Bout Of Exercise Research Articles

In vivo bioluminescence imaging revealed the change of the time window of BDNF expression in the brain elicited by a single bout of exercise following repeated exercise

Exercise increases the expression of brain-derived neurotrophic factor (BDNF) in the brain and contributes to cognitive and sensorimotor functions. This study aimed to elucidate how repeated exercise modifies BDNF expression elicited by a single bout of exercise in the brain using in vivo bioluminescence imaging (BLI). Bdnf-luciferase (Luc) mice with the firefly luciferase gene inserted at the translation start point of the Bdnf gene were used for BLI to monitor changes in BDNF expression in the brain. The treadmill exercise at a speed of 10 m/s for 60 min was repeated 5 days a week for 4 weeks. BLI in individual subjects was repeated four times: before the exercise intervention, on the first exercise day, and 14 and 28 days after the start of the intervention. Each BLI was performed after a single bout of exercise and monitored for 8 h after exercise. Repetitive BLI showed that the exercise regimen enhanced BDNF expression in the brain, specifically at 4–8 h after a single bout of exercise. Repeated exercise for 2 weeks accelerated the start of enhancement after a single bout of exercise, but not after 4 weeks of repeated exercise. This study showed that repeated exercise modulated the time window of exercise-enhanced BDNF expression, suggesting that repeated exercise could change the sensitivity of gene expression to a single bout of exercise. These findings can be attributed to the advantages of in vivo BLI, which allowed us to precisely measure the time course of BDNF expression after repeated exercise in individual subjects.

Direct assessment of leukocyte signalling and cytokine secretion reveals exercise intensity-dependent reductions in anti-inflammatory cytokine action.

Circulating interleukin (IL)-6 and IL-10 concentrations are widely used to evaluate the anti-inflammatory effects of exercise but do not capture cytokine action at the cellular level. Whether and how acute exercise impacts anti-inflammatory cytokine action in humans is unknown. To determine how exercise intensity and pattern impact IL-6 and IL-10 action in blood leukocytes, 16 active adults (eight males/eight females; age: 30±3years; body mass index: 22.8±2.3kg/m2; : 51±6mL/kg/min) completed a no-exercise control condition (CTL) or isocaloric bouts of cycling performed below (moderate continuous exercise; MCE) or above (heavy continuous or heavy intermittent exercise; HCE or HIE, respectively) lactate threshold. Venous blood (before, after, 30min after and 90min after exercise) was analysed for immune cell subpopulations, plasma cytokine concentrations, anti-inflammatory cytokine action and monocyte phenotype. Exercise induced rapid leukocytosis (P<0.001) and increased plasma IL-6 (P<0.001), IL-10 (P=0.0145) and tumour necrosis factor-⍺ (TNF-⍺) (P=0.0338) concentrations in an intensity-dependent manner (HCE and/or HIE vs. CTL). These systemic changes coincided with a diminished ability of IL-10/6 to phosphorylate STAT3 (P<0.001) and inhibit TNF-⍺ secretion (P=0.0238) in blood leukocytes following HCE and HIE. Monocyte polarization experiments revealed lower CD80 [MCE (P=0.0933) and HIE (P=0.0187) vs. CTL] and a tendency for higher CD163 expression (HCE vs. CTL, P=0.0985), suggesting that hyporesponsiveness to anti-inflammatory cytokine action does not impede the ability of exercise to promote an anti-inflammatory monocyte phenotype. These findings provide novel insights into the immunomodulatory effects of exercise in humans and highlight the importance of directly measuring cellular cytokine action when evaluating the anti-inflammatory effects of exercise. KEY POINTS: Circulating cytokine concentrations are frequently used to evaluate the anti-inflammatory effects of exercise but may not capture changes in cytokine action occurring at the cellular level. We directly assessed anti-inflammatory cytokine action - measured using a combination of intracellular signalling and cytokine secretion ex vivo - in distinct immune cell subpopulations after acute calorie-matched exercise bouts differing in intensity and pattern. Anti-inflammatory cytokine action was blunted following higher intensity exercise despite corresponding increases in circulating cytokine concentrations and immune cell counts. Changes in cytokine action were not explained by changes in cytokine receptor expression on circulating immune cells. Our findings provide new insights into the immunomodulatory effects of exercise in humans and highlight the importance of directly measuring cellular cytokine action when evaluating the anti-inflammatory effects of exercise.

Ascorbic Acid Supplementation and Immune Response in Healthy Women during High-intensity Exercise

Introduction the benefits of consuming extra Ascorbic Acid (AA) while exercising are not well understood. Aim This study aims to explore the effects of AA supplementation on oxidative stress, the immunological response, and inflammation in healthy women after a single bout of high-intensity exercise. Materials and Methods In a crossover design, 20 sedentary women (aged 18-22) underwent 30 minutes of vigorous cycling. They were divided into two groups: one receiving daily 1,000 mg ascorbic acid supplementation (1,000AA) and the other without supplementation (0AA). This regimen was maintained for one week. Blood samples obtained pre-exercise, immediately post-exercise, and 24 hours post-exercise underwent analysis for oxidative stress, inflammatory markers, CD4+ and CD8+ lymphocytes, and neutrophil phagocytic activity. Results An AA supplement significantly increased plasma concentrations of AA (p&lt;0.05) and reduced post-exercise plasma MDA levels (p&lt;0.05) but did not affect creatine kinase activity. White blood cells, CD8+ T cells, and IL-6 increased significantly after exercise but remained unchanged in the 1,000AA group compared to the 0AA group, while the neutrophil count increased (p&lt;0.05) after exercise with no change in phagocytic function. A slight drop in phagocytic function was observed 24 hours after exercise in the 1,000AA group. Exercise and AA supplements had no effect on CD4+ T cells. Conclusion a single session of high-intensity exercise caused oxidative stress, muscle injury, and inflammation, as well as a transient increase in CD8+ T cells. A short administration of AA attenuated the exercise-induced oxidative stress and reduced inflammation by limiting the increase in IL-6 and CD8+ T cells.

Enjoyment and Affective Responses to Moderate and High-Intensity Exercise: A Randomized Controlled Trial in Individuals with Subsyndromal PTSD.

This crossover randomized controlled trial examined the acute psychological effects of a bout of moderate-intensity continuous aerobic exercise (MICE) and a bout of high-intensity functional exercise (HIFE), relative to a no-exercise sedentary control (SED), in participants (N = 21; 15 f; 24.7 ± 9.3 years) with subsyndromal post-traumatic stress disorder (PTSD). Affective state (Energy, Tiredness, Tension, Calmness) was assessed before (Pre), immediately after (Post 0), 20-min after (Post 20), and 40-min after (Post 40) each condition. Affective valence was assessed during each condition, and exercise enjoyment was assessed at Post 0. Enjoyment was significantly greater following HIFE and MICE relative to SED. Energy was significantly increased Post 0 HIFE and MICE but decreased Post 0 SED. Tension was reduced following all conditions and was significantly lower at Post 40 relative to Pre for HIFE, MICE, and SED. Tiredness was significantly reduced at Post 40 relative to Pre following MICE only, while Calmness was significantly lower at Post 40 relative to Pre following MICE and SED. Overall, both exercise conditions were enjoyed to a greater extent than the control, but MICE may provide greater psychological benefits with respect to Calmness and Tiredness. This study is among the first to assess acute changes in affective states relative to various exercise modes in individuals living with subsyndromal PTSD.

Whole-blood transcriptome analysis reveals distinct gene expression signatures in paediatric patients with sickle cell anaemia before and after exercise.

Sickle cell anaemia (SCA) patients display elevated levels of circulating pro-inflammatory cytokines and endothelial activation markers compared to healthy peers. The impact of exercise on the pro-inflammatory state in SCA remains unclear. This study aimed to characterize the whole-blood transcriptome profile in response to an acute bout of exercise in paediatric SCA patients. Twenty-three SCA participants (13 ± 3 years, 52% girls) and 17 healthy controls (14 ± 3 years, 29% girls) performed eight 2-min bouts of cycle ergometry interspersed with 1-min rest intervals. Whole-blood transcriptome profile (RNA-seq) was performed before and after exercise. At baseline, gene pathways associated with gas transport in erythrocytes were up-regulated in SCA patients compared to controls. Following exercise, gene pathways associated with innate immunity were altered in both groups. Interaction analyses revealed 160 annotated genes (101 up- and 59 down-regulated) that differentially altered by exercise in SCA patients. Moreover, genes that exhibited a blunted response to exercise in SCA patients were enriched in the IL-17 signalling pathway, suggesting an impaired innate immune response to exercise. This data will contribute to the development of evidence-based exercise prescription guidelines for this patient population.

The Effects of Slow Breathing during Inter-Set Recovery on Power Performance in the Barbell Back Squat.

Slow breathing (SB) reduces sympathetic nervous system activity, the heart rate (HR), and blood pressure (BP) and increases parasympathetic nervous system activity, HR variability, and oxygen saturation which may lead to quicker recovery between bouts of exercise. Therefore, the purpose of this study was to examine whether a SB technique using the 4-7-8 method between sets of barbell back squats (SQs) would attenuate drops in power and bar velocity. In a randomized, crossover design, 18 healthy resistance-trained college-aged males (age: 20.7 ± 1.4 years, body height: 178.6 ± 6.4 cm, body mass: 82.2 ± 15.0 kg, 4.5 ± 2.4 years of experience) performed 5 sets of 3 repetitions of SQs with normal breathing (CON) or SB during the 3-min recovery between sets. Peak and average power and bar velocity were assessed using a linear positioning transducer. HR recovery (RHR), systolic BP recovery (RBP), the rating of perceived exertion (RPE) and the rating of perceived recovery score (RS) were assessed after each set. There were no significant differences between conditions for peak and average power and bar velocity, RBP, RPE, and RS (p > 0.211). SB led to a greater RHR after set 2 (SB: 51.0 ± 14.9 bpm vs. CON: 44.5 ± 11.5 bpm, p = 0.025) and 3 (SB: 48.3 ± 13.5 bpm vs. CON: 37.7 ± 11.7 bpm, p = 0.006) compared to the CON condition. SB was well tolerated, did not hinder nor improve training performance and improved RHR after the middle sets of SQs. Further investigations are warranted to examine the effects of other SB techniques and to determine SB's effects on different training stimuli as well as its effects over an entire workout and post-workout recovery metrics.

Exercise-induced cortical disinhibition mediates the relationship between fitness and memory in older adults.

Regular exercise benefits learning and memory in older adults, but the neural mechanisms mediating these effects remain unclear. Evidence in young adults indicates that acute exercise creates a favourable environment for synaptic plasticity by enhancing cortical disinhibition. As such, we investigated whether plasticity-related disinhibition mediated the relationship between cardiorespiratory fitness and memory function in healthy older adults (n=16, mean age=66.06). Participants completed a graded maximal exercise test and assessments of visual and verbal memory, followed by two counterbalanced sessions involving 20min of either high-intensity interval training exercise or rest. Disinhibition was measured following intermittent theta burst stimulation via paired-pulse transcranial magnetic stimulation. In line with our hypotheses, we observed a positive correlation between cardiorespiratory fitness and verbal memory, which was mediated by plasticity-related cortical disinhibition. Our novel finding implicates cortical disinhibition as a mechanism through which the effects of acute bouts of exercise may translate to improved memory in older adults. This finding extends current understanding of the physiological mechanisms underlying the positive influence of cardiorespiratory fitness for memory function in older adults, and further highlights the importance of promoting exercise engagement to maintain cognitive health in later life. KEY POINTS: There are well established benefits of regular exercise for memory function in older adults, but the mechanisms are unclear. Cortical disinhibition is important for laying down new memories, and is enhanced following acute exercise in young adults, suggesting it is a potential mechanism underlying these benefits in ageing. Older adults completed a fitness test and assessments of memory, followed by two sessions involving either 20min of exercise or rest. Disinhibition was measured following intermittent theta burst stimulation via paired-pulse transcranial magnetic stimulation. Cardiorespiratory fitness was positively associated with memory performance. Higher fitness was associated with enhanced cortical disinhibition following acute exercise. Cortical disinhibition completely mediated the relationship between fitness and memory. This novel finding provides a mechanistic account for the positive influence of cardiorespiratory fitness on memory in later life, and emphasises the importance of regular exercise for cognitive health in older populations.

Sustained Muscle EMG Activity to Contractile Failure During Incremental Exercise and Intense Constant Load Cycling: No Evidence of a Central Governor

Since 1997, debate has continued over the presence of a central governor that constrains neuromuscular activity during severe, intense exercise. This study aimed to challenge the central governor model (CGM) through acquiring surface electromyography (sEMG) data from the vastus lateralis (VL) and gluteus maximus (Gmax) muscles of 14 healthy participants during 4 different bouts of constant load, non-steady state cycling exercise (110, 125, 140, 160 %watts at the ventilation threshold), and 1 incremental bout to volitional exhaustion. sEMG activity was processed to isolate and capture each contraction of the VL and Gmax during all bouts of exercise. sEMG data was then graphed to profile sEMG root mean square (rms) activity over time with linear curve fitting used to quantify this relationship for data preceding (segment 1) and during the final 30s of each test (segment 2). Two-way repeated measures ANOVA was used to test for differences between the slopes of the two linear segments of the sEMG rms response of the VL for each bout. Results during the VO2max trial revealed a significant main effect for SEGMENT where segment 2 was significantly greater than segment 1 (F=6.741, p=0.023). During the critical power trails there were significant differences in sEMG rms for each of INTENSITY (F=9.349, p&lt;0.001), SEGMENT (F=5.443, p=0.036), and the interaction effect (F=2.837, p=0.005). Muscle sEMG rms data revealed sustained increases in muscle activity in all bouts of intense exercise to volitional exhaustion in both the VL and Gmax, which is inconsistent with the predictions made from the CGM.

Resting-State Functional Connectivity Change in Frontoparietal and Default Mode Networks After Acute Exercise in Youth.

A single bout of aerobic exercise can provide acute benefits to cognition and emotion in children. Yet, little is known about how acute exercise may impact children's underlying brain networks' resting-state functional connectivity (rsFC). Using a data-driven multivariate pattern analysis, we investigated the effects of a single dose of exercise on acute rsFC changes in 9-to-13-year-olds. On separate days in a crossover design, participants (N = 21) completed 20-mins of acute treadmill walking at 65-75% heart rate maximum (exercise condition) and seated reading (control condition), with pre- and post-fMRI scans. Multivariate pattern analysis was used to investigate rsFC change between conditions. Three clusters in the left lateral prefrontal cortex (lPFC) of the frontoparietal network (FPN) had significantly different rsFC after the exercise condition compared to the control condition. Post-hoc analyses revealed that from before to after acute exercise, activity of these FPN clusters became more correlated with bilateral lPFC and the left basal ganglia. Additionally, the left lPFC became more anti-correlated with the precuneus of the default mode network (DMN). An opposite pattern was observed from before to after seated reading. The findings suggest that a single dose of exercise increases connectivity within the FPN, FPN integration with subcortical regions involved in movement and cognition, and segregation of FPN and DMN. Such patterns, often associated with healthier cognitive and emotional control, may underlie the transient mental benefits observed following acute exercise in youth.

Affective Responses to Acute Exercise: A Meta-Analysis of the Potential Beneficial Effects of a Single Bout of Exercise on General Mood, Anxiety, and Depressive Symptoms.

Acute exercise elicits various biobehavioral and psychological responses, but results are mixed with regard to the magnitude of exercise-induced affective reactions. This meta-analysis examines the magnitude of general mood state, anxiety, and depressive symptom responses to acute exercise while exploring exercise protocol characteristics and background health behaviors that may play a role in the affective response. A total of 2770 articles were identified from a MEDLINE/PubMed search and an additional 133 articles from reviews of reference sections. Studies had to have measured general mood before the acute exercise bout and within 30 minutes after exercise completion. Effect sizes were estimated using Hedges' g , with larger values indicating improvement in the outcome measure. A total of 103 studies were included presenting data from 4671 participants. General mood state improved from preexercise to postexercise ( g = 0.336, 95% confidence interval [CI] = 0.234-0.439). Anxiety ( g = 0.497, 95% CI = 0.263-0.730) and depressive symptoms ( g = 0.407, 95% CI = 0.249-0.564) also improved with exercise. There was substantial and statistically significant heterogeneity in each of these meta-analyses. This heterogeneity was not explained by differences in participants' health status. Meta-regression analyses with potential moderators (intensity of exercise, mode of exercise, usual physical activity level, or weight status of participants) also did not reduce the heterogeneity. This meta-analysis shows significantly improved general mood, decreased anxiety, and lower depressive symptoms in response to an acute bout of exercise. There was substantial heterogeneity in the magnitude of the effect sizes, indicating that additional research is needed to identify determinants of a positive affective response to acute exercise.

Acute response to resistance exercise and later development of arm lymphedema in breast cancer survivors: An exploratory follow-up of a randomized cross-over trial

BackgroundIn breast cancer survivors at risk for lymphedema, variation in lymphatic function and arm volume has been observed related to a bout of exercise, with potential for prediction of breast cancer-related arm lymphedema (BCRaL). This novel, exploratory study examined the acute lymphatic response to resistance exercise and later development of BCRaL in women at high risk for BCRaL. MethodsOne year after participation in a cross-over trial evaluating the acute lymphatic response to upper-extremity resistance exercise (low-and heavy-load), participants were assessed for BCRaL (n ​= ​16). The response to exercise was assessed before and after (post, 24- and 72-hrs) each exercise bout as extracellular fluid (L-Dex; bioimpedance spectroscopy (BIS)), interarm volume % difference (IVD; Dual-energy x-ray absorptiometry (DXA)) and symptoms (Numeric rating scale, 0–10 (NRS)). BCRaL at follow-up was defined as presence of one objective indicator (L-Dex >10, change ≥+6.5, IVD >5%) plus one objective or subjective indicator (interarm symptom ≥1 or visual inspection). Descriptive statistics were used to compare the acute response between participants with and without BCRaL at follow-up. ResultsNo trends indicating a similar acute response to exercise was observed in participants who later developed BCRaL (n ​= ​5). There were no observable differences in acute lymphatic response between participants that developed BCRaL and those who did not, both at an individual and group level. ConclusionsFindings from this exploratory study showed no evidence to suggest that the acute response to resistance exercise can predict BCRaL development.

Study protocol to examine the effects of acute exercise on motor learning and brain activity in children with developmental coordination disorder (ExLe-Brain-DCD)

Introduction Developmental coordination disorder (DCD) is one of the most prevalent pediatric chronic conditions. Without proper intervention, significant delays in motor skill performance and learning may persist until adulthood. Moderate-to-vigorous physical exercise has been proven to improve motor learning (adaptation and consolidation) in children with or without disorders. However, the effect of a short bout of physical exercise on motor adaptation and consolidation in children with DCD has not been examined. Furthermore, the role of perceptual-motor integration and attention as mediators of learning has not been examined via neuroimaging in this population. Objectives Therefore, the primary aims of this project will be to compare children with and without DCD to (a) examine the effect of acute exercise on motor learning (adaptation and consolidation) while performing a rotational visuo-motor adaptation task (rVMA), and (b) explore cortical activation in the dorsolateral- and ventrolateral-prefrontal cortex areas while learning the rVMA task under rest or post-exercise conditions. Methods One hundred twenty children will be recruited (60 DCD, 60 controls) and within-cohort randomly assigned to either exercise (13-minute shuttle run task) or rest prior to performing the rVMA task. Adaptation and consolidation will be evaluated via two error variables and three retention tests (1h, 24h and 7 days post adaptation). Cortical activation will be registered via functional near-infrared spectroscopy (fNIRS) during the baseline, adaptation, and consolidation. Discussion We expect to find exercise benefits on motor learning and attention so that children with DCD profiles will be closer to those of children with typical development. The results of this project will provide further evidence to: (a) better characterize children with DCD for the design of educational materials, and (b) establish acute exercise as a potential intervention to improve motor learning and attention.

Effect of 60-Min Single Bout of Resistance Exercise, Reformer Pilates, on Vascular Function Parameters in Older Adults: A Randomized Crossover Study

Introduction: Aging leads to vascular endothelial dysfunction and muscle impairment. While resistance exercise improves muscular function, its acute effects on vascular function vary in the literature, with some studies reporting detrimental effects. These findings indicate the need for exercises that optimize muscle function without compromising vascular function. Reformer Pilates (RP) is a low-impact exercise involving an adjustable sliding platform. However, the acute effects of RP on vascular function among older adults remain unknown. Therefore, this study aimed to investigate the acute effects of RP on vascular function in older adults. Methods: Overall, 17 participants (age: 65 ± 2.76 years, body mass index: 23.42 ± 3.68 kg/m2) were examined and assigned to control and RP conditions under a randomized crossover design. The RP condition involved a 3.5–5 omnibus perceived exertion scale with 19 exercise postures for 60 min. Brachial artery flow-mediated dilation (FMD), brachial-ankle pulse wave velocity (baPWV), and blood pressure were measured at baseline and 0, 10, 30, and 60 min after exercise. Results: RP significantly improved FMD at all time points compared with that at baseline (p < 0.05). baPWV increased at 0 min post-RP but returned to baseline levels at other time points. Additionally, RP showed improved FMD at 0, 10, and 30 min compared with that in the control condition (p < 0.05). However, no significant differences were observed in blood pressure or mean arterial pressure in either condition. Conclusion: RP enhanced FMD and regulated blood pressure for approximately 60 min post-exercise, suggesting its suitability for older adults to enhance vascular function and control blood pressure during exercise. Nonetheless, longitudinal resistance training intervention studies are needed to validate these findings.

Is breathing frequency a potential means for monitoring exercise intensity in people with atrial fibrillation and coronary heart disease when heart rate is mitigated?

PurposeModerate-intensity aerobic exercise is safe and beneficial in atrial fibrillation (AF) and coronary heart disease (CHD). Irregular or rapid heart rates (HR) in AF and other heart conditions create a challenge to using HR to monitor exercise intensity. The purpose of this study was to assess the potential of breathing frequency (BF) to monitor exercise intensity in people with AF and CHD without AF.MethodsThis observational study included 30 AF participants (19 Male, 70.7 ± 8.7 yrs) and 67 non-AF CHD participants (38 Male, 56.9 ± 11.4 yrs). All performed an incremental maximal exercise test with pulmonary gas exchange.ResultsPeak aerobic power in AF (V˙\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\\dot{\ ext{V}}}$$\\end{document}O2peak; 17.8 ± 5.0 ml.kg−1.min−1) was lower than in CHD (26.7 ml.kg−1.min−1) (p < .001). BF responses in AF and CHD were similar (BF peak: AF 34.6 ± 5.4 and CHD 36.5 ± 5.0 breaths.min−1; p = .106); at the 1st ventilatory threshold (BF@VT-1: AF 23.2 ± 4.6; CHD 22.4 ± 4.6 breaths.min−1; p = .240). %V˙\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\\dot{\ ext{V}}}$$\\end{document}O2peak at VT-1 were similar in AF and CHD (AF: 59%; CHD: 57%; p = .656).ConclusionWith the use of wearable technologies on the rise, that now include BF, this first study provides an encouraging potential for BF to be used in AF and CHD. As the supporting data are based on incremental ramp protocol results, further research is required to assess BF validity to manage exercise intensity during longer bouts of exercise.

Can just 15 minutes of moderate-intensity exercise mobilize cytotoxic NK cells into circulation?

Intro: Acute exercise transiently mobilizes natural killer (NK) cells into the bloodstream with the degree of mobilization directly related to the intensity of the exercise. This increase in NK cells is thought to offer a period of heightened immune activity during exercise and is of particular interest to cancer patients as NK cells can kill tumor cells without prior sensitization. Previous work demonstrating the benefits of exercise on NK cells used vigorous bouts of exercise lasting 30 minutes or longer, which may not be attainable for cancer patients. The objective of this study was to determine whether a short bout of moderate-intensity exercise can mobilize activated, cytotoxic NK cells into circulation. We hypothesized that i) a bout of moderate-intensity exercise would significantly increase NK cells in the blood and ii) the exercise-induced NK-cell mobilization would occur rapidly, such that the relative increase in blood NK cells would not differ after 15 minutes of exercise and 30 minutes of exercise. Methods: In this pilot study, ten healthy, non-athletes (4 female; aged 18-40 years) cycled for 30 minutes at 55% of their heart rate reserve. Venous blood was obtained pre-, after 15 minutes, and after 30 minutes of exercise, and was analyzed by flow cytometry. The proportion of NK cells, CD16+ and CD57+ NK-cells were compared between the three time points by repeated measures ANOVA with Greenhouse Geisser corrections. Sidak-corrected post-hoc tests were used to further analyze significant main effects. Results: All subjects successfully completed the exercise (mean ± standard deviation heart rate: 144 ± 2 bpm; rating of perceived exertion: 11 ± 0.25 (of 20)). There was a significant main effect of time on the proportion of NK cells present in the blood (F(1.253, 10.025)= 7.719, p= 0.016). Post-hoc analyses indicate that there was a significant increase at minute 15 relative to baseline (p=.050), with no further increase at minute 30 relative to minute 15 (p=.175). There was no main effect of time on the proportion of CD57+NK cells (F(1.451, 10.159)= 0.335, p= 0.656) or CD16+ NK cells (F(1.154, 9.231)= 3.020, p= 0.113) in our sample. Conclusion: The results from this pilot study indicate that 15 minutes of moderate-intensity cycling mobilizes NK cells into the bloodstream. However, we did not detect significant differences in NK cells with an activated, highly cytotoxic phenotype. While limited by a small sample, these results build upon prior work demonstrating a significant effect of longer-lasting, vigorous-intensity exercise. The current results suggest that a more accessible exercise intervention for individuals with health limitations can also significantly increase NK cells into the blood, but that greater intensity exercise may be required to mobilize particular subsets of NK cells. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Vascular responses during handgrip exercise in healthy postmenopausal females and older males

Introduction: Aerobic exercise interventions improve peripheral endothelial function in healthy older males. However, this effect is not always observed in healthy postmenopausal females and possible mechanisms underlying this sex-related difference remain unknown. Greater vascular shear stress during acute exercise is a key stimulus mediating longer-term improvements in vascular function. It remains unknown if postmenopausal females display a reduced endothelial sensitivity to exercise-induced shear stress relative to males of similar age. Objective and hypothesis: The objective of this study is to test the hypothesis that healthy postmenopausal females exhibit a lower endothelial sensitivity to exercise-induced shear stress relative to males. Methods: Fourteen healthy postmenopausal females (67 ± 8 years) not under hormone replacement therapy and 9 males of similar age (65 ± 7 years) performed handgrip exercise for 4 minutes at 20%, 40%, 60%, and 80% of their maximal voluntary contraction. Each exercise bout was separated by a 10-min recovery period. Brachial artery diameter and blood velocity were continuously measured using high-resolution ultrasound and analyzed using edge-detection software. Endothelial sensitivity to shear rate was quantified as the slope of the linear regression between brachial artery dilation (% change from baseline) and shear stress and compared between groups with an independent t-test. Workload, vascular conductance, diameter dilation, and shear stress were analyzed with mixed-effects models. Results: Males exercised at greater workloads relative to females across all exercise bouts (M: 17 ± 11 vs. F: 9 ± 5 kg, p&lt;0.01). Forearm vascular conductance was greater in males throughout each exercise intensity (M: 2.23 ± 1.70 vs. F: 1.03 ± 0.51 ml/min/mmHg, p=0.02). Despite these differences, arterial dilation (M: 5.32 ± 5.55 vs. F: 5.20 ± 4.80%, p=0.96) and shear stress (M: 142 ± 80 vs. F: 171 ± 86 s−1, p=0.27) did not differ between groups across exercise intensities. Endothelial sensitivity to exercise-induced shear stress did not differ between males (0.02 ± 0.05%/s−1) and females (0.03 ± 0.01%/s−1, p=0.67). Conclusion: These data suggest that a reduced endothelial sensitivity to exercise-induced shear stress may not explain why aerobic exercise interventions do not consistently improve peripheral endothelial function in healthy postmenopausal females. Montreal Heart Institute Foundation. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Oral bacteriotherapy is associated with decreased blood lactate concentration during exercise at high altitude

Exposure to high altitude leads to decreased oxygen saturation (SpO2) and, in some individuals, the development of adverse outcomes such as acute high-altitude sickness. A further decrease in oxygen availability during exercise at altitude leads to greater anaerobic metabolism and increased lactate production. Previous studies show that ingestion of the probiotic SLAB51 (O2BOOSTER; Hecto, Seoul, South Korea) improved SpO2 in individuals exercising in a hypobaric chamber (simulated altitude 16,732 ft (~5100 m) above sea level) compared to individuals who did not ingest the probiotic. However, the use of SLAB51 during exercise at high terrestrial altitude has yet to be studied. We hypothesized that individuals who ingest SLAB51, relative to those given a placebo, will exhibit less of a difference in lactate production during sub-maximal exercise when paired high-altitude and sea-level values pre- and post-exercise are compared. We recruited 17 participants of Latino ancestry, ages 19-63 years, for studies at sea level (University of California, San Diego) and at high altitude (University of California White Mountain Barcroft Research Station, 3801 m). At sea level and on the third or fourth day at high altitude, we measured SpO2 and heart rate (HR) via pulse oximetry (forehead probe) before and during the last 30 seconds of a 10-minute submaximal (1 watt/kg) bout of exercise on a cycle ergometer (n = 5 for each group). Blood lactate concentration was measured before and after exercise from fingertip capillary blood samples. The respective differences between SpO2 and HR pre-exercise and during the final 30 seconds of exercise (the ΔSpO2 and ΔHR) were calculated for all individuals. The Δlactate blood concentration was calculated by the difference between lactate pre- and post-exercise. ΔSpO2, ΔHR, and Δlactate values were computed for sea level and high altitude. The difference between the respective sea-level Δ and the high-altitude Δ values were quantified for each measurement and compared between the groups who received either SLAB51 or the placebo upon arrival, and the same treatment for three days at high altitude. As expected, exercise increased HR and blood lactate concentration at sea level and high altitude and decreased SpO2 at high altitude. The difference of Δlactate between sea level and high altitude was lower (p = 0.023) in the SLAB51 (n = 4, 0.93 ± 0.18 mmol/L) versus placebo (n = 4, 1.63 ± 0.13 mmol/L) group. However, there were no significant differences of ΔSpO2 and ΔHR between groups. Our findings show that taking SLAB51 could lower the production of lactate during submaximal exercise at high altitude. This means that anaerobic glycolysis may play a smaller role in energy production when the probiotic is taken compared to the placebo. To further understand the influence of SLAB51 as a supplement on exercise performance at altitude, more research with a bigger sample size is necessary. Supported by LEA Altitude Performance Fund. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Sleep Duration Irregularity is Associated with Elevated Blood Pressure During Submaximal Exercise in Young Adults.

Irregularity in nightly sleep duration is reported to associate with elevated blood pressure (BP), but it is unclear whether this association can be observed with BP measured during exercise after controlling for factors known to influence the exercise pressor reflex. Twenty-nine young adults (22±4y; 19 men, 10 women) performed cycling exercise until volitional fatigue to assess peak oxygen uptake (VO2). Actigraphy was used to monitor sleep duration and daily physical activity for seven consecutive days after which participants completed two bouts of moderate-intensity cycling while BP and VO2 were measured using a Tango+ device and indirect calorimetry, respectively. Systolic BP was averaged from the two bouts of exercise and expressed as a change from seated rest (∆SBP). Sleep duration regularity was calculated as standard deviation (SD) and coefficient of variation (CV). Systolic BP at seated rest, during exercise, and ∆SBP was 113±13, 152±21, and 38±13 mmHg, respectively. Sleep duration SD (range 10-146 min) and sleep duration CV (range 2-54%) when excluding weekend nights were significantly correlated with ∆SBP (r = 0.58 and r = 0.62, respectively; both p<0.01) after adjusting for age, sex, body mass index, peak VO2, physical activity, resting systolic BP, chronotype, and the VO2 response to exercise. Sleep duration regularity analyzed with weekend nights included (across all seven days) was also significantly correlated with ∆SBP (p≤0.01), but had weaker correlation coefficients. These results indicate that sleep regularity, especially when excluding weekend nights, is associated with the rise in systolic BP during moderate-intensity exercise in young adults. Sleep duration regularity may be a useful tool to capture the impact of intermittent nights of insufficient sleep on BP dysregulation.

Impaired exercise-induced increase in serum IGF-1 in humans with obesity

Changes in circulating insulin-like growth factor 1 (IGF-1) implicate regulation of skeletal muscle metabolism, including protein and glucose metabolism. Previous studies have shown that an acute bout of exercise increases serum IGF-1 concentrations in healthy, lean humans. However, exercise-induced changes in serum IGF-1 concentrations in humans with obesity remain unknown. We compared changes in plasma IGF-1 during and after an acute bout of endurance exercise between humans with and without obesity. Eight subjects with obesity (i.e., OB: BMI = 34.48 ± 2.96) and eight subjects without obesity (i.e., LN: BMI = 24.45 ± 2.43 kg/m2) exercised for 45 min in a cycle ergometer at 65% of their maximum oxygen uptake, after an overnight 10-h fast. Blood draws were taken immediately before exercise, at 15 and 30 minutes (i.e., during exercise), and at 55, 75, 95, and 115 minutes after the start of the exercise. Serum concentrations of total IGF-1 and insulin were determined using commercially available ELISA assays (Alpco 22-IGFHU-E01 and 80-INSHU-E10.1, respectively). Plasma glucose concentrations were determined using an automatic analyzer (YSI glucose analyzer). One-way repeated measures analyses of variance were carried out to detect significant changes over time within each group. Independent t tests were used to determine group differences at each time point. Alpha level was set at p ≤ 0.05 and data are reported as mean ± SD. There were no significant ( p &gt; 0.05) differences between groups for IGF-1 serum concentrations at baseline (LN = 205.61 ± 40.07 ng/mL, OB = 200.89 ± 80.40 ng/mL) nor during or after exercise. Significant increases from baseline in serum IGF-1 concentrations were detected in the LN group at 15 min (231.30 ± 50.47 ng/mL, p = 0.007) and 30 min (227.94 ± 49.02 ng/mL, p = 0.04) during exercise, followed by significant decreases from baseline at 95 min (189.99 ± 34.73 ng/mL, p = 0.052) and 115 min (196.42 ± 40.39 ng/mL, p = 0.023). No significant ( p &gt; 0.05) differences from baseline were observed in the obese group neither during nor after exercise. Higher serum insulin concentrations were observed in the OB group at baseline (LN = 5.55 ± 2.62 μIU/mL, OB = 11.07 ± 5.76 μIU/mL, p = 0.027) but significant group differences no longer existed ( p &gt; 0.05) during exercise and up to 55 min after exercise; however, insulin concentrations for the OB group were significantly greater than those measured in the LN group at 75 min ( p = 0.028), 95 min ( p = 0.008), and 115 min ( p = 0.007) after exercise. Moreover, a significant increase from baseline was measured 55 min after exercise in the lean group (8.22 ± 3.13 μIU/mL, p = 0.005), whereas no significant changes were observed in the OB groups at any time point ( p &gt; 0.05). No significant ( p &gt; 0.05) group differences were detected for plasma glucose concentrations at any time point, and despite a significant decrease from baseline observed in the LN group at 115 min after exercise (baseline = 83.32 ± 7.66 mg/dL, 115 min = 81.02 ± 7.00 mg/dL, p = 0.044). In conclusion, endurance exercise increases serum IGF-1 concentrations in humans without obesity, but this response is impaired in humans with obesity. National Institute of Health (NIH)\National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK). Grant/Award Number: R01DK123441. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Divergent roles of purinergic 2X receptors in the pressor response to treadmill exercise in male and female rats

Our objective was to investigate the role played by ATP sensitive purinergic 2X (P2X) receptors in evoking the pressor response to treadmill running in male and female rats with and without simulated peripheral artery disease (PAD). We hypothesized that PPADS (P2X receptor antagonist, 10 mg i.v.), would reduce the pressor and end-exercise plasma norepinephrine (NE) response to four minutes of treadmill exercise (15 m×min−1; 1° incline) in male and female rats with a greater magnitude of effect in rats with simulated PAD compared to sham-operated rats. Methods: Ten rats had both femoral arteries ligated ~72 hours prior to experimental protocols. Fourteen rats had sham procedures performed in which the femoral arteries were exposed, and 5-0 suture was passed under the arteries but not tied. These groups are referred to as “ligated” and “sham”, respectively. In all rats, the right carotid artery was cannulated (PE-25) for blood pressure measurement and arterial blood samples and the right jugular vein was cannulated (PE-25) for administration of PPADS. After the rats recovered (~2 hrs), treadmill exercise was initiated (15 m·min−1, 1° incline) and the rat completed a four minute exercise bout. While the rat was still running, an arterial blood sample (~100 μl) was drawn for plasma NE assessment. Following a 20 minute rest, PPADS (10 mg, dissolved in 0.2 mL saline) was infused into the jugular vein over 10 min. After PPADS infusion, a second treadmill exercise bout and blood collection were performed as described for the control condition. The pressor and plasma NE responses to submaximal treadmill running before and after the injection of PPADS (10 mg) were compared. Data are expressed as mean ± SD. Statistical significance was defined as P≤0.05. Results: In male rats, PPADS significantly reduced the mean arterial pressure (MAP) response to exercise in both sham ( n=6, Peak ΔMAP control: 19±6; PPADS: 11±9 mmHg; P=0.033) and ligated rats ( n=4; control: 24±3 mmHg; PPADS: 16±6 mmHg; P=0.021) with a similar magnitude of effect observed between groups (p=0.544). In female rats, PPADS had no effect on the MAP response to exercise in either sham (n=6, 13±8; PPADS: 10±5 mmHg; P=0.171) or ligated (n=6, 17±5; PPADS: 18±6 mmHg; P=0.375) rats. When NE values were grouped by sex independent of ligation/sham status, PPADS significantly reduced end-exercise plasma NE concentration in both male (n=11, 200±131; PPADS: 139±61 pg/mL; P=0.016) and female (n=10, 199±133; PPADS: 140±101 pg/mL; P=0.027) rats. Conclusions: The data indicate that P2X receptors contribute to the sympathetic response to exercise in both male and female sham and ligated rats, but that sympathoexcitatory roles for P2X receptors translates into an obligatory role in the blood pressure response to treadmill exercise in male but not female rats. National Institutes of Health R01HL161160. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.