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

BACKGROUND: 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. METHODS: 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. RESULTS: 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. CONCLUSION: 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.

Sweat lactate sensor for detecting anaerobic threshold in heart failure: a prospective clinical trial (LacS-001).

A simple method for determining the anaerobic threshold in patients with heart failure (HF) is needed. This prospective clinical trial (LacS-001) aimed to investigate the safety of a sweat lactate-monitoring sensor and the correlation between lactate threshold in sweat (sLT) and ventilatory threshold (VT). To this end, we recruited 50 patients with HF and New York Heart Association functional classification I-II (mean age: 63.5 years, interquartile range: 58.0-72.0). Incremental exercise tests were conducted while monitoring sweat lactate levels using our sensor. sLT was defined as the first steep increase in lactate levels from baseline. Primary outcome measures were a correlation coefficient of ≥ 0.6 between sLT and VT, similarities as assessed by the Bland-Altman analysis, and standard deviation of the difference within 15 W. A correlation coefficient of 0.651 (95% confidence interval, 0.391-0.815) was achieved in 32/50 cases. The difference between sLT and VT was -4.9 ± 15.0 W. No comparative error was noted in the Bland-Altman plot. No device-related adverse events were reported among the registered patients. Our sweat lactate sensor is safe and accurate for detecting VT in patients with HF in clinical settings, thereby offering valuable additional information for treatment.

A new objective method for determining exercise gas exchange thresholds by respiratory frequency in middle-aged men.

PURPOSE: To evaluate the agreement between the two Gas Exchange Thresholds (GETs = GET1 and GET2), identified by the conventional V-Slope method, and two Respiratory Frequency Thresholds (fRTs = fRT1 and fRT2) obtained from a novel, low-cost, and simple method of breakpoint determination. METHODS: Fifty middle-aged males (age: 50-58 years; V ˙ o2peak: 37.5 ± 8.6 mL·Kg-1·min-1), either healthy or with chronic illnesses, underwent an incremental cycle exercise test to determine maximal oxygen uptake ( V ˙ o2max/ V ˙ o2peak), GETs and fRTs. RESULTS: There were no statistical differences [P > 0.05; ES: 0.17 to 0.32, small] between absolute and relative (56-60% V ˙ o2peak) oxygen uptake ( V ˙ o2) values at GET1 with those obtained at fRT1, nor between V ˙ o2 values at GET2 with those at fRT2 (76-78% V ˙ o2peak). Heart rate (HR) at fRT1, and V ˙ o2 and HR at fRT2 showed very large correlations (r = 0.75-0.82; P < 0.001) and acceptable precision (SEE < 7-9%) in determination of their corresponding values at GET1 and GET2. The precision in the estimation of V ˙ o2 at GET1 from fRT1 was moderate (SEE = 15%), while those of power output at GET1 (SEE = 23%) and GET2 (SEE = 12%) from their corresponding fRTs values were very poor to moderate. CONCLUSION: HR at fRT1 and V ˙ o2 and HR at fRT2, determined using a new objective and portable approach, may potentially serve as viable predictors of their respective GETs. This method may offer a simplified, cost-effective, and field-based approach for determining exercise threshold intensities during graded exercise.

Hemodynamic and Metabolic Responses to Moderate and Vigorous Cycle Ergometry in Men Who Have Had Transtibial Amputation.

Adults who have had an amputation face barriers to having an active lifestyle which attenuates cardiorespiratory fitness. Prior studies in amputees typically involve treadmill walking or arm ergometry, yet physiological responses to bilateral leg cycling are less understood. This study assessed the hemodynamic and metabolic responses to moderate and vigorous cycle ergometry in men who have had a transtibial amputation (TTA). Five men who had had a unilateral TTA (age = 39 ± 15 yr) and six controls (CONs) without an amputation (age = 31 ± 11 yr) performed two 20 min bouts of cycling differing in intensity. Cardiac output (CO), stroke volume (SV), and oxygen consumption (VO2) were measured during moderate intensity continuous exercise (MICE) and high intensity interval exercise (HIIE) using thoracic impedance and indirect calorimetry. In response to MICE and HIIE, the HR and VO2 levels were similar (p > 0.05) between groups. Stroke volume and CO were higher (p < 0.05) in the CONs, which was attributed to their higher body mass. In men with TTAs, HIIE elicited a peak HR = 88%HRmax and substantial blood lactate accumulation, representing vigorous exercise intensity. No adverse events were exhibited in the men with TTAs. The men with TTAs show similar responses to MICE and HIIE versus the CONs.

Basketball Fatigue Impact on Kinematic Parameters and 3-Point Shooting Accuracy: Insights across Players' Positions and Cardiorespiratory Fitness Associations of High-Level Players.

This study investigated the impact of basketball-induced fatigue on 3-point jump shooting accuracy, the ball's entry angle (EA) into the hoop, shot release time (RT), their relationship with player positions in high-level basketball, and the correlation between cardiorespiratory fitness markers and potential shooting performance changes. Guards (n = 13), forwards (n = 13), and centers (n = 12) underwent physiological assessments. Sequentially, they performed 15 jump shots (PRE), a basketball exercise simulation (BEST) involving 24 × 30 s circuit activities, and a repeated shooting test (POST). The study design was double-blind. The results revealed significant differences (p ≤ 0.05) in RT, EA, and successful shots (SSs) between PRE and POST in each group. The percentage changes from PRE to POST conditions across guards, forwards, and centers were for RT: 25.34% [95%CI: 1.7-48.98], 19.73% [95%CI: -1.9-41.36], 14.95% [95%CI: -5.23-35.13]; for EA: -3.89% [95%CI: -14.82-7.04], -3.13% [95%CI: -12.9-6.64], -3.47% [95%CI: -14.19-7.25]; and for SS: -14.42% [95%CI: -36.5-7.66], -16.76% [95%CI: -40.81-7.29], -19.44% [95%CI: -46.7-7.82], respectively. Post-test differences (p ≤ 0.05) highlighted greater fatigue impact on RT, EA, and SS from guards to centers. Additionally, significant correlations (p ≤ 0.05) were found between the ventilatory threshold, mean HR during BEST, and changes in RT, EA, and SS. This study highlights the substantial impact of basketball-induced fatigue on 3-point shooting parameters across player positions and the interplay with cardiorespiratory factors post-fatigue. Tailored training, considering heart rate, is crucial to optimizing shooting performance.

Ergophysiological evaluation of heart failure patients with reduced ejection fraction undergoing exercise-based cardiac rehabilitation: A systematic review and meta-analysis.

BACKGROUND: This systematic review and meta-analysis aims to explore in heart failure (HF) patients with reduced ejection fraction (EF) undergoing exercise-based cardiac rehabilitation the following: 1) the comparison of temporal changes between peak oxygen uptake (VO2peak) and first ventilatory threshold (VO2VT1), 2) the association of VO2peak and VO2VT1 changes with physiological factors, and 3) the differential effects of continuous aerobic exercise (CAE) and interval training (IT) on VO2peak and VO2VT1. METHODS: A systematic literature search was conducted in PubMed, CENTRAL, and Scopus. Inclusion criteria were 1) original research articles using exercise-based cardiac rehabilitation, 2) stable HF patients with reduced EF, 3) available values of VO2peak and VO2VT1 (in mL/kg/min) both at baseline and after exercise training with comparison between these time points. RESULTS: Among the 30 eligible trials, 24 used CAE, 5 IT, and one CAE and IT. Multivariable meta-regression with duration of exercise training and percentage of males as independent variables and the change in VO2peak as a dependent variable showed that the change in VO2peak was negatively associated with duration of exercise training (coefficient=-0.061, p=0.027), implying the possible existence of a waning effect of exercise training on VO2peak in the long term. Multivariable meta-regression demonstrated that both age (coefficient=-0.140, p<0.001) and EF (coefficient=-0.149, p<0.001) could predict the change in VO2VT1, whereas only age (coefficient=-0.095, p=0.022), but not EF (coefficient = 0.082, p = 0.100), could predict the change in VO2peak. The posttraining peak respiratory exchange ratio, as an index of maximum effort during exercise testing, correlated positively with the change in VO2peak (coefficient=-0.021, p=0.044). The exercise-induced changes of VO2peak (p = 0.438) and VO2VT1 (p = 0.474) did not differ between CAE and IT groups. CONCLUSIONS: Improvement of endurance capacity during cardiac rehabilitation may be detected more accurately with the assessment of VO2VT1 rather than VO2peak.

Deep learning-based dynamic ventilatory threshold estimation from electrocardiograms.

BACKGROUND AND OBJECTIVE: The ventilatory threshold (VT) marks the transition from aerobic to anaerobic metabolism and is used to assess cardiorespiratory endurance. A conventional way to assess VT is cardiopulmonary exercise testing, which requires a gas analyzer. Another method for measuring VT involves calculating the heart rate variability (HRV) from an electrocardiogram (ECG) by computing the variability of heartbeats. However, the HRV method has some limitations. ECGs should be recorded for at least 5 minutes to calculate the HRV, and the result may depend on the utilized ECG preprocessing algorithms. METHODS: To overcome these problems, we developed a deep learning-based model consisting of long short-term memory (LSTM) and convolutional neural network (CNN) for a lead II ECG. Variables reflecting subjects' physical characteristics, as well as ECG signals, were input into the model to estimate VT. We applied joint optimization to the CNN layers to generate an informative latent space, which was fed to the LSTM layers. The model was trained and evaluated on two datasets, one from the Bruce protocol and the other from a protocol including multiple tasks (MT). RESULTS: Acceptable performances (mean and 95% CI) were obtained on the datasets from the Bruce protocol (-0.28[-1.91,1.34] ml/min/kg) and the MT protocol (0.07[-3.14,3.28] ml/min/kg) regarding the differences between the predictions and labels. The coefficient of determination, Pearson correlation coefficient, and root mean square error were 0.84, 0.93, and 0.868 for the Bruce protocol and 0.73, 0.97, and 3.373 for the MT protocol, respectively. CONCLUSIONS: The results indicated that it is possible for the proposed model to simultaneously assess VT with the inputs of successive ECGs. In addition, from ablation studies concerning the physical variables and the joint optimization process, it was demonstrated that their use could boost the VT assessment performance of the model. The proposed model enables dynamic VT estimation with ECGs, which could help with managing cardiorespiratory fitness in daily life and cardiovascular rehabilitation in patients.

A Preliminary Investigation into the Frequency Dose Effects of High-Intensity Functional Training on Cardiometabolic Health.

The objective of this study was to explore the effects of three weekly frequency doses of high-intensity functional training (HIFT) on an array of cardiometabolic markers in adults with metabolic syndrome (MetS). Twenty-one men and women, randomized into one (HIFT1), two (HIFT2), or three (HIFT3) days per week of HIFT, completed 3-weeks of familiarization plus a 12-week progressive training program. Pre- and post-intervention, several cardiometabolic, body composition, oxygen consumption, metabolic syndrome severity, and perceptions of fitness measurements were assessed. Additionally, an exercise enjoyment survey was administered post-intervention. A Cohen's d was used to demonstrate within-group change effect size. Although this study was not fully powered, a one-way and two-way ANOVA were used to compare the dose groups to provide provisional insights. No differences were found when frequency dose groups were compared. Many cardiometabolic, body composition, and fitness improvements were seen within each group, with clinically meaningful improvements in the metabolic syndrome severity score (MSSS) (HIFT1: -0.105, d = 0.28; HIFT2: -0.382, d = 1.20; HIFT3: -0.467, d = 1.07), waist circumference (HIFT1: -4.1cm, d = 3.33; HIFT2: -5.4cm, d = 0.89; HIFT3: -0.7cm, d = 0.20), and blood glucose (HIFT1: -9.5mg/dL, d = 0.98; HIFT2: -4.9mg/dL, d = 1.00; HIFT3: -1.7mg/dL, d = 0.23). All three groups similarly reported high exercise enjoyment and likeliness to continue after the intervention. In conclusion, HIFT performed once, twice, or thrice a week elicits improvements in MetS and is considered enjoyable. HIFT, even at a low weekly dose, therefore represents a potential strategy to reduce the global MetS burden.

The effect of saddle setback and cycling intensity on saddle pressures and comfort in male and female recreational cyclists.

Cycling is a recreational activity that helps to prevent different diseases. The practice of this popular worldwide sport requires the cyclist to maintain a particular posture in contact with the pedals, handlebars, and saddle for long periods of time. Therefore, the study of the pressure exerted on the saddle is of great importance as it is directly related to the reduction of perineal injuries and pathologies. The present research aims to study the effect on comfort and saddle pressures when performing a cycloergometer test using 3 saddle positions: own setback position (P1), forward [-10% (P2)], backward [+10% (P3)] at two exercise intensities (Ventilatory Threshold: VT1 and VT2). 34 amateur cyclists (14 women, 20 men) were analysed. The results showed that comfort was significantly reduced in P3 (p < 0.01) and significantly increased for some items in the VT1 condition and for men in P1 regarding overall comfort (p < 0.01, ES = 0.105). In addition, the average and maximum pressure in the pubic region were significantly higher at P3 (p < 0.001) and men show higher values for average pressure compared to women (p = 0.006, ES = 0.235). In conclusion, backward saddle setback positions increase pressure and discomfort to recreational cyclists in comparison with the forward and own setback position, which could increase the risk of injury.

Real-Time Estimation of Anaerobic Threshold during Exercise Using Electrocardiogram in Heart Failure Patients.

Exercise therapy at the aerobic level is highly recommended to improve clinical outcomes in patients with heart failure, in which cardiopulmonary exercise testing (CPX) is required to determine anaerobic thresholds (ATs) but is not available everywhere. This study aimed to validate a method to estimate the AT using heart rate variability (HRV) analysis from electrocardiography data in patients with heart failure. Between 2014 and 2019, 67 patients with symptomatic heart failure underwent CPXs in a single university hospital. During the CPX, RR intervals was measured continuously and the HRV threshold (HRVT), defined as the inflection point of <5 ms2 of a high-frequency component (HFC) using the power spectrum analysis, was determined. Patients were divided into two groups according to the mean HFC at rest (high-HFC group, n = 34 and low-HFC group, n = 33). The high-HFC group showed good correlation between the VO2 at AT and HRVT (r = 0.63, p < 0.001) and strong agreement (mean difference, -0.38 mL/kg, p = 0.571). The low-HFC group also showed modest correlation (r = 0.41, p = 0.017) but poor agreement (mean differences, 3.75 mL/kg, p < 0.001). In conclusion, the HRVT obtained from electrocardiography may be a useful indicator for estimating AT in patients with heart failure.

Evaluación del consumo máximo de oxígeno pre y post COVID-19en futbolista de élite en Argentina / Evaluation of maximal oxygen uptake pre- and post-COVID-19 in elite footballers in Argentina

Introducción y objetivos: La infección por SARS-CoV-2 parece provocar en muchos atletas un deterioro funcional delrendimiento cardiopulmonar. Se estudió el impacto post COVID-19 en el sistema cardiopulmonar, a través del test de ergoespirometría máxima, en futbolistas profesionales elite. Material y método: La muestra estuvo compuesta por 10 futbolistas de la primera división AFA (Asociación de Fútbol Argentino), a quienes se realizaron test de consumo de oxígeno máximo (VO2máx) pre y post infección por COVID-19. Las variablesanalizadas fueron VO2máx absoluto y relativo, velocidad aeróbica máxima (VAM), primer umbral ventilatorio (VT1), segundoumbral ventilatorio (VT2), frecuencia cardiaca máxima (FCmáx) y cociente respiratorio (RER). Resultados: El promedio de la edad fue 22,4 ± 6,9 años, masa corporal 71,5 ± 7,1 kg y estatura 176,2 ± 6,9 cm. Los sujetospost COVID-19 disminuyeron significativamente un 18% el VO2VT2 (p =0,028) y el RER disminuyó significativamente 5%(p =0,02). La FCmax, fue la única variable que post COVID-19 se incrementó significativamente 1,8% (p =0,04). No se observaron cambios significativos en la masa corporal; 71,5 ± 7,1 vs 73,9 ± 7,4 (p <0,118), VO2máx 61,7 ± 5,2 vs 59,0 ± 5,1 ml·kg·min-1(p <0,213), VAM 18,7 ± 0,9 vs 18,6 ± 0,5 km·h-1 (p <0,739), VO2VT1 39,2 ± 4,0 vs 37,8 ± 4,3 ml·kg·min-1 (p <0,460), Velocidad alVT1 11,6 ± 0,5 vs 11,8 ± 0,6 (p <0,480) y demás variables. Conclusión: Parece razonable y seguro evaluar a los atletas después de la infección por SARS-CoV-2 con ergoespirometríapara asegurar las condiciones de salud y entrenabilidad. En este tipo de atletas (futbolistas elite), la utilización del segundoumbral ventilatorio (VT2) puede ser utilizado como estrategia para observar cambios pos COVID-19. La disminución hallada,puede estar relacionada más al cese del entrenamiento que al daño cardiopulmonar.(AU)

Introduction and objectives: The SARS-CoV-2 infection appears to cause functional impairment of cardiopulmonaryperformance in many athletes. We studied the post-COVID-19 impact on the cardiopulmonary system, through the maximalergospirometry test, in elite professional soccer players. Material and method: The sample consisted of 10 AFA (Argentine Football Association) first division soccer players, whounderwent pre and post COVID-19 infection maximal oxygen uptake (VO2max) tests. The variables analyzed were absolute andrelative VO2max, maximal aerobic speed (MAS), first ventilatory threshold (VT1), second ventilatory threshold (VT2), maximalheart rate (HRmax) and respiratory exercise ratio (RER). Results: The mean age was 22.4 ± 6.9 years, body mass 71.5 ± 7.1 kg and height 176.2 ± 6.9 cm. Post COVID-19 subjects significantly decreased VO2VT2 by 18% (P = 0.028) and RER significantly decreased by 5% (P = 0.02). HRmax was the only variablethat significantly increased post COVID-19 by 1.8% (P = 0.04). No significant changes was observed in body mass 71.5 ± 7.1 vs73.9 ± 7.4 (P< 0.118), VO2max 61.7 ± 5.2 vs 59.0 ± 5.1 ml·kg·min-1 (P<0,213), MAS 18.7 ± 0.9 vs 18.6 ± 0.5 km·h-1 (P<0,739), VO2VT139.2 ± 4.0 vs 37.8 ± 4.3 ml·kg·min-1 (P<0.460), speed al VT1 11.6 ± 0.5 vs 11.8 ± 0.6 (P <0.480) and other variables. Conclusion: It seems reasonable and safe to evaluate athletes after SARS-CoV-2 infection with ergospirometry to ensurehealth conditions and trainability. In this type of athletes (elite soccer players), the use of the second ventilatory threshold(VT2) can be used as a strategy to observe post-COVID-19 changes. The decrease found may be related more to the cessationof training than to cardiopulmonary damage.(AU)

Cardiac output and arteriovenous oxygen difference contribute to lower peak oxygen uptake in patients with fibromyalgia.

BACKGROUND: Patients with fibromyalgia (FM) exhibit low peak oxygen uptake ([Formula: see text]O2peak). We aimed to detect the contribution of cardiac output to ([Formula: see text]) and arteriovenous oxygen difference [Formula: see text] to [Formula: see text] from rest to peak exercise in patients with FM. METHODS: Thirty-five women with FM, aged 23 to 65 years, and 23 healthy controls performed a step incremental cycle ergometer test until volitional fatigue. Alveolar gas exchange and pulmonary ventilation were measured breath-by-breath and adjusted for fat-free body mass (FFM) where appropriate. [Formula: see text] (impedance cardiography) was monitored. [Formula: see text] was calculated using Fick's equation. Linear regression slopes for oxygen cost (∆[Formula: see text]O2/∆work rate) and [Formula: see text] to [Formula: see text]O2 (∆[Formula: see text]/∆[Formula: see text]O2) were calculated. Normally distributed data were reported as mean ± SD and non-normal data as median [interquartile range]. RESULTS: [Formula: see text]O2peak was lower in FM patients than in controls (22.2 ± 5.1 vs. 31.1 ± 7.9 mL∙min-1∙kg-1, P < 0.001; 35.7 ± 7.1 vs. 44.0 ± 8.6 mL∙min-1∙kg FFM-1, P < 0.001). [Formula: see text] and C(a-v)O2 were similar between groups at submaximal work rates, but peak [Formula: see text] (14.17 [13.34-16.03] vs. 16.06 [15.24-16.99] L∙min-1, P = 0.005) and C(a-v)O2 (11.6 ± 2.7 vs. 13.3 ± 3.1 mL O2∙100 mL blood-1, P = 0.031) were lower in the FM group. No significant group differences emerged in ∆[Formula: see text]O2/∆work rate (11.1 vs. 10.8 mL∙min-1∙W-1, P = 0.248) or ∆[Formula: see text]/∆[Formula: see text]O2 (6.58 vs. 5.75, P = 0.122) slopes. CONCLUSIONS: Both [Formula: see text] and C(a-v)O2 contribute to lower [Formula: see text]O2peak in FM. The exercise responses were normal and not suggestive of a muscle metabolism pathology. TRIAL REGISTRATION: ClinicalTrials.gov, NCT03300635. Registered 3 October 2017-Retrospectively registered. https://clinicaltrials.gov/ct2/show/NCT03300635 .

A Physiological Anchor for the Perception of Effort.

This is a two-part study to determine one or more reliable physiological anchors for perception of effort. The purpose of Study 1 was to compare ratings of perceived exertion (RPE) at the ventilatory threshold (VT) in running, cycling, and upper body exercise with the premise that if RPE at VT did not differ across exercise modes, VT might provide a unique set of physiological inputs for perception of effort. For 27 participants, values for VT and for RPE at VT (Borg 6 to 20 scale) averaged 9.4 km⋅h-1 (SD = 0.7) and 11.9 km⋅h-1 (SD = 1.4) respectively in running, 135 W (SD = 24) and 12.1 W (SD = 1.6) in cycling, and 46 W (SD = 5) and 12.0 W (SD = 1.7) in upper body exercise. RPE did not differ, suggesting that VT may anchor effort perception. In Study 2, 10 participants performed cycle ergometer exercise for 30 minutes at their VT (M = 101 W, SD = 21), at their maximal lactate steady state (M = 143 W, SD = 22), and at their critical power (CP; M = 167 W, SD = 23). Mean end-exercise RPE were 12.1 (SD = 2.1), 15.0 (SD = 1.9), and 19.0 (SD = 0.5), respectively. The very close clustering of RPE during exercise at CP hints that the confluence of physiological responses at CP may (also) serve as a determinant in perception of effort.

Sex Differences in Maximal Oxygen Uptake Adjusted for Skeletal Muscle Mass in Amateur Endurance Athletes: A Cross Sectional Study.

Male athletes tend to outperform female athletes in several endurance sports. Maximum cardiac output can be estimated by maximal oxygen consumption (V˙O2max), and it has been established that men present V˙O2max values about 20% higher than women. Although sex differences in V˙O2max have already been well studied, few studies have assessed sex differences with regard to muscle oxidative capacity. The aim of this study was to compare aerobic muscle quality, accessed by V˙O2max and adjusted by lower limb lean mass, between male and female amateur triathletes. The study also aimed to compare sex differences according to V˙O2 submaximal values assessed at ventilatory thresholds. A total of 57 participants (23 women and 34 men), who had been training for Olympic-distance triathlon races, underwent body composition evaluation by dual-energy X-ray absorptiometry and performed a cardiorespiratory maximal test on a treadmill. Male athletes had significantly higher V˙O2max, both absolutely and when adjusted to body mass. Conversely, when V˙O2max was adjusted for lean mass, there was no significant difference between sexes. The same was observed at submaximal exercise intensities. In conclusion, differences in V˙O2max adjusted to body mass but not lean mass may explain, at least in part, sex differences in performance in triathlons, marathons, cycling, and other endurance sports.

Short-Term Effect of Bariatric Surgery on Cardiorespiratory Response at Submaximal, Ventilatory Threshold, and Maximal Exercise in Women with Severe Obesity.

PURPOSE: People with obesity have varying degrees of cardiovascular, pulmonary, and musculoskeletal dysfunction that affect aerobic exercise testing variables. Short time after bariatric surgery, these dysfunctions could affect both peak oxygen consumption ([Formula: see text] O2 peak), the gold standard for assessing cardiorespiratory fitness (CRF) and aerobic capacity evaluated with ventilatory threshold (VT1). The purpose of this study was to evaluate the short-term effect of bariatric surgery, i.e. before the resumption of physical activity, on submaximal, at VT1 and maximal cardiorespiratory responses in middle-aged women with severe obesity. MATERIALS AND METHODS: Thirteen middle-aged women with severe obesity (age: 36.7 ± 2.3 years; weight: 110.5 ± 3.6 kg, BMI: 41.8 ± 1.1 kg/m2) awaiting bariatric surgery participated in the study. Four weeks before and 6 to 8 weeks after surgery, body composition was determined by bioelectrical impedance. The participants performed an incremental cycling test to [Formula: see text] O2 peak. RESULTS: After bariatric surgery, all body composition parameters were reduced, absolute [Formula: see text] O2 peak and peak workload decline with a lower VT1. Relative [Formula: see text] O2 at peak and at VT1 (ml/min/kg or ml/min/kg of FFM) remained unchanged. Ventilation was lower after bariatric surgery during exercise with no change in cardiac response. CONCLUSION: Our results showed that weight loss alone at short-term after bariatric surgery decreased CRF as seen by a decrease in absolute [Formula: see text] O2 peak, and peak workload with lower VT1, whereas relative [Formula: see text] O2 (ml/min/kg or ml/min/kg of FFM) during exercise remained unchanged in women with obesity. Rapid FFM loss affects cardiorespiratory responses at submaximal and maximal.

Body composition, cardiorespiratory fitness, and neuromuscular adaptations induced by a home-based whole-body high intensity interval training.

Background/objective: Bodyweight exercises performed at home could be a complementary approach to improve health-related fitness in people having little spare time and during stay-at-home periods. This study then investigated body composition, cardiorespiratory fitness, and neuromuscular adaptations to a home-based, video-directed, whole-body high-intensity interval training (WB-HIIT). Methods: Fourteen subjects participated to an 8-week WB-HIIT (6 females, 23 ± 1 years) and fourteen were included in a non-exercise control group (CTL; 6 females, 24 ± 4 years). All took part to pre- and post-intervention assessments of body composition, peak oxygen uptake (VO2peak) and first ventilatory threshold (VT1; index of aerobic capacity), dynamic (leg press 3-repetition maximum) and isometric strength (knee extensors maximal isometric contractions with assessment of voluntary activation), and muscle endurance during an isometric submaximal contraction maintained till exhaustion. WB-HIIT consisted in 30-s all-out whole-body exercises interspaced with 30 s of active recovery. Training sessions were performed at home by means of videos with demonstration of exercises. Heart rate was monitored during sessions. Results: WB-HIIT increased VO2peak (5%), VT1 (20%), leg lean mass (3%), dynamic (13%) and isometric strength (6%), and muscle endurance (28%; p < 0.05), while they did not improve in CTL. VO2peak increase was correlated (r = 0.56; p < 0.05) with the time spent above 80% of maximal heart rate during training sessions. Isometric strength increase was correlated with change in voluntary activation (r = 0.74; p < 0.01). Conclusion: The home-based WB-HIIT induced concomitant cardiorespiratory fitness and neuromuscular improvements. The predominant effect was observed for aerobic capacity and muscle endurance which could improve exercise tolerance and reduce fatigability.

Amateur Female Athletes Perform the Running Split of a Triathlon Race at Higher Relative Intensity than the Male Athletes: A Cross-Sectional Study.

Maximal oxygen uptake (V˙O2max), ventilatory threshold (VT) and respiratory compensation point (RCP) can be used to monitor the training intensity and the race strategy, and the elucidation of the specificities existing between the sexes can be interesting for coaches and athletes. The aim of the study was to compare ventilatory threshold (VT), respiratory compensation point (RCP), and the percentage of the maximal aerobic speed (MAS) that can be maintained in a triathlon race between sexes. Forty-one triathletes (22 men and 19 women), 42.1 ± 8.4 (26 to 60) years old, that raced the same Olympic triathlon underwent a cardiorespiratory maximal treadmill test to assess their VT, RPC, and MAS, and race speed. The maximal oxygen uptake (V˙O2max) (54.0 ± 5.1 vs. 49.8 ± 7.7 mL/kg/min, p < 0.001) and MAS (17 ± 2 vs. 15 ± 2 km/h, p = 0.001) were significantly higher in male than in female athletes. Conversely, there were no sex differences according to the percentage of V˙O2max reached at VT (74.4 ± 4.9 vs. 76.1 ± 5.4%, p = 0.298) and RCP (89.9 ± 3.6 vs. 90.6 ± 4.0%, p = 0.560). The mean speed during the race did not differ between sexes (12.1 ± 1.7 km/h and 11.7 ± 1.8 km/h, p = 0.506, respectively). Finally, men performed the running split at a lower percentage of speed at RCP than women (84.0 ± 8.7 vs. 91.2 ± 7.0%, respectively, p = 0.005). Therefore, male and female athletes accomplished the running split in an Olympic triathlon distance at distinct relative intensities, as female athletes run at a higher RCP percentage.

Automatic Detection of Aerobic Threshold through Recurrence Quantification Analysis of Heart Rate Time Series.

During exercise with increasing intensity, the human body transforms energy with mechanisms dependent upon actual requirements. Three phases of the body's energy utilization are recognized, characterized by different metabolic processes, and separated by two threshold points, called aerobic (AerT) and anaerobic threshold (AnT). These thresholds occur at determined values of exercise intensity(workload) and can change among individuals. They are considered indicators of exercise capacities and are useful in the personalization of physical activity plans. They are usually detected by ventilatory or metabolic variables and require expensive equipment and invasive measurements. Recently, particular attention has focused on AerT, which is a parameter especially useful in the overweight and obese population to determine the best amount of exercise intensity for weight loss and increasing physical fitness. The aim of study is to propose a new procedure to automatically identify AerT using the analysis of recurrences (RQA) relying only on Heart rate time series, acquired from a cohort of young athletes during a sub-maximal incremental exercise test (Cardiopulmonary Exercise Test, CPET) on a cycle ergometer. We found that the minima of determinism, an RQA feature calculated from the Recurrence Quantification by Epochs (RQE) approach, identify the time points where generic metabolic transitions occur. Among these transitions, a criterion based on the maximum convexity of the determinism minima allows to detect the first metabolic threshold. The ordinary least products regression analysis shows that values of the oxygen consumption VO2, heart rate (HR), and Workload correspondent to the AerT estimated by RQA are strongly correlated with the one estimated by CPET (r > 0.64). Mean percentage differences are <2% for both HR and VO2 and <11% for Workload. The Technical Error for HR at AerT is <8%; intraclass correlation coefficients values are moderate (≥0.66) for all variables at AerT. This system thus represents a useful method to detect AerT relying only on heart rate time series, and once validated for different activities, in future, can be easily implemented in applications acquiring data from portable heart rate monitors.

Creatine supplementation and VO2max: a systematic review and meta-analysis.

Although creatine supplementation is well-known to increase exercise performance in acute high-intensity exercises, its role in aerobic performance based on VO2max is more controversial. Thus, we performed a systematic review and meta-analysis on the effects of creatine supplementation on VO2max. PubMed, Cochrane, Embase, and ScienceDirect were searched for randomized controlled trials (RCTs) reporting VO2max in creatine supplementation and placebo groups before and after supplementation. We computed a random-effects meta-analysis on VO2max at baseline, within groups following supplementation, on changes on VO2max between groups, and after supplementation between groups. Sensitivity analyses and meta-regression were conducted. We included 19 RCTs for a total of 424 individuals (mean age 30 years old, 82% men). VO2max did not differ at baseline between groups (creatine and placebo). Participants in both groups were engaged in exercise interventions in most studies (80%). Using changes in VO2max, VO2max increased in both groups but increased less after creatine supplementation than placebo (effect size [ES] = -0.32, 95%CI = -0.51 to -0.12, p = 0.002). Comparisons after creatine supplementation confirmed a lower VO2max in the creatine group compared to the placebo group (ES= -0.20, 95%CI = -0.39 to -0.001, p = 0.049). Meta-analysis after exclusion from meta-funnel resulted in similar outcomes in a subgroup of young and healthy participants. Meta-regressions on characteristics of supplementation, physical training, or sociodemographic were not statistically significant. Creatine supplementation has a negative effect on VO2max, regardless of the characteristics of training, supplementation, or population characteristics.Supplemental data for this article is available online at https://doi.org/10.1080/10408398.2021.2008864 .