Maximal Incremental Exercise Research Articles

Pattern of the heart rate performance curve in maximal graded treadmill running from 1100 healthy 18-65 Years old men and women: the 4HAIE study.

Introduction: The heart rate performance curve (HRPC) in maximal incremental cycle ergometer exercise demonstrated three different patterns such as downward, linear or inverse versions. The downward pattern was found to be the most common and therefore termed regular. These patterns were shown to differently influence exercise prescription, but no data are available for running. This study investigated the deflection of the HRPC in maximal graded treadmill tests (GXT) of the 4HAIE study. Methods: Additional to maximal values, the first and second ventilatory thresholds as well as the degree and the direction of the HRPC deflection (kHR) were determined from 1,100 individuals (489 women) GXTs. HRPC deflection was categorized as downward (kHR < -0.1), linear (-0.1 ≤ kHR ≤ 0.1) or inverse (kHR > 0.1) curves. Four (even split) age- and two (median split) performance-groups were used to investigate the effects of age and performance on the distribution of regular (= downward deflection) and non-regular (= linear or inverse course) HR curves for male and female subjects. Results: Men (age: 36.8 ± 11.9 years, BMI: 25.0 ± 3.3 kg m-2, VO2max: 46.4 ± 9.4 mL min-1. kg-1) and women (age: 36.2 ± 11.9 years, BMI: 23.3 ± 3.7 kg m-2, VO2max: 37.4 ± 7.8 mL min-1. kg-1) presented 556/449 (91/92%) downward deflecting, 10/8 (2/2%) linear and 45/32 (7/6%) inverse HRPC´s. Chi-squared analysis revealed a significantly higher number of non-regular HRPC´s in the low-performance group and with increasing age. Binary logistic regression revealed that the odds ratio (OR) to show a non-regular HRPC is significantly affected by maximum performance (OR = 0.840, 95% CI = 0.754-0.936, p = 0.002) and age (OR = 1.042, 95% CI = 1.020-1.064, p < 0.001) but not sex. Discussion: As in cycle ergometer exercise, three different patterns for the HRPC were identified from the maximal graded treadmill exercise with the highest frequency of regular downward deflecting curves. Older subjects and subjects with a lower performance level had a higher probability to show a non-regular linear or inverted curve which needs to be considered for exercise prescription.

Myocardial strain assessment by 2D Speckle Tracking to evaluate the effect of cardiac rehabilitation in patients with or without heart failure

Cardiac rehabilitation improves the subjective condition of the patient but little is known about associated structural and functional cardiac adaptations specifically the myocardial strain. To evaluate the impact of rehabilitation on structural and functional cardiac parameters using myocardial strain assessment by 2D Speckle Tracking. The study group consisted of 86 patients: 46 with heart failure with optimal medical treatment and 40 after acute myocardial infarction. A monocentric cohort study has included all patients who performed a 2-months cardiac rehabilitation program during 1 year. Clinical characteristics, a resting ECG, 2-dimensional Doppler echocardiography with tissue Doppler and strain imaging, and an incremental maximal exercise test on a bicycle ergometer were collected before and after the rehabilitation program. Paired student t-test for comparison and Pearson's correlation coefficient were used for the statistical analysis. Performance capacity was significantly improved after cardiac rehabilitation: performance in watts 112 W (±50) vs. 69.8 W (±34.5); effort test duration 10.7 min (±4.4) vs. 6.9 min (±3.1) and 6 min walking time 565 m (±127) vs. 496 m (±113). TEE parameters were significantly improved: LVFE 52.9% (±13) vs. 46.9% (±12.7), E/E’ 6.7 (±1.54) vs. 7.38 (±2.9). Significant difference of strain before and after cardiac rehabilitation 15.38% (+/4.72) vs. 14.12 (±4,79) has been also recorded. BNP level decreased by 29 ng/dL but not statistically significant from baseline. No significant correlation was found between biological, functional and TTE parameters. Strain imaging could be an interesting additional parameter to evaluate the positive response and structural improvement in patients with or without chronic heart failure who are undergoing cardiac rehabilitation (Table 1).

A computational predictor of the anaerobic mechanical power outputs from a clinical exercise stress test.

We previously were able to predict the anaerobic mechanical power outputs using features taken from a maximal incremental cardiopulmonary exercise stress test (CPET). Since a standard aerobic exercise stress test (with electrocardiogram and blood pressure measurements) has no gas exchange measurement and is more popular than CPET, our goal, in the current paper, was to investigate whether features taken from a clinical exercise stress test (GXT), either submaximal or maximal, can predict the anaerobic mechanical power outputs to the same level as we found with CPET variables. We have used data taken from young healthy subjects undergoing CPET aerobic test and the Wingate anaerobic test, and developed a computational predictive algorithm, based on greedy heuristic multiple linear regression, which enabled the prediction of the anaerobic mechanical power outputs from a corresponding GXT measures (exercise test time, treadmill speed and slope). We found that for submaximal GXT of 85% age predicted HRmax, a combination of 3 and 4 variables produced a correlation of r = 0.93 and r = 0.92 with % error equal to 15 ± 3 and 16 ± 3 on the validation set between real and predicted values of the peak and mean anaerobic mechanical power outputs (p < 0.001), respectively. For maximal GXT (100% of age predicted HRmax), a combination of 4 and 2 variables produced a correlation of r = 0.92 and r = 0.94 with % error equal to 12 ± 2 and 14 ± 3 on the validation set between real and predicted values of the peak and mean anaerobic mechanical power outputs (p < 0.001), respectively. The newly developed model allows to accurately predict the anaerobic mechanical power outputs from a standard, submaximal and maximal GXT. Nevertheless, in the current study the subjects were healthy, normal individuals and therefore the assessment of additional subjects is desirable for the development of a test applicable to other populations.

Cardiovascular Hemodynamic Response to Peak Exercise in Individuals with Multiple Sclerosis

Multiple sclerosis (MS) is a chronic, progressive neurological condition that results in physical disability brought about, in part, by decreased aerobic capacity. Physical disability and aerobic deconditioning may increase risks of cardiovascular morbidity and mortality. The reduction in aerobic capacity may be associated with low maximal heart rate and/or low cardiac output. Yet it is unclear if the cardiovascular hemodynamic response to peak exercise differs between individuals with and without MS who have similar aerobic capacities. Purpose: To compare the cardiovascular hemodynamic response to peak exercise between individuals with and without MS, with similar aerobic capacities. We hypothesized individuals with similar aerobic capacities would also exhibit similar hemodynamic responses, regardless of disease condition. Methods: Individuals with MS (n=14 (2 males), 38 ± 8 yrs, 24.6 ± 4.5 kg/m 2 ) and without MS (n=14 (1 male), 33 ± 9 yrs, 28.8 ± 13.8 kg/m 2 ) underwent maximal incremental cycle exercise test to assess maximal aerobic capacity (VO 2 peak). Heart rate (HR) was measured continuously via Polar Heart Rate Monitor. Ascending aortic blood flow velocity images (VTI) via continuous wave Doppler echocardiography, and brachial blood pressure (BP) via brachial sphygmomanometry were obtained every other minute of the exercise test. Stroke volume (SV) was calculated from VTI and the area of the aorta, cardiac output (Q) was calculated as SV × HR, and Mean arterial pressure (MAP) was calculated from BP. Maximal arteriovenous oxygen difference (avO2diff) was calculated as VO 2 peak ⁄ Q. Results: There was no significant difference in VO 2 peak between groups (MS: 30.8 ml/kg·min -1 vs CON: 28.2 ml/kg·min -1 , p=0.65). Both groups (MS and CON) had significant time (rest to peak) differences in SV (rest: MS = 74.6 ± 32.5 mL, CON = 65.7 ± 23.1 mL, peak: MS = 114.4 ± 42.4 mL, CON = 84.2 ± 33.3 mL; p&lt;0.001), HR (rest: MS = 65 ± 15 bpm, CON = 61 ± 10 bpm, peak: MS = 167 ± 13 bpm, CON = 175 ± 11 bpm; p&lt;0.001), Q (rest: MS = 4.7 ± 2.2 L/m, CON = 4.0 ± 1.3 L/m, peak: MS = 12.3 ± 5.0 L/min, CON = 12.3 ± 5.1 L/min; p&lt;0.001), and MAP (rest: MS = 84 ± 10 mmHg, CON = 83 ± 13 mmHg, peak: MS = 102 ± 7 mmHg, CON = 104 ± 17 mmHg, p &lt;0.001). There was also a significant group by time interaction in HR (p = 0.04), but no group by time interactions in SV, Q, or MAP. Finally, there was not significant difference in avO 2 diff between groups (MS: 2.3 ± 1.2 mL/100 mL vs CON: 2.7 ± 1.5 mL/100 mL). Conclusion: Our findings suggest that individuals with MS exhibit different cardiac hemodynamics to achieve maximal aerobic capacity than those without MS. Individuals with MS reached maximal Q via a slightly higher, although statistically non-significant, stroke volume but a lower HR. This suggests that people with MS may rely on different mechanisms for achieving VO2peak compared to controls, but future research is needed to elucidate this hemodynamic pattern. Department of Defense office of the Congressionally Directed Medical Research Program on Multiple Sclerosis 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.

Heliox improves minute-ventilation variability during incremental maximal exercise in COPD patients

Fundamento: A limitação do fluxo aéreo expiratório durante o exercício está presente em uma certa fração de pacientes com doença pulmonar obstrutiva crônica (DPOC) e está associada ao desempenho prejudicado do exercício. Objetivos: O objetivo deste estudo foi investigar se o Heliox normóxico (79% He-21%O 2 ) pode melhorar a variabilidade da ventilação minuto ( v V´E) em pacientes com DPOC. Métodos: Em um estudo cruzado duplo-cego, 13 homens não hipoxêmicos (FEV 1 = 36,1 + 9,32 previsto) realizaram testes cardiopulmonares incrementais até o limite de tolerância (T lim ) enquanto recebiam Heliox ou ar ambiente (AR). A análise da variabilidade ventilatória foi realizada com Poincaréanálises por SD 1 (desvio padrão 1) e SD 2 (desvio padrão 2), para ventilação minuto, volume corrente e frequência respiratória. As respostas da ventilação durante o exercício, o consumo de oxigênio e a tolerância ao exercício foram analisados. A resposta do débito cardíaco (QT) foi monitorada por cardiografia de impedância. Resultados: A ventilação com Heliox resultou em uma diminuição no consumo de oxigênio [V'O 2 , 1161,71 ± 351,11 vs. 1238,05 ± 330,93 mL/min, P &lt;0,05] e na produção de dióxido de carbono [V'CO 2, 1217,41 ± 300,90 vs. 1288,02 ± 321,66 mL/min, P &lt;0,05] em comparação com o ar ambiente, devido a um aumento na ventilação (35,37 ± 9,55 vs, 31,05 ± 7,75 L, P &lt;0,05) e na eficiência ventilatória após a inalação de Heliox ( 12,63 ± 2,91 vs 9,31 ± 4,15%, P &lt;0,05). As respostas da variabilidade da ventilação aumentaram significativamente com Heliox em comparação com o ar ambiente. Conclusões: Normóxico Heliox aumenta a variabilidade da ventilação minuto durante o exercício de alta intensidade em pacientes com DPOC moderada a grave.

NIRS-Derived Muscle-Deoxygenation and Microvascular Reactivity During Occlusion–Reperfusion at Rest Are Associated With Whole-Body Aerobic Fitness

ABSTRACT Purpose: Near-infrared spectroscopy (NIRS) indices during arterial occlusion–reperfusion maneuver have been used to examine the muscle’s oxidative metabolism and microvascular function—important determinants of whole-body aerobic-fitness. The association of NIRS-derived parameters with whole-body VO2max was previously examined using a method requiring exercise (or electrical stimulation) followed by multiple arterial occlusions. We examined whether NIRS-derived indices of muscle deoxygenation and microvascular reactivity assessed during a single occlusion–reperfusion at rest are (a) associated with maximal/submaximal indices of whole-body aerobic-fitness and (b) could discriminate individuals with different VO2max. We, also, investigated which NIRS-parameter during occlusion–reperfusion correlates best with whole-body aerobic-fitness. Methods: Twenty-five young individuals performed an arterial occlusion–reperfusion at rest. Changes in oxygenated- and deoxygenated-hemoglobin (O2Hb and HHb, respectively) in vastus-lateralis were monitored; adipose tissue thickness (ATT) at NIRS-application was assessed. Participants also underwent a maximal incremental exercise test for VO2max, maximal aerobic velocity (MAV), and ventilatory-thresholds (VTs) assessments. Results: The HHbslope and HHbmagnitude of increase (occlusion-phase) and O2Hbmagnitude of increase (reperfusion-phase) were strongly correlated with VO2max (r = .695–.763, p < .001) and moderately with MAV (r = .468–.530; p < .05). O2Hbmagnitude was moderately correlated with VTs (r = .399–.414; p < .05). After controlling for ATT, the correlations remained significant for VO2max (r = .672–.704; p < .001) and MAV (r = .407; p < .05). Individuals in the high percentiles after median and tritile splits for HHbslope and O2Hbmagnitude had significantly greater VO2max vs. those in low percentiles (p < .01–.05). The HHbslope during occlusion was the best predictor of VO2max. Conclusion: NIRS-derived muscle deoxygenation/reoxygenation indices during a single arterial occlusion–reperfusion maneuver are strongly associated with whole-body maximal indices of aerobic-fitness (VO2max, MAV) and may discriminate individuals with different VO2max.

Accuracy of the 20-m shuttle run test for individualizing exercise intensity of high-intensity interval training

The aim of the study was to investigate the accuracy of the 20 m shuttle run test (20mSRT) for the prescription of high-intensity interval training (HIIT) and to examine the appropriate intensity, prescribed by the 20mSRT end-test speed, for the execution of HIIT. Twenty physical education students (age: 22.4 ± 0.8 years, body height: 175.7 ± 8.9 cm, body weight: 73.8 ± 13.4 kg) participated in the study. On two separate occasions the participants were first tested with a maximal incremental exercise test and the 20mSRT. On another two occasions they were required to perform a 10-minute HIIT session comprised of 15-s runs interspersed with 15-s passive recovery. The intensities of the HIIT sessions were either 100% (T100%) or 110% (T110%) of the end-test speed reached in the 20mSRT. Mean oxygen uptake (VO2) (84.4 ± 5.5% vs 77.8 ± 6.9% of VO2max), mean heart rate (HR) (93 ± 2.8% vs 87.6 ± 4.6% of HRmax), blood lactate concentration (12.6 ± 2.1 vs 5.4 ± 2.6 mmol/l), and ratings of perceived exertion (9.5 ± 0.5 vs 6.7 ± 1) were all significantly (p&amp;lt;.01) higher during T110% vs T100%. The percentage of the total exercise time spent ≥ 90% VO2max (37.6 ± 25.3 vs 18.6 ± 18.0%, p&amp;lt;.05) and ≥ 90% HRmax (73.9 ± 17.7% vs 37.5 ± 33.3, p&amp;lt;.001) were also significantly higher during T110%. The mean VO2 and HR coefficient of variation during T110% were 6.5 and 3%, respectively. The cardiorespiratory, metabolic, and perceptual responses to T110% were reflective of the responses typical for HIIT, while T100% induced insufficient physiological stress to enable optimal cardiorespiratory adaptation. Therefore, the intensity of 110% 20mSRT is preferable for inducing the appropriate acute physiological responses and the 20mSRT can be used to accurately prescribe HIIT.

Myocardial strain assessment by 2D Speckle Tracking to evaluate the effect of cardiac rehabilitation in patients with or without heart failure

Cardiac rehabilitation improves the subjective condition of the patient, but little is known about associated structural and functional cardiac adaptations specifically the myocardial strain. To evaluate the impact of rehabilitation on structural and functional cardiac parameters using myocardial strain assessment by 2D Speckle Tracking. The study group consisted of 86 patients: 46 with heart failure with optimal medical treatment and 40 patients after acute myocardial infarction. A monocentric cohort study has included all patients who performed a 2-months cardiac rehabilitation program during one year. Clinical characteristics, a resting electrocardiogram, 2-dimensional Doppler echocardiography with tissue Doppler and strain imaging, and an incremental maximal exercise test on a bicycle ergometer were collected before and after the rehabilitation program. Paired Student t-test for comparison and Pearson's correlation coefficient were used for the statistical analysis. Eighty-six patients (46 with heart failure with optimal medical treatment and 40 patients after acute myocardial infarction) were included. Performance capacity was significantly improved after cardiac rehabilitation (Table 1): performance in watts 112 watts (±50) vs. 69.8 watts (±34.5); effort test duration 10.7 min (±4.4) vs. 6.9 min (±3.1) and 6 min walking time 565 m (±127) vs. 496 m (±113). Echographic parameters were also significantly improved: LVFE 52.9% (±13) vs. 46.9% (±12.7), E/E′ 6.7 (±1.54) vs. 7.38 (±2.9). Significant difference of strain before and after cardiac rehabilitation 15.38% (±4.72) vs. 14.12 (±4.79) has been also recorded. BNP level decreased by 29 ng/dL but not statistically significant from baseline. Nonetheless, no significant correlation was found between biological, functional and echocardiographic parameters. Both the performance capacity and left ventricular function on Doppler imaging were significantly improved in the 2 groups after the rehabilitation program in contrast to the BNP level. Strain imaging could be an interesting additional parameter to evaluate the positive response and structural improvement in patients with or without chronic heart failure who are undergoing cardiac rehabilitation.

The effect of tDCS on improving physical performance and attenuating effort perception during maximal dynamic exercise in non-athletes

ObjectivesThis study aimed to test the effects of transcranial direct current stimulation (tDCS), using different electrode positioning and montages, on physical performance in maximum incremental tests of healthy non-athlete subjects. DesignA double-blinded, crossover, sham-controlled study. MethodFifteen subjects (aged 25.8 ± 5 years, nine women) received one of five different tDCS protocols: (i) anodal tDCS on the primary motor cortex (M1) (a-tDCS/M1), (ii) anodal tDCS on the left temporal cortex (T3) (a-tDCS/T3), (iii) cathodal tDCS on M1 (c-tDCS/M1), (iv) cathodal on T3 (c-tDCS/T3), or (v) sham tDCS. The protocols were assigned in a random order in separate sessions. After tDCS, the volunteers performed the maximal incremental exercise test (MIT) on a cycle ergometer in each session. The following measures were used to evaluate physical performance (primary outcome) during MIT: time to exhaustion (TE), maximum power (MAX-P), and Borg Rating of Perceived Exertion (RPE) scale. In addition, as a secondary outcome measure, we assessed the lower-limb corticospinal excitability and electrical muscular activity. ResultstDCS applied over T3 or M1 did not influence electrical muscular activity or increase physical performance during MIT in healthy non-athlete subjects. However, our data confirmed that a-tDCS on the M1 increases lower-limb cortical excitability. ConclusionsOur results suggest that tDCS is not effective in improving performance during maximal dynamic exercise in non-athletes. However, we confirmed that the a-tDCS M1 protocol used in this study might increase cortical excitability in the lower limb motor cortex.

EXERCISE THERAPY TO COMBAT THE POSTACUTE SEQUELAE OF COVID-19: A CASE SERIES

EXERCISE THERAPY TO COMBAT THE POSTACUTE SEQUELAE OF COVID-19: A CASE SERIES

NO RELATIONSHIP BETWEEN PULMONARY FUNCTION AND EXERCISE CAPACITY IN PEOPLE WITH POSTACUTE SEQUELAE OF SARS-COV-2 INFECTION

NO RELATIONSHIP BETWEEN PULMONARY FUNCTION AND EXERCISE CAPACITY IN PEOPLE WITH POSTACUTE SEQUELAE OF SARS-COV-2 INFECTION

Comparison of Ventilatory and Blood Lactate Thresholds in Elite Soccer Players

Despite a long research history, the lactate threshold continues to be a widely controversial field. Notwithstanding the controversies and influence of multiple determinants, the estimation of lactate threshold in sports has been considered one of the essential parameters in the prescription of training intensity, load monitoring, and perfor- mance prediction. The study aimed to compare the anaerobic ventilatory and lactate thresholds as determined by different methods in elite soccer players. The study consisted of twenty-five division 1 elite soccer players. The players were separated into two groups based on their run times on the treadmill. Group 1 (age 24.38±7.33 years, height 180.33±7.03 cm, weight 75.53±7.68 kg) consisted of players who completed more than 17 minutes on the treadmill, while group 2 (age 25.11±6.07 years, height 182.11±10.03 cm, weight 79.72±7.54 kg) consisted of those who completed less than 17 minutes. The players completed an incremental maximal cardiopulmonary exercise testing from which ventilatory thresholds were determined. Furthermore, measurements of blood samples were obtained every 3 minutes after completing each stage of the test, with a total of 141 measurements completed. Multivariate tests indicated no significant differences in the speeds calculated with ventilatory and lactate thresh- old methods. These findings suggest that the anaerobic ventilatory threshold (VT2) can be used as an alternative to the invasive lactate threshold measurements. Therefore, identifying a threshold point without utilizing an inva- sive procedure enhances the potential application of the VT2 or respiratory compensation point.

Effect of individual characteristics and aerobic training on the %HRR-%V̇O2R relationship

ABSTRACT This study aimed to assess if, during incremental exercise, considering individual characteristics can make the relationship between the percentages of heart rate (HRR) and oxygen uptake (V̇O2R) reserve either 1:1 or more accurate. Cycle ergometer data of the maximal incremental exercise tests performed by 450 healthy and sedentary participants (17-66 years) of the HERITAGE Family Study, grouped for sex, ethnicity, age, body fat, resting HR, and V̇O2max, were used to calculate the individual linear regressions between %HRR and %V̇O2R. The mean slope and intercept of the individual linear regressions of each subgroup were compared with 1 and 0 (identity line), respectively, using Hotelling tests followed by post-hoc one-sample t-tests. Two multiple linear regressions were also performed, using either the slopes or intercepts of the individual linear regressions as dependent variables and sex, age, resting HR, and V̇O2max as independent variables. The mean %HRR-%V̇O2R relationships of all subgroups differed from the identity line. Moreover, individual linear regression intercepts (8.9 ± 16.0) and slopes (0.971 ± 0.190) changed (p < 0.001) after 20 weeks of aerobic training (13.1 ± 11.1 and 0.891 ± 0.122). The multiple linear regressions could explain only 3.8% and 1.3% of the variance in the intercepts and slopes, whose variability remained high (standard error of estimate of 15.8 and 0.189). In conclusion, the %HRR-%V̇O2R relationship differs from the identity line regardless of individual characteristics and their difference increased after aerobic training. Moreover, due to the high interindividual variability, using a single equation for the whole population seems not suitable for representing the %HRR-%V̇O2R relationship of a given subject, even when several individual characteristics are considered. Highlights The association between %HRR and %V̇O2R is not 1:1 even when individuals are grouped by age, sex, ethnicity, body composition, HRrest, and V̇O2max. Using several subject characteristics to identify the individual’s %HRR-%V̇O2R relationship does not meaningfully increase its prediction accuracy or reduce the interindividual variability of %HRR-%V̇O2R relationships Using a single equation for the whole population is not suitable for representing the relationship of a given subject; hence, individual relationships should be preferred when prescribing the intensity of aerobic exercise. The individual %HRR-%V̇O2R relationship should be periodically assessed due to the potential training induced changes in the relationship.

Relationship Between Skin Temperature Response And Metabolic Flexibility In Endurance Runners And Professional Soccer Players

During endurance exercise, skin temperature (Tsk) plays a fundamental role in thermoregulation and might be influenced by aerobic fitness (VO2peak) and metabolic flexibility, both powerful predictors of athletic performance. PURPOSE: The aim was to study the correlation between Tsk response and metabolic flexibility and stress by measuring blood lactate concentrations ([La-]), fat oxidation (FATox) and carbohydrate oxidation (CHOox) rates in highly trained (HT) competitive endurance runners, moderately active (MA) runners and professional soccer (PS) players. METHODS: we used indirect calorimetry, [La-] measurements, and monitored the Tsk response in HT (n = 22; VO2peak = 58.57 ± 2.33 ml/kg/min), MA (n = 20; VO2peak = 49.07 ± 4.67 ml/kg/min), and PS (n = 23; VO2peak = 53.34 ± 3.67 ml/kg/min) during an incremental maximal treadmill test (3-min intervals) until exhaustion, followed by a recovery period of five minutes. Descriptive were obtained for all variables. One-way ANOVA with post-hoc Bonferroni test were performed to compare the groups, and Pearson’s r correlation coefficients to assess the relationships among the variables studied. RESULTS: MA group exhibited lower VO2peak, Speedpeak, and higher BMI and fat mass % (all p < 0.05) than both HT and PS groups. Average FATox rates and Tsk were significantly higher in HT (0.30 ± 0.08 g.min-1; 35.55 ± 0.48 °C) and PS (0.23 ± 0.13 g.min-1; 35.62 ± 0.50 °C) compared with the MA (0.19 ± 0.11 g.min-1; 34.98 ± 0.50 °C) group, respectively (all p < 0.001). Significant correlations were found between [La-] and Tsk for each group (HT: r = 0.572; MA: r = 0.589; PS: r = 0.603), and there were correlations among the average [La-] and the average rates of FATox across the three groups studied (p < 0.05). CONCLUSIONS: These findings indicate that higher VO2peak and FATox rates and lower [La-] were associated with increased Tsk during incremental maximal exercise across individuals of widely different metabolic capabilities. Tsk seems to be a valid biomarker for metabolic fitness, as well as an attractive concept for the assessment and monitoring of athletes during competition. Furthermore, our data show significant differences which should be taken into account when developing individualized strategies for both nutrition and training in order to enhance athletic performance.

Performance fatigability and recovery after dynamic multi-joint maximal exercise in elbow flexors versus knee extensors.

Elbow flexors (EFs) and knee extensors (KEs) have shown differences in performance fatigability and recovery of neuromuscular function after isometric and isotonic single-joint fatiguing contractions. However, dynamic multi-joint movements are more representative of real-world activities. The aim of the study was to assess central and peripheral mechanisms of fatigability after either arm-cranking or cycling. Ten physically active men performed maximal incremental arm-cranking and cycling until task failure. Maximal voluntary isometric contraction (MVIC) and electrically evoked forces of both EF and KE were assessed before (PRE) and 1 (POST) and 20 (POST20) min after exercise. At POST, MVIC decreased similarly to 76 ± 8% and 81 ± 7% (both P < 0.001) of PRE for EF and KE, respectively. MVIC force remained lower than PRE at POST20 for both EF and KE (85 ± 8% vs. 95 ± 3% of PRE, P ≤ 0.033), having recovered less in EF than in KE (P = 0.003). Electrically evoked forces decreased similarly from PRE to POST in EF and KE (all P > 0.05). At POST20, the ratio of low-to-high frequency doublets was lower in EF than in KE (75 ± 13% vs. 85 ± 10% of PRE; P ≤ 0.034). Dynamic maximal incremental exercise acutely induced similar magnitudes of MVIC and evoked force loss in EF and KE. However, at POST20, impaired MVIC recovery and lower ratio of low-to-high frequency doublets in EF than in KE suggest the recovery of neuromuscular function after dynamic maximal exercises is specific to and dependent on changes within the muscles investigated.

Age‐Associated Changes in Autophagy in Peripheral Blood Mononuclear Cells following Maximal Exercise: Preliminary Observations

Aging represents the progressive deterioration in the efficacy of cellular survival mechanisms, including the important mechanism of autophagy. Deficiencies in autophagic function, which occur with increasing age, may contribute to the development of many diseases, including neurodegeneration, cardiovascular diseases, and the development of various cancers. Thus, it is imperative to understand the regulation of autophagy in the context of human physiology. Of note, it is suggested that engaging in exercise represents an optimal strategy to improve autophagic function, which may help explain the many health benefits associated with regular exercise. During acute cellular stress, such as exercise, autophagy degrades misfolded or damaged proteins to provide the base constituents (i.e. amino acids) for cellular energy production. Although, until the past decade, few studies have examined the autophagic response to exercise in humans. We have recently demonstrated that exercise‐induced autophagy is intensity‐dependent, with greater intensities required to elicit an increase in autophagic flux, as indicated by elevated levels of microtubule‐associated protein 1 light chain 3 beta (LC3‐II). However, no known studies have evaluated the autophagic response to maximal exercise in humans, and it is unknown if this response is altered by aging. Therefore, we aimed to examine whether autophagy would increase in response to an acute (&lt;15 min) incremental maximal exercise bout in peripheral blood mononuclear cells (PBMCs), and if this response would be altered in older adults. We evaluated the hypothesis that autophagy would increase in response to maximal exercise and that young adults would display greater elevations in autophagy than their older counterparts. To test this hypothesis, PBMCs were collected from 8 young (mean [SD], 20 [2.1] years; 4 women, 4 men) and 8 older (66 [5.5] years; 4 women, 4 men) adults before and immediately after a graded maximal exercise test performed on a semi‐recumbent cycle ergometer. The autophagic marker LC3‐II was assessed by Western blotting, which was normalized to β‐actin (an internal loading control) and reported as a fold change relative to its respective baseline. Data were analyzed using unpaired t‐tests with an alpha set at 0.05. Peak oxygen consumption (VO2peak) was significantly higher in young (41.6 [10.3] ml/kg/min) compared to older (30.3 [6.6] ml/kg/min) adults (p=0.02). Immediately following the maximal exercise bout, an increase in LC3‐II was observed in both young (1.64 [0.45], p=0.005) and older (1.21, [0.24] p=0.048) adults. When comparing between groups, the relative increase in LC3‐II was significantly greater (+27%) in young compared to older adults (p=0.03). Taken together, our preliminary findings show that autophagy is elevated in response to maximal exercise in young and older adults, albeit to a lesser extent in older adults, suggesting an impaired ability to respond to cellular stress. Further research is necessary to understand the mechanisms underlying age‐related impairments in autophagy in older adults and if these responses can be restored.

Physical Activity Capacity Assessment of Patients with Chronic Disease and the Six-Minute Walk Test: A Cross-Sectional Study.

Background: This study aimed to evaluate the efficacy of the Six-Minute Walk Test (6MWT) to determine the physical activity capacities of patients with chronic disease. Methods: For this cross-sectional study, we investigated 156 patients with chronic disease and no beta-blocker treatment. They systematically performed a maximal cardiopulmonary exercise test to determine their heart rate peak (HRPeak) and maximal oxygen uptake (V’O2max). We considered two groups of patients based upon the results of the functional evaluation of exercise performance: (1) No limitation in exercise performance (V’O2max greater or equal to 80% of the theoretical reference) and (2) limited exercise performance (V’O2max less than 80% of the theoretical value). All patients also received a 6MWT on the same day as the exercise test. Results: We found 68 (43.6%) patients with normal exercise capacities and 88 (56.4%) patients with limited exercise performance. In this sample, 6MWT mean distances were 510 (87) and 506 (86) m, respectively. There were no significant differences between the two groups for distance and end-test heart rate. The correlation between matrix V’O2max measured during the maximal incremental exercise test and the 6MWT distance displayed a positive slope (r = 0.549 CI95 [0.431–0.656]—p < 0.001). Conclusion: Our results showed a moderate relationship between 6MWT and physical activity capacity for patients with chronic disease.

Perceptual and Ventilatory Responses to Hypercapnia in Athletes and Sedentary Individuals.

PurposeHypercapnic chemosensitivity traditionally captures the ventilatory response to elevated pressures of carbon dioxide in the blood. However, hypercapnia also contributes to subjective breathing perceptions, and previously we demonstrated a closer matching of perception to changes in ventilation in athletes compared to controls. Here we investigated any potential underlying hypercapnic chemosensitivity differences between groups, and explored whether these measures relate to ventilatory and perceptual responses during exercise as well as trait levels of affect.MethodsA hypercapnic challenge, incremental maximal exercise test and affective questionnaires were completed by 20 endurance athletes and 20 age-/sex-matched sedentary controls. The hypercapnic challenge involved elevating end-tidal PCO2 by 0.8% (6.1 mmHg) and 1.5% (11.2 mmHg) for 3 min each (randomised), with constant end-tidal oxygen. Ventilatory and perceptual responses to hypercapnia were compared between groups, and within each group the relationships between hypercapnic chemosensitivity (slope analyses) and exercising ventilation and perceptions were calculated using Spearman’s non-parametric correlations.ResultsWhile absolute ventilation differences during hypercapnia and exercise were observed, no group differences were found across hypercapnic chemosensitivity (slope) measures. Correlation analyses revealed the anxiety hypercapnic response was related to maximal exercise anxiety, but only in sedentary individuals.ConclusionVentilatory and perceptual hypercapnic chemosensitivity do not differ between athletes and sedentary individuals. However, ventilatory and anxiety hypercapnic chemosensitivities were related to ventilatory and anxiety responses during exercise in untrained individuals only. Athletes may employ additional strategies during exercise to reduce the influence of chemosensitivity on ventilatory and perceptual responses.

Systolic and diastolic function during cycling at the respiratory threshold between elderly and young healthy individuals

The hemodynamic consequences of aging have been extensively investigated during maximal incremental exercise. However, less is known about the effects of aging on hemodynamics during submaximal steady-state exercise. The aim of the present investigation was to compare the hemodynamics of healthy elderly and young subjects during an exercise bout conducted at the gas threshold (GET) intensity. Two groups of healthy, physically active subjects were studied: the elderly group—EG (n = 11; > 60 years old) and the young group—YG (n = 13; < 35 years old). Both groups performed a 5-min rectangular exercise test at the GET intensity. Hemodynamics were measured using echocardiography. The main finding was that stroke volume responses were higher in the YG than the EG (72.5 ± 16.7 vs. 52.4 ± 8.4 ml, respectively). The increased stroke volume capacity in the YG was the consequence of a greater capacity to increase cardiac preload and contractility and, to a lesser extent, to reduce systemic vascular resistance. Importantly, the atrial contribution to ventricular diastolic filling was substantially higher in the YG when compared to the EG.

Dietary Nitrate Supplementation Does Not Alter Exercise Efficiency at High Altitude - Further Results From the Xtreme Alps Study.

IntroductionNitrate supplementation in the form of beetroot juice (BRJ) ingestion has been shown to improve exercise tolerance during acute hypoxia, but its effect on exercise physiology remains unstudied during sustained terrestrial high altitude exposure. We hypothesized that performing exercise at high altitude would lower circulating nitrate and nitrite levels and that BRJ ingestion would reverse this phenomenon while concomitantly improving key determinants of aerobic exercise performance.MethodsTwenty seven healthy volunteers (21 male) underwent a series of exercise tests at sea level (SL, London, 75 m) and again after 5–8 days at high altitude (HA, Capanna Regina Margherita or “Margherita Hut,” 4,559 m). Using a double-blind protocol, participants were randomized to consume a beetroot/fruit juice beverage (three doses per day) with high levels of nitrate (∼0.18 mmol/kg/day) or a nitrate-depleted placebo (∼11.5 μmoles/kg/day) control drink, from 3 days prior to the exercise trials until completion. Submaximal constant work rate cycle tests were performed to determine exercise efficiency and a maximal incremental ramp exercise test was undertaken to measure aerobic capacity, using breath-by-breath pulmonary gas exchange measurements throughout. Concentrations of nitrate, nitrite and nitrosation products were quantified in plasma samples collected at 5 timepoints during the constant work rate tests. Linear mixed modeling was used to analyze data.ResultsAt both SL and HA, plasma nitrate concentrations were elevated in the nitrate supplementation group compared to placebo (P < 0.001) but did not change throughout increasing exercise work rate. Delta exercise efficiency was not altered by altitude exposure (P = 0.072) or nitrate supplementation (P = 0.836). V̇O2peak decreased by 24% at high altitude (P < 0.001) and was lower in the nitrate-supplemented group at both sea level and high altitude compared to placebo (P = 0.041). Dietary nitrate supplementation did not alter other peak exercise variables or oxygen consumption at anaerobic threshold. Circulating nitrite and S-nitrosothiol levels unexpectedly rose in a few individuals right after cessation of exercise at high altitude.ConclusionWhilst regularly consumed during an 8 days expedition to terrestrial high altitude, nitrate supplementation did not alter exercise efficiency and other exercise physiological variables, except decreasing V̇O2peak. These results and those of others question the practical utility of BRJ consumption during prolonged altitude exposure.