Submaximal Exercise Research Articles

Glucosinolate-rich broccoli sprouts protect against oxidative stress and improve adaptations to intense exercise training

Oxidative stress plays a vital role for the adaptive responses to physical training. However, excessive oxidative stress can precipitate cellular damage, necessitating protective mechanisms to mitigate this effect. Glucosinolates, found predominantly in cruciferous vegetables, can be converted into isothiocyanates, known for their antioxidative properties. These compounds activate crucial antioxidant defence pathways and support mitochondrial function and protein integrity under oxidative stress, in both Nrf2-dependent and independent manners. We here administered glucosinolate-rich broccoli sprouts (GRS), in a randomized double-blinded cross-over fashion to 9 healthy subjects in combination with daily intense exercise training for 7 days. We found that exercise in combination with GRS significantly decreased the levels of carbonylated proteins in skeletal muscle and the release of myeloperoxidase into blood. Moreover, it lowered lactate accumulation during submaximal exercise, and attenuated the severe nocturnal hypoglycaemic episodes seen during the placebo condition. Furthermore, GRS in combination with exercise improved physical performance, which was unchanged in the placebo condition.

Rest Energy Expenditure and Energy Expenditure During Submaximal Exercise: New Approach to Assessment of Performance in Skiers

The aim of the present study was to analyse rest energy expenditure (REE) and energy expenditure (EE) during submaximal exercise according to performance of athletes. A retrospective analysis of data from 2014 to 2020 among cross-country skiers in the preparatory phase was performed. Depending on the potential performance athletes (n = 136) were divided into two groups: I – test completed to the anaerobic threshold (AnT), II – test completed until exhaustion. The present study included the data only before AnT for a correct comparison of the results. REE was 2058.5 ± 220.5 kcal/day in I group and 2023.1 ± 216.4 kcal/day in II group (p = 0.481). In REE structure, the contribution of fats and carbohydrates (CHOs) was 69 and 31% in I group, 48 (p = 0.021) and 52% (p 0.000) in II group. Correlations between VO2rest and REE, as well as the rate of fats and CHOs oxidation at rest were revealed. In I and II groups the VO2AnT (p 0.000) and relative values of VO2max (p 0.05) were significantly different. EE before AnT was 135.9 ± 31.2 and 134.0 ± 23.4 kcal (p = 0.399) for I and II groups. The present study showed that the balance 1 : 1 of fats and CHOs in the REE structure is a more informative performance marker than quantitative assessment of EE. VO2AnT reduced by 20% relative to VO2max may indicate the functional economization and the body’s ability to perform exercise during long time, including in the anaerobic exercise. Endurance athletes demonstrated economy of CHOs against actively using of fats during submaximal exercise. Complex estimated of performance indicators and EE (including contribution fats and CHOs) should be taken into account when studying the performance of athletes.

Effects of Sitting Recovery Protocols on Postexercise Heart Rate in Young Adults

Abstract Background We aimed to compare the effects of 3 different upright seated recovery protocols on heart rate recovery (HRR) after a submaximal ergometer exercise. Methods The study included 30 young adult volunteers (15 men and 15 women). Participants performed a submaximal cycle exercise test at a constant workload of 60 Watts until a steady HR was achieved. This was followed by 5 min of: (a) inactive, (b) active loadless, and (c) passive recovery protocols. The HRR was assessed as the difference between the peak exercise HR and the HR recorded following 1 min of recovery and as the percentage HR decline after 1 min postexercise. Abnormal HRR was defined as a reduction of 1-min HRR ≤12 b · min−1 or ≤15 b · min−1 or ≤18 b · min−1. Results In both sexes, HRR was faster during inactive recovery compared with active recovery. In males, HRR was faster during inactive recovery compared with passive recovery protocol. In females, HRR was faster during passive recovery compared with active recovery protocol. The prevalence of impaired HRR was greater in the active recovery compared with the passive and inactive recovery protocols in both sexes. Conclusion The present findings suggest that in both sexes, the postexercise HRR was mediated by a combined action of the central command and other inputs or stimuli arising from skeletal muscle activities. In addition, the active recovery protocol resulted to a slower HRR and elicited more abnormal postexercise HR responses compared with the other recovery protocols.

Effects Of Wearing A Surgical Mask On Psychological Distress And Intensity Perception During Submaximal Exercise

Effects Of Wearing A Surgical Mask On Psychological Distress And Intensity Perception During Submaximal Exercise

Decline In Maximal And Submaximal Pediatric Exercise Capacity Following Covid-19 Pandemic Onset

Decline In Maximal And Submaximal Pediatric Exercise Capacity Following Covid-19 Pandemic Onset

Interval Exercise Induces Greater Changes In Post-exercise Metabolism Compared To Submaximal Exercise In Middle-aged Adults

Interval Exercise Induces Greater Changes In Post-exercise Metabolism Compared To Submaximal Exercise In Middle-aged Adults

Reduced peripheral and respiratory muscle strength in pediatric patients after kidney transplantation.

Reduced muscle strength and low-exercise capacity are well documented in adults, but there are few studies examining those impairments in children and adolescents after kidney transplantation. The objective of this study was to evaluate peripheral and respiratory muscle strength and the association with submaximal exercise capacity in children and adolescents after kidney transplant. Forty-seven patients between six and 18 years of age clinically stable after transplantation were included. Peripheral muscle strength (isokinetic and hand-grip dynamometry), respiratory muscle strength (maximal inspiratory and expiratory pressure), and submaximal exercise capacity (six-minute walk test - 6MWT) were assessed. Patients had a mean age of 13.1 ± 2.7 years and an average of 34 months had elapsed since the transplantation. Flexors of the knee showed a significant reduction in muscle strength (77.3% of predicted) and knee extensors had normal values (105.4% of predicted). Hand-grip strength and maximal respiratory pressures (inspiratory and expiratory) also were significantly lower than expected (p < 0.001). Although distance walked in the 6MWT was significantly lower than predicted (p < 0.001), no significant correlation was found with peripheral and respiratory muscle strength. Children and adolescents after kidney transplantation have reduced peripheral muscle strength of knee flexors, hand-grip, and maximal respiratory pressures. No associations were found between peripheral and respiratory muscle strength and submaximal exercise capacity.

Validation of 6-Minute Walk Test and Development of VO2max Prediction Equation in the Elderly

vPURPOSE: Cardiorespiratory fitness is closely related to cardiovascular and chronic diseases and is an important predictor of mortality. Despite the significance of cardiorespiratory fitness, currently, a lack of research exists that validates the effectiveness of the 6-minute walk test, specifically in the Korean population. Therefore, the purpose of this study was to verify the validity of the 6-minute walk test for Korean older individuals and to develop a maximum oxygen consumption (VO&lt;sub&gt;2max&lt;/sub&gt;) prediction equation.METHODS: A total of 167 participants were included in the final analysis, after excluding 33 of the 200 participants. Moreover, VO&lt;sub&gt;2max&lt;/sub&gt; was measured by performing a submaximal exercise test on a treadmill, and the total distance and heart rate were measured using a 6-minute walk test. Pearson’s correlation coefficient was calculated to verify the criterion validity between VO&lt;sub&gt;2max&lt;/sub&gt; and total distance in the 6-minute walk test. To develop a VO&lt;sub&gt;2max&lt;/sub&gt; prediction equation, multiple regression analysis was conducted and cross-validation of the developed prediction equation was confirmed.RESULTS: The correlation coefficient between VO&lt;sub&gt;2max&lt;/sub&gt; and the 6-minute walk test was 0.575 (&lt;i&gt;p&lt;/i&gt;&lt;.001). The adjusted R2 of the VO&lt;sub&gt;2max&lt;/sub&gt; prediction equation using the 6-minute walk test was 0.449 (&lt;i&gt;p&lt;/i&gt;&lt;.001). The difference between the predicted VO&lt;sub&gt;2max&lt;/sub&gt; and measured VO&lt;sub&gt;2max&lt;/sub&gt; was 1.184±1.331 mL/kg/min, and the correlation coefficient was 0.594 (&lt;i&gt;p&lt;/i&gt;&lt;.001).CONCLUSION: The developed prediction equation consisted of explanatory variables that can be measured easily and were practical in the field. As entry into a post-aged society is imminent, managing older adult’s physical fitness has become a significant issue. In the future, if the validity verification is performed with a large number of people, the prediction formula developed in this study will be useful.

Cardiopulmonary Performance Among Heart Failure Patients Before and After Left Ventricular Assist Device Implantation

BackgroundPatients with heart failure with reduced ejection fraction (HFrEF) have persistent impairments in functional capacity after continuous-flow left ventricular assist device (CF-LVAD) implantation. ObjectivesThis study aims to characterize longitudinal changes in exercise hemodynamics and functional capacity among patients with HFrEF before and after CF-LVAD implantation. MethodsTen patients underwent 3 invasive cardiopulmonary exercise tests on upright cycle ergometry with pulmonary artery catheterization: 1) Visit 1 before CF-LVAD implantation; 2) Visit 2 after device implantation with CF-LVAD pump speed held constant at baseline speed; and 3) Visit 3 with increases in pump speed during exercise (median: 1,050 rpm [IQR: 750-1,150 rpm] and 220 rpm [IQR: 120-220 rpm] for HeartMate 3 and HeartWare VAD, respectively). Hemodynamics and direct Fick cardiac output were monitored using pulmonary artery catheterization. Gas exchange metrics were determined using indirect calorimetry. ResultsMaximal oxygen uptake (Visits 1, 2, and 3: 10.8 ± 2.5 mL/kg/min, 10.7 ± 2.2 mL/kg/min, and 11.5 ± 1.7 mL/kg/min; P = 0.92) did not improve after device implantation. Mean pulmonary arterial and pulmonary capillary wedge pressures increased significantly during submaximal and peak exercise on preimplantation testing (P < 0.01 for rest vs peak exercise) and remained elevated, with minimal change on Visits 2 and 3 regardless of whether pump speed was fixed or increased. ConclusionsAmong patients with HFrEF, cardiovascular hemodynamics and exercise capacity were similar after CF-LVAD implantation, regardless of whether patients exercised at fixed or adjusted pump speeds during exercise. Further research is needed to determine methods by which LVADs may alleviate the HFrEF syndrome after device implantation. (Effect of mechanIcal circulatoRy support ON exercise capacity aMong pAtieNts with heart failure [IRONMAN]; NCT03078972)

The fourth dimension: physiological resilience as an independent determinant of endurance exercise performance.

Endurance exercise performance is known to be closely associated with the three physiological pillars of maximal O2 uptake ( ), economy or efficiency during submaximal exercise, and the fractional utilisation of (linked to metabolic/lactate threshold phenomena). However, while 'start line' values of these variables are collectively useful in predicting performance in endurance events such as the marathon, it is not widely appreciated that these variables are not static but are prone to significant deterioration as fatiguing endurance exercise proceeds. For example, the 'critical power' (CP), which is a composite of the highest achievable steady-state oxidative metabolic rate and efficiency (O2 cost per watt), may fall by an average of 10% following 2h of heavy intensity cycle exercise. Even more striking is that the extent of this deterioration displays appreciable inter-individual variability, with changes in CP ranging from <1% to ∼32%. The mechanistic basis for such differences in fatigue resistance or 'physiological resilience' are not resolved. However, resilience may be important in explaining superlative endurance performance and it has implications for the physiological evaluation of athletes and the design of interventions to enhance performance. This article presents new information concerning the dynamic plasticity of the three 'traditional' physiological variables and argues that physiological resilience should be considered as an additional component, or fourth dimension, in models of endurance exercise performance.

Soluble Transferrin Receptor as Iron Deficiency Biomarker: Impact on Exercise Capacity in Heart Failure Patients.

The soluble transferrin receptor (sTfR) is a marker of tissue iron status, which could indicate an increased iron demand at the tissue level. The impact of sTfR levels on functional capacity and quality of life (QoL) in non-anemic heart failure (HF) patients with otherwise normal systemic iron status has not been evaluated. We conducted an observational, prospective, cohort study of 1236 patients with chronic HF. We selected patients with normal hemoglobin levels and normal systemic iron status. Tissue iron deficiency (ID) was defined as levels of sTfR > 75th percentile (1.63 mg per L). The primary endpoints were the distance walked in the 6 min walking test (6MWT) and the overall summary score (OSS) of the Minnesota Living with Heart Failure Questionnaire (MLHFQ). The final study cohort consisted of 215 patients. Overall QoL was significantly worse (51 ± 27 vs. 39 ± 20, p-value = 0.006, respectively), and the 6 MWT distance was significantly worse in patients with tissue ID when compared to patients without tissue ID (206 ± 179 m vs. 314 ± 155, p-value < 0.0001, respectively). Higher sTfR levels, indicating increased iron demand, were associated with a shorter distance in the 6 MWT (standardized β = -0.249, p < 0.001) and a higher MLHFQ OSS (standardized β = 0.183, p-value = 0.008). In this study, we show that in patients with normal systemic iron parameters, higher levels of sTfR are strongly associated with an impaired submaximal exercise capacity and with worse QoL.

Adding objectivity to submaximal exercise testing by assessment of heart rate recovery at home—a healthy volunteer study iv (search-iv)

Adding objectivity to submaximal exercise testing by assessment of heart rate recovery at home—a healthy volunteer study iv (search-iv)

Acute Changes on Left Atrial Function during Incremental Exercise in Patients with Heart Failure with Mildly Reduced Ejection Fraction: A Case-Control Study.

the aim of this study was to assess acute changes in left atrial (LA) function during incremental aerobic exercise in patients with heart failure with mildly reduced ejection fraction (HFmrEF) in comparison to healthy subjects (HS). twenty patients with established HFmrEF were compared with 10 HS, age-matched controls. All subjects performed a stepwise exercise test on a cycle ergometer. Echocardiography was performed at baseline, during submaximal effort, at peak of exercise, and after 5 min of recovery. HS obtained a higher value of METs at peak exercise than HFmrEF (7.4 vs. 5.6; between group p = 0.002). Heart rate and systolic blood pressure presented a greater increase in the HS group than in HFmrEF (between groups p = 0.006 and 0.003, respectively). In the HFmrEF group, peak atrial longitudinal strain (PALS) and conduit strain were both increased at submaximal exercise (p < 0.05 for both versus baseline) and remained constant at peak exercise. Peak atrial contraction strain (PACS) did not show significant changes during the exercise. In the HS group, PALS and PACS increased significantly at submaximal level (p < 0.05 for both versus baseline), but PALS returned near baseline values at peak exercise; conduit strain decreased progressively during the exercise in HS. Stroke volume (SV) increased in both groups at submaximal exercise; at peak exercise, SV remained constant in the HFmrEF, while it decreased in controls (between groups p = 0.002). patients with HFmrEF show a proper increase in LA reservoir function during incremental aerobic exercise that contributes to maintain SV throughout the physical effort.

AltitudeOmics: effects of 16 days acclimatization to hypobaric hypoxia on muscle oxygen extraction during incremental exercise.

Acute altitude exposure lowers arterial oxygen content ([Formula: see text]) and cardiac output ([Formula: see text]) at peak exercise, whereas O2 extraction from blood to working muscles remains similar. Acclimatization normalizes [Formula: see text] but not peak [Formula: see text] nor peak oxygen consumption (V̇o2peak). To what extent acclimatization impacts muscle O2 extraction remains unresolved. Twenty-one sea-level residents performed an incremental cycling exercise to exhaustion near sea level (SL), in acute (ALT1) and chronic (ALT16) hypoxia (5,260 m). Arterial blood gases, gas exchange at the mouth and oxy- (O2Hb) and deoxyhemoglobin (HHb) of the vastus lateralis were recorded to assess arterial O2 content ([Formula: see text]), [Formula: see text], and V̇o2. The HHb-V̇o2 slope was taken as a surrogate for muscle O2 extraction. During moderate-intensity exercise, HHb-V̇o2 slope increased to a comparable extent at ALT1 (2.13 ± 0.94) and ALT16 (2.03 ± 0.88) compared with SL (1.27 ± 0.12), indicating increased O2 extraction. However, the HHb/[Formula: see text] ratio increased from SL to ALT1 and then tended to go back to SL values at ALT16. During high-intensity exercise, HHb-V̇o2 slope reached a break point beyond which it decreased at SL and ALT1, but not at ALT16. Increased muscle O2 extraction during submaximal exercise was associated with decreased [Formula: see text] in acute hypoxia. The significantly greater muscle O2 extraction during maximal exercise in chronic hypoxia is suggestive of an O2 reserve.NEW & NOTEWORTHY During incremental exercise muscle deoxyhemoglobin (HHb) and oxygen consumption (V̇o2) both increase linearly, and the slope of their relationship is an indirect index of local muscle O2 extraction. The latter was assessed at sea level, in acute and during chronic exposure to 5,260 m. The demonstrated presence of a muscle O2 extraction reserve during chronic exposure is coherent with previous studies indicating both limited muscle oxidative capacity and decrease in motor drive.

Interleukin-6 in Patients With Heart Failure and Preserved Ejection Fraction

BackgroundInterleukin (IL)-6 is a central inflammatory mediator and potential therapeutic target in heart failure (HF). Prior studies have shown that IL-6 concentrations are elevated in patients with HF, but much fewer data are available in heart failure with preserved ejection fraction (HFpEF). ObjectivesThis study aims to determine how IL-6 relates to changes in cardiac function, congestion, body composition, and exercise tolerance in HFpEF. MethodsClinical, laboratory, body composition, exercise capacity, physiologic and health status data across 4 National Heart, Lung, and Blood Institute–sponsored trials were analyzed according to the tertiles of IL-6. ResultsIL-6 was measured in 374 patients with HFpEF. Patients with highest IL-6 levels had greater body mass index; higher N-terminal pro–B-type natriuretic peptide, C-reactive protein, and tumor necrosis factor-α levels; worse renal function; and lower hemoglobin levels, and were more likely to have diabetes. Although cardiac structure and function measured at rest were similar, patients with HFpEF and highest IL-6 concentrations had more severely impaired peak oxygen consumption (12.3 ± 3.3 mL/kg/min 13.1 ± 3.1 mL/kg/min 14.4 ± 3.9 mL/kg/min, P < 0.0001) as well as 6-minute walk distance (276 ± 107 m vs 332 ± 106 m vs 352 ± 116 m, P < 0.0001), even after accounting for increases in IL-6 related to excess body mass. IL-6 concentrations were associated with increases in total body fat and trunk fat, more severe symptoms during submaximal exercise, and poorer patient-reported health status. ConclusionsIL-6 levels are commonly elevated in HFpEF, and are associated with greater symptom severity, poorer exercise capacity, and more upper body fat accumulation. These findings support testing the hypothesis that therapies that inhibit IL-6 in patients with HFpEF may improve clinical status. (Clinical Trial Registrations: Phosphodiesterase-5 Inhibition to Improve Clinical Status and Exercise Capacity in Diastolic Heart Failure [RELAX], NCT00763867; Nitrate’s Effect on Activity Tolerance in Heart Failure With Preserved Ejection Fraction, NCT02053493; Inorganic Nitrite Delivery to Improve Exercise Capacity in HFpEF, NCT02742129; Inorganic Nitrite to Enhance Benefits From Exercise Training in Heart Failure With Preserved Ejection Fraction [HFpEF], NCT02713126)

Telerehabilitation in patients with recent hospitalisation due to acute decompensated heart failure: protocol for the Tele-ADHF randomised controlled trial

BackgroundCardiac rehabilitation in patients with chronic heart failure (CHF) has favourable effects on exercise capacity, the risk at hospital (re-)admission and quality of life. Although cardiac rehabilitation is generally recommended it is still under-utilised in daily clinical practice, particularly in frail elderly patients after hospital admission, mainly due to low referral and patient-related barriers. Cardiac telerehabilitation (CTR) has the potential to partially solve these barriers. The purpose of this study is to evaluate the effects of CTR as compared to standard remote care after hospital admission on physical functional capacity in CHF patients.MethodsIn this randomised controlled trial, 64 CHF patients will be recruited during hospitalisation for acute decompensated heart failure, and randomised to CTR combined with remote patient management (RPM) or RPM alone (1:1). All participants will start with RPM after hospital discharge for early detection of deterioration, and will be up titrated to optimal medical therapy before being randomised. CTR will start after randomisation and consists of an 18-week multidisciplinary programme with exercise training by physical and occupational therapists, supported by a (remote) technology-assisted dietary intervention and mental health guiding by a physiologist. The training programme consists of three centre-based and two home-based video exercise training sessions followed by weekly video coaching. The mental health and dietary programme are executed using individual and group video sessions. A wrist-worn device enables remote coaching by the physical therapist. The web application is used for promoting self-management by the following modules: 1) goal setting, 2) progress tracking, 3) education, and 4) video and chat communication. The primary outcome measure is physical functional capacity evaluated by the Short Physical Performance Battery (SPPB) score. Secondary outcome measures include frailty scoring, recovery after submaximal exercise, subjective health status, compliance and acceptance to the rehabilitation programme, and readmission rate.DiscussionThe Tele-ADHF trial is the first prospective randomised controlled trial designed for evaluating the effects of a comprehensive combined RPM and CTR programme in recently hospitalised CHF patients. We hypothesize that this intervention has superior effects on physical functional capacity than RPM alone.Trial registrationNetherlands Trial Registry (NTR) NL9619, registered 21 July 2021.

The Between-Day Reliability of Correlation Properties of Heart Rate Variability During Running.

The short-term scaling exponent of detrended fluctuation analysis (DFA-a1) of heart rate variability may be a helpful tool to assess autonomic balance as a prelude to daily, individualized training. For this concept to be useful, between-session reliability should be acceptable. The aim of this study was to explore thereliability of DFA-a1 during a low-intensity exercise session in both a non-fatigued and a fatigued condition in healthy males and females. Ten participants completed two sessions with each containing an exhaustive treadmill ramp protocol. Before and after the fatiguing ramp, a standardized submaximal low-intensity exercise bout was performed during which DFA-a1, heart rate, and oxygen consumption (VO2) were measured. We compared between-session reliability of all metrics prior to the ramps (i.e., non-fatigued status) and after the first ramp (i.e., fatigued status). Intraclass correlation coefficients (ICC) with 95% confidence intervals (CI), the standard error of measurement, and the smallest worthwhile change (SWC) were determined. The ICC and SWC pre fatiguing ramp were 0.85 (95% CI 0.39-0.96) and 5.5% for DFA-a1, 0.85 (0.38-0.96) and 2.2% for heart rate, and 0.84 (0.31-0.96) and 3.1% for VO2. Post fatiguing ramp, the ICC and SWC were 0.55 (0.00-0.89) and 7.9% for DFA-a1, 0.91 (0.62-0.98) and 1.6% for heart rate, and 0.80 (0.17-0.95) and 3.0% for VO2. DFA-a1 shows generally acceptable to good between-session reliability with a SWC of 0.06 and 0.07 (5.5-7.9%) during non-fatigued and fatigued conditions. This suggests that this metric may be useful to inform on training readiness.

The impact of natural menstrual cycle and oral contraceptive pill phase on substrate oxidation during rest and acute submaximal aerobic exercise.

Previous research has identified sex differences in substrate oxidation during submaximal aerobic exercise including a lower respiratory exchange ratio (RER) in females compared with males. These differences may be related to differences in sex hormones. Our purpose was to examine the impact of the natural menstrual cycle (NAT) and second- and third-generation oral contraceptive pill (OCP2 and OCP3) cycle phases on substrate oxidation during rest and submaximal aerobic exercise. Fifty female participants (18 NAT, 17 OCP2, and 15 OCP3) performed two experimental trials that coincided with the low (i.e., nonactive pill/early follicular) and the high hormone (i.e., active pill/midluteal) phase of their cycle. RER and carbohydrate and lipid oxidation rates were determined from gas exchange measurements performed during 10 min of supine rest, 5 min of seated rest, and two 8-min bouts of submaximal cycling exercise at ∼40% and ∼65% of peak oxygen uptake (V̇o2peak). For all groups, there were no differences in RER between the low and high hormone phases during supine rest (0.73 ± 0.05 vs. 0.74 ± 0.05), seated rest (0.72 ± 0.04 vs. 0.72 ± 0.04), exercise at 40% (0.77 ± 0.04 vs. 0.78 ± 0.04), and 65% V̇o2peak (0.85 ± 0.04 vs. 0.86 ± 0.03; P > 0.19 for all). Similarly, carbohydrate and lipid oxidation rates remained largely unchanged across phases during both rest and exercise, apart from higher carbohydrate oxidation in NAT vs. OCP2 at 40% V̇o2peak (P = 0.019) and 65% V̇o2peak (P = 0.001). NAT and OCPs do not appear to largely influence substrate oxidation at rest and during acute submaximal aerobic exercise.NEW & NOTEWORTHY This study was the first to examine the influence of NAT and two generations of OCPs on substrate oxidation during rest and acute submaximal aerobic exercise. We reported no differences across cycle phases or groups on RER, and minimal impact on carbohydrate or lipid oxidation apart from an increase in carbohydrate oxidation in NAT compared with OCP2 during exercise. Based on these findings, NAT/OCP phase controls may not be necessary in studies investigating substrate oxidation.

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

Whole Body Substrate Metabolism during Different Exercise Intensities with Special Emphasis on Blood Protein Changes in Trained Subjects-A Pilot Study.

Contrary to carbohydrate and fat metabolism, the influence of a single exercise dose on protein metabolism has not been adequately explored yet. We assessed the effects of different exercise intensities and durations on blood protein changes and their association with carbohydrate (CHO) and fat metabolism in six eligible trained subjects. Subjects performed maximal incremental (IE100: at 100%VO2max) and submaximal continuous exercise (CE) at 75%VO2max for 30 min (CE75) and at 50%VO2max for 90 min (CE50). Blood samples were collected at rest (R), end of exercise (EE), and 1 h after recovery to assess blood urea nitrogen (BUN), plasma amino acids (AA), glucose, lactate, FFA, and glycerol. In IE100 blood lactate, CHO-oxidation (g/min), energy expenditure (kcal/min), and RER were significantly increased during rest (p < 0.05). CE50 induced significantly higher BUN, FFA, glycerol, and fat oxidation (g/min) (p < 0.05). At recovery, the mean sum of the free AA pool (µmol/L) reduced by 8% (p < 0.03) during CE50. Values for CE75 were between IE100 and CE50. Beside lipolysis, also proteolysis (BUN) was an important source of fuel for low-to-moderate intensity CE50. An increased uptake of AA from the plasma bed during CE50 suggests the importance for oxidation and synthesis of other metabolic sources such as gluconeogenesis necessary for recovery. Therefore, one needs to be cautious of protein diet following prolonged cycle exercise training.