Ventilatory Threshold Research Articles

Third ventilatory threshold in heart failure patients undergoing CPET: a prognostic analysis

Abstract Introduction One crucial element in cardiopulmonary exercise testing (CPET) involves identifying the first and second ventilatory thresholds (VT), VT1 and VT2, which hold known prognostic implications. If the individual can sustain exercise considerably beyond VT2, a third breakpoint (VT3 – Figure A) may emerge, coinciding with heightened hyperventilation to counter metabolic acidosis. Historically, this point has been mainly described among athletes and its meaning is still not entirely clear. We aimed to assess the prognostic value of VT3 in patients with heart failure (HF). Methods Retrospective, single-center study enrolling HF patients undergoing CPET from 2015 to 2021. We evaluated the typical CPET parameters along with the three ventilatory thresholds: VT1, VT2, and the newly introduced VT3. The primary outcome was a composite of cardiovascular death, urgent heart transplant, need for left ventricle assistance device and HF hospitalizations. Results We included 221 patients (82% men, mean age 58±12 years), among whom 69% had ischemic heart failure aetiology. The mean left ventricular ejection fraction (LVEF) was 34±9%, with a mean respiratory exchange ratio 1.15±0.082, mean pVO2 18.5±6.3, and a mean VE/VCO2 slope of 41.3±12.9. VT3 was attained by 43% (n = 94) of the patients. In comparison to those who did not achieve VT3, patients who reached this threshold were younger (56±11 vs 60±12; p = 0.05), had a higher pVO2 (20.5±6.9 vs 17±5.4; p = 0.05), higher RER (1.16±0.86 vs 1.13±0.78; p = 0.05), and lower VE/VCO2 slope (39±10.3 vs 43±14.3; p = 0.05). Regarding the three ventilatory thresholds (VT1, VT2, VT3), 7% (n=17) achieved a maximum of one threshold, 50% (n=110) achieved two thresholds, and 43% (n=94) reached all three thresholds. After a median follow-up of 2,3 years patients with identifiable VT3 had significantly better prognosis (HR 0,434; 95%CI 0,246-0,767; p=0,004) than those without this threshold. Furthermore, the number of identifiable ventilatory thresholds correlated positively with prognosis. In fact, patients with only 2 thresholds have twice the probability of developing an event and those with one or zero identifiable thresholds have a 4-fold increase in the probability of events (Figure C). Conclusion In a cohort of patients with HF, those with identifiable VT3 had a lower incidence of events. This parameter may aid in prognostic stratification in this population. However, this findings warrant further prospective validation.Figure 1

Acute Effects of Overload Running on Physiological and Biomechanical Variables in Trained Trail Runners

Background: The biomechanical and physiological adaptations to resisted running have been well documented in sprinting; however, their impact at submaximal speeds, such as those typical of long-distance running, remains unclear. This study aimed to evaluate the impact of running with a weighted vest, loaded with 5% and 10% of body mass, on the physiological and mechanical variables of trained trail runners. Methods: Fifteen male trail runners completed an incremental protocol to exhaustion on a treadmill with 0%, 5%, and 10% of their body mass (BM), in random order, with one week of separation between the tests. The maximality of the test was confirmed by measuring lactate concentrations at the end of the test. Oxygen consumption (V˙O2) and respiratory exchange ratio (RER) were recorded using a portable gas analyzer (Cosmed K5), and ventilatory thresholds 1 and 2 (VT1, VT2) were calculated individually. Running power was averaged for each speed stage using the Stryd device. Finally, the peak values and those associated with VT1 and VT2 for speed, power (absolute and normalized by body mass), V˙O2, RER, and the cost of transport (CoT) were included in the analysis. Results: One-way repeated-measures ANOVA revealed a detrimental effect of the extra load on maximum speed and speed at ventilatory thresholds (p ≤ 0.003), with large effect sizes (0.34–0.62) and a nonlinear trend detected in post hoc analysis. Conclusions: Using running power to control the intensity of effort while carrying extra weight provides a more stable metric than speed, particularly at aerobic intensities. Future research in trail running should investigate the effects of weighted vests across various terrains and slopes.

Importance of cardiac rehabilitation on cardiorrespiratory fitness in patients undergoing percutaneous aortic valve replacement

Abstract Background Percutaneous Aortic Valve Replacement (TAVR) significantly improves cardiac function in patients with severe aortic stenosis. However, the vast majority of these patients do not reach an adequate functional class despite the valve change, due to the deterioration of hemodynamic function and the repercussions of afterload over time. Cardiac rehabilitation (CR) program is an interdisciplinary intervention aimed at restoring functionality in Post-TAVR patients and the key to optimizing the recovery and enhancing cardiorrespiratory fitness (CRFit). The Purpose of the study is to provide an analysis of the effects of CR on exercise capacity and CRFit in TAVR patients. Methods Quasi-experimental study in TAVR patients that underwent a 4-6 week CR program, including personalized aerobic and strength training. Outcomes assessed pre- and post-rehabilitation included VO2 max, ventilatory thresholds (VT1 and VT2), and exercise capacity. The study also evaluated METs efficiency by comparing actual to predicted METs values before and after the therapy, alongside expired gas analysis test to examine exercise tolerance and its relation to VO2max gains. Results A total of 28 patients were analyzed, with an average age of 73 years (±8.1), initial weight of 68 kg (±12.32), and final weight of 65 kg (±11.13). The average ejection fraction (EF) from echocardiographic parameters was 62% (±10.1). All patients underwent cardiopulmonary exercise testing (CPET) after post-TAVR with improvements in CRFit. Initial exercise test parameters showed an average METs-load at 8.1 (±1.98), VO2max at 4.75 (±1.86), VT1 at 3.05 (±1.86), VAT at 3.85 (±1.62), VT2 at 4.5 (±2.28), and VE/VCO2 at 38 (±5.32). Final test parameters revealed VO2max at 5.8 (±2.09), VT1 at 3.2 (±1.33), VAT at 4.65 (±1.60), VT2 at 5.15 (±2.3), and VE/VCO2 at 36.4 (±69.95). Pearson's correlation analysis between CPET variables and the percentage improvement of various exercise test parameters found no statistically significant correlation. Except for METs-load and final time in Bruce, which show a significant and inversely proportional correlation (r=-0.67, p< 0.001). Conclusions The study demonstrates the effect of cardiac rehabilitation program in enhancing cardiorespiratory fitness and exercise capacity in post-TAVR patients. Notably, improvements in VO2max and ventilatory thresholds highlight the program's efficacy in promoting cardiovascular health. The inverse correlation between initial time in Bruce and METs improvement underscores the importance of baseline exercise capacity in predicting rehabilitation outcomes. Our results allow us to conclude that training volume is not the only variable to consider for proper CR. This insight could guide personalized rehabilitation strategies, making a significant contribution to the field of cardiac recovery post-TAVR.Measured METsBruce time - METs correlation

Recent cardiac rehabilitation and its impact on cardiopulmonary exercise test variables in Brazilian cardiac transplant recipients

Abstract Introduction Heart transplantation (HTx) is an option for restoring the functional capacity of individuals with end-stage heart failure (HF). Cardiac rehabilitation (CR) plays an important role in improving variables related to cardiopulmonary exercise testing (CPET) in post-HTx patients. Purpose To evaluate whether CR is effective in improving CPET variables in Brazilian patients post-recent HTx compared to a Control Group (CG). Methods Retrospective comparative study composed of two groups: CR group (CRG) and CG. These recent HTx patients (aged 14 to 73 years) initiated CR within 150 days and were recruited from an HTx outpatient clinic at a south Brazilian public university hospital between 2014 and 2023. CPET was performed at three different times: pre-HTx (Time 01), post-recent HTx (Time 02), and post-CR or post-follow-up for CG (Time 03). This study was approved by the Institutional Review Board (protocol No. 20180651). Statistical analysis used Generalized Estimating Equations with alpha ≤ 0.05, and the mean difference (MD) data were presented along with 95% confidence interval (CI). Results CRG (n=18) had a mean age of 47.3±15.6 years and CG (n=11) 48.6±12.5 years (P=0.81). The mean time to start CRG was 62.2±9.6 days (minimum: 21; maximum: 147). There was an interaction for the Group*Time factor for the following CPET variables: VO2peak (P=0.039); VEmax (P=0.009); VO2 on second ventilatory threshold (P<0.001); HR on VT2 (P=0.030) and T½ (P=0.002). The main results are summarized in Table 1. We highlight that there was a difference in the comparison between groups at Time 03 for the variable VO2peak: MD: 5.16 ± 1.95 (95% CI: 1.3 to 9.0; P = 0.008), favorable to CRG. Conclusion Early CR after very recent HTx significantly increase peak VO2peak, VEmax, T½ and VO2 and HR at the VT2 compared to the control group (CG).

Relationship between six-minute walk distance and cardiopulmonary exercise testing in non-obstructive hypertrophic cardiomyopathy

Abstract Background Recent studies have shown the promise of new approaches to the management of hypertrophic cardiomyopathy (HCM) symptoms. However, as HCM is a chronic disorder that evolves slowly over decades with low annual event rates, therapeutic trials in the disease rely on surrogate measures of disease severity and progression rather than hard endpoints such as mortality. Exercise capacity is one potential surrogate endpoint. Purpose To examine the relationship between peak oxygen uptake (VO2) and six-minute walk test distance (6MWD) in patients with non-obstructive hypertrophic cardiomyopathy (nHCM) and describe the association with clinical parameters and quality of life. Methods We examined baseline data from patients with nHCM enrolled in a randomised placebo-controlled trial of trimetazidine therapy. The study was conducted in a single European centre. Cardiopulmonary exercise testing (CPET) was performed to assess peak oxygen consumption (pVO2), ventilatory anaerobic threshold (VAT) and ventilatory equivalent for carbon dioxide (minute ventilation to carbon dioxide production (VEVCO2). Health related quality of life was assessed with the Minnesota Living with Heart Failure Questionnaire (MLHFQ). ECG and echocardiography were performed on the same day and biomarkers (NT-proBNP and cardiac Troponin T, cTnT) were measured prior to exercise testing. Results In 51 patients (age 50 ± 13 years; 71% male) with nHCM, pVO2 ranged from 10 to 24.3 ml/kg/min and 6MWD from 188 to 650 metres. 6MWD correlated with peak VO2 (Pearson r=0.41, 95% CI 0.15 to 0.67, p=0.003) and anaerobic threshold (r=0.32, 95%CI 0.04 to 0.55, p=0.024). After adjusting for age and sex, NT-proBNP concentration correlated with peak VO2 (radi=-0.35, 95% CI -0.69 to -0.01, p=0.042) but not 6MWD (radj=-0.05, 95% CI -0.42 to 0.32, p=0.779). Health related quality of life assessed by the Minnesota Living with Heart Failure Questionnaire (MLHFQ) correlated moderately with 6MWD (radi=-0.54, 95% CI -0.79 to -0.29, p<0.001) but weakly with peak VO2 (radi 0.28, 95% CI -0.55 to -0.01, p=0.042). I Conclusions There is a modest correlation between peak VO2 and 6MWD in nHCM. The pVO2 correlates more strongly with NT-proBNP whereas 6MWD better reflects quality of life. These data suggest pVO2 and 6MWD provide complementary information about health status in nHCM.Relationship between 6MWD and CPETCharacteristics of study cohort

What is the true normal: comparison of different equations for estimating peak oxygen uptake for outcome prediction in heart failure

Abstract Background and Objectives One of the strongest prognostic parameters obtained during Cardiopulmonary exercise testing (CPET) in patients with heart failure (HF) is the peak oxygen uptake (pVO2), as a standalone or as a percentage of the predicted peak oxygen uptake (ppVO2) reached. However, traditional standards by which ppVO2 is calculated have limitations, having been derived from small cohorts, lacking portability and poorly represented by women. Thus, we aim to compare the FRIEND Registry equation to previously used methods of calculating ppVO2 as it relates to prognostic value imparted by the percentage of ppVO2 (%ppVO2) reached during CPET and portability to the Portuguese HF population. Methods Single centre retrospective study of patients with HF with LVEF < 50% who underwent CPET between 2015-2021. Patients who did not reach RER≥ 1.05 were excluded from our analysis. All tests were evaluated and ventilatory thresholds determined by 3 independent, experienced operators. ppVO2 was calculated according to 1) the Wasserman equation; 2) the Wasserman equation using ideal body weight; 3) the Neder equation, 4) the SHIP equation and 5) the FRIEND equation. Our primary endpoint was a composite of CV death, urgent transplant or left ventricular assist device implantation and HF hospitalization. Results We included 238 patients (mean age 59 ± 11 years, 83% males). The HF aetiology was mostly ischemic in nature (68%), with LVEF of 34 ± 9% and median NTproBNP of 776 (2566 – 2342) pg/mL. Most patients (67%) were in class NYHA I-II and with high prevalence of GDMT (93% ACEi/ARB; 97% beta-blockers and 64% on MRA). Mean BMI in this group was 27.3 ± 4.7 kg/min. Patients performed CPET on a treadmill with a protocol adjusted to their predicted exercise capacity. Mean pVO2 was 18.1 ± 6.2mL/kg/min, corresponding to a median %ppVO2 that ranges from 51 ± 16% to 71 ± 22%, depending on the equation that is used. Mean VE/VCO2 Slope was 42 ± 13 and 48 % (n = 98) of patients showed exercise oscillatory ventilation (EOV). Mean ppVO2 as per the FRIEND and Wasserman equations was 18.9 ± 6.6 and 21.2 ± 4.5 mL/kg/min, with no statistically significant difference between both. %ppVO2 as calculated through all equations was an independent predictor of prognosis on multivariate analysis adjusted for LVEF, NTproBNP and VE/VCO2 Slope (p < 0.001 for values derived from all equations). However, the FRIEND and Wasserman equations showed a slight advantage over the remaining 2 equations, with higher AUC on ROC curve analysis (see figure). Conclusions In our population of Portuguese patients with HF, both the FRIEND registry and Wasserman equations for predicting pVO2 yielded strong prognostic power. However, these equations provide different absolute predicted VO2 values for the same patients and thus should not be used interchangeably. Standardisation of the type ppVO2 equation used should be recommended by local scientific societies.

Ventilatory thresholds in professional female soccer players.

This study investigated the ventilatory thresholds (VT1 and VT2) along with the corresponding heart rates, velocities and % of V̇O2 max at which these thresholds are reached in professional female soccer players. It also examined positional differences in the aforementioned parameters. Thirty-three professional players from two teams (age range 18-31 years) were recruited. The players underwent maximal exercise testing on the treadmill for the detection of VT1 (V̇E versus V̇O2 plot) and VT2 (V̇E versus V̇CO2 plot). The test began at a speed of 6km/h and was increased by 2 km/h every 3.15 minutes, with the inclination constant at 1%. Results indicated that the players had an average V̇O2 max of 50.24 ml·kg- 1.min- 1. VT1 (% max) and VT2 (% max) were shown at 72.87% and 91.26% of V̇O2 max, respectively. The respective velocities at VT1 and VT2 were indicated at 10.85 km/h and 12.91 km/h, respectively, while the average VV̇O2 max was 14.61 km/h. The average heart rates at VT1, VT2 and V̇O2 max were 159.33, 185.15 and 192.85 beats per minute, respectively. Furthermore, analysis of variance ANOVA indicated significant differences in velocity at V̇O2max. This study provides important normative data regarding the ventilatory thresholds of female soccer players.

Acute ergogenic effects of repetitive maximal breath-holding maneuvers on hematological and physiological responses: a graded exercise test investigation.

Repetitive maximal breath-holds (BHs or apneas) have been noted to induce advantageous hematological and blood buffering changes. Building on this, the hypothesis was formulated that the execution of repeated maximal BH efforts might lead to subsequent enhancements in performance during a time-to-exhaustion test. This study investigated the acute effects of five static maximal breath-holding maneuvers conducted with face immersion in cold water (10°C) on subsequent graded exercise test (GET) performance. Seventeen well-trained participants completed a GET on a motorized treadmill under two randomized cross-over conditions: baseline measurement (CON) and after five repeated maximal breath-holding efforts (EXP). The GET protocol consists of incremental increases in speed until exhaustion. After the fifth breath-hold, participants in the EXP condition exhibited significant (P < 0.05) increases in hematocrit, hemoglobin concentration, red blood cell count, and muscle deoxygenation, accompanied by a reduction in blood lactate concentration (4.09 ± 2.21%, 3.9 ± 1.76%, 3.96 ± 2.1%, 81.48 ± 23.83%, and 15.22 ± 17.64%, respectively), compared to CON. During GET, the EXP condition showed a significantly (P < 0.05) delayed onset time of the second ventilatory threshold (3.14 ± 5.85%) and (P < 0.05) increased time to exhaustion (0.75 ± 1.02%). This evidence suggests that repeated maximal static breath-holding maneuvers enhance the oxygen delivery system by increasing the circulation of reserve red blood cells, heightened muscle oxygen deoxygenation, enhanced aerobic metabolism utilization, and postponing the transition from aerobic to anaerobic metabolism, implying a potential ergogenic effect. While pre-exercise breath-holding shows promise for improving time-to-exhaustion and optimizing subsequent distance running performance, further in-depth investigation is essential to fully elucidate the underlying mechanistic factors.

Comparison of Awake Respiratory Control Versus Sleep Obstructive Sleep Apnea Endotypes.

Most approaches to advance simplified physiology-based precision medicine strategies for obstructive sleep apnea (OSA) focus on sleep parameters (i.e., OSA endotypes). However, wakefulness physiology measures can also provide prediction insight for certain OSA therapies yet their relationship with sleep parameters has not been extensively investigated. This study aimed to investigate potential relationships between awake ventilatory control parameters and sleep OSA endotypes and their potential to predict changes in OSA severity with morphine. Data were acquired from a randomised, cross-over trial that investigated effects of morphine versus placebo on OSA severity and underlying mechanisms. Here, awake ventilatory chemoreflex testing prior to overnight polysomnography was compared with direct measures of sleep respiratory control (e.g., hypercapnic ventilatory responses and loop gain) and OSA endotypes during a separate overnight physiology study (pharyngeal critical closure pressure-Pcrit, muscle responsiveness via genioglossus intramuscular electromyography and arousal threshold via epiglottic pressure catheter to transient continuous positive airway pressure reductions). Twenty-one men with OSA completed both study arms. During placebo, 1) awake chemosensitivity correlated with Pcrit (r=0.726, p=0.001), 2) arousal threshold correlated with awake CO2 ventilatory response threshold (r=-0.467, p=0.047) and basal ventilation (r=-0.500, p=0.029). Awake chemosensitivity and Pcrit also correlated with the apnea-hypopnea index (p<0.001) during placebo. Awake chemosensitivity was predictive of changes in OSA severity with morphine(r=-0.535, p=0.013). In conclusion, awake measures of respiratory control are related to physiological endotypes such as airway collapsibility and arousal threshold during sleep and OSA severity. Awake ventilatory chemosensitivity has the best potential to predict changes in OSA severity with morphine.

Agreement Between Heart Rate Variability - Derived vs. Ventilatory and Lactate Thresholds: A Systematic Review with Meta-Analyses.

Determining thresholds by measuring blood lactate levels (lactate thresholds) or gas exchange (ventilatory thresholds) that delineate the different exercise intensity domains is crucial for training prescription. This systematic review with meta-analyses aims to assess the overall validity of the first and second heart rate variability - derived threshold (HRVT1 and HRVT2, respectively) by computing global effect sizes for agreement and correlation between HRVTs and reference - lactate and ventilatory (LT-VTs) - thresholds. Furthermore, this review aims to assess the impact of subjects' characteristics, HRV methods, and study protocols on the agreement and correlation between LT-VTs and HRVTs. Systematic computerised searches for studies determining HRVTs during incremental exercise in humans were conducted. The agreements and correlations meta-analyses were conducted using a random-effect model. Causes of heterogeneity were explored by subgroup analysis and meta-regression with subjects' characteristics, incremental exercise protocols, and HRV methods variables. The methodological quality was assessed using QUADAS-2 and STARDHRV tools. The risk of bias was assessed by funnel plots, fail-safe N test, Egger's test of the intercept, and the Begg and Mazumdar rank correlation test. Fifty included studies (1160 subjects) assessed 314 agreements (95 for HRVT1, 219 for HRVT2) and 246 correlations (82 for HRVT1, 164 for HRVT2) between LT-VTs and HRVTs. The standardized mean differences were trivial between HRVT1 and LT1-VT1 (SMD = 0.08, 95% CI -0.04-0.19, n = 22) and between HRVT2 and LT2-VT2 (SMD = -0.06, 95% CI -0.15-0.03, n = 42). The correlations were very strong between HRVT1 and LT1-VT1 (r = 0.85, 95% CI 0.75-0.91, n = 22), and between HRVT2 and LT2-VT2 (r = 0.85, 95% CI 0.80-0.89, n = 41). Moreover, subjects' characteristics, type of ergometer, or initial and incremental workload had no impact on HRVTs determination. HRVTs showed trivial differences and very strong correlations with LT-VTs and might thus serve as surrogates. These results emphasize the usefulness of HRVTs as promising, accessible, and cost-effective means for exercise and clinical prescription purposes.

Effects of polarized and pyramidal training, with or without mindfulness, on race time and performance in amateur runners: Protocol for a randomized controlled trial

Problem: Road races in athletics has increased worldwide in recent years, leading to a growth in amateur runners (AR). Despite this growth, research aimed at this population is scarce and has methodological weaknesses. One topic of recent interest in AR is the effects of training intensity distribution (TID) and mindfulness on race time (RT); however, there is not enough evidence to establish a consensus among scientists, trainers, and athletes. Objective: To compare the effects of four training programs with polarized and pyramidal TID models on 10 km RT, ventilatory thresholds one and two, maximum aerobic speed, maximum oxygen consumption and body composition in AR. Method: A randomized controlled clinical trial with four parallel arms. The study groups include two with a polarized TID model and two with a pyramidal TID model, both combined with and without a mindfulness program over 12 weeks. Mindfulness practice will consist of 65 minutes per week through individual sessions and group workshops. Discussion: The practice of recreational athletics is increasing; however, the effect of TID and mindfulness on RT in this population have not been extensively studied. Keywords: Training intensity distribution, mindfulness, amateur runners, race time, body composition, polarized training, pyramidal training.

Physiological and Performance Adaptations to Varying Rest Distributions During Short Sprint Interval Training Trials in Female Volleyball Players: A Comparative Analysis of Interindividual Variability.

This study aimed to examine the impact of different rest periods between short sprint interval training (SSIT) trials on the physiological and performance adaptations of female volleyball players. Twenty-four trained collegeathletes volunteered to participate in this study and were randomly assigned to 3 SSIT groups with different work-to-rest ratios (1:2 [5-s run:10-s rest], 1:4 [5-s run:20-s rest], and 1:6 [5-s work:30-s rest]). Before and after 6-week training, physiological parameters (maximum oxygen uptake, first and second ventilatory thresholds, and peak and mean power output) and physical performance measures (ie,countermovement vertical jump, 10-m sprint, and T-test change-of-direction speed) were evaluated. After the training period, all groups improved (P = .001) their sport-related performance and physiological parameters, ranging from moderate to very large effect sizes. Comparative analysis of the magnitude of training effects indicated thatthe 1:6 SSIT group had in a significantly greater change in countermovement vertical jump (P = .007), 10-m sprint (P = .014), peak power output (P = .019), and mean power output (P = .05) compared with 1:2 SSIT group. By contrast, the 1:2 SSIT group demonstrated significantly (P = .022) greater changes in maximum oxygen uptake than the 1:6 SSIT group. However, the change-of-direction speed and changes infirst and second ventilatory thresholds were the same among the groups (P > .05). When performing SSIT, longer rest intervals are suitable for physical and anaerobic performance, and shorter rest periods are appropriate for enhancing the cardiorespiratory fitness of female volleyball players' performance.

Communication During Exertion: Language Production And Comprehension Performance During Exercise At The Ventilatory Threshold.

Communication During Exertion: Language Production And Comprehension Performance During Exercise At The Ventilatory Threshold.

Changes In Peak Oxygen Uptake, Ventilatory Anaerobic Threshold, And Power Output During Treatment Of A Stage II Breast Cancer Patient

Changes In Peak Oxygen Uptake, Ventilatory Anaerobic Threshold, And Power Output During Treatment Of A Stage II Breast Cancer Patient

Intra And Inter-rater Reliability Of The Exercise Thresholds App In Identifying Ventilatory Thresholds Using Undergraduate Raters

Intra And Inter-rater Reliability Of The Exercise Thresholds App In Identifying Ventilatory Thresholds Using Undergraduate Raters

Machine Learning Model To Automate Ventilatory Threshold Determination During Vo2max Assessments

Machine Learning Model To Automate Ventilatory Threshold Determination During Vo2max Assessments

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.

Aerobic capacity and respiratory indices of junior cross-country skiers and biathletes during incremental exercise testing.

The present study compared the isocapnic buffering phase (ICB), hypocapnic hyperventilation phase, ventilatory threshold (VT), respiratory compensation point (RCP), and maximum oxygen uptake (VO2max) among biathlon and cross-country ski athletes during an incremental exercise test. 37 male and 33 female Turkish National Team athletes volunteered to participate in the research. Body fat percentage, lean mass, and fat mass values of athletes were measured using the bioelectrical impedance analysis method, and oxygen consumption (VO2) was measured with a portable cardiopulmonary exercise test system with a ramp protocol on the treadmill. In VT, RCP, and VO2max phases, male athletes had higher VO2 and speed values than female athletes (p < 0.05). In contrast, they had similar values across different categories of sports (biathlon and cross-country skiing) (p > 0.05). Additionally, XC skiers and males had higher absolute (Abs) VO2 and mass-normalized (Rel) VO2 values than biathletes and females in exhaustion times and ICBs (p < 0.05). In contrast, they had similar Abs VO2 and Rel VO2 values in hypocapnic hyperventilation phases (p > 0.05). In addition, XC skiers and males had higher absolute (Abs) VO2 and relative (Rel) VO2 values than biathletes and females in exhaustion times and ICBs (p < 0.05). In contrast, they had similar Abs VO2 and Rel VO2 values in hypocapnic hyperventilation phases (p > 0.05). These results indicate significant differences in physiological profiles between male and female athletes and between XC skiers and biathletes.

Differences in the ventilatory thresholds in treadmill according to training status in 971 males and 301 females: a cross-sectional study.

To analyze the influence of training status on the percentage of maximum oxygen consumption, heart rate and velocity (%VO2max, %HRmax and %Vmax) at which ventilatory threshold 1 and ventilatory threshold 2 occur (VT1 and VT2, respectively), in males and females separately considering age, during a ramp incremental treadmill test. 791 males (36.8 ± 9.9years) and 301 females (33.9 ± 11.0years) performed a ramp incremental exercise test until fatigue where VT1 and VT2 were determined. Participants were classified as low, medium or high training status combining the oxygen consumption at VT1, VT2 and VO2max by clustering analysis. VO2max is poorly correlated with the %VO2max, %HRmax and %Vmax at which VT1 and VT2 occur (r < 0.3), in contrast, there is a positive correlation between oxygen consumption at VT1 and VT2 with the %VO2max, %HRmax and %Vmax at which VT1 and VT2, respectively, occur in males and females (r = 0.203-0.615). Furthermore, we observed the %VO2max, %HRmax and %Vmax at which thresholds occur were greater the higher the training status (all p < 0.003). The physiological determinants of the percentage of maximum at which VT1 and VT2 occur are more related to oxygen consumption at VT1 and VT2, respectively, than to VO2max. Moreover, due to the higher percentage of maximum at which VT1 and VT2 occur in individuals with a higher training status, the common strategy consisting of establishing exercise intensity as a fixed percentage of maximum might not be effective to match intensity across individuals with different training status. NCT06246760.

Comparison of local muscle oxygenation and whole-body VO2 during incremental exercise

The use of near-infrared spectroscopy (NIRS) in sports science has become increasingly important in the past few years (Perrey et al., 2024). One application is to determine thresholds from different NIRS parameters like oxygenated (O2Hb) or deoxygenated (HHb) hemoglobin to distinguish between hard and severe-intensity exercise (Caen et al., 2018). Such applications are frequently validated by comparison to established threshold determination concepts. However, it is not yet known which of the two parameters is more closely related to classical concepts. Therefore, the aim of this project was do analyze which NIRS parameter (oxygenated [O2Hb] or deoxygenated [HHb] hemoglobin) better reflects systemic behavior determined from ventilation (VE). Thirteen physically active participants (4 females, 9 males; mean age: 26.3 ± 4.4 years, height: 176.0 ± 10.3 cm, weight: 71.9 ± 9.3 kg) were included in the study. VE and NIRS data from a major locomotor muscle (vastus lateralis) during a step-incremental single leg cycle ergometer test were recorded. We used a custom MATLAB script to fit piecewise linear continuous functions by regression to estimate NIRS and VE thresholds. We used two distinct segments for NIRS data and three distinct segments for VE data. NIRS thresholds were defined as the point of intersection of the two segments in O2Hb and HHb signals, respectively. The ventilatory threshold was defined as the second increase in VE. We used a resampling strategy to reduce the impact of outliers or peculiar data distributions on threshold estimates. Thresholds from O2Hb and HHb in the active leg and VE were observed at 78.24%, 76.37%, and 84.15% of the maximum power achieved. Both O2Hb (r = 0.85, p &lt; 0.001) and HHb (r = 0.75, p = 0.0051) thresholds were significantly correlated, but mean values were significantly different (p &lt; 0.05) from the respiratory compensation point (RCP) mean value. Correlations between O2Hb and HHb values from the passive leg and the RCP values were in the same range (r = 0.88, p &lt; 0.001 and r = 0.79, p = 0.0023, respectively). The results indicate that, based on the correlations, O2Hb is slightly closer related to the second ventilatory threshold compared to HHb. The present study shows that thresholds from both NIRS parameters are closely related to the second ventilatory threshold which indicates a physiological relationship. However, thresholds cannot be used interchangeably as NIRS parameters derived from the working muscle appear earlier than systemic thresholds that demonstrate a delay in kinetics between the working muscle and the system.