Volitional Fatigue Research Articles

Variability in musculoskeletal fatigue responses associated with repeated exposure to an occupational overhead drilling task completed on successive days

Emerging research suggests that muscular and kinematic responses to overhead work display a high degree of variability in fatigue-related muscular and kinematics changes, both between and within individuals when evaluated across separate days. This study examined whether electromyographic (EMG), kinematic, and kinetic responses to an overhead drilling task performed until volitional fatigue were comparable to those of a repeated identical exposure of the task completed 1 week later. Surface EMG and intramuscular EMG, sampled from 7 shoulder muscles, and right upper limb kinematics and kinetics were analyzed from 15 male and 14 female participants. No significant day-to-day changes in EMG mean power frequency (MPF) were observed, though serratus anterior displayed significantly less fatigue-related increase in EMG root-mean-squared (RMS) signal amplitude on day 2. Unfatigued upper kinematics on day 2 featured an increase in thoracohumeral elevation, elbow flexion, and decrease in wrist ulnar deviation compared to unfatigued state on day 1. Fatigue-related changes in shoulder joint flexion moment that were present on day 1 were reduced on day 2, suggesting that a more efficient overhead work strategy was learned and preserved across successive days. Day-to-day changes in upper limb joint angle variability, quantified by median absolute deviation (MdAD), were joint dependent. Despite yielding a variable fatigue-related kinetic strategy on both days, kinematic and kinetic fatigue-related changes on a second day of completing an overhead drilling task suggested a potential kinematic learning effect.

Head and neck cooling enhance exercise tolerance in individuals with multiple sclerosis

BackgroundIndividuals with Multiple Sclerosis (MS) experience impairments in heat dissipation, compromising core temperature regulation during exercise. ObjectiveTo examine the efficacy of combined head-and-neck cooling as administered via a commercially available cooling cap and neck wrap in mitigating increases in core temperature during exercise. MethodsOn separate days, ten (7 females) adults (46.1 ± 11.6 years) with relapsing-remitting MS performed semi-recumbent cycling consisting of an incremental exercise bout to volitional fatigue in a temperate environment (23 °C, 50 % relative humidity) while undergoing head-and-neck cooling using a cooling cap and neck wrap maintained at 10 °C (COLD) or 24–26 °C (NEUTRAL). Prior to and following a 30-minute post-exercise recovery, functional capacity was assessed by a battery of tests consisting of a 2-minute walk test, Timed 25-Foot Walk test, sit-to-stand test, and Berg Balance Scale. Core (ingestible pill) and skin temperatures were recorded continuously. The level of fatigue was measured with questionnaires. ResultsThe duration of the incremental exercise test increased with the application of COLD (28.4 ± 5.1 min) versus NEUTRAL water (vs 20.8 ± 5.1 min) (p = 0.001) and was paralleled by a significant reduction in body temperatures (∼1 °C, p < 0.05). The distance covered during the 2-min walk test performed after the incremental exercise test increased with the COLD (176.5 ± 0.6 m), relative to the NEUTRAL condition (147.7 ± 43.5 m) (p = 0.01). Fatigue levels did not change between conditions. ConclusionWe show that head-and-neck cooling with cold water effectively enhances exercise tolerance and mitigates increases in core temperature during exercise in individuals with MS.

Does exercise modality and posture influence cerebrovascular and cardiovascular systems similarly?

Cerebral hemodynamics have been quantified during exercise via transcranial Doppler ultrasound, as it has high-sensitivity to movement artifacts and displays temporal superiority. Currently, limited research exists regarding how different exercise modalities and postural changes impact the cerebrovasculature across the cardiac cycle. Ten participants (4 females and 6 males) ages 20-29 completed three exercise tests (treadmill, supine, and upright cycling) to volitional fatigue. Physiological data collected included middle cerebral artery velocity (MCAv), blood pressure (BP), heart rate, and respiratory parameters. Normalized data were analyzed for variance and effect sizes were calculated to examine differences between physiological measures across the three exercise modalities. Systolic MCAv was greater during treadmill compared to supine and upright cycling (p<0.001, (large) effect size), and greater during upright versus supine cycling (p<0.017, (large)). Diastolic MCAv was lower during treadmill versus cycling exercise only at 60% maximal effort (p<0.005, (moderate)) and no differences were observed between upright and supine cycling. No main effect was found for mean and diastolic BP (p>0.05, (negligible)). Systolic BP was lower during treadmill versus supine cycling at 40% and 60% intensity (p<0.05, (moderate-large)) and greater during supine versus upright at only 60% intensity (p<0.003, (moderate)). The above differences were not explained by partial pressure of end-tidal carbon dioxide levels (main effect: p=0.432). The current study demonstrates the cerebrovascular and cardiovascular systems respond heterogeneously to different exercise modalities and aspects of the cardiac cycle. As physiological data were largely similar between tests, differences associated with posture and modality are likely contributors.

Evaluation of self-contained breathing apparatus (SCBA) weight on firefighter stamina, comfort, and postural stability

Firefighters wear personal protective equipment to protect them from the thermal and chemical environment in which they operate. The self-contained breathing apparatus (SCBA) provides isolation of the airway from the hazardous fireground. National standards limit SCBA weight, however, integration of additional features could result in an SCBA exceeding the current limit. The purpose of this study was to examine the effects of increased SCBA weight on firefighters’ physiological responses, work output, dynamic stability, and comfort. Completion of simulated firefighting activities induced a strong physiological response. Peak oxygen consumption was higher with the lightest SCBA than the heaviest SCBA. Few other physiological differences were noted as SCBA weight increased. Importantly, increased SCBA weight resulted in significantly more negative perceptions by the firefighters and a trend towards significance for the duration of work time prior to reaching volitional fatigue. These results should be considered when assessing changes to existing SCBA weight limits.

Effects of short-term dietary nitrate supplementation on exercise and coronary blood flow responses in patients with peripheral artery disease.

Peripheral arterial disease (PAD) is a prevalent vascular disorder characterized by atherosclerotic occlusion of peripheral arteries, resulting in reduced blood flow to the lower extremities and poor walking ability. Older patients with PAD are also at a markedly increased risk of cardiovascular events, including myocardial infarction. Recent evidence indicates that inorganic nitrate supplementation, which is abundant in certain vegetables, augments nitric oxide (NO) bioavailability and may have beneficial effects on walking, blood pressure, and vascular function in patients with PAD. We sought to determine if short-term nitrate supplementation (via beetroot juice) improves peak treadmill time and coronary hyperemic responses to plantar flexion exercise relative to placebo (nitrate-depleted juice) in older patients with PAD. The primary endpoints were peak treadmill time and the peak coronary hyperemic response to plantar flexion exercise. Eleven PAD patients (52-80 yr.; 9 men/2 women; Fontaine stage II) were randomized (double-blind) to either nitrate-rich (Beet-IT, 0.3 g inorganic nitrate twice/day; BRnitrate) or nitrate-depleted (Beet-IT, 0.04 g inorganic nitrate twice/day, BRplacebo) beetroot juice for 4 to 6 days, followed by a washout of 7 to 14 days before crossing over to the other treatment. Patients completed graded plantar flexion exercise with their most symptomatic leg to fatigue, followed by isometric handgrip until volitional fatigue at 40% of maximum on day 4 of supplementation, and a treadmill test to peak exertion 1-2 days later while continuing supplementation. Hemodynamics and exercise tolerance, and coronary blood flow velocity (CBV) responses were measured. Although peak walking time and claudication onset time during treadmill exercise did not differ significantly between BRplacebo and BRnitrate, the diastolic blood pressure response at the peak treadmill walking stage was significantly lower in the BRnitrate condition. Increases in CBV from baseline to peak plantar flexion exercise after BRplacebo and BRnitrate showed a trend for a greater increase in CBV at the peak workload of plantar flexion with BRnitrate (p = 0.06; Cohen's d = 0.56). Overall, these preliminary findings suggest that inorganic nitrate supplementation in PAD patients is safe, well-tolerated, and may improve the coronary hyperemic and blood pressure responses when their calf muscles are most predisposed to ischemia.Clinical trial registration:https://clinicaltrials.gov/, identifier NCT02553733.

Androgenic Steroid Hormones and Endurance Exercise in Athletic Women.

This study investigated the impact of intensive endurance exercise on circulating androgenic steroid hormones in women. Fifteen normally menstruating athletic women participated. They completed intensive endurance exercise (treadmill running) until volitional fatigue in their follicular phase, with blood samples collected at pre-exercise, volitional fatigue, 90 min and 24 h into recovery. The steroid hormones (total, free testosterone, dehydroepiandrosterone [DHEA], and DHEA-sulfate [DHEA-S], cortisol) were analyzed in blood sera. Non-parametric statistics were used to assess changes across exercise and recovery. At volitional fatigue, all hormones, except free testosterone, were significantly (p < 0.05) increased compared to pre-exercise levels. Most hormones remained elevated through 90 min of recovery, with DHEA, DHEA-S, and total testosterone changes being significant (p < 0.05). At 24 h of recovery, hormonal levels were reduced; specifically, DHEA, DHEA-S, and total testosterone compared to baseline (p < 0.01 to 0.06). Increases in cortisol levels at volitional fatigue and 90 min of recovery were correlated with reductions in total testosterone, DHEA, and DHEA-S observed at 24 h of recovery (rho > -0.62, p < 0.05). In conclusion, in menstruating women performing intensive endurance exercise during their follicular phase, their androgenic steroid hormones remain elevated during early recovery but are suppressed at 24 h of recovery. The latter finding indicates that establishing a resting endocrine equilibrium requires a longer recovery period than 24 h.

The effect of different breathing conditions on cerebral blood flow in young males during maximal aerobic exercise: A pilot study

BackgroundDuring aerobic exercise, cerebral blood flow (CBF) decreases past 70 % of maximal oxygen uptake (VO2), but transient hypercapnia could mitigate the reduction. AimsTo examine the effect of oral (OB), nasal (NB), and combined (CB) breathing on CBF during a graded maximal exercise test (GXT). MethodsSix young males (age: 21.8 ± 2.3 years) performed three GXTs until volitional fatigue using a randomized breathing condition (OB, NB, or CB) order. Respiratory gases were assessed via a metabolic cart. Ultrasound sonography (7.5 MHz linear transducer) was utilized to assess the peak systolic velocity (PSV), end-diastolic velocity (EDV), and vessel diameter of the internal (ICA) and external (ECA) carotid artery. A one-way ANCOVA, with VO2 as a covariate, followed by a Bonferroni post-hoc analysis, was utilized to examine the differences between the breathing conditions. ResultsThe end-tidal partial pressure of CO2 (PetCO2) was significantly greater (p = 0.006) during NB (33.16 ± 1.37 mmHg) than that of CB (26.63 ± 1.32 mmHg) and OB (26.72 ± 1.37) at 100 % VO2max. There was a trend of a greater PSV in the ICA throughout the entire GXT that was only significantly greater (p = 0.027) during NB (126.12 ± 7.51 cm/s) compared to OB (92.47 ± 7.34 cm/s) but not CB (111.91 ± 7.14 cm/s) at 70 % VO2max. ConclusionsDuring a GXT, NB demonstrated a superior capacity to increase CBF, denoted by a higher PSV in the ICA compared to CB and OB, which might be partly related to an increased PetCO2.

Muscle activity and hypoalgesia in blood flow restricted versus unrestricted effort-matched resistance exercise in healthy adults.

This study assessed muscle activity (root mean square, RMS, and median frequency, MDF) to evaluate the acute response to blood flow restriction (BFR) resistance exercise (RE) and conventional moderate intensity (MI) RE. We also performed exploratory analyses of differences based on sex and exercise-induced hypoalgesia (EIH). Fourteen asymptomatic individuals performed four sets of unilateral leg press with their dominant leg to volitional fatigue under two exercise conditions: BFR RE and MI RE. Dominant side rectus femoris (RF) and vastus lateralis (VL) muscle activity were measured using surface electromyography (sEMG) through exercise. RMS and MDF were calculated and compared between conditions and timepoints using a linear mixed model. Pressure pain thresholds (PPT) were tested before and immediately after exercise and used to quantify EIH. Participants were then divided into EIH responders and nonresponders, and the differences on RMS and MDF were compared between the two groups using Hedges' g. RMS significantly increased over time (RF: p = 0.0039; VL: p = 0.001) but not between conditions (RF: p = 0.4; VL: p = 0.67). MDF decreased over time (RF: p = 0.042; VL: p < 0.001) but not between conditions (RF: p = 0.74; VL: p = 0.77). Consistently lower muscle activation was found in females compared with males (BRF, RF: g = 0.63; VL, g = 0.5. MI, RF: g = 0.72; VL: g = 1.56), with more heterogeneous findings in MDF changes. For BFR, EIH responders showed greater RMS changes (Δ RMS) (RF: g = 0.90; VL: g = 1.21) but similar MDF changes (Δ MDF) (RF: g = 0.45; VL: g = 0.28) compared to nonresponders. For MI, EIH responders demonstrated greater increase on Δ RMS (g = 0.61) and decrease on Δ MDF (g = 0.68) in RF but similar changes in VL (Δ RMS: g = 0.40; Δ MDF: g = 0.39). These results indicate that when exercising to fatigue, no statistically significant difference was observed between BFR RE and conventional MI RE in Δ RMS and Δ MDF. Lower muscle activity was noticed in females. While exercising to volitional fatigue, muscle activity may contribute to EIH.

Low-Load and High-Load Resistance Exercise Completed to Volitional Fatigue Induce Increases in Postexercise Metabolic Responses With More Prolonged Responses With the Low-Load Protocol.

Grisebach, D, Bornath, DPD, McCarthy, SF, Jarosz, C, and Hazell, TJ. Low-load and high-load resistance exercise completed to volitional fatigue induce increases in post-exercise metabolic responses with more prolonged responses with the low-load protocol. J Strength Cond Res 38(8): 1386-1393, 2024-Comparisons of high-load with low-load resistance training (RT) exercise have demonstrated no differences in postexercise metabolism when volume is matched. This important limitation of matching or equating volume diminishes benefits of the low-load RT protocol. Therefore, the purpose of this study was to determine the effects of acute low-load high volume and high-load low volume RT protocols completed to volitional fatigue on postexercise metabolism. Eleven recreationally active resistance-trained male subjects (24 ± 2 years; BMI: 25.3 ± 1.5 kg·m -2 ) completed 3 experimental sessions: (a) no-exercise control (CTRL); (b) RT at 30% 1 repetition maximum (1RM; 30% 1RM); and (c) RT at 90% 1RM (90% 1RM) with oxygen consumption (V̇ o2 ) measurements 2 hours postexercise. The RT sessions consisted of 3 sets of back squats, bench press, straight-leg deadlift, military press, and bent-over rows to volitional fatigue completed sequentially with 90 seconds of rest between sets and exercises. Changes were considered important if p < 0.100 with a ≥medium effect size. V̇ o2 1 hour postexercise was elevated following 30% 1RM (25%; p = 0.003, d = 1.40) and 90% 1RM (14%; p = 0.010, d = 1.15) vs. CTRL and remained elevated 2 hours postexercise following 30% 1RM (16%; p = 0.010, d = 1.15) vs. CTRL. Total O 2 consumed postexercise increased following 30% 1RM and 90% 1RM (∼17%; p < 0.044, d > 0.91) vs. CTRL. Fat oxidation was elevated 1 hour postexercise following 30% 1RM and 90% 1RM (∼155%; p < 0.001, d > 2.97) and remained elevated 2 hours postexercise following 30% 1RM compared with CTRL and 90% 1RM (∼69%; p < 0.030, d > 1.03). These data demonstrate beneficial changes to postexercise metabolism following high- and low-load RT sessions, with more prolonged effects following the low-load RT protocol completed to volitional fatigue.

Abstract PO2-12-03: Home-based Resistance Exercise Improves Fatigue and Functional Strength in Female Breast Cancer Survivors Post Chemotherapy

Abstract Introduction: Chemotherapy is associated with an increase in fatigue and loss of strength in female breast cancer (BCa) survivors. Strength training has been found to reverse these effects, however, the COVID pandemic added a complexity to clinic-based exercise intervention. The purpose of this study is to determine if a home-based resistance exercise program can attenuate these debilitating effects in a cohort of breast cancer survivors that have recently completed chemotherapy. Methods: Ten BCa survivors who completed chemotherapy within the previous 6 months were recruited to participate in a 12-week home-based resistance exercise proof of concept study. Exercise was performed 3 times per week, supervised via Zoom. Participants completed 2-3 sets of upper body and lower body exercises to volitional fatigue. Self-reported fatigue was measured using the respective subscale from the EORTC QLQ-C30. Strength was measured using hand grip dynamometry and isometric leg strength. Physical function was measured using the 6-minute walk test. Assessments were completed at baseline and end of study. As a comparison, age matched controls (AMCs) were recruited to complete cross-sectional analysis of each of these variables. A one-way analysis variance was done with Tukey’s post hoc test. Significance was set at p&amp;lt; 0.05. Results: BCa survivors were 46.4 ± 12.5 years old with a BMI of 28.11 ± 5.25. AMCs were 50.3 ±13.3 years old with a BMI of 30.8 ± 5.8. There was no significant difference in patient characteristics. A significant difference in self-reported fatigue was found between groups (F=18.52; p&amp;lt; 0.0001). Post hoc analysis found significant difference in fatigue between BCa survivors at baseline (48 ± 23) and the age matched controls (p&amp;lt; 0.0001). Exercise was able to significantly reduce fatigue in BCa survivors (21 ± 15; p=0.003) to levels not significantly different to AMCs (3.3 ± 7.5). A significant difference was also observed between groups for right-hand grip strength (F= 4.923; p=0.015) and left-hand grip strength (F=8.685, p=0.001). Post hoc analysis found a significant increase in right hand grip strength in the BCa survivor group following the intervention (p=0.012). Left hand grip strength was found to be significantly lower at baseline than AMCs (p=0.048). Left hand grip strength was significantly increased in BCa survivors at end of study (p&amp;lt; 0.001). Finally, a significant difference was observed between groups for isometric leg strength (F= 3.699; p=0.038). Post hoc analysis found a significant difference in leg strength in the BCa survivor group following intervention (pre: 105.9 ± 50.6 N-M; post: 158.4 ± 13.2 N-M; p=0.030) which was 16.5% higher than AMCs (127.4 ± 36.5 N-M). No significant difference was found in 6-minute walk distance. However, there was a 21% increase in the distance walked for BCa survivors after interventions (pre: 441.2 ± 66.5m; post: 501.4 ± 123m), identical to distances walked by AMCs (501.4 ± 90.8m). Conclusion: The results of our study suggest that a virtually supervised resistance exercise program can attenuate the negative effects of chemotherapy in BCa survivors to levels similar to their peers that never had breast cancer. Further research using powered sample sizes is needed to validate these results. Citation Format: Taylor Moncrief, Crisann Moon, Angela Gonzalez, Allison Stepanenko, Tiffany Cortes, Darpan Patel. Home-based Resistance Exercise Improves Fatigue and Functional Strength in Female Breast Cancer Survivors Post Chemotherapy [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO2-12-03.

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.

Applicability of Ratings of Perceived Exertion as a Measure of Subjective Fatigue in First Responders: An Exploratory Study

Introduction: Many researchers use Ratings of Perceived Exertion (RPE) as an indicator of subjective fatigue. Recent findings suggest that energy and fatigue are two distinct unipolar moods. Methods: Eleven first responders (FR) participated in a 90-minute strenuous exercise battery where they ended the protocol by completing a graded VO2max test where they were asked to perform until volitional fatigue, measured through RPE. Subjective feelings of mental energy (ME) and fatigue (MF) and physical energy (PE) and fatigue (PF) were measured before the beginning of the protocol and right after. Data was not normally distributed and presented in median and interquartile ranges. Spearman correlation coefficients were calculated for RPE, post mood state, and changes in mood states. Results: Participants’ self-reported RPE at the conclusion of the VO2max test was 18.27 [18.00,19.00]. Post PE (r=-0.012, p=0.97), PF (r=-0.036, p=0.92), ME (r=-0.13, p=0.69), and MF (r=0.43, p=0.19) displayed insignificant correlations with RPE. Similarly, insignificant correlations were observed between changes in PE (r=0.26, p=0.44), PF (r=0.46, p=0.15), ME (r=0.35, p=0.30), MF (r=-0.43, p=0.19), and RPE. Five participants reported an increase in feelings of PE (15.00 [13.00,19.00]) and seven participants reported lower feelings of PF (-12.00 [-19.50,-8.00]) post assessment. Seven participants reported improvements in ME (22.00 [8.00,68.00]) and three reported a reduction in MF (-13.00 [-27.00, -7.00]). Conclusions: Our findings suggests that self-reported RPE may not be a reliable measure of subjective fatigue in FR populations during acute strenuous exercise. Further our findings support previous work that ME, MF, PE, and PF are four distinct unipolar moods, and researchers seeking to assess fatigue in FR should use RPE with caution as it seems to be a measure of subjective perception of exercise intensity instead of a true measure of subjective fatigue.

Agreement between measured and self-reported physiological strain in males and females during simulated occupational heat stress.

Monitoring physiological strain is recommended to safeguard workers during heat exposure, but is logistically challenging. The perceptual strain index (PeSI) is a subjective estimate thought to reflect the physiological strain index (PSI) that requires no physiological monitoring. However, sex is known to influence perceptions of heat stress, potentially limiting the utility of the PeSI. The objective of this study was to assess whether sex modifies the relationship between PeSI and PSI. Thirty-four adults (15 females) walked on a treadmill (moderate intensity; ~200 W/m2) for 180 min or until termination (volitional fatigue, rectal temperature ≥39.5°C) in 16°C, 24°C, 28°C, and 32°C wet-bulb globe temperatures. Rectal temperature and heart rate were recorded to calculate PSI (0-10 scale). Rating of perceived exertion and thermal sensation were recorded to calculate PeSI (0-10 scale). Relationships between PSI and PeSI were evaluated via linear mixed models. Mean bias (95% limits of agreement [LoA]) between PSI and PeSI was assessed via Bland-Altman analysis. Mean absolute error between measures was calculated by summing absolute errors between the PeSI and the PSI and dividing by the sample size. PSI increased with PeSI (p < 0.01) but the slope of this relation was not different between males and females (p = 0.83). Mean bias between PSI and PeSI was small (-0.4 points), but the 95% LoA (-3.5 to 2.7 points) and mean absolute error were wide (1.3 points). Our findings indicate that sex does not appreciably impact the agreement between the PeSI and PSI during simulated occupational heat stress. The PeSI is not a suitable surrogate for the PSI in either male or female workers.

Low- and high-load resistance training exercise to volitional fatigue generate exercise-induced appetite suppression

Research on exercise-induced appetite suppression often does not include resistance training (RT) exercise and only compared matched volumes. PurposeTo compare the effects of low-load and high-load RT exercise completed to volitional fatigue on appetite-regulation. Methods11 resistance-trained males (24 ± 2 y) completed 3 sessions in a crossover experimental design: 1) control (CTRL); 2) RT exercise at 30% 1-repetition maximum (RM); and 3) RT exercise at 90% 1-RM. RT sessions consisted of 3 sets of 5 exercises completed to volitional fatigue. Acylated ghrelin, active glucagon-like peptide-1 (GLP-1), active peptide tyrosine (PYY), lactate, and subjective appetite perceptions were measured pre-exercise, 0-, 60-, and 120-min post-exercise. Energy intake was recorded the day before, of, and after each session. ResultsLactate was elevated following both 30% (0-, 60-, 120-min post-exercise) and 90% (0-, 60-min post-exercise; P < 0.001, d > 3.92) versus CTRL, with 30% greater than 90% (0-min post-exercise; P = 0.011, d = 1.14). Acylated ghrelin was suppressed by 30% (P < 0.007, d > 1.22) and 90% (P < 0.028, d > 0.096) post-exercise versus CTRL, and 30% suppressed concentrations versus 90% (60-min post-exercise; P = 0.032, d = 0.95). There was no effect on PYY (P > 0.171, ηp2 <0.149) though GLP-1 was greater at 60-min post-exercise in 90% (P = 0.052, d = 0.86) versus CTRL. Overall appetite was suppressed 0-min post-exercise following 30% and 90% versus CTRL (P < 0.013, d > 1.10) with no other differences (P > 0.279, d < 0.56). There were no differences in energy intake (P > 0.101, ηp2 <0.319). ConclusionsRT at low- and high-loads to volitional fatigue induced appetite suppression coinciding with changes in acylated ghrelin though limited effects on anorexigenic hormones or free-living energy intake were present.

Insulin resistance without coexisting hyperglycaemia is not independently associated with cardiorespiratory fitness or its components in women

Abstract Background Insulin resistance (IR) is a globally prevalent condition in which tissues’ response to insulin is diminished. Cardiorespiratory fitness (peak O2 uptake (VO2peak)) is determined by Fick’s equation (VO2 = cardiac output (CO) × arteriovenous O2 difference (Ca-vO2) = heart rate × stroke volume (SV) × Ca-vO2) and diffusion law (VO2 = diffusive O2 conductance (DO2) × constant k × venous O2 pressure (PvO2)). Several studies suggest an association between IR and decreased VO2peak, but the association has been questioned by analyses taking account of body size and composition, and potential mechanisms behind the association are unknown. Purpose To test a hypothesis that IR is not independently associated with VO2peak or its components. Methods Fifty of 144 women, who had participated in baseline experiments of three intervention studies, were included in this retrospective cross-sectional study; see Table 1 for subject characteristics. The inclusion criteria were age 18-40 years, body mass index 18.5-40 kg/m2, Caucasian origin, and available data on key measures. The exclusion criteria were diseases, medications, and other factors possibly affecting VO2peak. We measured haemoglobin, fasting glucose, and fasting insulin concentrations (blood), assessed IR (homeostasis model assessment (HOMA-IR)), and measured body size and composition (bioimpedance). The subjects performed an incremental cycling test to volitional fatigue; we measured ventilatory gas exchange (spiroergometry), arterial O2 saturation (oximetry), and SV and CO (impedance cardiography), and calculated Ca-vO2, DO2, and PvO2. We analysed VO2peak and its components as absolute (e.g. L/min) and ratiometrically scaled values (e.g. mL/min/kg), and when appropriate, also as allometrically scaled values (e.g. mL/min/kg^x, where 0 &amp;lt; x &amp;lt; 1) after identifying optimal variable-specific exponents. Results VO2peak scaled to body mass (BM) as well as SVpeak and COpeak scaled to body surface area (BSA) were inversely associated with the body size variables they were scaled to (all P &amp;lt; 0.013). Contrariwise, this was not the case when we optimally scaled VO2peak to fat-free mass (FFM), SVpeak to FFM^0.55, COpeak to FFM^0.50, and DO2peak to FFM (all 0.066 &amp;lt; P &amp;lt; 0.977). HOMA-IR was inversely associated with VO2peak scaled to BM but not in a multivariate analysis, whereas HOMA-IR was not associated with VO2peak scaled to FFM (Table 2); we made alike observations with SVpeak and COpeak (data not shown). Further, VO2peak scaled to BM as well as SVpeak and COpeak scaled to BSA were or tended to be up to 15 % higher in a group with HOMA-IR&amp;lt;3.0 than in a group with HOMA-IR≥3.0, while other peak exercise data did not differ between the groups (Table 1). Conclusion Body size and composition significantly affect conclusions drawn regarding VO2peak and its components. Taking this into account, IR without coexisting hyperglycaemia is not independently associated with VO2peak or its components in women.Table 1Table 2

Abstract 16878: Exercise Intolerance in Heart Failure With Preserved Ejection Fraction is More Closely Related to Energetic Decline During Exercise Than to Mitochondrial Oxidative Capacity in Recovery

Introduction: Heart failure (HF) with preserved ejection fraction (HFpEF) is associated with severe exercise intolerance (EI) and exertional fatigue. Impaired skeletal muscle high-energy phosphate metabolism has been reported in HFpEF patients and postulated as a potential contributor to EI. However, whether EI is more closely related to rapid energetic decline during exercise, or reduced mitochondrial oxidative capacity remains unknown. Hypothesis: We hypothesized that six-minute walk distance (6MWD) is more closely related to the rate of skeletal muscle energetic decline during exercise than mitochondrial oxidative capacity in HFpEF. Methods: Calf muscle energetics were measured by phosphorus magnetic resonance spectroscopy ( 31 PMRS). The rate of phosphocreatine (PCr) decline normalized to work performed during graded plantar flexion exercise to volitional fatigue and the time for PCr post-exercise recovery, an established metric inversely related to mitochondrial oxidative capacity, were measured in 64 HFpEF patients (age: 65 ± 11 years; 53% women). Results: The mean rate of PCr decline, PCr recovery time, and 6MWD were 52 ± 108 μmol/g wet weight/KJ, 80 ± 45 seconds, and 296 ± 109 meters, respectively. The 6MWD was inversely related to the rate of PCr decline (r = -0.46; P = 0.0002; Figure, A ) but not significantly related to the PCr recovery time (r = -0.06; P = 0.66; Figure, B ), as determined by Pearson’s correlation coefficients. Conclusions: EI, as measured by 6MWD, in HFpEF patients is closely associated with impaired skeletal muscle metabolism, specifically rapid skeletal muscle PCr decline during exercise rather than mitochondrial oxidative capacity. This suggests that impaired glycolytic metabolism and substrate delivery may contribute metabolically to EI in HFpEF patients.

Autoregulated and Non-Autoregulated Blood Flow Restriction on Acute Arterial Stiffness.

This study aimed to investigate the acute effects of autoregulated and non-autoregulated applied pressures during blood flow restriction resistance exercise to volitional fatigue on indices of arterial stiffness using the Delfi Personalized Tourniquet System. Following a randomized autoregulated or non-autoregulated blood flow restriction familiarization session, 20 physically active adults (23±5 years; 7 females) participated in three randomized treatment-order sessions with autoregulated and non-autoregulated and no blood flow restriction training. Participants performed four sets of dumbbell wall squats to failure using 20% of one repetition maximum. Blood flow restriction was performed with 60% of supine limb occlusion pressure. Testing before and post-session included an ultrasonic scan of the carotid artery, applanation tonometry, and blood pressure acquisition.Carotid-femoral pulse wave velocity increased in the non-autoregulated and no blood flow restriction training groups following exercise while carotid-radial pulse wave velocity increased in the no blood flow restriction training group (all p<0.05). Carotid-femoral pulse wave velocity exhibited an interaction effect between autoregulated and non-autoregulated blood flow restriction in favor of autoregulated blood flow restriction (p<0.05). Autoregulated blood flow restriction training does not influence indices of arterial stiffness while non-autoregulated and no blood flow restriction training increases central stiffness.

Cardiac output and arteriovenous oxygen difference contribute to lower peak oxygen uptake in patients with fibromyalgia

BackgroundPatients with fibromyalgia (FM) exhibit low peak oxygen uptake (dot{text{V}}O2peak). We aimed to detect the contribution of cardiac output to (dot{text{Q}}) and arteriovenous oxygen difference [text{C}(text{a-v})text{O}_{2}] to dot{text{V}}text{O}_{2} from rest to peak exercise in patients with FM.MethodsThirty-five women with FM, aged 23 to 65 years, and 23 healthy controls performed a step incremental cycle ergometer test until volitional fatigue. Alveolar gas exchange and pulmonary ventilation were measured breath-by-breath and adjusted for fat-free body mass (FFM) where appropriate. dot{text{Q}} (impedance cardiography) was monitored. text{C}(text{a-v})text{O}_{2} was calculated using Fick’s equation. Linear regression slopes for oxygen cost (∆dot{text{V}}O2/∆work rate) and dot{text{Q}} to text{V}O2 (∆dot{text{Q}}/∆dot{text{V}}O2) were calculated. Normally distributed data were reported as mean ± SD and non-normal data as median [interquartile range].Resultsdot{text{V}}O2peak was lower in FM patients than in controls (22.2 ± 5.1 vs. 31.1 ± 7.9 mL∙min−1∙kg−1, P < 0.001; 35.7 ± 7.1 vs. 44.0 ± 8.6 mL∙min−1∙kg FFM−1, P < 0.001). dot{text{Q}} and C(a-v)O2 were similar between groups at submaximal work rates, but peak dot{text{Q}} (14.17 [13.34–16.03] vs. 16.06 [15.24–16.99] L∙min−1, P = 0.005) and C(a-v)O2 (11.6 ± 2.7 vs. 13.3 ± 3.1 mL O2∙100 mL blood−1, P = 0.031) were lower in the FM group. No significant group differences emerged in ∆dot{text{V}}O2/∆work rate (11.1 vs. 10.8 mL∙min−1∙W−1, P = 0.248) or ∆dot{text{Q}}/∆dot{text{V}}O2 (6.58 vs. 5.75, P = 0.122) slopes. ConclusionsBoth dot{text{Q}} and C(a-v)O2 contribute to lower dot{text{V}}O2peak in FM. The exercise responses were normal and not suggestive of a muscle metabolism pathology.Trial registrationClinicalTrials.gov, NCT03300635. Registered 3 October 2017—Retrospectively registered. https://clinicaltrials.gov/ct2/show/NCT03300635.

Divulging the Impetus of Yoga on Cardiorespiratory Fitness and Its Persona in Alleviating Anxiety Experienced by Youth: A Cohort Interventional Study.

Globalization endangers youngsters worldwide with new standards and possibilities. Hereat of being exposed to greater demands and expectations, when it comes to performance review, their life may become more distressed. Yoga with revolutionary methods may assistyoungsters in bettering their physical health regardingtheir maximal oxygen uptake, and also help manage their anxiety. This study ascertains the effect of yoga on youth's anxiety levels and cardio-respiratory fitness. It was a longitudinal interventional study recruiting 99 medical students wherein VO2max (maximal oxygen uptake) on thetreadmill/ergometer exercise and anxiety scores throughSpielberger's anxiety scale was assessed at baseline and evaluated after 6 months of a regular yogic regime.The VO2max wasrecorded by the metabolic module of Labchart software (Bella Vista,New South Wales, Australia). The VO2max evaluated by incremental exercise to volitional fatigue was found to be 2.64 ± 0.49 L/min in males and 1.51 ± 0.44 L/min in females pre-yoga and 2.81 ± 0.52 L/min in males and 1.69 ± 0.47 L/min in females post yoga. The difference in the endline and baseline VO2max values of yoga-performing males (t=6.595, p<0.001) and females (t = 2.478, p = 0.017) was found to be significantly higher than non-yoga performers. The METS value obtained in males was 11.96 and in females was 7.68 before yoga. Post-yoga values were 13.44 and 8.37, respectively. The difference in total anxiety scores post-intervention was 34.6 which was statistically significant (t= 4.959, p <0.001). From the viewpoint of a physiologist, higher VO2max in young adults links to better physical fitness which is the potential outcome of regular yogic practice. As a result ofregular yogic practice, initial soaring anxiety levels of subjects culminated in a drastic observable reduction in anxiety, which helped inculcate a judicious acumen in youngsters.

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.