Maximal Incremental Exercise Test Research Articles

Breathing variability during running in athletes: The role of sex, exercise intensity and breathing reserve

Highly trained aerobic athletes progressively use most of their breathing reserve with increased exercise intensity during whole-body exercise. Additionally, females typically present proportionally smaller lungs than males. Therefore, sex, exercise intensity, and breathing reserve use likely influence the volume and time in which respiratory parameters vary between consecutive breaths during whole-body exercise. However, breath-by-breath variability has been scarcely investigated during exercise. Accordingly, we sought to investigate breath-by-breath pulmonary ventilation (V̇E), tidal volume (VT), and respiratory frequency (fR) variability during a maximal treadmill incremental exercise test in 17 females and 18 males highly trained professional endurance runners. The breath-by-breath variability was analyzed by root mean square of successive differences (RMSSD) within 1-minute windows. Females had lower absolute and percent predicted forced expiratory volume in one second (FEV1) and forced vital capacity (FVC) than males, as well as lower height-adjusted absolute FVC than males. V̇E and VT reserve use were similar between the sexes at peak exercise. While RMSSDV̇E and RMSSDfR did not change over exercise (P > 0.05), RMSSDVT progressively decreased (P < 0.001). RMSSDVT was negatively correlated with VT reserve use only in males. Females showed lower RMSSDV̇E than males during the entire exercise test (P < 0.001). At iso-V̇E reserve use, between-sex differences in RMSSDV̇E persisted (P = 0.003). Our findings indicate that exercise intensity decreases VT variability in professional runners, which is linked to VT reserve use in males but not females. Additionally, the female sex lowers V̇E variability regardless of exercise intensity and V̇E reserve use.

Recovery of heart rate and heartrate variability after a maximal cardiopulmonary exercise test in novice female runners.

Previous studies have shown delayed cardiac vagal reactivation after high-intensity endurance exercise when estimated with heartrate variability (HRV). However, the recovery dynamics of RR intervals (RRI) and HRV after a maximal incremental exercise test have been studied less in non-athletic population and especially in females. The main aim of the study was to examine the recovery dynamics of RRI and HRV immediately after a maximal cardiopulmonary exercise test (CPET) in adult females. Twenty-eight healthy, novice recreational female runners (33.7 ± 4.2years) were selected to participate in this study from a larger group of participants (Run RCT). RRIs were collected continuously during a controlled rest, a CPET on a treadmill and a 15-min controlled, passive recovery. Minute-by-minute recovery dynamics were analyzed. The dynamic phase of RRI and heart rate recovery (HRR) (from 192.2 ± 9.9 to 111.4 ± 2.4, P < 0.001) occurred during the first 4.5min with HRR of 36 ± 10 beats during the first minute of the recovery. Resting heart rate was negatively associated (r = - 0.53, P = 0.016) with HRR during the recovery. No recovery of root mean square of successive RRIs (RMSSD) was detected during the 15-min recovery. RMSSD was 15.0 ± 9.2% of resting values at the end of the recovery. No recovery of vagal-derived HRV was detected immediately after a CPET in novice recreational female runners despite marked changes in sympathovagal balance, detected by rapid recovery of RRI during the first 5min after exercise cessation.

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

Moderate-intensity aerobic exercise is safe and beneficial in atrial fibrillation (AF) and coronary heart disease (CHD). Irregular or rapid heart rates (HR) in AF and other heart conditions create a challenge to using HR to monitor exercise intensity. The purpose of this study was to assess the potential of breathing frequency (BF) to monitor exercise intensity in people with AF and CHD without AF. This observational study included 30 AF participants (19 Male, 70.7 ± 8.7 yrs) and 67 non-AF CHD participants (38 Male, 56.9 ± 11.4 yrs). All performed an incremental maximal exercise test with pulmonary gas exchange. Peak aerobic power in AF ( O2peak; 17.8 ± 5.0ml.kg-1.min-1) was lower than in CHD (26.7ml.kg-1.min-1) (p < .001). BFresponses in AF and CHD were similar (BF peak:AF34.6 ± 5.4 and CHD36.5 ± 5.0 breaths.min-1; p = .106);at the 1st ventilatory threshold (BF@VT-1: AF 23.2 ± 4.6; CHD 22.4 ± 4.6 breaths.min-1; p = .240). % O2peak at VT-1were similar inAF and CHD (AF: 59%; CHD: 57%; p = .656). With the use of wearable technologies on the rise, that now include BF, this first study provides an encouraging potential for BF to be used in AF and CHD. As the supporting data are based on incremental ramp protocol results, further research is required to assess BF validity to manage exercise intensity during longer bouts of exercise.

White Matter Microstructure of the Genu of the Corpus Callosum Measured Using Neurite Orientation Dispersion and Density Imaging (NODDI) Is Associated with Cardiorespiratory Fitness in Older Adults

Changes in white matter microstructure of the genu of the corpus callosum are predictive of cognitive decline in patients with mild cognitive impairment. Cardiorespiratory fitness (CRF) is positively associated with brain health; however, the relationship between cardiorespiratory fitness and white matter microstructure of the genu of the corpus callosum is unknown. Further, a novel diffusion method for assessing white matter microstructure, neurite orientation dispersion and density imaging (NODDI), can detect specific microstructural features that are not observed with conventional diffusion tensor imaging (DTI). Young (n=27, age=25±5, m=12, f=15) and older (n=23, age=64±5, m=12, f=11) adults free of underlying disease participated in this study. CRF was assessed using an incremental maximal exercise test on a cycle ergometer. On a separate visit, white matter microstructure of the genu of the corpus callosum was measured using both DTI and NODDI MRI scans. In young adults, there were no associations between CRF and white matter microstructure of the genu of the corpus callosum measured using either DTI or NODDI (p&gt;0.05). In older adults, there were no associations between CRF and white matter microstructure of the genu of the corpus callosum measured with DTI. However, in older adults, there was a positive association between CRF and orientation dispersion index of the genu of the corpus callosum measured with NODDI (r=0.47, p=0.02). In conclusion, using conventional DTI, no associations between CRF and white matter microstructure of the genu of the corpus callosum were observed. However, using NODDI, which can detect specific microstructural features, our results suggest that older adults with higher CRF demonstrated enhanced white matter microstructure, specifically orientation dispersion index, of the genu of the corpus callosum. Conventional DTI may underestimate the impact of CRF on age-related changes in white matter microstructure. National Institutes of Health - HL118154 (JNB), HL007936 (KBM). This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Determining V̇O2max in competitive swimmers: Comparing the validity and reliability of cycling, arm cranking, ergometer swimming, and tethered swimming

ObjectivesThis study aims to identify the optimal method for determining V̇O2max in competitive swimmers in terms of validity and test–retest reliability. DesignControlled experiment. MethodsTwenty competitive swimmers performed four maximal incremental exercise tests: cycling, arm cranking, ergometer swimming, and tethered swimming. Gas analysis was conducted to estimate V̇O2max. Validity was assessed in terms of the amount of variance of the performance on a 1500-m time trial explained by the estimated V̇O2max . Test–retest reliability was evaluated using the intraclass correlation coefficient (ICC). ResultsV̇O2max obtained from tethered swimming, ergometer swimming, and cycling explained a similar amount of variance of the 1500-m performance (R2 = 0.64, 0.64 and 0.65, respectively). However, ergometer swimming yielded significantly lower V̇O2max estimates (40.54 ± 6.55 ml/kg/min) than tethered swimming (54.40 ± 6.21 ml/kg/min) and cycling (54.39 ± 5.63 ml/kg/min). Arm cranking resulted in both a lower explained variance (R2 = 0.41) and a significantly lower V̇O2max (43.14 ± 7.81 ml/kg/min). Tethered swimming showed good reliability (ICC = 0.81). ConclusionsBicycle and tethered swimming tests demonstrated high validity with comparable V̇O2max estimates, explaining a large proportion of differences in endurance performance. Choosing between these two methods involves a trade-off between a higher practical applicability and reliability of the bicycle test and the more sport-specific nature of the tethered swimming test.

Impaired muscle oxygenation despite normal pulmonary function in type 2 diabetes without complications.

Long-term hyperglycemia in individuals with type 2 diabetes (T2D) can detrimentally impact pulmonary function and muscle oxygenation. As a result, these factors can impede the body's adaptation to physical exertion. We aimed to evaluate the oxygen pathway during maximal exercise among overweight/obese individuals with type 2 diabetes free from complications, in comparison with a group of matched overweight/obese individuals without diabetes, specifically concentrating on the effects on pulmonary function and muscle oxygenation. Fifteen overweight/obese adults with type 2 diabetes [glycated hemoglobin (HbA1c) = 8.3 ± 1.2%] and 15 matched overweight/obese adults without diabetes underwent pre- and post exercise lung function assessment. A maximal incremental exercise test was conducted, monitoring muscle oxygenation using near-infrared spectroscopy and collecting arterial blood gas samples. Both groups exhibited normal lung volumes at rest and after exercise. Spirometric lung function did not significantly differ pre- and post exercise in either group. During maximal exercise, the type 2 diabetes group showed significantly lower augmentation in total hemoglobin and deoxygenated hemoglobin compared with the control group. Despite comparable usual physical activity levels and comparable heart rates at exhaustion, the type 2 diabetes group had a lower peak oxygen consumption than controls. No significant differences were found in arterial blood gas analyses ([Formula: see text], [Formula: see text], [Formula: see text], and [Formula: see text]) between the groups. Individuals with type 2 diabetes free from complications displayed normal pulmonary function at rest and post exercise. However, impaired skeletal muscle oxygenation during exercise, resulting from reduced limb blood volume and altered muscle deoxygenation, may contribute to the lower V̇o2peak observed in this population.NEW & NOTEWORTHY Individuals with type 2 diabetes free from micro- and macrovascular complications have normal resting pulmonary function, but their V̇o2peak is impaired due to poor skeletal muscle oxygenation during exercise. Tailoring exercise regimes for this population should prioritize interventions aimed at enhancing muscle oxygenation and blood flow improvement.

Persistence of expiratory flow limitations between normoxia and hypoxia

Introduction&#x0D; Expiratory flow limitation (EFL) refers to the inability to generate higher airflow despite greater respiratory effort and is common in both men and women. In normoxic condition, EFL is contingent upon an imbalance between ventilatory demands and capacity. Since hypoxia is known to alter ventilatory drive and pattern, it may influence the development of EFL. Therefore, the aim of this study was to investigate the origin of EFL in hypoxia and its repeatability and persistence during exercise in hypoxia.&#x0D; Method&#x0D; Fifty-one healthy active individuals (27 men and 24 women) performed a lung function test and a maximal incremental exercise test on a cycle-ergometer in normoxia and hypoxia (inspired oxygen fraction = 0.14) on two separate visits. Ventilatory capacity, assessed using the slope ratio (SR), were evaluated from maximal flow volume curve analyses.&#x0D; Results&#x0D; During exercise in normoxia, 28 participants exhibited EFL (55%). Another set of 28 participants exhibited EFL in hypoxia but they were not all the same individuals as those in normoxia. In normoxia, both SR and maximum minute ventilation (V̇E) were higher in the EFL group than the non-EFL group (p = 0.029 and p &lt;0.001; respectively). However, in hypoxia, only maximum V̇E was higher in the EFL group compared to non-EFL group (p = 0.006).&#x0D; Participants were then classified into 4 groups according to the occurrence of EFL in both normoxia and hypoxia: non-EFL in both conditions (non-EFLN/H, n = 18), EFL in both conditions (EFLN/H, n = 23), EFL developed only in normoxia (EFLN+/H-, n = 5), EFL developed only in hypoxia (EFLN-/H+, n = 5).&#x0D; The EFLN+/H- group showed different V̇E changes between normoxia and hypoxia (-13.5 ± 7.8%) compared to the EFLN-/H+ (+6.7 ± 6.3%) and the non-EFLN/H groups (+5.1 ± 10.3%; p = 0.004 and p &lt; 0.001, respectively). The difference with the EFLN/H (-1.7 ± 8.0%) did not reach significance (p = 0.057). Breathing frequency changes between normoxia and hypoxia were different between the EFLN-/H+ group (+4.6 ± 12.9%) and the EFLN+/H- group (-11.7 ± 13.1%) (p = 0.039). Normoxia to hypoxia decrease in maximal oxygen uptake was not significantly larger in the EFL N+/H- group (-18.4 ± 3.4%) than in the EFL EFLN-/H+ group (-10.3 ± 5.4%; p = 0.087).&#x0D; Discussion/Conclusion&#x0D; Hypoxia altered EFL development since there was a shift in the individuals who exhibited flow limitation between normoxia and hypoxia. This can be attributed to the extent of ventilatory reserve utilization. Specifically, those who developed EFL exclusively in hypoxia exhibited a significant increase in V̇E whereas those with EFL only in normoxia experienced a significant decrease in V̇E. Notably in hypoxia, the ventilatory capacity did not differ between individuals with EFL and those without. This observation suggests that in hypoxia, the development of EFL relied more on ventilatory demands than on ventilatory capacity.

Performance metrics to predict national-level competition outcomes in a cluster of road cyclists

ABSTRACT Quantifying the pivotal elements that contribute to success in cycling and their strength, is of paramount importance in the formulation of sound and effective training regimens. Here we evaluated the power and differences of distinct performance indicators in predicting cycling competition outcomes. A total of 38 competitive male Lithuanian cyclists participated in this study, engaging in a maximal incremental exercise test, a cycling efficiency protocol, and a maximal sprint performance evaluation, from which multiple performance variables were derived. The cyclists were involved in two distinct competitions, where completion average speed and power profiles underwent analysis. Qualitative visual assessment was also employed to explore supplementary performance dimensions within these competitions. Notably, the principal explanatory variables for the two competitions were peak oxygen consumption relative to body mass (r = 0.74, p < 0.05) and cycling gross efficiency (r = 0.72, p < 0.05), respectively. Qualitative analysis unveiled divergences in terms of challenges and race dynamics inherent to the two competitions, while power profile comparisons yield no significant differences (p > 0.05). In conclusion, this study profiled Lithuanian cyclists, revealing power and differences among various performance metrics in predicting outcomes in diverse competitions. The comprehensive methodology highlighted the advantages of evaluating competition results, offering insights for improved training and tailored performance assessments.

Cycling through the ranks: a cross-sectional analysis of endurance, strength and body composition indicators in junior, elite, and amateur competitive road cyclists.

The objective of the present study was to compare different performance indicators, encompassing endurance, body composition, and maximal and explosive strength markers, among competitive Lithuanian cyclists across different age and performance categories. Thirty Lithuanian male cyclists in elite (EL, N.=10), amateur (AM, N.=10), and junior (JU, N.=10) categories underwent body composition analysis, knee extensors' isometric strength and ultrasound measurements, maximal incremental exercise tests, cycling efficiency protocol, and sprint performance evaluations. Additionally, competition results and power profiles were analyzed. EL cyclists had greater experience and higher annual kilometers (P<0.05). Quadriceps muscle size exhibited significant differences, being greater in EL than JU (P<0.05), whereas no noteworthy variations were observed in body fat or isometric strength. EL athletes demonstrated higher maximal oxygen consumption, maximal aerobic power, and sprint performance compared to JU and AM, particularly when considering absolute power metrics (P<0.05). Interestingly, despite JU achieving lower ranks in competitions, power profiles differed minimally between EL and JU. Furthermore, both JU and AM expended more energy during competitions (P<0.05). The study highlights disparities among Lithuanian cyclists, with EL cyclists showcasing advantages in endurance capacity and better competition outcomes, possibly due to their extensive experience, leading to a more efficient energy utilization. This research enhances our understanding of the multifaceted nature of the sport performance within the realm of Lithuanian cycling.

Attenuated peripheral oxygen extraction and greater cardiac output in women with posttraumatic stress disorder during exercise.

Posttraumatic stress disorder (PTSD) is associated with an increased risk of developing cardiovascular disease, especially in women. Evidence indicates that men with PTSD exhibit lower maximal oxygen uptake (V̇o2max) relative to controls; however, whether V̇o2max is blunted in women with PTSD remains unknown. Furthermore, it is unclear what determinants (i.e., central and/or peripheral) of V̇o2max are impacted by PTSD. Therefore, we evaluated the central (i.e., cardiac output; Q̇c) and peripheral (i.e., arteriovenous oxygen difference) determinants of V̇o2max in women with PTSD; hypothesizing that V̇o2max would be lower in women with PTSD compared with women without PTSD (controls), primarily due to smaller increases in stroke volume (SV), and therefore Q̇c. Oxygen uptake (V̇o2), heart rate (HR), Q̇c, SV, and arteriovenous oxygen difference were measured in women with PTSD (n = 14; mean [SD]: 43 [11] yr,) and controls (n = 17; 45 [11] yr) at rest, and during an incremental maximal treadmill exercise test, and the Q̇c/V̇o2 slope was calculated. V̇o2max was not different between women with and without PTSD (24.3 [5.6] vs. 26.4 [5.0] mL/kg/min; P = 0.265). However, women with PTSD had higher Q̇c [P = 0.002; primarily due to greater SV (P = 0.069), not HR (P = 0.285)], and lower arteriovenous oxygen difference (P = 0.002) throughout exercise compared with controls. Furthermore, the Q̇c/V̇o2 slope was steeper in women with PTSD relative to controls (6.6 [1.4] vs. 5.7 [1.0] AU; P = 0.033). Following maximal exercise, women with PTSD exhibited slower HR recovery than controls (P = 0.046). Thus, despite attenuated peripheral oxygen extraction, V̇o2max is not reduced in women with PTSD, likely due to larger increases in Q̇c.NEW & NOTEWORTHY The current study indicates that V̇o2max is not different between women with and without PTSD; however, women with PTSD exhibit blunted peripheral extraction of oxygen, thus requiring an increase in Q̇c to meet metabolic demand during exercise. Furthermore, following exercise, women with PTSD demonstrate impaired autonomic cardiovascular control relative to sedentary controls. We interpret these data to indicate that women with PTSD demonstrate aberrant cardiovascular responses during and immediately following fatiguing exercise.

The Effect of Skeletal Muscle Oxygenation on Hemodynamics, Cerebral Oxygenation and Activation, and Exercise Performance during Incremental Exercise to Exhaustion in Male Cyclists.

This study aimed to elucidate whether muscle blood flow restriction during maximal exercise is associated with alterations in hemodynamics, cerebral oxygenation, cerebral activation, and deterioration of exercise performance in male participants. Thirteen healthy males, cyclists (age 33 ± 2 yrs., body mass: 78.6 ± 2.5 kg, and body mass index: 25.57 ± 0.91 kg·m-1), performed a maximal incremental exercise test on a bicycle ergometer in two experimental conditions: (a) with muscle blood flow restriction through the application of thigh cuffs inflated at 120 mmHg (with cuffs, WC) and (b) without restriction (no cuffs, NC). Exercise performance significantly deteriorated with muscle blood flow restriction, as evidenced by the reductions in V˙O2max (-17 ± 2%, p < 0.001), peak power output (-28 ± 2%, p < 0.001), and time to exhaustion (-28 ± 2%, p < 0.001). Muscle oxygenated hemoglobin (Δ[O2Hb]) during exercise declined more in the NC condition (p < 0.01); however, at exhaustion, the magnitude of muscle oxygenation and muscle deoxygenation were similar between conditions (p > 0.05). At maximal effort, lower cerebral deoxygenated hemoglobin (Δ[HHb]) and cerebral total hemoglobin (Δ[THb]) were observed in WC (p < 0.001), accompanied by a lower cardiac output, heart rate, and stroke volume vs. the NC condition (p < 0.01), whereas systolic blood pressure, rating of perceived exertion, and cerebral activation (as assessed by electroencephalography (EEG) activity) were similar (p > 0.05) between conditions at task failure, despite marked differences in exercise duration, maximal aerobic power output, and V˙O2max. In conclusion, in trained cyclists, muscle blood flow restriction during an incremental cycling exercise test significantly limited exercise performance. Exercise intolerance with muscle blood flow restriction was mainly associated with attenuated cardiac responses, despite cerebral activation reaching similar maximal levels as without muscle blood flow restriction.

An Examination of Heart Rate Variability at Anaerobic Threshold and Respiratory Compensation Points During Cardiopulmonary Exercise Test

The aim of this study is to examine the changes in HRV values before, during (at AT and RC) and after maximal incremental cardiopulmonary exercise test. The sample comprised 121 healthy men who recreational do exercise 2-3 days a week. (age: 30.5 ± 4.6 years, height: 177.8 ± 6.1 cm; weight: 80.2 ± 10.2 kg). Anthropometric measurements were measured by using body analyzer, and aerobic capacities of participants were measured by using the cardiopulmonary exercise test via the Bruce protocol. According to this, heart rate variability recordings were taken at seven stages during the cardiopulmonary exercise test: before the test (1), at the beginning of the test (2), between the beginning of the test and the anaerobic threshold (3), at the anaerobic threshold (4), between the anaerobic threshold and the respiratory threshold (5), at the respiratory threshold (6), and finally (7), 30 seconds after the cardiopulmonary exercise test. Repeated measures analysis of variance (ANOVA) was used to compare the HRV values obtained from the test stages. In conclusion, using a gas analyzer during cardiovascular exercise testing, HRV values (MeanRR, SDNN, RMSSD, LFnu) determined at seven stages continue to decrease from the beginning. A rest period of 30 seconds (passive rest) immediately after completing the exercise does not seem to be sufficient for recovery. According to the results of this study, it can be considered that the sympathetic nervous system activity (LFnu) exhibits a more pronounced appearance at threshold zones.

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).

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.

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.

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.

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.

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.

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.