies. Depending on the mutation load and work intensity, training can bring the muscle from severe- to very-heavy- to moderate-exercise-like behavior, thus lessening the exertional fatigue and lengthening the physical activity of a given intensity. Training significantly increases critical power (CP) and slightly decreases the curvature constant (W') of the power-duration relationship. Generally, a mechanism underlying the training-induced changes in the skeletal muscle bioenergetic system in MM patients is proposed.

Exercise Dosage in Reducing the Risk of Dementia Development: Mode, Duration, and Intensity-A Narrative Review.

Senile dementia, also known as dementia, is the mental deterioration which is associated with aging. It is characterized by a decrease in cognitive abilities, inability to concentrate, and especially the loss of higher cerebral cortex function, including memory, judgment, abstract thinking, and other loss of personality, even behavior changes. As a matter of fact, dementia is the deterioration of mental and intellectual functions caused by brain diseases in adults when they are mature, which affects the comprehensive performance of life and work ability. Most dementia cases are caused by Alzheimer's disease (AD) and multiple infarct dementia (vascular dementia, multi-infarct dementia). Alzheimer's disease is characterized by atrophy, shedding, and degenerative alterations in brain cells, and its occurrence is linked to age. The fraction of the population with dementia is smaller before the age of 65, and it increases after the age of 65. Since women live longer than men, the proportion of women with Alzheimer's disease is higher. Multiple infarct dementia is caused by a cerebral infarction, which disrupts blood supply in multiple locations and impairs cerebral cortex function. Researchers worldwide are investigating ways to prevent Alzheimer's disease; however, currently, there are no definitive answers for Alzheimer's prevention. Even so, research has shown that we can take steps to reduce the risk of developing it. Prospective studies have found that even light to moderate physical activity can lower the risk of dementia and Alzheimer's disease. Exercise has been proposed as a potential lifestyle intervention to help reduce the occurrence of dementia and Alzheimer's disease. Various workout modes will be introduced based on various physical conditions. In general, frequent exercise for 6-8 weeks lessens the risk of dementia development.

Prognostic Role of Cardiopulmonary Exercise Testing in Wild-Type Transthyretin Amyloid Cardiomyopathy Patients Treated With Tafamidis.

BACKGROUND: The prognostic value of cardiopulmonary exercise testing (CPET) in patients with wild-type transthyretin cardiac amyloidosis treated with tafamidis is unknown. METHODS AND RESULTS: This retrospective study included patients with wtATTR who underwent baseline cardiopulmonary exercise testing and were treated with tafamidis from August 31, 2018, until March 31, 2020. Univariate logistic and multivariate cox-regression models were used to predict the occurrence of the primary outcome (composite of mortality, heart transplant, and palliative inotrope initiation). A total of 33 patients were included (median age 82 years, interquartile range [IQR] 79-84 years), 84% were Caucasians and 79% were males). Majority of patients had New York Heart Association functional class III disease at baseline (67%). The baseline median peak oxygen consumption (VO2) and peak circulatory power (CP) were 11.35 mL/kg/min (IQR 8.5-14.2 mL/kg/min) and 1485.8 mm Hg/mL/min (IQR 988-2184 mm Hg/mL/min), respectively, the median ventilatory efficiency was 35.7 (IQR 31-41.2). After 1 year of follow-up, 11 patients experienced a primary end point. Upon multivariate analysis, the low peak VO2 (hazard ratio [HR] 0.43, 95% confidence interval [CI] 0.23-0.79, P = .007], peak CP (HR 0.98, 95% CI 0.98-0.99, P = .02), peak oxygen pulse (HR 0.62, 95% CI 0.39-0.97, P = .03), and exercise duration of less than 5.5 minutes (HR 5.82, 95% CI 1.29-26.2, P = .02) were significantly associated with the primary outcome. CONCLUSIONS: Tafamidis-treated patients with wtATTR who had baseline low peak VO2, peak CP, peak O2 pulse, and exercise duration of less than 5.5 minutes had worse outcomes.

Effects of acute moderate-intensity exercise at different duration on blood pressure and endothelial function in young male patients with stage 1 hypertension.

PURPOSE: The studies regarding the effects of exercise duration on blood pressure have reported inconsistent and conflicting results. Nitric oxide (NO) is a well-known vasodilator released by endothelial cells, and endothelial microparticles (EMPs) are membranous vesicles released into the circulation from activated or apoptotic endothelial cells, both of whose level can reflect the endothelial function. But few studies have been done to explore the effect of exercise duration on blood pressure and endothelial function, especially, the EMPs response to exercise in young male patients with hypertension. This study aimed to investigate the blood pressure response during moderate-intensity exercise performed in different durations and the acute effects on post-exercise hypotension and endothelial function in hypertensive patients. METHODS: Eighteen young male hypertensive patients who did not take antihypertensive drugs were recruited in this study. They randomly performed twice exercises on a cycle ergometer at a moderate intensity of 40%-50% of their HR reserve; one was 20 min (E20 session), the other one was 40 min (E40 session); there was 1-week break between the two exercises. Blood pressure was monitored by the YUWELL blood pressure monitor at rest, every 5 min during exercise, and 3 and 6 min post-exercise. The level of NO (nitrate/nitrite reduction) and EMPs (flow cytometry) in plasma were detected before and immediately following exercise. CD31+/CD42b- events were classified as EMPs and events per microliter plasma were calculated. This study was approved by the Beijing Sport University Institutional Review Board (protocol number 2019087 H). RESULTS: Mean age of patients was 34.8 ± 3.5 yrs, and BMI was 27.6 ± 2.7 kg/m2. Systolic blood pressure (SBP) in the two sessions increased significantly during exercise. The SBP in the E20 session increased by 37 mmHg (P < .01) at 5 min during exercise and remained stable afterward. In the E40 session, the SBP increased by 35 mmHg (P < .01) at 5 min during exercise and was stable at 5 through 25 min, decreased by 8 mmHg at 25 through 35 min during exercise, and then stabilized (P < .01). There was no obvious change of diastolic blood pressure (DBP) in the two sessions during exercise. In the E20 session, SBP at 6 min following exercise was no different from the rest; in the E40 session, SBP at 6 min following exercise was 14 mmHg lower than at the rest (P < .01). DBP in the E20 session was the same as rest at 3 min following exercise and decreased by 4 mmHg at 6 min following exercise compared with the rest (P < .05), while DBP in the E40 session decreased by 3 mmHg at 3 min following exercise compared with the rest (P < .05). The plasma NO levels of E20 and E40 increased significantly following exercise (P < .01 for both). There was no difference in plasma NO level between the two sessions pre- and post-exercise, but the increased magnitude of NO level in E40 was greater than that in E20 (24.47% vs. 9.24%, P < .01). The plasma EMPs level of E20 and E40 decreased significantly following exercise (P < .01 for both). There was no difference in plasma EMPs level between the two sessions pre- and post-exercise, but the decreased magnitude of EMPs level in E40 was greater than that in E20 (15.66% vs. 8.00%, P < .01). CONCLUSION: There is no exaggerated blood pressure response to 20-min and 40-min acute moderate-intensity exercise in young hypertensive men with no antihypertensive drugs. Both 20-min and 40-min acute moderate exercise can reduce the rest blood pressure, and improve endothelial function by increasing NO and decreasing EMPs in young male patients with hypertension, and the effects of 40-min exercise on lowering SBP and improving endothelial function are better than that of 20-min.

Effect of Oxidative Stress on Diaphragm Dysfunction and Exercise Intervention in Chronic Obstructive Pulmonary Disease.

Chronic obstructive pulmonary disease (COPD) can cause extrapulmonary injury such as diaphragm dysfunction. Oxidative stress is one of the main factors causing diaphragm dysfunction in COPD. Exercise plays a positive role in the prevention and treatment of diaphragm dysfunction in COPD, and the changes in diaphragm structure and function induced by exercise are closely related to the regulation of oxidative stress. Therefore, on the basis of the review of oxidative stress and the changes in diaphragm structure and function in COPD, this article analyzed the effects of exercise on oxidative stress and diaphragm dysfunction in COPD and explored the possible mechanism by which exercise improves oxidative stress. Studies have found that diaphragm dysfunction in COPD includes the decline of muscle strength, endurance, and activity. Oxidative stress mainly affects the structure and function of the diaphragm in COPD through protein oxidation, protease activation and calcium sensitivity reduction. The effects of exercise on oxidative stress level and diaphragm dysfunction may differ depending on the intensity, duration, and style of exercise. The mechanism of exercise on oxidative stress in the diaphragm of COPD may include improving antioxidant capacity, reducing oxidase activity and improving mitochondrial function.

VO2max as an exercise tolerance endpoint in people with cystic fibrosis: Lessons from a lumacaftor/ivacaftor trial.

BACKGROUND: The impact of lumacaftor/ivacaftor on exercise tolerance in people with cystic fibrosis (CF) has not been thoroughly studied. METHODS: We conducted a multisite Phase 4 trial comparing the impact of lumacaftor/ivacaftor on exercise tolerance with that of placebo in participants ≥ 12 years of age with CF homozygous for F508del-CFTR. The primary endpoint was relative change from baseline in maximum oxygen consumption (VO2max) during cardiopulmonary exercise testing (CPET) at Week 24. The key secondary endpoint was relative change from baseline in exercise duration during CPET at Week 24. Other secondary endpoints included changes in other indices of exercise tolerance and changes in CF assessments; safety and tolerability were assessed as an endpoint. RESULTS: Seventy participants were randomized to receive lumacaftor/ivacaftor (n = 34) or placebo (n = 36). The least-squares mean difference for lumacaftor/ivacaftor versus placebo in relative change in VO2max from baseline at Week 24 was -3.2% (95% CI: -9.2, 2.9; P=0.3021); the least-squares mean difference in relative change from baseline in exercise duration at Week 24 was -3.2% (95% CI: -8.0, 1.6). Safety results were consistent with the known lumacaftor/ivacaftor safety profile. CONCLUSIONS: Definitive conclusions regarding the impact of lumacaftor/ivacaftor on exercise tolerance cannot be drawn from these results; however, multicenter studies using CPETs can be reliably performed with multiple time points and conventional methods, provided that calibration can be achieved. Future studies of exercise tolerance may benefit from lessons learned from this study. NCT02875366.

Cognitive effects of acute aerobic exercise: Exploring the influence of exercise duration, exhaustion, task complexity and expectancies in endurance-trained individuals.

The cognitive effects of acute aerobic exercise were investigated in endurance-trained individuals. On two occasions, 21 cyclists; 11 male (VO2max: 57 ± 9 mL·kg-1·min-1) and 10 female (VO2max: 51 ± 9 mL·kg-1·min-1), completed 45 min of fixed, moderate-intensity (discontinuous) cycling followed by an incremental ride to exhaustion. Cognitive function was assessed at Baseline, after 15 and 45 min of exercise (15EX and 45EX) and at Exhaustion using a 4-Choice Reaction Time (CRT) test and the Stroop test (Incongruent and Congruent Reaction Time [RT]). A sham capsule was administered on one occasion to determine whether the cognitive response to exercise was robust to the influence of a placebo. CRT, Congruent RT and Incongruent RT decreased (improved) at 15EX, 45EX and Exhaustion compared to Baseline (p's<0.005). While CRT and Congruent RT were faster at 45EX than 15EX (p's<0.020), Incongruent RT was not (p= 1.000). The sham treatment did not affect cognition. When performed at a moderate-intensity, longer duration exercise (up to 45 min) may improve cognition to a greater extent than shorter duration exercise; however, the magnitude of improvement appears to decrease with increasing task complexity. HI/EE performed following a sustained bout of dehydrating activity may not impair cognition.

Effect of endurance exercise duration on muscle hypertrophy induced by functional overload.

For many ball games, both resistance and endurance training are necessary to improve muscle strength and endurance capacity. Endurance training has been reported to inhibit muscle strength and hypertrophy, but some studies have reported that endurance exercise (EE) does not inhibit the effects of resistance exercise. Here, we examined the effect of short- or long-duration EE on mouse skeletal muscle hypertrophy induced by functional overload (OL) at the molecular level. Plantaris muscle hypertrophy was induced by OL with synergist ablation in mice. Body mass was reduced with endurance training, but EE duration (30 or 90 min) had no effect. The ratio of plantaris muscle weight to body weight was higher in the OL and EE for 30 min (OL+EE30) and OL and EE for 90 min (OL+EE90) groups compared with the OL group. Expression of mechanistic target of rapamycin signaling proteins, which is related to protein synthesis and hypertrophy, was increased in the OL+EE30 group. Expression of Forkhead box-containing protein O1, which is related to protein breakdown and atrophy, remained unchanged. However, microtubule-associated protein 1 light chain 3, a known marker of autophagy, and MAFbx, which is related to protein breakdown, were significantly increased in the OL+EE90 group. Furthermore, markers of oxidative stress, ubiquitin and 4-hydroxynonenal were also significantly increased in the OL+EE90 group compared with other groups. In conclusion, EE duration did not affect body mass and plantaris mass and did not interfere with mechanistic target of rapamycin signaling, but it did increase ubiquitinated proteins and oxidative stress. It is therefore necessary to consider training durations for EE when combining endurance and resistance training.