Graded Exercise Test Research Articles

Relationship between rolling resistance, preferred speed, and manual wheelchair propulsion mechanics in non-disabled adults

Purpose To characterize the relationship among rolling resistance (RR), preferred speed, and propulsion mechanics. Methods N = 11 non-disabled individuals (mean (SD)); Age 24 years (2), BMI 23.8 kg/m2 (4.3) completed a submaximal graded wheelchair exercise test (GXTsubmax, fixed speed, terminated at Rating of Perceived Effort (RPE)=8 (0-10 scale)) and a single-blind, within-subject repeated measures wheelchair propulsion experiment (RME). RR at RPE = 10 (estimated maximum workload, Maxestimated) was estimated from the GXTsubmax RPE-RR relationship. RME consisted of N = 19 1-minute trials (self-selected speed) each followed by 2-minutes rest. The trials included N = 16 unique RR between 25-100% of Maxestimated. Averages of all pushes in N = 16 unique 1-minute trials were computed for average RR (N), speed (m/s), peak force (Fpeak (N)), force rate of rise (Fror (N/s)), push frequency (PF (pushes/min)), and push length (PL (deg)). Results Repeated measures correlation assessed relationships among outcome variables (α = 0.05). RR was associated with decreased speed (r=–0.81, p < 0.001), increased Fpeak (r = 0.92), Fror (r = 0.26), and PL (r = 0.32) (all p > 0.001), and unrelated to PF (r = 0.02, p = 0.848). Increased speed was associated with increased Fror (r = 0.23, p = 0.003) and PF (r = 0.27, p < 0.001) and decreased Fpeak (r=–0.66, p < 0.001) and PL (r=-0.25, p < 0.001). Conclusion Increasing RR increases Fpeak despite reducing self-selected speed. RR and speed were strongly and moderately related to Fpeak, respectively, but weakly related to other propulsion mechanics. These results suggest that reducing user-system RR may confer dual benefits of improved mobility and decreased upper extremity loading. Further testing among wheelchair users is required. Clinical trial registration number: NCT04987177

Maximal oxygen uptake prediction from submaximal bicycle ergometry using a differential model

The maximal oxygen uptake (VO2max) estimation has been a subject of research for many years. Cardiorespiratory measurements during incremental tests until exhaustion are considered the golden yard stick to assess VO2max. However, precise VO2max determination based on submaximal tests is attractive for athlete as well for clinical populations. Here, we propose and verify such a method based on experimental data. Using a recently developed model of heart rate (HR) and VO2 kinetics in graded exercise tests, we applied a protocol, which is terminated at 80% of the estimated maximal HR during ergometer cycling. In our approach, initially, formula for maximal HR is selected by retrospective study of a reference population (17 males, 23.5 ± 2.0 years, BMI: 23.9 ± 3.2 kg/m2). Next, the subjects for experimental group were invited (nine subjects of both sexes: 25.1 ± 2.1 years, BMI 23.2 ± 2.2 kg/m2). After calculation of maximal HR using cardiorespiratory recordings from the submaximal test, VO2max is predicted. Finally, we compared the prediction with the values from the maximal exercise test. The differences were quantified by relative errors, which vary from 1.2% up to 13.4%. Some future improvements for the procedure of VO2max prediction are discussed. The experimental protocol may be useful for application in rehabilitation assessment and in certain training monitoring settings, since physical exertion is not a prerequisite and the approach provides an acceptable VO2max estimation accuracy.

Changes in body satisfaction during and after a 5-month handcycle training period and associations with physical capacity and body composition in individuals with a physical impairment

Purpose To investigate: (1) changes in body satisfaction during five months of handcycle training and one year after the training period; (2) whether longitudinal changes are dependent on sex, waist circumference and severity of the physical impairment; (3) associations between changes in physical capacity or body composition, and body satisfaction. Materials and methods Individuals (N = 143) with health conditions such as spinal cord injury filled out the Adult Body Satisfaction Questionnaire: at the start of the training (T1), directly after the training period (T2); and four months (T3) and one year after the training period (T4). At T1 and T2, physical capacity was determined with an upper-body graded exercise test, and waist circumference was measured. Handcycling classification was used as a proxy for the severity of impairment. Results Multilevel regression analyses showed that body satisfaction significantly increased during the training period and significantly decreased back to pre-training levels at follow-up. Individuals with more severe impairments showed a larger decrease at T4. Improvements in physical capacity and waist circumference were significantly associated with improvements in body satisfaction. Conclusions Body satisfaction significantly increased during the training period, but significantly decreased during follow-up. Additional efforts might be necessary to keep individuals engaged in long-term exercise.

The Impact of Acute Mild Normobaric Hypoxia and a Single Bout of Exercise to Volitional Exhaustion on Cognitive Performance in Endurance and Strength-Trained Athletes: The role of BDNF, EP-1, Catecholamines and Lactate.

The aim of the study was to examine whether a single bout of exercise to volitional exhaustion, performed under moderate normobaric hypoxia (H), would affect psychomotor performance (PP) in differently trained athletes. For this purpose, ten strength-trained (S) athletes, ten endurance-trained (E) athletes and ten healthy men leading a sedentary lifestyle as a control (C) group performed voluntarily two graded exercise tests until volitional exhaustion (EVE) under normoxia (N) and H (FiO2 = 14.7%). We measured the peripheral level of the brain derived neurotrophic factor (BDNF), choice reaction time (CRT) and the number of correct reactions (NCR) as indices of PP. Psychomotor tests were performed at rest, immediately after the EVE and 3 minutes after the EVE. Venous blood samples were collected at rest, immediately after cessation of each EVE, and 1 h after each EVE. The results showed that the EVE significantly (p < 0.05) impaired CRT under N and H, and NCR under H only in the E group. The higher WRmax in the E compared to the S and C groups was associated with a significant (p < 0.005) increase in adrenaline (A) and noradrenaline (NA). There were no significant differences between conditions (N vs. H) in the BDNF at rest and after exercise. The EVE impaired cognitive function only in the E group; higher involvement of the sympathetic nervous system, A and NA may also play a role in this phenomenon. Therefore, it can be concluded that exposure to H did not have a negative impact on CRT or NCR. Moreover, BDNF did not improve cognitive function.

Physiological and Energetic Demands During Still-Rings Routines of Elite Artistic Gymnasts.

The aim of the study was to analyze physiological and energetic demands of elite gymnasts during still-rings routines (SRRs). Eleven male gymnasts (mean [SD] 23.6 [3.9]y, 65.9 [5.6]kg, 171.1 [6.7]cm) performed a maximal graded exercise test and an individual SRR, during which respiratory gas and heart rate (HR) were measured using a mobile spiroergometer and a paired HR sensor. Metabolic energy and the energy contribution in terms of aerobic, anaerobic lactic, and anaerobic alactic were determined by oxygen uptake (VO2) during exercise, net lactate production, and the fast component of postexercise VO2 kinetics. Mean routine duration of the SRRs was 48.3 (4.5)seconds. VO2 and HR during SRRs were shown to be 86.9% (5.9%) and 91.0% (3.3%), respectively, of the maximal values measured during the graded exercise test. The anaerobic alactic, aerobic, and anaerobic lactic systems provided 50.9% (6.6%), 28.6% (4.8%), and 20.5% (5.2%), respectively, of the total energy required during SRRs. The energy contribution of the anaerobic lactic system correlated negatively with individual anaerobic threshold (r = -.715) and maximal VO2 (r = -.682). The anaerobic alactic system is the predominant energy source for ATP resynthesis during SRRs. The high relative VO2 and HR values reached during SRRs showthat these routines strongly stress the cardiovascular system.

Comparison of Heart Rate, Ventilation, Maximal Oxygen Uptake, Lactate Level, and Recovery Rate During Two Types of Walking Graded Exercise Testing in Elite Race Walkers

PURPOSE The purpose of this study was to identify a sport-specific assessment for elite race walking athletes by comparing physiological responses to different types of walking graded exercise test (GTX) protocols.METHODS Six elite race walking athletes completed two types of walking protocols in a randomized crossover design with 1 week of interval between trials. Exercise time, oxygen uptake (VO&lt;sub&gt;2&lt;/sub&gt;), ventilation (VE), and heart rate (HR) were measured in each trial; the lactate level was measured during the recovery period.RESULTS VO&lt;sub&gt;2&lt;/sub&gt;, VE, and HR differed significantly between the trials (&lt;i&gt;p&lt;/i&gt;&lt;.01~.05). Exercise time (&lt;i&gt;p&lt;/i&gt;&lt;.01) and VO&lt;sub&gt;2&lt;/sub&gt; (&lt;i&gt;p&lt;/i&gt;&lt;.05) differed significantly between the walking protocols; however, VE and HR did not differ significantly. During the recovery period, lactate levels differed significantly between the trials (&lt;i&gt;p&lt;/i&gt;&lt;.01), but not the walking protocol.CONCLUSIONS These results suggest that modified walking GXT protocols were appropriate to assess elite race walking athletes.

Does Cardiorespiratory Fitness Protect Memory from Sleep Deprivation?

Animal studies have demonstrated that physical exercise can protect memory from the effects of sleep deprivation (SD). We examined whether having a high cardiorespiratory fitness (V̇O 2peak ) is associated with an enhanced capacity to encode episodic memory after one night of SD. Twenty-nine healthy young participants were allocated into either an SD group ( n = 19) that underwent 30 h of uninterrupted wakefulness, or a sleep control (SC) group ( n = 10) that followed a regular sleep routine. Following either the SD or SC period, participants were asked to view 150 images as the encoding part of the episodic memory task. Ninety-six hours after viewing the images, participants returned to the laboratory to perform the recognition part of the episodic memory task, which required the visual discrimination of the 150 images previously presented from 75 new images introduced as distractors. Cardiorespiratory fitness (V̇O 2peak ) was assessed with a bike ergometer graded exercise test. Group differences in memory performance were assessed with independent t tests and associations between V̇O 2peak and memory with multiple linear regression. The SD group showed a significant increase in subjective fatigue (mean difference [MD] [standard error {SE}] = 38.94 [8.82]; P = 0.0001) and a worse capacity to identify the original 150 images (MD [SE] = -0.18 [0.06]; P = 0.005) and discriminate them from distractors (MD [SE] = -0.78 [0.21] P = 0.001). When adjusted for fatigue, higher V̇O 2peak was significantly associated with better memory scores in the SD (R 2 = 0.41; β [SE] = 0.03 [0.01]; P = 0.015) but not in the SC group ( R2 = 0.23; β [SE] = 0.02 [0.03]; P = 0.408). These results confirm that SD before encoding impairs the capacity to create robust episodic memories and provide preliminary support to the hypothesis that maintaining high levels of cardiorespiratory fitness could have a protective effect against the disruptive effects of sleep loss on memory.

Responses to Exercise at the Critical Heart Rate vs. the Power Output Associated With the Critical Heart Rate.

Succi, PJ, Dinyer-McNeely, TK, Voskuil, CC, Abel, MG, Clasey, JL, and Bergstrom, HC. Responses to exercise at the critical heart rate vs. the power output associated with the critical heart rate. J Strength Cond Res XX(X): 000-000, 2023-This study examined the physiological (volume of oxygen consumption [V̇o2], heart rate [HR], power output [PO], respiration rate [RR], muscle oxygen saturation [%SmO2]), neuromuscular (electromyographic and mechanomyographic amplitude [EMG AMP and MMG AMP] and mean power frequency [EMG MPF and MMG MPF]), and perceptual (rating of perceived exertion [RPE]) responses during exercise anchored at the critical heart rate (CHR) vs. the PO associated with CHR (PCHR). Nine subjects (mean ± SD; age = 26 ± 3 years) performed a graded exercise test and 4 constant PO trials to exhaustion at 85-100% of peak PO (PP) to derive CHR and PCHR on a cycle ergometer. Responses were recorded during trials at CHR (173 ± 9 b·min-1, time to exhaustion [TLim] = 45.5 ± 20.2 minutes) and PCHR (198 ± 58 W, TLim = 21.0 ± 17.8 minutes) and normalized to their respective values at PP in 10% intervals. There were significant (p ≤ 0.05) mode (CHR vs. PCHR) × time (10%-100% TLim) interactions for all variables (p < 0.001-0.036) except MMG AMP (p > 0.05). Post hoc analyses indicated differences across time for CHR V̇o2 (%change = -22 ± 16%), PCHR V̇o2 (19 ± 5%), CHR RR (24 ± 23%), PCHR RR (45 ± 14%), CHR PO (-33 ± 11%), PCHR HR (22 ± 5%), CHR RPE (22 ± 14%), PCHR RPE (39 ± 6%), CHR %SmO2 (41 ± 33%), PCHR %SmO2 (-18 ± 40%), CHR EMG AMP (-13 ± 15%), PCHR EMG AMP (13 ± 13%), CHR EMG MPF (9 ± 8%), CHR MMG MPF (7 ± 11%), and PCHR MMG MPF (-3 ± 14%). The critical heart rate was more sustainable than PCHR but required adjustments in PO which traversed intensity domains and caused dissociations of the responses previously observed in exercise anchored to PO. These dissociations indicated the demands to exercise varied with anchoring scheme and provides an important consideration for practitioners prescribing endurance exercise.

598-P: No Relationship between Sedentary Behavior Patterns and Peak Oxygen Consumption (VO2peak) among Overweight Individuals With and Without Type 2 Diabetes

Background: Sedentary behavior (SB) has negative effects on health, even in the context of achieving physical activity (PA) guidelines. It is unclear how total volume and patterns of accumulation of SB may vary among overweight/obese adults with and without uncomplicated type 2 diabetes (T2D) and whether SB is related to aerobic capacity. Purpose: To examine SB patterns and their relationship to estimated peak oxygen consumption (VO2peak) among adults with uncomplicated T2D and overweight controls. Methods: This was a secondary analysis of baseline data from VA-MIXED (NCT03419195), a trial in physically inactive, overweight/obese adults aged 30-55 with and without T2D. Daily pattern of PA/SB was assessed via activPAL for 7 days. Participants completed a cycle ergometer graded exercise test to measure maximal workload. VO2peak was estimated using the American College of Sports Medicine metabolic equation. Pearson correlation, two-sample t-tests, and multiple linear regression analyses were used to examine relationships between variables overall and by T2D status. Results: Baseline data were available for 21 participants (8 T2D, 13 overweight controls), mean (SD) age 43.3 (7.6) yrs, BMI 34.6 (5.6) kg/m2. Participants were sedentary (11.7 [2.2] h/day). There were no differences in step count; stepping, standing, or sedentary time; sit-to-stand transitions, and time in SB bouts ≥1 hour by T2D status (all p&amp;gt;0.11). Correlations between SB variables and VO2peak were not significant (all p&amp;gt;0.20). The relationship between total SB and VO2peak did not change when T2D status was included in the model (β −2.22, p=0.39). Discussion: Objectively measured SB patterns were similar between overweight controls and adults with uncomplicated T2D and did not correlate with VO2peak. Future studies should examine these variables in larger cohorts and evaluate if SB patterns are associated with variability in response to exercise. Disclosure M.O.Whipple: None. J.E.B.Reusch: Advisory Panel; Medtronic. A.J.Pinto: None. D.Rafferty: None. R.L.Scalzo: None. L.Abushamat: None. I.E.Schauer: None. A.G.Huebschmann: None. E.Clark: None. J.G.Regensteiner: None. Funding American Diabetes Association (1-21-CMF-003 to L.A.); National Institutes of Health (P50CA244688, P30DK116073, UL1TR001082, R01AG066562, R01DK124344, K12HD057022); Ludeman Family Center for Women’s Health Research; U.S. Department of Veterans Affairs (BX004533, BX002046, CX001532)

Thirteen-Year Associations of Occupational and Leisure-Time Physical Activity with Cardiorespiratory Fitness in CARDIA.

Differential effects on fitness are hypothesized to contribute to the opposing health effects of leisure-time physical activity (LTPA) and occupational physical activity (OPA). As such, this study examined cross-sectional and longitudinal associations of fitness with LTPA and OPA. This study examined fitness associations with LTPA and OPA across 13 yr in the Coronary Artery Risk Development in Young Adults study (years 7 (baseline), 10, 15, and 20 (follow-up) examinations). Fitness was measured at baseline and follow-up via symptom-limited maximal graded exercise test (GXT) duration (in seconds), whereas LTPA and OPA were self-reported during each examination. Baseline and follow-up cross-sectional associations of LTPA (low, medium, high) and OPA (0, 1-6, and ≥6 months with OPA) with fitness were examined using linear regression. Longitudinal linear regression examined associations between 13-yr LTPA (low, medium, or high) and OPA (no, decreasing, or increasing) trajectories with fitness at follow-up, adjusted for baseline values. All models adjusted for center, sex, race, age, education, smoking history, alcohol intake, resting blood pressure, diabetes status, and body mass index. Stratified analyses examined associations by sex (female/male), race (Black/White), and LTPA groups. Compared with low, medium, and high LTPA were positively associated with fitness in all analyses ( P < 0.001). Reporting 1-6 or ≥6 months with OPA was negatively associated with fitness in cross-sectional follow-up models ( β = -15.6 and -15.4, respectively; P ≤ 0.01). Longitudinally, those with increasing OPA had lower follow-up fitness compared with no OPA ( β = -16.41, P < 0.01). Negative associations of OPA with fitness were not meaningfully different across sex and race groups. Significant LTPA-OPA interactions were observed ( P < 001). Physical activity research and public health promotion should consider domain-specific associations on cardiovascular health.

Accuracy of a Clinical Applicable Method for Prediction of VO2max Using Seismocardiography.

Cardiorespiratory fitness measured as ˙VO2max is considered an important variable in the risk prediction of cardiovascular disease and all-cause mortality. Non-exercise ˙VO2max prediction models are applicable, but lack accuracy. Here a model for the prediction of ˙VO2max using seismocardiography (SCG) was investigated. 97 healthy participants (18-65 yrs., 51 females) underwent measurement of SCG at rest in the supine position combined with demographic data to predict ˙VO2max before performing a graded exercise test (GET) on a cycle ergometer for determination of ˙VO2max using pulmonary gas exchange measurements for comparison. Accuracy assessment revealed no significant difference between SCG and GET ˙VO2max (mean±95% CI; 38.3±1.6 and 39.3±1.6 ml·min-1·kg-1, respectively. P=0.075). Further, a Pearson correlation of r=0.73, a standard error of estimate (SEE) of 5.9 ml·min-1·kg-1, and a coefficient of variation (CV) of 8±1% were found. The SCG ˙VO2max showed higher accuracy, than the non-exercise model based on the FRIENDS study, when this was applied to the present population (bias=-3.7±1.3 ml·min-1·kg-1, p<0.0001. r=0.70. SEE=7.4 ml·min-1·kg-1, and CV=12±2%). The SCG ˙VO2max prediction model is an accurate method for the determination of ˙VO2max in a healthy adult population. However, further investigation on the validity and reliability of the SCG ˙VO2max prediction model in different populations is needed for consideration of clinical applicability.

The efficacy of a verification stage for determining O2max and the impact of sampling intervals.

It is unknown whether oxygen uptake (V̇O2) sampling intervals influence the efficacy of a verification stage following a graded exercise test (GXT). Fifteen females and 14 males (18-25 years) completed a maximal treadmill GXT. After a 5​min recovery, the verification stage began at the speed and grade corresponding with the penultimate stage from the GXT. Maximal oxygen consumption (V̇O2max) from the incremental GXT (iV̇O2max) and V̇O2max from the verification stage (verV̇O2max) were determined using 10 seconds (s), 30​s, and 60​s from breath​×​breath averages. There was no main effect for V̇O2max measure (iV̇O2maxvs. verV̇O2max) 10​s ([47.9​±​8.31] ml∙kg-1∙min-1 vs [48.85​±​7.97] ml∙kg-1∙min-1), 30​s ([46.94​±​8.62] ml∙kg-1∙min-1 vs [47.28​±​7.97] ml∙kg-1∙min-1), and 60​s ([46.17​±​8.62] ml∙kg-1∙min-1 vs [46.00​±​8.00] ml∙kg-1∙min-1]. There was a stage​×​sampling interval interaction as the difference between (verV̇O2max-iV̇O2max) was greater for 10-s than 60-s sampling intervals. The verV̇O2max was > 4% higher than iV̇O2maxin 31%, 31%, and 17% of the tests for the 10-s, 30-s, and 60-s sampling intervals respectively. Sensitivity for the plateau was < 30% for 10-s, 30-s, and 60-s sampling intervals. Specificity ranged from 44% to 60% for all sampling intervals. Sensitivity for heart rate​+​respiratory exchange ratio was > 90% for all sampling intervals; while specificity was < 25%. Findings from the present study suggest that the efficacy of verification stages for eliciting a higher V̇O2max may be influenced by the sampling interval utilized.

Stride-to-stride variability and fluctuations at intensities around lactate threshold in distance runners

Stride-to-stride variability and fluctuations in running have been widely investigated in relation to fatigue, injury, and other factors. However, no studies have examined the relationship of stride-to-stride variability and fluctuations with lactate threshold (LT), a well-known performance indicator for distance runners that represents the threshold at which fast-twitch muscle fibers are activated and the glycolytic system is hyperactivated. In this study, we examined a relationship between LT and stride-to-stride variability and fluctuations in trained middle- and long-distance runners (n = 33). All runners were asked to perform multistage graded exercise tests while wearing accelerometers on the upper surface of their shoes. The LT was determined by measuring blood lactate concentrations after each stage. Three gait parameters for each step were calculated based on the acceleration data: stride time (ST), ground contact time (CT), and peak acceleration (PA). The coefficient of variation (CV) and the long-range correlations (α) for each parameter were also calculated. The effects of the runner's group and the relative intensity for CV and α on gait parameters were evaluated using a two-way repeated measures analysis of variance. Although no significant effect was observed in the CV and α of ST, significant intensity main effects were observed for the CV and α of CT and PA. The lack of significant changes in ST might be the result of runners' adequate control of ST to minimize energy cost. All the parameters showing significant changes with increasing intensity decreased dramatically when they were close to LT. This might have been caused by an increase in physiological load near LT and be interpreted as a variation in motor control because of alternations in the mobilized muscle fibers and physiological changes around the LT. The α should be useful for non-invasive LT detection.

Physical activity and exercise capacity as composite versus single categorical endpoints for trials of exercise-based cardiac rehabilitation interventions: comparison of sample size requirements

Abstract Funding Acknowledgements Type of funding sources: None. Introduction A composite primary endpoint consists of two or more component endpoints, events or outcomes. If any one of these is observed, it is considered that the composite primary endpoint has been reached. A potential advantage of a composite over a single primary endpoint in a randomised controlled trial (RCT) is a reduction of the required sample size. Purpose The combined endpoint "major adverse cardiac events" (MACE) is well-established in cardiovascular research, but MACE is often unsuitable in trials of exercise-based cardiac rehabilitation interventions with short follow-up periods. We therefore explored the application of a composite primary endpoint incorporating exercise capacity and physical activity for parallel-group RCTs of exercise-based cardiac rehabilitation (CR) interventions. Methods Our composite endpoint combines two categorical (binary) single endpoints, i.e., exercise capacity (given as maximum mechanical power output of a graded exercise test) and physical activity. Thresholds for categorisation were defined on literature-based minimal clinically worthwhile changes and defined as an increase of 15 W or more for improving exercise capacity and an increase of 10 min/day or more for improving moderate to vigorous physical activity (MVPA). If the aim of an intervention is to avoid clinically meaningful deterioration (i.e., to achieve maintenance as opposed to improvement), the threshold is defined as deterioration in exercise capacity of less than 15 W and a reduction in MVPA of less than 10 min/day (figure 1). To illustrate the impact of a single versus a composite primary end point on sample size requirements, we used real-world data from two completed phase 3 CR trials ([1] and [2]). We applied the commonly used formula for estimating sample sizes to detect the difference between the probabilities of an event in two independent groups [3]. Results Sample size requirements for detecting a between-group difference of 5%, 10%, 15% and 20% under the different endpoint approaches are shown in table 1. If the aim of the intervention is to achieve improvement, the composite endpoint results in approximately equivalent sample size requirements to the single endpoint. If the aim of the intervention is to achieve maintenance, the composite endpoint results in markedly lower sample size requirements compared to the primary endpoint. Statistically, these differences are driven by the percentage of improvers or maintainers in the control group of the reference population. Conclusion The composite primary endpoint approach can be a useful alternative to the single primary endpoint in trials of exercise-based CR. Depending on the baseline probability, it may be possible to reduce the sample size requirement by applying a composite endpoint. In our examples, the composite endpoint results in smaller sample size requirements when the intervention aim is to avoid clinically meaningful deterioration.

Large-Scale Network Connectivity and Cognitive Function Changes After Exercise Training in Older Adults with Intact Cognition and Mild Cognitive Impairment.

Despite growing evidence regarding the association between exercise training (ET) and functional brain network connectivity, little is known about the effects of ET on large-scale within- and between-network functional connectivity (FC) of core brain networks. We investigated the effects of ET on within- and between-network functional connectivity of the default mode network (DMN), frontoparietal network (FPN), and salience network (SAL) in older adults with intact cognition (CN) and older adults diagnosed with mild cognitive impairment (MCI). The association between ET-induced changes in FC and cognitive performance was examined. 33 older adults (78.0±7.0 years; 16 MCI and 17 CN) participated in this study. Before and after a 12-week walking ET intervention, participants underwent a graded exercise test, Controlled Oral Word Association Test (COWAT), Rey Auditory Verbal Learning Test (RAVLT), a narrative memory test (logical memory; LM), and a resting-state fMRI scan. We examined the within (W) and between (B) network connectivity of the DMN, FPN, and SAL. We used linear regression to examine associations between ET-related changes in network connectivity and cognitive function. There were significant improvements in cardiorespiratory fitness, COWAT, RAVLT, and LM after ET across participants. Significant increases in DMNW and SALW, and DMN-FPNB, DMN-SALB, and FPN-SALB were observed after ET. Greater SALW and FPN-SALB were associated with enhanced LM immediate recall performance after ET in both groups. Increased within- and between-network connectivity following ET may subserve improvements in memory performance in older individuals with intact cognition and with MCI due to Alzheimer's disease.

Added Breathing Resistance during Exercise Impairs Pulmonary Ventilation and Exaggerates Exercise-Induced Hypoxemia Leading to Impaired Aerobic Exercise Performance.

Protective masks impose variable breathing resistance (BR) on the wearer and may adversely affect exercise performance, yet existing literature shows inconsistent results under different types of masks and metabolic demands. The present study was undertaken to determine whether added BR impairs cardiopulmonary function and aerobic performance during exercise. Sixteen young healthy men completed a graded exercise test on a cycle ergometer under the four conditions of BR using a customized breathing resistor at no breathing resistance (CON), 18.9 (BR1), 22.2 (BR2), and 29.9 Pa (BR3). The results showed that BR significantly elevates respiratory pressure (p < 0.001) and impairs ventilatory response to graded exercise (reduced VE; p < 0.001) at a greater degree with an increased level of BR which caused mild to moderate exercise-induced hypoxemia (final mean SpO2: CON = 95.6%, BR1 = 94.4%, BR2 = 91.6%, and BR3 = 90.6%; p < 0.001). Especially, such a marked reduction in SpO2 was significantly correlated with maximal oxygen consumption at the volitional fatigue (r = 0.98, p < 0.001) together with exaggerated exertion and breathing discomfort (p < 0.001). In conclusion, added BR commonly experienced when wearing tight-fitting facemasks and/or respirators could significantly impair cardiopulmonary function and aerobic performance at a greater degree with an increasing level of BR.

Metabolic Signatures of Performance in Elite World Tour Professional Male Cyclists.

Metabolomics studies of recreational and elite athletes have been so far limited to venipuncture-dependent blood sample collection in the setting of controlled training and medical facilities. However, limited to no information is currently available to determineif findings in laboratory settings are translatable to a real-world scenario in elite competitions.The goal of this study was to define molecular signatures of exertion under controlled exercise conditions and use these signatures as a framework for assessing cycling performance in a World Tour competition. To characterize molecular profiles of exertion in elite athletes during cycling, we performed metabolomics analyses on blood isolated from 28 international-level, elite, World Tour professional male athletes from a Union Cycliste Internationale World Team taken before and after a graded exercise test to volitional exhaustion and before and after a long aerobic training session. Moreover, established signatures were then used to characterize the metabolic physiology of five of these cyclists who were selected to represent the same Union Cycliste Internationale World Team during a seven-stage elite World Tour race. Using dried blood spot collection to circumvent logistical hurdles associated with field sampling, these studies defined metabolite signatures and fold change ranges of anaerobic or aerobic exertion in elite cyclists, respectively. Blood profiles of lactate, carboxylic acids, fatty acids, and acylcarnitines differed between exercise modes. The graded exercise test elicited significant two- to three-fold accumulations in lactate and succinate, in addition to significant elevations in free fatty acids and acylcarnitines. Conversely, the long aerobic training session elicited a larger magnitude of increase in fatty acids and acylcarnitines without appreciable increases in lactate or succinate. Comparable signatures were revealed after sprinting and climbing stages, respectively, in a World Tour race. In addition, signatures of elevated fatty acid oxidation capacity correlated with competitive performance. Collectively, these studies provide a unique view of alterations in the blood metabolome of elite athletes during competition and at the peak of their performance capabilities. Furthermore, they demonstrate the utility of dried blood sampling for omics analysis, thereby enabling molecular monitoring of athletic performance in the field during training and competition.

Peak substrate oxidation and peak oxygen consumption are diminished in individuals with mild cognitive impairment

The number of persons with Alzheimer’s Disease (AD) is projected to double within the coming decades, placing great emphasis on identifying accessible risk factors. Prior to AD, there is an important transitional phase, called mild cognitive impairment (MCI), where individuals first display objective declines in cognitive functioning. Growing evidence suggests that the risk factors of AD and MCI adversely affect mitochondrial function, presenting a potential measure that may be useful in risk stratification. Metabolic flexibility represents the capacity of the mitochondria to oxidize a variety of fuel substrates (i.e., carbohydrates and fatty acids), and can be assessed using a graded exercise test. Thus, metabolic flexibility may be a useful index of mitochondrial health that can be evaluated prior to the development of clinical AD. OBJECTIVE: To determine whether cardiorespiratory fitness and metabolic flexibility are attenuated in older adults with MCI in response to a graded exercise test. HYPOTHESIS: We hypothesized that individuals with MCI would have similar baseline, but reduced peak oxygen consumption (VO2peak), fat oxidation (FatOx), and carbohydrate oxidation (CHOOx) compared to healthy controls. METHODS: 22 older adults with MCI and 21 sedentary healthy controls (HCs) matched for both age and sex underwent a modified Bruce Protocol treadmill test to assess VO2peak. FatOx and CHOOx were calculated based on ventilatory equivalents using the equations: FatOx = 1.67VO2 - 1.70VCO2 [L/min] and CHOOx = 4.585VO2 - 3.2255VCO2 [L/min], respectively. Unpaired t-tests were conducted to determine whether baseline or peak oxygen consumption, FatOx, and CHOOx were different between groups. RESULTS: The MCI and the HC groups were similar in age (73.5 + 8.81 vs. 71.2 + 6.33, p=0.33) and BMI (26.2 + 4.92 vs. 26.8 + 5.16, p=0.70). Baseline FatOx (0.09 + 0.03 vs. 0.10 + 0.05 g/min, p=0.47) and CHOOx (0.51 + 0.17 vs. 0.59 + 0.21 g/min, p=0.23) were not different between the MCI and HC groups. Peak FatOx (0.31 + 0.13 vs. 0.39 + 0.10 g/min, p=0.018*), and peak CHOOx (1.89 + 0.41 vs. 2.18 + 0.49 g/min, p=0.047*) were lower in the MCI group relative to HCs. Additionally, the MCI group had a lower absolute (1.32 + 0.33 vs. 1.61 + 0.47 L/min, p=0.027*), and relative (22.0 + 5.0 vs. 19.1 + 5.30 mL/kg/min, p=0.070) VO2peak, although the latter was not statistically significant. CONCLUSION: Peak FatOx, CHOOx, and absolute VO2peak are diminished in older adults with MCI, which may suggest impaired whole body mitochondrial capacity and metabolic flexibility. However, future studies are necessary to determine the exact physiological and behavioral components to these observed reductions. Supported by NIH Grants R01 AG058853 and K01 AG054731 This is the full abstract presented at the American Physiology Summit 2023 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.

A comparison of passive heat treatment-induced vascular adaptations relative to exercise training

Epidemiological data indicate that repeated heat stress improves cardiovascular health, making passive heat therapy (PHT) a potential alternative for those unable to exercise. Few studies to date have examined the potential exercise mimetic effects in humans, and it is unclear how adaptations compare in magnitude to exercise training. OBJECTIVE: To examine the effects of 6 weeks of localized, muscle-focused PHT on resistance artery vascular function, exercise hemodynamics, and exercise performance relative to the adaptations observed following high-intensity aerobic exercise training focused on the same muscles. HYPOTHESIS: 6 weeks of PHT, applied through pulsed shortwave diathermy (2 hr, 3 days/week), would increase resistance artery function, improve exercise hemodynamics, and enhance exercise performance more than a sham treatment, but less than single-leg knee extension (KE) exercise training (EX; 40 min, 3 days/week). We also hypothesized that these functional adaptations would be accompanied by increased skeletal muscle capillarity. METHODS: We randomized 34 sedentary but otherwise healthy, young adults (ages 18–36; n = 17 female, 17 male) to receive PHT, EX, or sham heating sessions (SHAM; 2 hr, 3 days/week) over 6 weeks. Vascular function was determined through the blood flow response during both a passive leg movement (PLM) assessment and a knee extension graded exercise test (GXTmax). Muscle biopsies were taken from the vastus lateralis at baseline and after 6 weeks of intervention. RESULTS: Peak muscle treatment temperature was significantly different between all groups with PHT exhibiting a higher peak temperature (~40.80°C) than those in the EX (~37.75°C, P&lt;0.001) and SHAM groups (~36.10°C, P&lt;0.001). Peak blood flow during PLM increased to the same extent (P=0.625) in both the EX (~10.5% increase, P=0.009) and PHT groups (~8.5% increase, P=0.044); but tended to decrease in the SHAM group (P=0.087). KE peak flow increased in EX (~19%, P=0.005), but did not change in PHT (P=0.523) and decreased in SHAM (~7%, P=0.020). Peak vascular conductance during KE significantly increased by ~25% in EX (P=0.030) and PHT (P=0.012). KE peak power increased in EX by ~27% (P=0.001) but did not significantly change in PHT(P=0.175) and SHAM groups (P=0.111). EX, but not PHT or SHAM increased muscle capillary-to-fiber ratio (P = 0.0003), capillary density (P = 0.0428), and the Capillary to Fiber Perimeter Exchange Index (P = 0.0089). CONCLUSIONS: 6 weeks of localized PHT, when applied to young healthy individuals, improved resistance artery function at rest and during exercise to the same extent as exercise training. However, PHT did not lead to increased KE peak flow, microvascular remodeling, or improved exercise performance. Therefore, PHT mimics many, but not all the vascular benefits of exercise training. Further research is necessary to determine the mechanism by which 6 weeks of PHT led to improved vascular function at rest and during exercise. This is the full abstract presented at the American Physiology Summit 2023 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.

Performing one or more verification VO2 workload(s) immediately after an incremental to maximal graded exercise test significantly increases the proportion of participants who meet the job-related aerobic fitness standard for structural firefighters.

Graded exercise tests (GXTs) are commonly used to determine the maximal oxygen consumption (VO2max) of firefighter applicants. However, the criteria used to confirm VO2max are inconsistent and have a high inter-subject variability, which can compromise the reliability of the results. To address this, a verification phase (VP) after the GXT has been proposed as a "gold standard" protocol for measuring VO2max. 4179 male and 283 female firefighter applicants completed a GXT and a VP to measure their VO2max. VO2peak values measured during the GXT were compared to the VO2 values measured during the VP. The proportion of participants who met the job-related aerobic fitness standard during the GXT was compared to that of those who met the required standard during the VP. For male and female participants that required the VP to attain their VO2max, the VO2peak values measured during the GXT (47.3 ± 6.0 and 41.6 ± 5.3mLkg-1min-1) were, respectively, 10.1% and 10.3% lower than the VO2 values measured during the VP (52.1 ± 6.7 and 45.9 ± 6.4mLkg-1min-1), p < 0.001. Furthermore, the proportion of male and female participants who met the job-related aerobic fitness standard significantly increased from the GXT to the VP by 11.6% and 29.9%, respectively, p < 0.001. These results strongly support the use of a VP to confirm VO2max, especially for females, older and overweight individuals. These findings are applicable to other physically demanding public safety occupations and when examining the efficacy of training interventions on VO2max.