Exercise Of Varying Intensity Research Articles

V̇O2PEAK PROVIDES A BETTER PREDICTOR OF ERGOMETER MEAN MAXIMAL POWER THAN MAXIMAL OXYGEN EXTRACTION IN TRAINED ROWERS

INTRODUCTION & AIMS Muscle oxygenation characteristics are suggested to better explain performance than peak oxygen uptake (V̇O2peak) in highly trained canoe-kayak athletes (Paquette et. al, 2018), but this has not been explored with rowers. Therefore, this investigation aimed to 1) determine whether maximal oxygen extraction improved prediction of rowing ergometer mean maximal power (MMP; W/kg) compared to V̇O2peak alone, and 2) assess differences in muscle oxygen extraction between anatomical sites during incremental rowing. METHODS Trained male (n=16) and female (n=6) rowers completed a 7x4min graded exercise test on a rowing ergometer to determine mean power output for each stage and V̇O2peak and MMP during the final stage. Change in muscle oxygen extraction (Δ[HHb]) during each stage was determined using near infrared spectroscopy (NIRS) at the vastus lateralis (VL), gastrocnemius medialis (GM), and biceps brachii (BB). The best predictor of MMP was determined using linear regression, and mixed-effects models were used to assess Δ[HHb] across sites and stage. RESULTS V̇O2peak was a significant predictor of MMP (R2=0.74); however, Δ[HHb] (at each site individually or combined) had no association with MMP (R2≤0.05). The strongest model included V̇O2peak and GM Δ[HHb] (R2=0.83); however, the improvement in model fit was modest (mean absolute error decreased from 0.211W.kg-1 to 0.193W.kg-1). A significant site x stage interaction was observed for Δ[HHb] at each site across all stages. Post-hoc analysis revealed VL Δ[HHb] was higher than GM Δ[HHb] for each stage; VL Δ[HHb] was lower than BB Δ[HHb] from stages 1-4, then higher from stages 5-7; and GM Δ[HHb] was lower than BB Δ[HHb] for stages 1-6, but higher in the final stage. CONCLUSION Maximal oxygen extraction alone cannot predict ergometer MMP in trained rowers. However, NIRS derived muscle oxygen extraction may provide additional useful information regarding relative muscle contributions at varying exercise intensities.

Trehalose Improved 20-min Cycling Time-Trial Performance After 100-min Cycling in Amateur Cyclists.

Carbohydrate (CHO) supplementation during endurance exercise can improve performance. However, it is unclear whether low glycemic index (GI) CHO leads to differential ergogenic and metabolic effects compared with a standard high GI CHO. This study investigated the ergogenic and metabolic effects of CHO supplementation with distinct GIs, namely, (a)trehalose (30g/hr), (b)isomaltulose (30g/hr), (c)maltodextrin (60g/hr), and (d)placebo (water). In this double-blind, crossover, counterbalanced, placebo-controlled study, 13 male cyclists cycled a total of 100min at varied exercise intensity (i.e.,10-min stages at 1.5, 2.0, and 2.5W/kg; repeated three times plus two 5-min stages at 1.0W/kg before and after the protocol), followed by a 20-min time trial on four separated occasions. Blood glucose and lactate (every 20min), heart rate, and ratings of perceived exertion were collected throughout, and muscle biopsies were taken before and immediately after exercise. The results showed that trehalose improved time-trial performance compared with placebo (total work done 302 ± 39 vs. 287 ± 48kJ; p = .01), with no other differences between sessions (all p ≥ .07). Throughout the 100-min protocol, blood glucose was higher with maltodextrin compared with the other supplements at all time points (all p < .05). Heart rate, ratings of perceived exertion, muscle glycogen content, blood glucose, and lactate were not different between conditions when considering the 20-min time trial (all p > .05). Trehalose supplementation throughout endurance exercise improved cycling performance and appears to be an appropriate CHO source for exercise tasks up to 2hr. No ergogenic superiority between the different types of CHO was established.

The effect of varied exercise intensity on antioxidant function, aortic endothelial function, and serum lipids in rats with non-alcoholic fatty liver disease.

This study aimed to compare the effects of diet and exercise of different intensities on antioxidant function, aortic endothelial cell function and serum lipids in NAFLD (nonalcoholic fatty liver disease) rats. Fifty Sprague-Dawley (SD) rats (180-220g) were randomly divided into two experimental groups and fed either a standard rodent chow diet (CON; n=10) or a high-fat diet (HFD; n=40). After 16 weeks, the animals that received the HFD were randomly separated into a high-fat control group (HFC; n=10) or three ex-ercise training groups: HFD and low-intensity exercise (LE; n=10), HFD and moderate-intensity exercise (ME; n=10), and HFD and incremental intensity exercise (IE; n=10). These experimental rats keep sedentary or trained for the next six weeks. A detection kit was used to detect nitric oxide synthase (NOs), nitric oxide (NO), malondialdehyde (MDA) and other markers of aor-tic oxidative stress. The expression levels of endothelial nitric oxide synthase (e-NOS) and endothelin-1 (ET-1) were detected by immunohistochemistry. TC, TG, and other lipid metabolism parameters were detected by an auto-matic analyzer. Exercise with different intensities could improve lipid me-tabolism, enhance antioxidant function, reduce MDA (P&lt;0.01), increase NO (P&lt;0.01), and improve the expression of e-NOS and ET-1 (P&lt;0.01) protein levels in NAFLD rats. Decreased blood lipids were exhibited in all exercise groups. Notably, the moderate-intensity exercise demonstrated more effecton increasing glutathione (GSH) contents (P&lt;0.01) and decreased the ex-pression of ET-1protein levels (P&lt;0.01). The results showed that exercise at different intensities improved lipid metabolism and enhanced anti-oxidation function. Moderate exercise could improve the function of aortic endothelial cells.

Higher Levels of Shear Stress Downregulate Endothelin‐1 mRNA Expression

BackgroundPhysical inactivity has been shown to be a risk factor in the development of endothelial dysfunction. Endothelin‐1 (EDN‐1), a potent vasoconstrictor contributes to the pathogenesis of cardiovascular disease. Exercise‐induced endothelial shear stress (ESS) is a mechanical stimulus caused by alterations in blood flow patterns that regulates vascular function. Although it has been reported that higher levels of ESS may act as a protective mechanism to prevent vascular dysfunction, the role of pulsatile exercise‐induced ESS with varying exercise intensities has not been explored. Therefore, the purpose of this study was to determine the effects of pulsatile exercise‐induced ESS based on in vivo exercise intensity on EDN‐1 expression.MethodsCommercially available human umbilical vein endothelial cells (HUVEC; Sigma‐Aldrich, St Louis, MO) were cultured until 90–100% confluence. Exercise‐induced ESS in vivo was obtained from our previous reports. Cultured HUVEC cells were exposed to pulsatile resting ESS (18 dynes/cm2) for 2 hours, followed by 1 hour at resting ESS, low‐intensity exercise‐induced ESS (35 dynes/cm2), moderate exercise‐induced ESS, or high‐intensity exercise‐induced ESS (75 dynes/cm2) on a closed circuit pump and channeled slide (Ibidi pump system (PumpControl Software 1.5.4) and slides, Ibidi Inc., Fitchburg, WI). A set of cells were exposed to physiologically low shear stress levels (10 dynes/cm2) for 3 hours as a control. Total RNA was extracted and reverse transcribed followed by measurement of EDN‐1 mRNA expression via qRT‐PCR. qRT‐PCRs were performed in duplicates and changes in gene expression were calculated using the ΔΔ‐CT method with GAPDH used as the normalizing control gene. Statistical analysis was performed using graphpad prism 8 software (Graphpad Software.). Significance was considered at p&lt;0.05.ResultsEDN‐1 mRNA expression was significantly downregulated following low and high intensity exercise‐induced ESS compared to resting conditions (p&lt;0.05). Moderate intensity exercise induced ESS showed a trend downregulation in EDN‐1 mRNA expression compared to resting conditions (p&lt;0.10).ConclusionsOur data suggests that higher levels of pulsatile exercise‐induced ESS are needed to suppress mRNA expression of EDN‐1. Although moderate intensity exercise induced ESS showed only a trend difference in mRNA expression compared to resting conditions, we have previously reported that moderate exercise‐induced ESS was shown to upregulate endothelial nitric oxide gene expression, a key vasodilatory enzyme that may prevent vascular dysfunction.

The Impact of Varying Caffeine‐Induced Contractile Activity on Metabolic Enzyme Activity

Exercise intensity is widely known to differentially affect skeletal muscle metabolic approaches, with a general understanding that short duration, high intensity exercise is associated with an increased reliance on anaerobic glycolysis, while long duration, low to moderate intensity exercise is associated with a greater reliance on aerobic processes. In cell culture, caffeine is a commonly used method to pharmaceutically stimulate contractile activity in skeletal muscle cells; upon exposure to caffeine, ryanodine receptors are stimulated to release calcium, thereby allowing crossbridge cycling and subsequent contractile activity to occur. This technique for exercising muscle cells in culture offers a controlled, experimental platform to study the effect of contractile activity on isolated muscle cells; presumably, varying doses of caffeine should mimic varying levels of exercise intensity, though the degree to which caffeine dose impacts metabolic shifts has yet to be fully elucidated. Here, we exposed C2C12 cells, an immortalized line of mouse skeletal muscle cells, to varying levels of caffeine supplementation throughout myotube differentiation in an attempt to recapitulate metabolic signatures consistent with varying exercise intensities. Following standard proliferation protocols, mature myotubes were differentiated for 7 days. On differentiation days 4‐7, experimental cohorts of cells were exposed to either a low dosage (10mM) or a high dosage (40 mM) of caffeine‐supplemented differentiation media for 20 minutes daily. All cells were harvested for protein on differentiation day seven. Protein concentration across cohorts was measured using a Bradford protein assay. Metabolic changes were characterized by running functional enzyme assays for lactate dehydrogenase (LDH) and citrate synthase (CS) to compare anaerobic and aerobic changes, respectively. Preliminary data suggest that, relative to controls, cells exposed to 10mM caffeine have a decrease in LDH activity, and a trend toward increased CS activity. Conversely, cells exposed to 40mM caffeine show no change in LDH and a trend toward decreased CS activity. Collectively, these preliminary data suggest that C2C12 cells exposed to low doses of caffeine simulating low intensity exercise may have less reliance on anaerobic metabolism with a potential greater reliance on aerobic metabolism, while those exposed to high doses of caffeine simulating high intensity exercise may have a lesser reliance on aerobic metabolism. While more research needs to be done to characterize the precise impact of varying caffeine dosages on C2C12 cells, these initial findings are consistent with previously established trends in exercise intensity and metabolism.

Exercise‐Induced Shear Stress Upregulates eNOS Protein in vitro

BackgroundEndothelial cell dysfunction has been shown to be the first step in the pathogenesis of cardiovascular disease. A risk factor in the development of cardiovascular disease is physical inactivity. Endothelial shear stress (ESS) involves mechanoreceptors on the surface of endothelial cells that are capable of sensing different forces, triggering a biochemical response leading to cellular adaptations. Exercise‐induced ESS might act as a protective mechanism in preventing endothelial cell dysfunction. Endothelial nitric oxide synthase (eNOS), a key enzyme involved maintaining vascular homeostasis has been shown to be upregulated in response to higher shear stress levels. Although exercise has been shown to improve endothelial cell function, the role of varying exercise intensities on endothelial cell homeostasis has not been explored. The purpose of this study was to determine the effects of in vitro exercise‐induced ESS during 3 different exercise intensities on eNOS expression.MethodsCommercially available human umbilical vein endothelial cells (HUVEC; Sigma‐Aldrich, St Louis, MO) were cultured until 90‐100% confluence. Exercise‐induced ESS in vivo was obtained from our previous reports. Cultured cells were exposed to pulsatile resting ESS (18 dynes/cm2) for 2 hours, followed by 1 hour at resting ESS, low‐intensity exercise‐induced ESS (35 dynes/cm2), moderate‐intensity exercise‐induced ESS (50 dynes/cm2), or high‐intensity exercise‐induced ESS (75 dynes/cm2) on a closed circuit pump and channeled slide (Ibidi pump system (PumpControl Software 1.5.4) and slides, Ibidi Inc., Fitchburg, WI). A set of cells were exposed to physiologically low shear stress levels (10 dynes/cm2) for 3 hours as a control. Following ESS conditions, total protein was extracted, and western immunoblotting was performed to measure eNOS protein expression with GAPDH used as the normalizing protein. Statistical analysis was performed using graphpad prism 8 software (Graphpad Software.). Significance was considered at p&lt;0.05.ResultsLow and moderate intensity ESS increased eNOS protein expression compared to physiologically low conditions (P&lt;0.05). There was a trend showing high intensity ESS increasing eNOS expression compared to physiologically low conditions (p&lt;0.10). Additionally, moderate intensity ESS showed a significant increase in eNOS compared to resting conditions (P&lt;0.05).ConclusionsOur data shows that exercise‐induced ESS upregulates eNOS expression. Moderate intensity exercise was shown to produce the highest levels of eNOS expression. Our results from previous studies also show that moderate intensity exercise is capable of activating eNOS, which may act as a protective mechanism to prevent atherosclerosis development.

Moderate Intensity Exercise‐Induced Shear Stress Upregulates eNOS mRNA Expression

BackgroundPhysical activity has been shown to reduce the risk of cardiovascular disease. Exercise‐induced endothelial shear stress (ESS) produces a mechanical force on the surface of endothelial cells that triggers an intracellular signaling response regulating vascular function. SIRT‐1 and eNOS are mechanosensitive genes that have been shown to improve vascular function and their expression levels may be upregulated in response to higher ESS levels. Although it has been reported that higher physiological levels of ESS may improve vascular function, the role of pulsatile exercise induced ESS varying in exercise intensities has not been studied. Therefore, the purpose of this study was to determine the effects of varying pulsatile exercise‐induced ESS intensities on NOS3 and SIRT‐1 mRNA expression.MethodsCommercially available human umbilical vein endothelial cells (HUVEC; Sigma‐Aldrich, St Louis, MO) were cultured until 90–100% confluence. Exercise‐induced ESS in vivo was obtained from our previous reports. Cultured HUVEC cells were exposed to pulsatile resting ESS (18 dynes/cm2) for 2 hours, followed by 1 hour at low‐intensity exercise‐induced ESS (35 dynes/cm2), moderate exercise‐induced ESS, or high‐intensity exercise‐induced ESS (75 dynes/cm2) on a closed circuit pump and channeled slide (Ibidi pump system (PumpControl Software 1.5.4) and slides, Ibidi Inc., Fitchburg, WI). Total RNA was extracted and reverse transcribed followed by measurement of SIRT‐1 and eNOS mRNA expression via qRT‐PCR. qRT‐PCRs were performed in duplicates and changes in gene expression were calculated using the ΔΔ‐CT method with GAPDH used as the normalizing control gene. Statistical analysis was performed using graphpad prism 8 software (Graphpad Software.). Significance was considered at p&lt;0.05.ResultsThere were no alterations in mRNA expression of SIRT‐1 in response to varying exercise intensities. Moderate intensity exercise‐induced ESS produced significantly higher eNOS mRNA expression compared to low and high intensity exercise‐induced ESS (p&lt;0.05).ConclusionsOur data shows that moderate intensity of exercise‐induced ESS may promote an anti‐atherogenic phenotype due to higher expression levels of eNOS. Although SIRT‐1 mRNA levels were not altered in response to varying exercise intensities, it is possible that SIRT‐1 is chronically activated and one bout of exercise will not alter its expression. Further research needs to be performed on the role of exercise and molecular pathways for endothelial health.

Impact of Varying Exercise Intensity on Oxygen Uptake and Cardiovascular Response during Body Weight Supported Treadmill Walking in Healthy Adults

Body Weight Supported Treadmill Training (BWSTT) is effectively used in locomotive training for patients with neurologic and musculoskeletal deficits. The impact of BWSTT on oxygen uptake (VO₂) and cardiovascular (HR and BP) response in patients has been shown to be variable, possibly due to level of Body Weight Support (BWS) or exercise intensity.

Do anxiety sensitivity and impulsivity interact in predicting exercise involvement in emerging adult drinkers and cannabis users?

ABSTRACT Anxiety sensitivity (AS; i.e. fear of arousal-related sensations) and impulsivity (i.e. tendency to act quickly without regard for longer-term consequences) represent risks for low physical activity participation. Theoretically, higher impulsivity may exacerbate the negative exercise behaviours of high AS individuals given the tendency of impulsive individuals to favour immediate (e.g. watching TV) over delayed rewards (e.g. the benefits of exercise). Our goal was to investigate the main and interactive effects of AS and impulsivity on physical activity levels at varying exercise intensities. Participants were 178 emerging adults (Mean age = 21.9; 68.8% women). Higher AS was associated with less engagement in vigorous intensity exercise. Moderator analyses revealed an AS x impulsivity interaction: high AS predicted significantly less engagement in moderate intensity exercise at low impulsivity levels and marginally more engagement in moderate intensity exercise at high impulsivity levels. Finally, higher impulsivity was associated with more time spent walking. Cognitive behavioural therapy for high AS, or teaching individuals with high AS to focus on immediate, external rewards of exercise, may help them engage in more physical activity. Given the wide-ranging physical and mental health benefits of exercise involvement, developing effective strategies to increase such involvement in high AS individuals is vital.

Effects of Endurance Training Intensity on Pulmonary Diffusing Capacity at Rest and after Maximal Aerobic Exercise in Young Athletes.

This study compared the effects of varying aerobic training programs on pulmonary diffusing capacity (TLCO), pulmonary diffusing capacity for nitric oxide (TLNO), lung capillary blood volume (Vc) and alveolar–capillary membrane diffusing capacity (DM) of gases at rest and just after maximal exercise in young athletes. Sixteen healthy young runners (16–18 years) were randomly assigned to an intense endurance training program (IET, n = 8) or to a moderate endurance training program (MET, n = 8). The training volume was similar in IET and MET but with different work intensities, and each lasted for 8 weeks. Participants performed a maximal graded cycle bicycle ergometer test to measure maximal oxygen consumption (VO2max) and maximal aerobic power (MAP) before and after the training programs. Moreover, TLCO, TLNO and Vc were measured during a single breath maneuver. After eight weeks of training, all pulmonary parameters with the exception of alveolar volume (VA) and inspiratory volume (VI) (0.104 < p < 0889; 0.001 < ES < 0.091), measured at rest and at the end of maximal exercise, showed significant group × time interactions (p < 0.05, 0.2 < ES < 4.0). Post hoc analyses revealed significant pre-to-post decreases for maximal heart rates (p < 0.0001, ES = 3.1) and improvements for VO2max (p = 0.006, ES = 2.22) in the IET group. Moreover, post hoc analyses revealed significant pre-to-post improvements in the IET for DM, TLNO, TLCO and Vc (0.001 < p < 0.0022; 2.68 < ES < 6.45). In addition, there were increases in Vc at rest, VO2max, TLNO and DM in the IET but not in the MET participants after eight weeks of training with varying exercise intensities. Our findings suggest that the intensity of training may represent the most important factor in increasing pulmonary vascular function in young athletes.

Moderate Exercise‐Induced Endothelial Shear Stress Increases eNOS Expression in vitro

Background Sedentary lifestyle is a risk factor in the development of coronary artery disease. Moreover, endothelial cell dysfunction has been shown to be the first step in the pathogenesis of coronary artery disease. Endothelial shear stress (ESS) involves mechanoreceptors that sense different forces produced through the alterations in blood flow, triggering a biochemical response leading to cellular adaptations. Exercise induced ESS might act as a protective mechanism in preventing endothelial cell dysfunction. Although exercise has been shown to improve endothelial cell function, the role of varying exercise intensities on endothelial cell homeostasis has not been explored. The purpose of this study was to determine the effects of pulsatile exercise induced-ESS varying in exercise intensity on endothelial cell function determined through oxidative stress and pro-vasodilatory protein expression. Hypothesis It was hypothesized that exercise induced ESS would increase nitric oxide synthase (eNOS) expression and reduce oxidative stress. Methods Commercially available human umbilical vein endothelial cells (HUVEC; Sigma-Aldrich, St Louis, MO) were cultured until 90-100% confluence. Exercise-induced ESS in vivo was obtained from our previous reports. Cultured cells were exposed to pulsatile resting ESS (18 dynes/cm2) for 5 hours, followed by 1 hour at resting ESS, low-intensity exercise-induced ESS (35 dynes/cm2), or moderate-intensity exercise-induced ESS (50 dynes/cm2) on parallel fluidic units (Ibidi USA, Fitchburg, WI.). After ESS, cells were fixed and immunocytochemistry was used to assess endothelial cell function by measuring the expression of eNOS and nitrotyrosine, a marker of endothelial oxidative stress. A Friedman test was used to assess differences in protein expression using the SPSS 25.0 (IBM, Armonk, NY). Significance was considered at p<0.05. Results There was a higher expression of eNOS in cells exposed to moderate ESS (4.39 ± 2.78 AU) compared to cells exposed to low ESS (3.66 ± 0.72 AU) and resting ESS (1.52 ± 0.41 AU). The analysis of nitrotyrosine content resulted in a non-statistically significant difference between ESS conditions (p=1.00). Conclusion Our results suggest that exposure to moderate intensity exercise induced ESS increases the expression of eNOS content in vitro. Higher intensities of exercise have been shown to result in a greater amount reactive oxygenated species (ROS) produced; however, exercise has also been shown to combat these effects through the increase of antioxidant production with the capability of scavenging free radicals. It is possible that the fixing of the cells immediately after ESS exposure did not allow the time needed for antioxidants to scavenge the ROS produced leading to no changes in oxidative stress. Further studies need to be performed investigating the effects of exercise induced ESS on endothelial function.

The Impact of Varied Exercise Intensity in Heart Failure with Preserved Ejection Fraction

Physical limitation is a cardinal symptom of heart failure. While endurance training can help improve peak oxygen consumption (peak VO2) in individuals

Lower-Limb Electromyography Signal Analysis of Distinct Muscle Fitness Norms under Graded Exercise Intensity

Physical fitness is the overall ability of the body to adapt to the working environment and perform sporting and daily activities. The aim of this study was to analyze the correlation between muscle fitness and the electromyography (EMG) signals of lower limbs under varying exercise intensity. The standing long jump was used as a test task for assessing the power of the lower limb muscles. Participants were university freshmen who belonged to the top 20%, middle 20%, and bottom 20% groups in terms of physical fitness norms. The EMG signals of the participants’ lower limbs while they performed squats were collected under four exercise intensities of repetitions maximum (RM): no load, 8RM, 18RM, and 28RM; the features of the signals were extracted using time-domain and frequency-domain analysis. Statistical analysis was also performed. The top and bottom groups exhibited significant differences time-domain indicators mean absolute value (MAV) and average amplitude change (AAC) in the low-intensity exercise (28RM). The MAV, variance of EMG (VAR), root mean square (RMS), and AAC were significantly different between the top and bottom groups in the three graded intensities (8RM, 18RM, and 28RM). The mean frequency (MNF) and median frequency (MDF), which are frequency-domain indicators, were significantly different between the top and bottom groups in the low-intensity (28RM) and moderate-intensity (18RM) exercises.

Optimal exercise intensity and volume to impact rats with Traditional Chinese Medicine phlegm-dampness constitution

ObjectiveWe aim to investigate the effects of different exercise intensities and volumes on Phlegm-dampness constitution (PDC). MethodsThe rats were fed with high-fat food and lived in 75%–85% humidity for 6 weeks to establish the model of PDC. Then PDC rats were screened and intervened by varying exercise intensities for 8 weeks. Weight, constitution scores, blood and liver tissues were collected to detect the concentration of serum total cholesterol (Tch), triglyceride (TG), low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), homocysteine (Hcy), blood glucose (GLU), alanine transaminase (ALT) and percentage of lipid droplet area in liver tissue (PLDA). ResultsThe weight, Tch, TG, HDL-C, LDL-C, Hcy, GLU, and ALT of rats in moderate-intensity exercise group returned to normal. The rats with high-intensity or low-intensity exercise did not recover as well as moderate-intensity. ConclusionDifferent exercise intensities and volumes have different effects on PDC, moderate-intensity exercise over an 8-week intervention is most appropriate.

Cycling Performance and Training Load: Effects of Intensity and Duration.

To examine the effect of cycling exercise intensity and duration on subsequent performance and to compare the resulting acute performance decrement (APD) with total work done (TWD) and corresponding training-load (TL) metrics. A total of 14 male cyclists performed a 5-minute time trial (TT) as a baseline and after 4 initial exercise bouts of varying exercise intensity and duration. The initial exercise bouts were performed in a random order and consisted of a 5- and a 20-minute TT and a 20- and a 40-minute submaximal ride. The resulting APD was calculated as the percentage change in 5-minute TT from baseline, and this was compared with the TWD and TL metrics for the corresponding initial exercise bout. Average power output was different for each of the 4 initial exercise bouts (ηp2=.971; P < .001), and all bouts resulted in an APD. But APD was only different when comparing maximal with submaximal bouts (ηp2=.862; P < .001). The APD contradicted TWD and TL metrics and was not different when comparing 5- and 20-minute maximal TTs or the 20- and 40-minute submaximal bouts. In contrast, TL metrics were different for all training sessions (ηp2=.970; P < .001). An APD is found after initial exercise bouts consisting of 5- and 20-minute TTs and after 20- and 40-minute of submaximal exercise that is not consistent with the corresponding values for TWD or TL. This discrepancy highlights important shortcomings when using TWD and TL to compare exercise bouts of different intensity and duration.

Effect Of Exercise Setting On Energy Expenditure And Enjoyment During Active Virtual Reality Gaming

PURPOSE: Recent work by our lab (Gomez, et al., 2018) has shown that active virtual reality games (AVRGs) can elicit exercise intensities that meet American College of Sports Medicine (ACSM) recommended exercise guidelines for preventative health benefits. However, much of the work focusing on this topic has been limited to laboratory settings. The purpose of this study was to investigate differences in energy expenditure (VO2) and enjoyment of college-aged students while playing AVRGs in different settings (i.e., lab, gym, home). METHODS: A repeated measures design was used with 32 participants (16 males, 16 females, Age = 22.6 ± 2.6 years), all of whom completed two 45-minute AVRG sessions in the lab and gym. A subset of 4 participants completed an additional AVRG session at home. RESULTS: Significant differences in VO2 were observed among the three AVRGs (F (1, 28) = 9.128, p = .005; range = 13.53 - 23.04 ml/kg/min). However, there were no differences between settings in VO2 or enjoyment (p > .05). CONCLUSIONS: Different AVRGs elicit varying exercise intensities, yet the setting in which they are played does not affect VO2 or perceived enjoyment. These results suggest AVRGs can be studied reliably across multiple settings (lab, gym, and home) without having to consider environmental influences. As VR systems become more accessible and affordable, future research should continue investigating the effects of AVRGs during at-home play.

Effects of in Vitro Exercise‐Induced Endothelial Shear Stress on Oxidative Stress and Vasoconstriction Gene Expression

BackgroundSedentary lifestyle contributes to endothelial dysfunction through increasing oxidative stress and endothelin‐1, a potent vasoconstrictor that contributes to the pathogenesis of vascular disease. Exercise‐induced endothelial shear stress (ESS) elicits a mechanical stimulus leading to intracellular signaling transduction regulating cellular function that might protect against endothelial dysfunction through promotion of the expression of anti‐oxidative and pro‐vasodilatory genes. Although it has been reported that increments on steady ESS has led to improvements in endothelial function in vivo, the role of pulsatile exercise induced ESS and varying exercise intensities in vitro has not been explored yet. Therefore, the purpose of this study was to determine the effects of pulsatile exercise‐induced ESS based on in vivo exercise intensity on anti‐oxidative (superoxide dismutase, SOD2) and vasoconstrictive (endothelin 1, EDN‐1) gene expression.MethodsCommercially available human carotid artery endothelial cells (Sigma‐Aldrich Comp.) were cultured until 95–100% confluence and exposed to pulsatile resting ESS (18 dynes/cm2) for 5 hours, followed by 1 hour at resting ESS, low‐intensity exercise‐induced ESS (35 dynes/cm2), or high‐intensity exercise‐induced ESS (80 dynes/cm2) on parallel fluidic units (Ibidi USA, Inc.). Ibidi pump software (PumpControl Software 1.5.4) was used to control shear stress intensity. Total RNA was extracted and reverse transcribed followed by measurement of EDN‐1 and SOD2 mRNA expression via qRT‐PCR. qRT‐PCRs were performed in duplicates and changes in gene expression were calculated using the ΔΔ‐CT method with GAPDH used as the normalizing control gene. Statistical analysis was performed using graphpad prism 8 software (Graphpad Software.). Significance was considered at p&lt;0.05.ResultsmRNA expression of SOD2 increased 2.5‐fold after exposure to low‐intensity exercise‐induced ESS (p&lt;0.05). EDN‐1 showed a 5‐fold increase following exposure to low‐intensity exercise‐induced ESS (p&lt;0.05) in comparison to resting conditions. High‐intensity pulsatile exercise‐induced ESS decreased the expression of EDN‐1 in comparison to resting and low‐intensity conditions (p&lt;0.05).ConclusionPulsatile exercise‐induced ESS improved anti‐oxidative properties in human carotid artery endothelial cells. It seems that higher exercise intensities are required to downregulate the expression of vasoconstrictive genes.

Substrate oxidation and the influence of breakfast in normobaric hypoxia and normoxia

PurposePrevious research has reported inconsistent effects of hypoxia on substrate oxidation, which may be due to differences in methodological design, such as pre-exercise nutritional status and exercise intensity. This study investigated the effect of breakfast consumption on substrate oxidation at varying exercise intensities in normobaric hypoxia compared with normoxia.MethodsTwelve participants rested and exercised once after breakfast consumption and once after omission in normobaric hypoxia (4300 m: FiO2 ~ 11.7%) and normoxia. Exercise consisted of walking for 20 min at 40%, 50% and 60% of altitude-specific dot{text{V}}O2max at 10–15% gradient with a 10 kg backpack. Indirect calorimetry was used to calculate carbohydrate and fat oxidation.ResultsThe relative contribution of carbohydrate oxidation to energy expenditure was significantly reduced in hypoxia compared with normoxia during exercise after breakfast omission at 40% (22.4 ± 17.5% vs. 38.5 ± 15.5%, p = 0.03) and 60% dot{text{V}}O2max (35.4 ± 12.4 vs. 50.1 ± 17.6%, p = 0.03), with a trend observed at 50% dot{text{V}}O2max (23.6 ± 17.9% vs. 38.1 ± 17.0%, p = 0.07). The relative contribution of carbohydrate oxidation to energy expenditure was not significantly different in hypoxia compared with normoxia during exercise after breakfast consumption at 40% (42.4 ± 15.7% vs. 48.5 ± 13.3%, p = 0.99), 50% (43.1 ± 11.7% vs. 47.1 ± 14.0%, p = 0.99) and 60% dot{text{V}}O2max (54.6 ± 17.8% vs. 55.1 ± 15.0%, p = 0.99).ConclusionsRelative carbohydrate oxidation was significantly reduced in hypoxia compared with normoxia during exercise after breakfast omission but not during exercise after breakfast consumption. This response remained consistent with increasing exercise intensities. These findings may explain some of the disparity in the literature.

Physical Activity versus Psychological Stress: Effects on Salivary Cortisol and Working Memory Performance.

Background and Objective: The present study was designed to investigate whether acute physical activity and psychological stress produce different effects on cortisol release and working memory performance. Materials and Methods: Male subjects (N = 12; 18–35 years) were recruited and scheduled to come four times to our lab (within-subject design). For each counterbalanced visit, they performed one of the following four protocols: control, moderate physical activity (MOD), vigorous physical activity (VIG), and acute stress. Heart rate was monitored during every protocol. MOD and VIG were performed for 15 min and were defined as 40–50% and 70–80%, respectively, of their maximum heart rate. Acute stress was imposed via the Trier Social Stress Test (TSST). Salivary samples were collected before and after every protocol to assess cortisol concentrations. Working memory (WM) performance was evaluated through the 2N-Back task right after ending the protocol (early WM) and after a delay of 35 min (late WM). Results: VIG and stress, but not MOD, increased salivary cortisol concentrations. However, the increases of cortisol produced by VIG and stress were not significantly different. Also, there were no significant differences in working memory performance (late and early) in any of the experimental protocols tested. Conclusions: These results show that exercise (VIG) and stress produce similar effects on cortisol release and do not support the hypothesis that working memory capacity is influenced by elevated cortisol levels, either from varying exercise intensities or psychological stress.

Acute Supplementation with Molecular Hydrogen Benefits Submaximal Exercise Indices. Randomized, Double-Blinded, Placebo-Controlled Crossover Pilot Study.

BackgroundClinical studies have reported hydrogen-rich water (HRW) to have therapeutic and ergogenic effects. The aim of this study was to determine the effect of acute supplementation with HRW on exercise performance as measured by VO2, respiratory exchange ratio (RER), heart rate (HR), and respiratory rate (RR).MethodsBaseline levels of all exercise indices were determined in nineteen (4 female, 23.4 ± 9.1 yr; 15 male, 30.5 ± 6.8 yr) healthy subjects using a graded treadmill exercise test to exhaustion. Each subject was examined two additional times in a randomized double-blinded, placebo-controlled crossover fashion. Subjects received either HRW or placebo, which was consumed the day before and the day of the testing. HRW was delivered using the hydrogen-producing tablets, DrinkHRW (5 mg of H2). All data was analyzed with SPSS using pairwise comparisons with Bonferroni adjustment.ResultsHRW supplementation did not influence maximal or minimal indices of exercise performance (VO2, RER, HR and RR) (p < 0.05). However, HRW significantly decreased average exercising RR and HR (p < 0.05). HRW decreased exercising HR during minutes 1–9 of the graded exercise test (121 ± 26 bpm) compared to placebo (126 ± 26 bpm) and baseline (124 ± 27 bpm) (p < 0.001) without substantially influencing VO2.ConclusionAcute supplementation of DrinkHRW tablets may benefit submaximal aerobic exercise performance by lowering exercising HR. Further studies are needed to determine the influence and practical significance of HRW on varying exercise intensities as well as optimal dosing protocols and the effects of chronic use.