Influence Of Exercise Intensity Research Articles

Exercise intensity impacts the improvement of metabolic dysfunction-associated steatotic liver disease via variations of monoacylglycerol O-acyltransferase 1 expression

BackgroundThe involvement of monoacylglycerol O-acyltransferase 1 (MOGAT1) in the pathogenesis of metabolic dysfunction-associated steatotic liver disease (MASLD) has been recognized. While exercise is recommended for the improvement of obesity and MASLD, the impact of exercise intensity remains unclear. This study aimed to examine the influence of exercise intensity on MOGAT1 expression in high-fat diet (HFD)-induced obese mice with MASLD. MethodMale C57BL/6 mice aged 6 weeks were subjected to either a regular or HFD with 60 % fat content for 8 weeks. The mice were categorized into 5 groups based on their diet and exercise intensity: normal diet group (ND), HFD group, low-intensity exercise with HFD group (HFD+LIE), moderate-intensity exercise with HFD group (HFD+MIE), and high-intensity exercise (HIE) with HFD group (HFD+HIE). The duration of running was adjusted to ensure uniform exercise load across groups (total distance = 900 m): HFD+LIE at 12 m/min for 75 min, HFD+MIE at 15 m/min for 60 min, and HFD+HIE at 18 m/min for 50 min. ResultsLipid droplet size and MASLD activity score were significantly lower in the HFD+HIE group compared to other exercise-intensity groups (p < 0.05). Among the 3 intensity exercise groups, the lowest MOGAT1 protein expression was found in the HFD+HIE group (p < 0.05). ConclusionThis study reveals that high-intensity exercise has the potential to mitigate MASLD development, partly attributed to the downregulation of MOGAT1 expression.

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

This study investigates the effects of exercise intensity and duration on executive functions among college students in China. 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. 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. Both exercise intensity and exercise duration were found to enhance executive functions in college students, with exercise intensity showing greater effectiveness than exercise duration.

Critical power is a key threshold determining the magnitude of post-exercise hypotension in non-hypertensive young males.

The effect of different exercise intensities on the magnitude of post-exercise hypotension has not been rigorously clarified with respect to the metabolic thresholds that partition discrete exercise intensity domains (i.e., critical power and the gas exchange threshold (GET)). We hypothesized that the magnitude of post-exercise hypotension would be greater following isocaloric exercise performed above versus below critical power. Twelve non-hypertensive men completed a ramp incremental exercise test to determine maximal oxygen uptake and the GET, followed by five exhaustive constant load trials to determine critical power and W' (work available above critical power). Subsequently, criterion trials were performed at four discrete intensities matched for total work performed (i.e., isocaloric) to determine the impact of exercise intensity on post-exercise hypotension: 10% above critical power (10%>CP), 10% below critical power (10%<CP), 10% above GET (10%>GET) and 10% below GET (10%<GET). The post-exercise decrease (i.e., the minimum post-exercise values) in mean arterial (10%>CP: -12.7±8.3 vs. 10%<CP: v3.5±2.9mmHg), diastolic (10%>CP: -9.6±9.8 vs. 10%<CP: -1.4±5.0mmHg) and systolic (10%>CP: -23.8±7.0 vs. 10%<CP: -9.9±4.3mmHg) blood pressures were greater following exercise performed 10%>CP compared to all other trials (all P<0.01). No effects of exercise intensity on the magnitude of post-exercise hypotension were observed during exercise performed below critical power (all P>0.05). Critical power represents a threshold above which the magnitude of post-exercise hypotension is greatly augmented. NEW FINDINGS: What is the central questions of this study? What is the influence of exercise intensity on the magnitude of post-exercise hypotension with respect to metabolic thresholds? What is the main finding and its importance? The magnitude of post-exercise hypotension is greatly increased following exercise performed above critical power. However, below critical power, there was no clear effect of exercise intensity on the magnitude of post-exercise hypotension.

Time course efficiency of MICE and HIIE on inhibitory control and HRV in adolescents with obesity and different cardiorespiratory fitness.

Adolescent obesity is associated with impaired inhibitory control. Acute exercise can improve executive function. However, due to the influence of exercise intensity, cognitive test timing, and cardiorespiratory fitness (CF) level, the most effective exercise program remains controversial. The current study investigated the time-course effects of moderate-intensity continuous exercise (MICE) and high-intensity interval exercise (HIIE) on inhibitory control (Stroop) and task-related heart rate variability (HRV) in adolescents with different CF. A mixed experimental design of 2 CF levels (high CF, HCF; low CF, LCF) × 3 exercise methods (MICE, HIIE, CON) × 3 test timing (pre, post-0, post-20) was adopted. Heart rate variability (HRV) and Stroop task tests were conducted before exercise (pre), immediately after exercise (post-0), and 20 min after exercise (post-20). Individuals with HCF exhibited a positive decrease in Stroop response time immediately and 20 min after MICE and HIIE, compared to pretest response times (RT). Conversely, individuals with LCF showed a slight increase in Stroop task (RT) only immediately after HIIE. All individuals had a slight increase in ACC after MICE and HIIE compared to before exercise. In addition, compared with the control group, the time-domain index (the square root of the mean squared differences of successive NN intervals, RMSSD) of HRV was significantly decreased, the frequency-domain index (the absolute power of the Low-Frequency band/the absolute power of the High-Frequency band ratio, LF/HF) was significantly increased after MICE and HIIE, and the effect of HIIE on RMSSD and LF/HF was significantly greater than that of MICE. The current study found that the acute effects of MICE and HIIE on inhibitory control in obese adolescents were influenced by the interaction of cognitive test timing and cardiorespiratory fitness. Individuals with high cardiorespiratory fitness performed better on the Stroop task than individuals with low cardiorespiratory fitness. The inhibitory control of HIIE in high-cardiorespiratory obese adolescents produced positive effects similar to those in MICE but more lasting, suggesting that HIIE is more beneficial for high-cardiorespiratory obese adolescents. MICE promoted inhibitory control in obese adolescents with low cardiorespiratory fitness, but HIIE impaired inhibitory control in obese adolescents with low cardiorespiratory fitness immediately after exercise, suggesting that low cardiopulmonary fitness obese adolescents may be suitable for MICE rather than HIIE exercise intervention. The shift from balanced HRV to sympathetic dominance after acute exercise reflects increased arousal levels and may be one of the underlying mechanisms by which acute exercise brings benefits to executive function.

The Influence of Exercise Intensity on Tryptophan Metabolites in Thoroughbred Horses.

Catabolism of tryptophan (Trp) is modulated by physical activity and provides a pool of active compounds: Trp is considered a calmative agent, kynurenine (Kyn) and 3-hydroxykynurenine (3-HKyn) show neurotoxic effects, kynurenic acid (Kyna) and xanthurenic acid (XA) have neuroprotective properties like nicotinamide (NAm), while serotonin is the neurotransmitter. The study was conducted to investigate the dependence of exercise intensity, measured by plasma lactic acid (LA) concentration, on the level of Trp, its catabolites (serotonin, Kyn, 3-HKyn, Kyna and XA), and NAm in Thoroughbred horses. A total of 18 young race Thoroughbred horses were investigated during exercise tests. Blood samples for analysis were collected: at rest, 10 min after the end of the exercise, and 60 min after the end of the exercise. Plasma LA was determined by the enzymatic method, Trp, and other metabolites using liquid chromatography coupled with mass spectrometry. In horses performing intense exercise, the concentration of LA, Kyn, XA and NAm was increased, while Trp was decreased. Significant correlations were detected for exercise-induced increase in LA and 3-HKyn, XA, and NAm. Considering the scope of changes in analyzed data, there is an expected neutral effect on the health status of exercised horses.

The Mode of Endurance Exercise Influences Changes in EEG Resting-State Graphs among High-Level Cross-Country Skiers.

Acute bouts of exercise influence the communication and organization of brain networks, with exercise intensity and volume regarded as key moderators. However, differences in coordination demands and limb involvement between exercise modes may also affect the communication and organization of brain networks after exercise and should be considered additionally. This study aimed to investigate the effect of mode on exercise-induced changes in electroencephalogaphy (EEG) resting-state networks comparing running (RUN) and cross-country skating (XC). Fifteen male, highly trained participants were tested for peak oxygen uptake (V̇O 2peak ) during RUN (65.3 mL·min -1 ·kg -1 ) and XC (63.5 mL·min -1 ·kg -1 ) followed by incremental protocols at 50%, 70%, and 90% of speed at V̇O 2peak in both modes on the treadmill. After each exercise bout, 5-min resting-state EEG assessments using 64 channels were performed. Upon graph theory, small world index (SWI), clustering coefficient (CC), and path length (PL) were assessed in theta, alpha-1 and alpha-2 frequency bands. Repeated-measures ANOVA was applied to analyze the influence of exercise intensity and mode on modulations in brain network efficiency. Main effects of mode on SWI ( P = 0.047), CC ( P < 0.001), and PL ( P = 0.031) in the alpha-2 network indicated stronger modulations in network efficiency after XC. Main effects of exercise intensity in the theta network indicated modulated SWI ( P < 0.001), CC ( P < 0.001), and PL ( P = 0.003) after exercise at 90% of V̇O 2peak speed. Physiological outcomes (heart rate, blood lactate concentration, and rating of perceived exertion) were influenced by intensity solely. The present study demonstrates that an acute bout of coordinatively challenging endurance exercise may affect brain networks differently compared with running. Future studies may consider exercise mode as a potential moderator in the acute interaction between exercise and the brain.

Assessing Asymmetry in Exercise Intensity Domains between Lower Limbs in Persons with Multiple Sclerosis: A Pilot Study

Persons with multiple sclerosis (PwMS) experience a variety of physical impairments that can present in an asymmetrical pattern, resulting in significant differences between contralateral limbs (i.e., &gt;10%). Asymmetries in PwMS have been associated with walking impairment and postural instability. Exercise intensity has been shown to influence the degree of asymmetry outcomes in healthy populations, and may have an impact on appropriate exercise prescriptions. The purpose of the current pilot study was to investigate the potential presence of asymmetry in metabolic events demarcating exercise intensity domains during single-leg cycling in PwMS. Five PwMS (Expanded Disability Status Scale range 2.0 to 4.5) completed a single leg incremental cycling test (SLICT) and a series of single-leg constant power time-to-exhaustion trials to determine gas exchange threshold (GET), peak oxygen consumption (VO2peak), peak power output (PPO), critical power (CP), and W’ (exercise tolerance above CP) for both lower limbs. Statistical analysis revealed no significant between-limb differences for VO2peak, GET, CP, PPO, and W’. Only W’ asymmetry score was significantly (49.5 ± 28.7 vs. 10.0, p = 0.04) greater than 10%. No significant differences between asymmetry scores at the GET, CP, and PPO were observed. Results from the current pilot investigation suggest that exercise intensity may not influence asymmetry outcomes in PwMS. Future studies with larger sample sizes and those with higher disability levels are required to fully understand the influence of exercise intensity on asymmetry in PwMS.

Influence Of Aerobic Exercise Intensity On Post-exercise Cerebrovascular Function

Peripheral vascular function is acutely improved, in an intensity dependent manner, following a single session of aerobic exercise. While previous studies have examined the effects of acute exercise on cerebrovascular function, the influence of exercise intensity on post-exercise cerebrovascular function remains unclear. PURPOSE: To determine the influence of aerobic exercise intensity on post-exercise cerebrovascular function. METHODS: Eleven participants (age: 27 ± 4 y; VO2max = 51 ± 8 mL/kg/min; men = 4, women = 7) completed 2 study days, in a randomized order, in which they either walked at 30% VO2max for 30 min (WALK) or ran at 70% VO2max for 30 min (RUN). Cerebrovascular reactivity to hypercapnia (CVR) was measured pre and 30 min post-exercise. Middle cerebral artery velocity (MCAv), mean arterial pressure (MAP), and end-tidal CO2 (ETCO2) were continuously monitored during the hypercapnia protocol. Cerebrovascular conductance index (CVCi) was calculated as MCAv/MAP. CVR was calculated as the slope between the percent changes in MCAv or CVCi and ETCO2. RESULTS: During WALK and RUN, there was no difference in MCAv from pre to post-exercise (p ≥ 0.05 for both), despite a significant post-exercise reduction in ETCO2 (WALK: pre = 42 ± 3 mmHg, post = 40 ± 2 mmHg; RUN: pre = 41 ± 3 mmHg, post = 40 ± 3 mmHg; p < 0.05 for both). While WALK had no significant change in MAP and CVCi from pre to post-exercise (p ≥ 0.05 for both), RUN had a significant decrease in MAP and increase in CVCi (MAP: pre = 95 ± 13 mmHg, post = 85 ± 8 mmHg; CVCi: pre = 0.67 ± 0.14 cm/s/mmHg, post = 0.80 ± 0.12 cm/s/mmHg; p < 0.05 for both). There was no significant change in MCAv CVR or CVCi CVR from pre to post-exercise for WALK (p ≥ 0.05 for both); however, there was a decline in both MCAv CVR and CVCi CVR from pre to post-exercise during RUN (MCAv CVR: pre = 1.7 ± 0.5 AU, post = 1.3 ± 0.4 AU; CVCi CVR: pre = 1.3 ± 0.5 AU, post = 0.9 ± 0.4 AU; p < 0.05 for both). Finally, there was no significant difference in the magnitude of change in MCAv CVR and CVCi CVR from pre to post-exercise between the study days (p ≥ 0.05 for both). CONCLUSION: Exercise intensity influences post-exercise cerebrovascular hemodynamics and function as RUN, but not WALK, had a significant increase in CVCi and a reduced MCAv CVR and CVCi CVR from pre to post-exercise. Supported by UW-Madison’s Fall Research Competition, NHLBI 118154

Influence of exercise intensity and hypoxic exposure on physiological, perceptual and biomechanical responses to treadmill running

ABSTRACT Acute physiological, perceptual and biomechanical consequences of manipulating both exercise intensity and hypoxic exposure during treadmill running were determined. On separate days, eleven trained individuals ran for 45 s (separated by 135 s of rest) on an instrumented treadmill at seven running speeds (8, 10, 12, 14, 16, 18 and 20 km.h−1) in normoxia (NM, FiO2 = 20.9%), moderate hypoxia (MH, FiO2 = 16.1%), high hypoxia (HH, FiO2 = 14.1%) and severe hypoxia (SH, FiO2 = 13.0%). Running mechanics were collected over 20 consecutive steps (i.e. after running ∼25 s), with concurrent assessment of physiological (heart rate and arterial oxygen saturation) and perceptual (overall perceived discomfort, difficulty breathing and leg discomfort) responses. Two-way repeated-measures ANOVA (seven speeds × four conditions) were used. There was a speed × condition interaction for heart rate (p = 0.045, ηp2 = 0.22), with lower values in NM, MH and HH compared to SH at 8 km.h−1 (125 ± 12, 125 ± 11, 128 ± 12 vs 132 ± 10 b.min−1). Overall perceived discomfort (8 and 16 km.h−1; p = 0.019 and p = 0.007, ηp2 = 0.21, respectively) and perceived difficulty breathing (all speeds; p = 0.023, ηp2 = 0.37) were greater in SH compared to MH, whereas leg discomfort was not influenced by hypoxic exposure. Minimal difference was observed in the twelve kinetics/kinematics variables with hypoxia (p > 0.122; ηp 2 = 0.19). Running at slower speeds in combination with severe hypoxia elevates physiological and perceptual responses without a corresponding increase in ground reaction forces. Highlights The extent to which manipulating hypoxia severity (between normoxia and severe hypoxia) and running speed (from 8 to 20 km.h−1) influence acute physiological and perceptual responses, as well as kinetic and kinematic adjustments during treadmill running was determined. Running at slower speeds in combination with severe hypoxia elevates heart rate, while this effect was not apparent at faster speeds. Arterial oxygen saturation was increasingly lower as running speed and hypoxic severity increased. Overall perceived discomfort (8 and 16 km.h−1) and perceived difficulty breathing (all speeds) were lower in moderate hypoxia than in severe hypoxia, whereas leg discomfort remained unchanged with hypoxic exposure.

Nephroprotective effect of exercise training in cisplatin-induced renal damage in mice: influence of training protocol.

Cisplatin is an effective antineoplastic agent, but its use is limited by its nephrotoxicity caused by the oxidative stress in tubular epithelium of nephrons. On the other hand, regular exercise provides beneficial adaptations in different tissues and organs. As with many drugs, dosing is extremely important to get the beneficial effects of exercise. Thus, we aimed to investigate the influence of exercise intensity and frequency on cisplatin-induced (20 mg/kg) renal damage in mice. Forty male Swiss mice were divided into five experimental groups (n=8 per group): 1) sedentary; 2) low-intensity forced swimming, three times per week; 3) high-intensity forced swimming, three times per week; 4) low-intensity forced swimming, five times per week; and 5) high-intensity forced swimming, five times per week. Body composition, renal structure, functional indicators (plasma urea), lipid peroxidation, antioxidant enzyme activity, expression of genes related to antioxidant defense, and inflammatory and apoptotic pathways were evaluated. Comparisons considered exercise intensity and frequency. High lipid peroxidation was observed in the sedentary group compared with trained mice, regardless of exercise intensity and frequency. Groups that trained three times per week showed more benefits, as reduced tubular necrosis, plasma urea, expression of CASP3 and Rela (NFkB subunit-p65) genes, and increased total glutathione peroxidase activity. No significant difference in Nfe2l2 (Nrf2) gene expression was observed between groups. Eight weeks of regular exercise training promoted nephroprotection against cisplatin-mediated oxidative injury. Exercise frequency was critical for nephroprotection.

Influence of exercise intensity and regional differences in the sudomotor recruitment pattern in exercising prepubertal boys and young men

We investigated the influence of exercise intensities and regional differences in the sudomotor recruitment pattern in boys. Six prepubertal boys (age 11 ± 1 yr) cycled at light, moderate, and high exercise intensity (35%, 50%, and 65% VO2max) for 30 min in a temperate condition (28 °C, 40% relative humidity). Local sweat rate (ventilated capsule) and number of activated sweat glands (starch-iodine technique) at five body sites were assessed and sweat gland output was calculated. Responses in boys were compared with those in nine young men (23 ± 1 yr) tested under identical conditions. The forehead, chest, back, and forearm, but not thigh, sweat rate increased from light to moderate and at high intensities in boys (all p ≤ 0.005) but not from moderate to high (all p ≥ 0.071). The sweat rate on the forehead was relatively higher (p ≤ 0.045) and thigh was lower (p ≤ 0.050) than other sites in boys at moderate and high intensities. Exercise intensity-dependent sweating was associated with activating more sweat glands but not increasing glandular output in boys. The sweat rate in boys was attenuated versus men heterogeneously across body sites concurrent to low glandular outputs (all p ≤ 0.027). We conclude that exercise intensity modulates the sweat rate in boys by changing the number of activated sweat glands heterogeneously among skin sites. Age-related differences in the sudomotor pattern are evident at higher exercise intensities. Development of glandular output per gland occurring from boys to young men may play a key role in modulating sweat rate with respect to exercise intensity and regional differences.

Constant low-to-moderate mechanical asymmetries during a treadmill graded exercise test

ABSTRACT This study describes asymmetry in key mechanical variables during a treadmill-based, running graded exercise test (GXT). Twenty-one recreationally trained male runners completed a continuous, maximal GXT on an instrumented treadmill, starting at 9 km.h−1 with speed increases of +0.5 km.h−1 every 30 s, for the determination of ventilatory threshold (VT), respiratory compensation point (RCP), and maximal oxygen uptake (MAX). Ground reaction forces were recorded continuously and subsequently averaged from 10 consecutive steps corresponding to VT, RCP and MAX intensity stages (13.4 ± 1.2 km.h−1, 16.0 ± 1.6 km.h−1 and 18.2 ± 1.5 km.h−1, respectively). Asymmetry scores were assessed from the “symmetry angle” (SA) formulae, where a score of 0%/100% indicates perfect symmetry/asymmetry; these were then compared between the three intensity stages. There was no influence of exercise intensity on SA scores for any of the sixteen biomechanical variables (P > 0.222). The group mean SA scores did not exceed 1.5% for spatio-temporal variables (contact time, aerial time, frequency and step length). There were larger mean SA scores for mean loading rate (3.7 ± 2.7%) and most spring-mass model variables (vertical stiffness: 2.2 ± 1.6% and leg stiffness: 1.7 ± 1.4%). The SA scores were ∼1.0–3.5% for braking and propulsive phase durations, peak forces, and resulting impulses. Lower extremities behave similarly at submaximal and maximal intensities during GXT, indicating that runners maintained relatively even strides as intensity increased. However, practitioners must be careful not to infer the presence of asymmetry during GXT based on a single variable, given the lower SA scores for spatio-temporal parameters. Highlights Our comprehensive list of sixteen mechanical variables provides a mechanical norm of expected asymmetry during treadmill graded exercise testing for recreationally trained runners. The stride pattern across submaximal and maximal exercise intensities remains consistent between limbs, with mechanical asymmetries being more individual-specific than intensity stage-dependent. Low to moderate asymmetry is a natural phenomenon in recreationally trained runners during treadmill graded exercise testing; notwithstanding, asymmetry scores appear inconsistent between mechanical parameters.

Heart Rate Variability Analysis and The Influence of Exercise Intensity Over Time in Young-healthy Women

Our heart is a vital organ that pumps blood and through the vessels of the circulatory system. In medical applications, we can observe the heart rate using Electrocardiograph (ECG). Currently, people tend to have high working activity without a proper exercise intensity. This study was conducted to observe the heart rate variability (HRV) on the healthy young woman who was not doing any exercise. We evaluated the HRV characteristics while exercising with a regular period and different intensity (light to hard) and how the difference before and after of evaluation period. Seven young-healthy women (19 - 21 years old) women were observed during three observation stages: pre-exercise, main exercise-period, and post-exercise for 2 months. We analyzed MeanRR, SDRR, CVRR, rMSSD, VLF, LF, HF, and the Poincaré plot parameters (SD1 and SD2) as the HRV properties. We found that SDRR was decreased from the first week (0.08 s) to the last week of the evaluation period (0.03 s) followed by the HF component (0.15 – 0.2 Hz). The Poincaré plot properties also reduced from the first week to the last week of the exercise period (0.07 s to 0.03 s). We indicated the characteristics of a woman's HRV during regular exercise periods with different intensity have made the heart more effective in pumping blood. We concluded that the heart condition would be improved during regular exercise with the increment of intensity even in a short of a period. Finally, the heart rate performance may be decreased during absent from regular exercise for a month.

The influence of exercise intensity and exercise mode on gastrointestinal damage.

Strenuous exercise increases gastrointestinal damage, but the dose-response relationship is yet to be elucidated. It is also commonly believed that running causes greater gastrointestinal damage than cycling. Two randomised, crossover studies aimed to 1) quantify gastrointestinal damage with increasing exercise intensity, and 2) determine if running was associated with greater gastrointestinal damage than cycling. Following a maximal oxygen uptake (V̇O2max) test, participants completed 3 cycling trials at different intensities (60min at 40%, 60% and 80% V̇O2max; n= 10 (5 female, 5 male)) (INTENSITY), or 1 running and 1 cycling trial (45 min at 70% V̇O2max; n= 11 (3 female, 8 male)) (MODE). Venous blood samples were collected pre- and post-exercise to measure gastrointestinal damage via intestinal fatty acid binding protein (I-FABP). In INTENSITY, I-FABP magnitude of change was greater at 80% V̇O2max than 40% V̇O2max (p< 0.01). In MODE, I-FABP magnitude of change was greater with cycling (mean (SD)) (84.7 (133.2)% d= 1.07) compared with running (19.3 (33.1)%, d= 0.65) with a moderate effect (d= 0.68, p= 0.024). Rating of perceived exertion (RPE) and heart rate (HR) were higher during cycling (RPE p< 0.0001; HR p< 0.0001) but rectal temperature was not different between modes (p= 0.94). While gastrointestinal damage increases with increasing exercise intensity, running was not associated with greater gastrointestinal damage than cycling. Novelty: A fraction of the anaerobic threshold, rather than a fraction of V̇O2max, may be more predictive of intensity that results in exercise induced gastrointestinal damage. The mode of exercise may not be as important as intensity for inducing gastrointestinal damage. Improving anaerobic threshold may reduce susceptibility to gastrointestinal damage when exercising at high intensities.

An expanded repertoire of intensity-dependent exercise-responsive plasma proteins tied to loci of human disease risk

Routine endurance exercise confers numerous health benefits, and high intensity exercise may accelerate and magnify many of these benefits. To date, explanatory molecular mechanisms and the influence of exercise intensity remain poorly understood. Circulating factors are hypothesized to transduce some of the systemic effects of exercise. We sought to examine the role of exercise and exercise intensity on the human plasma proteome. We employed an aptamer-based method to examine 1,305 plasma proteins in 12 participants before and after exercise at two physiologically defined intensities (moderate and high) to determine the proteomic response. We demonstrate that the human plasma proteome is responsive to acute exercise in an intensity-dependent manner with enrichment analysis suggesting functional biological differences between the moderate and high intensity doses. Through integration of available genetic data, we estimate the effects of acute exercise on exercise-associated traits and find proteomic responses that may contribute to observed clinical effects on coronary artery disease and blood pressure regulation. In sum, we provide supportive evidence that moderate and high intensity exercise elicit different signaling responses, that exercise may act in part non-cell autonomously through circulating plasma proteins, and that plasma protein dynamics can simulate some the beneficial and adverse effects of acute exercise.

Acute high-intensity and moderate-intensity interval exercise do not change corticospinal excitability in low fit, young adults.

Previous research has demonstrated a lack of neuroplasticity induced by acute exercise in low fit individuals, but the influence of exercise intensity is unclear. In the present study, we assessed the effect of acute high-intensity (HI) or moderate-intensity (MOD) interval exercise on neuroplasticity in individuals with low fitness, as determined by a peak oxygen uptake (VO2peak) test (n = 19). Transcranial magnetic stimulation (TMS) was used to assess corticospinal excitability via area under the motor evoked potential (MEP) recruitment curve before and following training. Corticospinal excitability was unchanged after HI and MOD, suggesting no effect of acute exercise on neuroplasticity as measured via TMS in sedentary, young individuals. Repeated bouts of exercise, i.e., physical training, may be required to induce short-term changes in corticospinal excitability in previously sedentary individuals.

The Influence of Exercise Intensity on the Association Between Kilojoules Spent and Various Training Loads in Professional Cycling.

A valid measure for training load (TL) is an important tool for cyclists, trainers, and sport scientists involved in professional cycling. The aim of this study was to explore the influence of exercise intensity on the association between kilojoules (kJ) spent and different measures of TL to arrive at valid measures of TL. Four years of field data were collected from 21 cyclists of a professional cycling team, including 11,716 training and race sessions. kJ spent was obtained from power output measurements, and others TLs were calculated based on the session rating of perceived exertion (sRPE), heart rate (Lucia training impulse [luTRIMP]), and power output (training stress score [TSS]). Exercise intensity was expressed by the intensity factor (IF). To study the effect of exercise intensity on the association between kJ spent and various other TLs (sRPE, luTRIMP, and TSS), data from low- and high-intensity sessions were subjected to regression analyses using generalized estimating equations. This study shows that the IF is significantly different for training and race sessions (0.59 [0.03] vs 0.73 [0.03]). Significant regression coefficients show that kJ spent is a good predictor of sRPE, and luTRIMP, as well as TSS. However, IF does not influence the associations between kJ spent and sRPE and luTRIMP, while the association with TSS is different when sessions are done with low or high IF. It seems that the TSS reacts differently to exercise intensity than sRPE and luTRIMP. A possible explanation could be the quadratic relation between IF and TSS.

Left Ventricular Function and Cardiac Biomarker Release-The Influence of Exercise Intensity, Duration and Mode: A Systematic Review and Meta-Analysis.

We performed a systematic review, meta-analysis and meta-regression of exercise studies that sought to determine the relationship between cardiac troponin (cTn) and left ventricular (LV) function. The second objective was to determine how study-level and exercise factors influenced the variation in the body of literature. A systematic search of Pubmed Central, Science Direct, SPORTDISCUS and MEDLINE databases. Original research articles published between 1997 and 2018 involving > 30 mins of continuous exercise, measuring cardiac troponin event rates and either LV ejection fraction (LVEF) or the ratio of the peak early (E) to peak late (A) filling velocity (E/A ratio). Random-effects meta-analyses and meta-regressions with four a priori determined covariates (age, exercise heart rate [HR], duration, mass). The systematic search strategy was registered on the PROSPERO database (CRD42018102176). Pooled cTn event rates were evident in 45.6% of participants (95% confidence interval (CI) 33.6-58.2); however, the overall effect was non-significant (P > 0.05). There were significant (P < 0.05) reductions in E/A ratio of - 0.38 (SMD = - 1.2, 95% CI - 1.4 to - 1.0), and LVEF of - 2.02% (SMD = - 0.38, 95% CI - 0.7 to - 0.1) pre- to post-exercise. Increased exercise HR was a significant predictor of troponin release and E/A ratio. Participant age was negatively associated with cTn release.There was a significant negative association between E/A ratio with increased rates of cTn release (P < 0.05). High levels of statistical heterogeneity and methodological variability exist in the majority of EICF studies. Our findings show that exercise intensity and age are the most powerful determinants of cTn release. Diastolic function is influenced by exercise HR and cTn release, which implies that exercise bouts at high intensities are enough to elicit cTn release and reduce LV diastolic function. Future EICF studies should (1) utilise specific echocardiographic techniques such as myocardial speckle tracking, (2) ensure participants are euhydrated during post-exercise measurements, and (3) repeat measures in the hours following exercise to assess symptom progression or recovery. It is also recommended to further explore the relationship between aging, training history, and exercise intensity on cTn release and functional changes.

Left Ventricular Function and Cardiac Biomarker Release -The Influence of Exercise Intensity, Duration and Mode: A Systematic Review and Meta-Analysis

Left Ventricular Function and Cardiac Biomarker Release -The Influence of Exercise Intensity, Duration and Mode: A Systematic Review and Meta-Analysis

Carotid Chemoreflex Regulation of Post‐Exercise Cardiac Autonomic Control in Healthy Humans: Influence of Exercise Intensity

The recovery of cardiac autonomic control from exercise has two phases. The fast phase lasts about 60 s after exercise, and is largely dependent on the cardiac vagal reactivation. The slow phase is 300 s in duration, and is dependent on both the cardiac vagal reactivation and sympathetic withdrawal. Indexes of post‐exercise cardiac autonomic control are widely used in the clinical practice to predict morbidity and mortality. However, the mechanisms that regulate the post‐exercise cardiac autonomic control remain unclear. The carotid chemoreflex regulates cardiac autonomic control at rest, and carotid chemoreceptors are stimulated by humoral and neural signals related to exercise. As the extent of the humoral and neural responses are dependent upon exercise intensity, we hypothesized the carotid chemoreflex could regulate post‐exercise cardiac autonomic control in an exercise‐intensity‐dependent manner.Thirteen healthy humans performed ramp incremental exercise up to either moderate‐intensity (MI; i.e., ventilatory threshold) or high‐intensity exercise (HI; i.e., 90% peak workload). Both MI and HI exercise were followed by 5 min of active recovery (i.e., unloaded cycling) while breathing, in random order, normoxia (21% of O2, control), hyperoxia (100% of O2, carotid chemoreflex inhibition) or hypoxia (12% of O2, carotid chemoreflex stimulation). Gas administration started 10 s before the onset of recovery from exercise. The fast phase of cardiac autonomic control recovery from exercise was assessed by the heart rate (HR) reduction at 60 s post‐exercise (HRR60s). The slow phase was assessed by the time constant of exponential HR decay (HRRτ) over 300 s and the HR reduction at 300 s post‐exercise (HRR300s). Fast and slow phases were assessed by the square root of mean squared differences of successive R‐R intervals of 30‐s data segments (RMSSD30s).As compared to normoxia, hyperoxia did not change HRR60s at either exercise intensities. Hypoxia did not change HRR60s at MI, but decreased HRR60s at HI (normoxia: 29 ± 8 vs hypoxia: 17 ± 9 bpm; P &lt; 0.01). Hyperoxia and hypoxia did not change HRRτ. Hyperoxia did not affect HRR300s, but hypoxia decreased HRR300s similarly at both exercise intensities (MI: normoxia = 32 ± 14 vs hypoxia = 26 ± 17 bpm; HI: normoxia = 55 ± 7 vs hypoxia = 48 ± 11 bpm; post hoc for gas main effect: P = 0.03). Finally, regardless of the time, hyperoxia increased RMSSD30s (MI: normoxia = 15 ± 7 vs hyperoxia = 19 ± 10 ms; HI: normoxia = 5 ± 3 vs hyperoxia = 6 ± 3 ms, post hoc for gas main effect: P &lt; 0.01), whereas hypoxia decreased RMSSD30s (MI: hypoxia = 13 ± 9 ms vs normoxia; HI: hypoxia = 4 ± 2 vs normoxia, post hoc for gas main effect: P &lt; 0.01) at both exercise intensities.In conclusion, the carotid chemoreflex regulates both the fast and slow phases of post‐exercise cardiac autonomic control in healthy humans; however, only the fast phase regulation is dependent on the exercise intensity. These results suggest that sensitization of the carotid chemoreflex with exercise plays an important role for the post‐exercise cardiac vagal reactivation.Support or Funding InformationFAPESP 2015/22198‐2; 2018/03501‐4This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.