Maximal Incremental Test Research Articles

Comparación de los umbrales ventilatorios y los parámetros cardiorrespiratorios entre hombres adultos con paraplejia torácica baja e individuos sin lesión medular: Un estudio observacional transversal

Introduction: People with spinal cord injury (SCI) experience sensory, motor, and autonomic alterations that influence cardiovascular and respiratory responses during exercise. In this context, the objective of the present study was to compare the first and second ventilatory thresholds (VT1 and VT2), peak oxygen uptake (VO2 peak), and peak heart rate (HRpeak) between adult men with low thoracic paraplegia and men without SCI. Material or Patients and Methods: A cross-sectional observational comparative study, n = 8 adult males with low thoracic paraplegia (neurological level T6-T12, ASIA A) (PARA group) and n = 19 adult males without SCI (CON group). A maximal incremental test was performed on an upper limb cycle ergometer, using a MetaMax®3B ergos- pirometer and a Polar H7 cardiac transmitter. The data obtained were analyzed with SPSS 17.0, applying the nonparametric Mann-Whitney U test for group comparison. Results: Statistically significant differences were found in VT1 (U = 32, p = 0.019) and VT2 (U = 18.5, p = 0.002) in favor of the CON group. In contrast, no significant differences were observed in VO2peak (PARA = 2.7ml/kg/ min vs. CON=3.0ml/kg/min; p = 0.200) or HRpeak (PARA = 186 bpm vs. CON = 173 bpm; p = 0.099). Conclusion: This study revealed significant differences in ventilatory thresholds between men with and without low thoracic paraplegia, suggesting variations in submaximal exercise efficiency and capacity. Howe­ver, no notable differences were recorded in VO2 peak or HRpeak. These findings reinforce the importance of ventilatory thresholds as a tool for the assessment and prescription of exercise in individuals with SCI.

Validity and reliability of the step test to estimate maximal oxygen consumption in pediatric population

Cardiorespiratory fitness is the most important variable related to health and a strong predictor of mortality. However, it is rarely used in clinics due to costs, specialized equipment, space needs, and the requirements of expert staff such as an exercise physiologist, physician, or other health professional. This work aims to validate and test the reliability of a submaximal step test to estimate VO2max of 8-to 16-year-old pediatric populations as a simple and low-cost tool for clinical practice. A cross-sectional study included 242 children and adolescents (42.1% girls) aged 8–16. Cardiorespiratory fitness was determined by a maximal incremental test on a treadmill until exhaustion. The step test entailed maintaining a steady pace of 22 steps per minute for 3 min (60 bpm), with the heart rate being recorded at the end of the test. Nutritional status was computed through BMI z-score. A multiple linear regression model validated the step test and developed a new equation to predict VO2max, including the third-minute heart rate, weight, and height. The reliability among predicted and measured VO2max was assessed by Bland-Altman analysis. The mean age was 12.5 ± 2.6; 51.6% were overweight or obese. The cardiorespiratory fitness measured as VO2max was 35.01 ± 0.58 ml·min-1·kg−1. A robust correlation was observed between the predicted VO2max from the step test and the measured VO2max (r = 0.86, p < 0.001). Bland-Altman analysis indicated statistical concordance between predicted and measured VO2max. Our findings indicate that the step test protocol is valid and reliable for estimating VO2max in children and adolescents. Furthermore, the predictive equation is suitable for application among children aged 8–16.

Sex differences in exercise-induced arterial hypoxemia and pulmonary edema following high-intensity exercise in highly trained endurance athletes.

This study investigated sex differences in the development of pulmonary edema and exercise-induced arterial hypoxemia (EIAH) in well-trained endurance athletes during near-maximal exercise in a real-world setting. Twenty participants (10M vs. 10F; V̇O2peak: 69.3 (8.8) vs. 50.7 (4.1) ml∙kg-1∙min-1) underwent a maximal incremental treadmill test (visit 1) and a time trial on a steep trail (~2.5 km, ~800 m elevation gain) in North Vancouver (visit 2). Pulmonary edema was evaluated using handheld lung ultrasound ~10-15 min post-exercise and oxygen saturation (SpO2) was monitored using finger pulse oximetry. Males completed the time trial significantly faster than females (M: 31.5 (6.5) vs. F: 40.4 (7.5) min, p = 0.006), while females sustained a higher percentage of their visit 1 heart rate (M: 94 (1) vs. F: 96 (1) %max, p = 0.02). All participants developed EIAH, with no sex differences in end-exercise SpO2 (M: 89 (4) % vs. F: 90 (3) %, respectively, p = 0.35). There was no evidence of pulmonary edema, assessed through ultrasound b-line scores, with no differences between sexes (M: 0.3 (1.0) vs. F: 0.5 (1.5), respectively, p = 0.60). Pulmonary edema is an unlikely contributor to EIAH in endurance athletes performing near-maximal time trial exercise in a real-world setting.

Impact of elbow stiffness on running economy in trained athletes.

Elbow injuries are likely to generate a decreased range of motion (ROM), which might negatively affect athletic performance. To date, the effect of elbow stiffness on endurance running performance has never been studied. We conducted an observational, prospective, cross-over study to examine the impact of elbow stiffness on running economy. Twenty trained athletes performed running economy tests at 12 km·h-1, with and without a limited elbow ROM (flexion: 90°, extension: 45°), imposed by a dynamic brace mimicking a severe elbow stiffness. Relative intensity and performance indexes were measured during a subsequent maximal incremental exercise test. Running economy was measured at 180 ± 10.6 mlO2·km-1·kg-1 with a full ROM, and 180.2 ± 12.3 mlO2·km-1·kg-1 with the limited ROM showing a non-significant 0.1% difference (p = 0.871). Athletes experiencing post-traumatic elbow stiffness can find reassurance in knowing that it does not seem to impact a crucial metric of endurance running performance, namely running economy. Further research could explore elbow movement at different intensities of running, from higher aerobic speeds to sprinting.

Replication Study of the Effect of Different Loading Conditions on Running Mechanics at Different Velocities

The aim of this study was to replicate the study titled “Effect of different loading conditions on running mechanics at different velocities” by Carretero-Navarro et al., (2019) as part of a large replication project. The selected variable of interest was leg stiffness. Twenty-six recreationally active and healthy males (age: 23 ± 2 years, body mass: 80.20 ± 11.54kg, height: 177.96 ± 6.29cm) participated in two testing sessions, one week apart. Subjects completed an incremental maximal running test on a treadmill to determine their maximal aerobic speed (MAS). During the second session, participants completed nine, one-minute runs under different loading (+0%, +10%, and +20% of body mass using a weighted vest) and speed (60%, 80%, and 100% of their MAS) conditions. A two-way repeated measures ANOVA showed a significant main effect for speed on leg stiffness (F1.7, 38.6 = 5.94, p = 0.008, ηp2 = 0.205), similar to the original study (F2, 24 = 52.577, p &lt; 0.001). However, the replication effect size estimate for speed on leg stiffness (ηp2 = 0.205) was significantly smaller than the original (ηp2 = 0.814) (z = 4.56, p &lt; 0.001). The original effect size estimate for the main effect of speed was deemed incompatible with the replication estimate, therefore, the original study was not replicated fully. As there are growing demands for enhancing the quality of sports science research, one should focus on the accumulation of evidence for the effect of speed on leg stiffness to maximize athletic performance.

Energy balance analysis suggests that lactate is not a direct cause of the slow component of oxygen uptake kinetics.

The mechanisms of oxygen uptake ( ) slow component in the severe exercise intensity domain are still a matter of debate. We tested the hypothesis that the rate of blood lactate ([La]) accumulation above maximal lactate steady state (MLSS) is a major cause of slow component. On 13 males exercising on a cycle-ergometer, we measured gas exchanges, heart rate, and [La] during maximal incremental exercise test to determine maximal aerobic power ( max) and at constant power exercise tests at 60%, 65%, 70%, and 80% of max. Maximal was 3.19 ± 0.37l·min-1, max was 283 ± 28 W. At 60% max all variables attained steady state in all subjects. Power at MLSS was 177 ± 21 W. At 80% max a clear slow component was observed in all subjects, exercise lasted 11.3 ± 3.1min and [La] was 7.4 ± 2.2mmol at 5min and 11.5 ± 3.6mmol at 10min. The energy balance computed at 80% max resulted compatible with the principles of the energetics of muscular exercise, if we assume linear [La] increase, and thus constant metabolic power provided by [La] accumulation. Conversely, the metabolic power provided by slow component increases with time. This contrast is incompatible with the tested hypothesis that consequently must be rejected. This study excluded [La] accumulation as a main cause of slow component.

A089: The Relationship Between LTHR and the HRDP Based on The Dmax

Introduction: Blood lactate serves as a physiological biomarker, offering insights into an individual's health and training status. Lactate threshold (LT) is commonly used to determine training zones and intensity for endurance athletes. The Dmax method and its modified version, Dmaxmod, are currently prevalent for LT determination. The heart rate deflection point (HRDP) is a specific point on the heart-velocity curve used to assess the transition between aerobic and anaerobic. The purpose of this study was to explore the relationship between LT determined by Dmax and Dmaxmod, as well as the relationship between the HRDP determined using the Dmax (HRDP-Dmax) and the lactate threshold heart rate (LTHR). Methods: Twenty amateur runners underwent treadmill maximal incremental load tests. Prior to testing, a 5-15-minute warm-up was conducted. The formal test began with the treadmill at an initial speed of 4 km/h, with each load level lasting 3 minutes, followed by the collection of 10 μL of fingertip blood. The speed then increased incrementally by 1.2 km·h−1, repeating the process until the participant reached exhaustion. Participants were required to wear a Polar H10 heart rate monitor to record heart rate during the test. Post-experiment, blood lactate concentrations were analyzed using the EKF blood lactate analyzer. LT was determined using the Dmax and Dmaxmod methods with third-order polynomial interpolation. Additionally, the HRDP was determined using the Dmax method, based on the heart rate and speed. Results: After confirming normal distribution of the data, repeated measures ANOVA tests were used to verify potential differences among different thresholds determined in the maximal incremental running test. In addition to intraclass correlation coefficient (ICC), Cohen's d (d), and Pearson’s (r), Bland-Altman plots provided a visual analysis of dataset bias. (1) The LT were calculated using both the Dmax and Dmaxmod methods, they were 3.10 ± 0.82 and 4.22 ± 1.19 mmol·L−1 respectively, r = 0.544 (p &lt; 0.05), with d = 1.10, bias ± LoA = -1.12 ± 1.02 mmol·L−1 (95% CI, -3.112 - 0.869), and ICC = 0.672 (p &lt; 0.05). (2) LTHR was 175 ± 11 bpm, and HRDP-Dmax was 175 ± 12 bpm, p = 0.29, r = 0.58 (p &lt; 0.05), d = 0.85, bias ± LoA = -8.45 ± 9.93 bpm (95% CI, -27.91 -11.01), and ICC = 0.722 (p &lt; 0.05). Conclusion: The Dmax and Dmaxmod methods for determining LT demonstrate good consistency; HRDP-Dmax showed consistent results with the LTHR. This indicates that the HRDP by the Dmax method exhibited favorable reliability and practical utility in predicting LTHR during incremental running.

Cardiovascular hemodynamic response to peak exercise in individuals with multiple sclerosis.

Multiple sclerosis (MS) is a chronic neurological condition resulting in decreased aerobic capacity (peak VO2). The hemodynamic responses to peak exercise in MS are unknown. Further, it is unknown if the hemodynamic responses are due to disease or fitness. Therefore, the purpose was to compare hemodynamic response to peak exercise between individuals with and without MS, with similar peak VO2. Individuals with MS (n = 21) and CON (n = 21) underwent maximal incremental cycle exercise test to assess peak aerobic capacity (peak VO2). Heart rate, stroke volume, cardiac output, and blood pressure were obtained every other minute of the exercise test. There were no significant group differences in peak VO2. All hemodynamic variables increased similarly from baseline to peak exercise in both MS and CON. There was a significant group by time interaction for HR in individuals with MS (p < 0.01), accounted for by age, but no group by time interactions in MAP (p = 0.78), SV (p = 0.11), or Q (p = 0.86). Our findings suggest that individuals with and without MS, with similar peak VO2, have similar hemodynamic responses to peak exercise. Our data suggest that fitness is a key underlying determinants of hemodynamics responses in individuals with MS.

Peak V̇O2 during handcycling in spinal cord injured athletes: incremental versus verification testing.

The present study aimed to compare peak oxygen uptake (V̇O2peak), peak heart rate (HRpeak) and peak O2 pulse during an incremental and a verification test performed on the same day in hand-cyclists with spinal cord injury (SCI). Eight competitive SCI hand-cyclists (age: 23 ± 2.7 years; V̇O2peak: 2.24 ± 0.79 l.min-1 or 36.3 ± 14.0 ml.kg-1.min-1) performed a maximal incremental handcycling test and a verification test to exhaustion at 100% of V̇O2peak speed on an oversized treadmill. The V̇O2peak, HRpeak and peak O2pulse (i.e. VO2/HR) were compared between incremental and verification tests. V̇O2peak obtained in the verification test (2.51 ± 0.96 l.min-1) was significantly higher than values obtained in the incremental test (2.24 ± 0.79 l.min-1; P = 0.018). There was no difference in HRpeak (Incremental: 169 ± 24 bpm; Verification 167 ± 25 bpm; P = 0.130). Peak O2pulse from the verification test (14.6 ± 4.7 ml.beat-1) was higher than incremental test (13.0 ± 3.8 ml.beat-1; P = 0.007). Six subjects presented variability greater than ± 4% in verification test compared with the incremental exercise. In conclusion, the verification test elicited higher V̇O2peak than the incremental test despite the similar HR, suggesting the relevance of verification phase to determine V̇O2peak of hand-cyclists with spinal cord injuries.

Ketogenic diet in adult patients with mitochondrial myopathy

BackgroundThis study aimed to explore the feasibility, safety and efficacy of a Modified Atkins Diet (MAD) in patients with mitochondrial myopathy (MM). MethodsPatients with genetically proven mitochondrial disorder and exercise intolerance or muscle weakness followed a twelve week MAD. Feasibility was measured by diet duration and ketone levels. Safety was assessed by monitoring adverse events (AE). Efficacy was assessed by a maximal incremental test and a muscle performance test. ResultsEight out of twenty patients completed the twelve week intervention. Reasons to discontinue were the occurrence of AE: rhabdomyolysis (n = 3), vomiting (n = 1), fatigue (n = 6), constipation (n = 1), in combination with a lack of improvement and adherence difficulties. On an individual level, various positive effects were reported including improvements in VO2peak (n = 6), anaerobic threshold (n = 9), muscle fatigue resistance (n = 5), muscle strength (n = 7), fatigue (n = 6), glucose tolerance (n = 7), migraine (n = 3), sleep (n = 3), and gastrointestinal complaints (n = 2). Lipid profile improved and thirteen patients lost weight. All patients with mitochondrial DNA (mtDNA) deletions, experienced muscle related AE. The five patients with the m.3243A>G mutation achieved the longest diet duration. Discussion/conclusionMAD feasibility, safety and efficacy is variable in MD patients. MAD appears to be unsuitable for MD patients with mtDNA deletions. All patients should be monitored closely for adverse events when initiating the diet. Further research should focus on predictive factors to consider the diet, effectiveness of less stringent carbohydrate restricted diets.

Pulmonary gas exchange in relation to exercise pulmonary hypertension in patients with heart failure with preserved ejection fraction.

Exercise pulmonary hypertension (ePH), defined as a mean pulmonary artery pressure (mPAP)/cardiac output (Qc) slope >3 WU during exercise, is common in patients with heart failure with preserved ejection fraction (HFpEF). However, the pulmonary gas exchange-related effects of an exaggerated ePH (EePH) response are not well-defined, especially in relation to dyspnea on exertion (DOE) and exercise intolerance. 48 HFpEF patients underwent invasive (pulmonary and radial artery catheters) constant-load (20W) and maximal incremental cycle testing. Hemodynamic measurements (mPAP and Qc), arterial blood and expired gases, and ratings of breathlessness (RPB, Borg 0-10) were obtained. The mPAP/Qc slope was calculated from rest-to-20W. Those with a mPAP/Qc slope >4.2 (median) were classified as HFpEF+EePH (n=24) and those with a mPAP/Qc slope <4.2 were classified as HFpEF (without EePH) (n=24). The A-aDO2, VD/VT (Bohr equation), and the VE/VCO2 slope (from rest-to-20W) were calculated. PaO2 was lower (p=0.03), and VD/VT was higher (p=0.03) at peak exercise in HFpEF+EePH compared with HFpEF. A-aDO2 was similar at peak exercise between groups (p=0.14); however, HFpEF+EePH achieved the peak A-aDO2 at a lower peak work rate (p<0.01). The VE/VCO2 slope was higher in HFpEF+EePH compared with HFpEF (p=0.01). RPB was ≥1-unit higher at 20W and VO2peak was lower (p<0.01) in HFpEF+EePH compared with HFpEF. These data suggest that EePH contributes to pulmonary gas exchange impairments during exercise by causing a V/Q mismatch that provokes both ventilatory inefficiency and hypoxemia, both of which seem to contribute to DOE and exercise intolerance in patients with HFpEF.

Females have better metabolic flexibility in different metabolically challenging stimuli.

The first aim was to explore the difference in metabolic flexibility between sexes in response to changing exercise intensity under control conditions. The second aim was to evaluate metabolic flexibility between sexes in response to exercise intensity adding two different metabolically challenging stimuli (glycogen depletion and heat). Eleven males (22±3 years, 176.2±4cm, 68.4±4.9kg, and 60.2±4.1mL/kg FFM/min) and nine females (22±2 years, 166.7±4.5cm, 61.9±2.9kg, and 64.2±5.6mL/kg FFM/min) performed a maximal incremental exercise test (30W every 3min) on a cycle ergometer under three conditions: control (24h high-carbohydrate diet followed by the incremental test), glycogen depletion (glycogen-depletion protocol followed by 24h low-carbohydrate diet and then the incremental test), and heat (24h high-carbohydrate diet followed by 30min passive heating and then the incremental test in heat). In the last minute of each step, lactate was analysed, fat (FATox/FFM) and carbohydrate oxidation (CHox/FFM), and energy expenditure (EE/FFM) normalized to fat-free mass (FFM) was estimated by indirect calorimetry. Females presented a greater FATox/FFM as exercise intensity increases across conditions (control, glycogen depletion, and heat) (p=0.006). In contrast, CHox/FFM was not significantly different between sexes at any specific intensity across conditions (p>0.05). Consequently, EE/FFM was higher in females throughout the different intensities across conditions (p=0.002). Finally, lactate concentration was not different between sexes at the same intensities across conditions (p=0.87). In conclusion, females present a greater metabolic flexibility, due to the higher FATox/FFM throughout the different intensities, regardless of whether the test is performed in conditions emphasizing the oxidative pathway (glycogen depletion) or the glycolytic pathway (heat). Clinical trials: NCT05703100.

Fractional utilization of the 10-minute treadmill test velocity in running performance.

This study aimed to evaluate the applicability of the 10-minute submaximal treadmill test (T10 test), a self-paced test, in determining critical speed (CS) and predicting running performance. Specifically, we sought to identify the percentage of T10 velocity (vT10) that runners performed in official distance races, and to compare physiological and performance indicators between sexes. 60 recreational runners (n = 34 males and n = 26 females) underwent a maximum incremental test, the novel T10 test, and ran 1200-m and 2400-m on the track. Runners self-reported their best performance times. Generalized Linear Model was used to compare running performances between sexes. For both males and females, the %vT10 in 5km, 10km, and half-marathon races occurred at 107.5% and 106.5%, 99.9% and 100.8%, and 92.6% and 97.1%, respectively. There was no interaction effect (p = .520) and no main effect of sex (p = .443). There was a main effect of distance (p < .001), indicating that %vT10 in the 5km race differed from that found in the 10km race (p = .012), as well as in the half-marathon (p < .001). Our findings suggest that %vT10 values can be used to determine pace in recreational endurance runners for race distances regardless of sex.

No evidence of improvements in energy metabolism after 1week of nitrate and citrulline co-supplementation in elite rowers.

Citrulline (CIT) and beetroot extract (BR) supplements positively impacts exercise performance in elite rowers. However, its influence on metabolic outcomes such as whole-body volumes of oxygen consumption (VO2) and carbon dioxide production (VCO2), substrate oxidation, energy expenditure (EE), and gross efficiency remains unknown. We studied the effects of 1week of daily co-supplementation of 3.5g BR (500mg NO3-) plus 6g CIT on VO2 and VCO2 kinetics, substrate utilization, EE, and gross efficiency in elite male rowers compared to a placebo and to a BR supplementation. Twenty elite rowers participated in this randomized, double-blind, placebo-controlled crossover trial completing 1week of supplementation in each group of study: Placebo (PLAG); BRG; and BR-CITG. Efficiency (70% VO2max) and performance (incremental maximal) tests were performed, and gas-exchange data were collected via indirect calorimetry. Analysis of covariance (ANCOVA) showed no mean between-condition differences on respiratory exchange ratio (RER), EE, and gross efficiency in the efficiency test (all P > 0.06), and in the performance test (all P > 0.28). Moreover, in both tests no interaction Time × Supplement effects were observed for VO2, VCO2, RER, EE, substrate oxidation, and, gross efficiency (all P > 0.12). After 1week, no effects on energy metabolism and substrate utilization were observed after the daily co-ingestion of BR extract plus CIT supplement, therefore longer (> 7days) and higher doses of supplementation might be needed to influence metabolism.

Reduced cardiovascular and metabolic responses during eccentric stepping exercise: A pilot study.

This study compared cardiovascular and metabolic responses during concentric and eccentric stepping. Eight participants (5 m, 3f; 22 ± 2 years) performed maximal concentric and eccentric ramp incremental tests on a modified stepping ergometer. Subsequently, three randomized 15-min constant-power tests were performed (1) concentric stepping at 90% of the concentric lactate threshold (LT), (2) eccentric stepping at the same power, and (3) eccentric stepping at the same oxygen uptake (V̇O2). At equivalent power (36 ± 6 W, p = 0.62), eccentric stepping resulted in 46 ± 8% lower V̇O2, 16 ± 6% lower heart rate (HR), and 11 ± 5% lower mean arterial blood pressure compared to concentric (p < 0.01). Matching V̇O2 required 65 ± 19% more power during eccentric stepping (p < 0.01). During this test, eccentric V̇O2 and HR continued to increase, resulting in a 22 ± 29% higher V̇O2 and 19 ± 16% higher HR in the final minute (p < 0.001). Reduced cardiorespiratory demand during eccentric stepping at the same power as concentric demonstrates a higher eccentric power is required to produce the same V̇O2. However, despite being below the concentric LT, eccentric V̇O2 and HR continued to increase past the predicted steady state, indicating a higher exercise intensity.

Detrended fluctuation analysis to determine physiologic thresholds, investigation and evidence from incremental cycling test.

Training zones are generally assessed by gas-exchange thresholds (GET). Several mathematical analyses of heart rate variability (HRV) are proposed for indirect GET determination. Our study aimed to investigate the accordance of the detrend fluctuation analysis (DFA α1) for determining GET with first (VT1) and second ventilatory (VT2) thresholds in well-trained subjects. Eighteen female and 38 male sub-elite cyclists performed a maximal incremental cycling test of 2-min stage duration with continuous gas exchange and HR measurements. Power output (PO), Oxygen uptake ( O2) and HR at VT1 and VT2 were compared with DFA α1 0.75 (HRVT1) and 0.50 (HRVT2). Agreements between PO, O2 and HR values were analyzed using Bland-Altman analysis. Large limits of agreement between VT1 and HRVT1 were observed for measures of O2 expressed in mL.min-1.kg-1 [-21.3; + 14.1], HR [39.2; + 26.9] bpm and PO [-118; + 83] watts. Indeed, agreements were also low between VT2 and HRVT2 for measures of O2 [-26.7; + 4.3] mL.min-1.kg-1, HR [-45.5; + 10.6] bpm and PO [-157; + 35] watts. Our results also showed a sex effect: women obtained worst predictions based on DFA α1 than men for HR (p = 0.014), PO (p = 0.044) at VT1 and (p = 0.045), HR (p = 0.003) and PO (p = 0.004) at VT2. There was unsatisfactory agreement between the GET and DFA α1 methods for VT1 and VT2 determination in both sex well-trained cyclists. Trial registrationnumber 2233534 on 2024/03/05 retrospectively registered.

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.

Difference in expiratory flow limitations development in normoxia and hypoxia in healthy individuals

The present study investigated the maintenance/repeatability of expiratory flow limitation (EFL) between normoxia and hypoxia.Fifty-one healthy active individuals (27 men and 24 women) performed a lung function test and a maximal incremental cycling test in both normoxia and hypoxia (inspired oxygen fraction = 0.14) on two separate visits.During exercise in normoxia, 28 participants exhibited EFL (55 %). In hypoxia, another cohort of 28 participants exhibited EFL. The two groups only partly overlapped.Individuals with EFL only in normoxia reported lower maximal ventilation values in hypoxia than in normoxia (n=5; −13.5 ± 7.8 %) compared to their counterparts with EFL only in hypoxia (n=5; +6.7 ± 6.3 %) or without EFL (n=18; +5.1 ± 10.3 %) (p=0.004 and p<0.001, respectively).EFL development may be induced by different mechanisms in hypoxia vs. normoxia since the individuals who exhibited flow limitation were not the same between the two environmental conditions. This change seems influenced by the magnitude of the maximal ventilation change.

Assessing Leg Blood Flow and Cardiac Output During Running Using Thermodilution.

Cardiac output (Q̇C) and leg blood flow (Q̇LEG) can be measured simultaneously with high accuracy using transpulmonary and femoral vein thermodilution with a single-bolus injection. The invasive measure has offered important insight into leg hemodynamics and blood flow distribution during exercise. Despite being the natural modality of exercise in humans, there has been no direct measure of Q̇LEG while running in humans. We sought to determine the feasibility of the thermodilution technique for measuring Q̇LEG and conductance during high-intensity running, in an exploratory case study. A trained runner (30 years male) completed two maximal incremental tests on a cycle ergometer and motorized treadmill. Q̇LEG and Q̇C were determined using the single-bolus thermodilution technique. Arterial and venous blood were sampled throughout exercise, with continuous monitoring of metabolism, intra-arterial and venous pressure, and temperature. The participant reached a greater peak oxygen uptake (V̇O2peak) during running relative to cycling (74 vs. 68 mL/kg/min) with comparable Q̇LEG (19.0 vs. 19.5 L/min) and Q̇C (27.4 vs. 26.2 L/min). Leg vascular conductance was greater during high-intensity running relative to cycling (82 vs. 70 mL/min/mmHg @ ~80% V̇O2peak). The "beat phenomenon" was apparent in femoral flow while running, producing large gradients in conductance (62-90 mL/min/mmHg @ 70% V̇O2peak). In summary, we present the first direct measure of Q̇LEG and conductance in a running human. Our findings corroborate several assumptions about Q̇LEG during running compared with cycling. Importantly, we demonstrate that using thermodilution in running exercise can be completed effectively and safely.