Noninvasive prediction of Blood Lactate through a machine learning-based approach.

We hypothesized that blood lactate concentration([Lac]blood) is a function of cardiopulmonary variables, exercise intensity and some anthropometric elements during aerobic exercise. This investigation aimed to establish a mathematical model to estimate [Lac]blood noninvasively during constant work rate (CWR) exercise of various intensities. 31 healthy participants were recruited and each underwent 4 cardiopulmonary exercise tests: one incremental and three CWR tests (low: 35% of peak work rate for 15 min, moderate: 60% 10 min and high: 90% 4 min). At the end of each CWR test, venous blood was sampled to determine [Lac]blood. 31 trios of CWR tests were employed to construct the mathematical model, which utilized exponential regression combined with Taylor expansion. Good fitting was achieved when the conditions of low and moderate intensity were put in one model; high-intensity in another. Standard deviation of fitting error in the former condition is 0.52; in the latter is 1.82 mmol/liter. Weighting analysis demonstrated that, besides heart rate, respiratory variables are required in the estimation of [Lac]blood in the model of low/moderate intensity. In conclusion, by measuring noninvasive cardio-respiratory parameters, [Lac]blood during CWR exercise can be determined with good accuracy. This should have application in endurance training and future exercise industry

Relationship between maximal incremental and high-intensity interval exercise performance in elite athletes

This descriptive study aimed to explore the physiological factors that determine tolerance to exertion during high-intensity interval effort. Forty-seven young women (15–28 years old) were enrolled: 23 athletes from Taiwan national or national reserve teams and 24 moderately active females. Each participant underwent a maximal incremental INC (modified Bruce protocol) cardiopulmonary exercise test on the first day and high-intensity interval testing (HIIT) on the second day, both performed on a treadmill. The HIIT protocol involved alternation between 1-min effort at 120% of the maximal speed, at the same slope reached at the end of the INC, and 1-min rest until volitional exhaustion. Gas exchange, heart rate (HR), and muscle oxygenation at the right vastus lateralis, measured by near-infrared spectroscopy, were continuously recorded. The number of repetitions completed (Rlim) by each participant was considered the HIIT tolerance index. The results showed a large difference in the Rlim (range, 2.6–12.0 repetitions) among the participants. Stepwise linear regression revealed that the variance in the Rlim within the cohort was related to the recovery rates of oxygen consumption (), HR at the second minute after INC, and muscle tissue saturation index at exhaustion (R = 0.644). In addition, age was linearly correlated with Rlim (adjusted R = −0.518, p \u3c 0.0001). In conclusion, the recovery rates for and HR after the incremental test, and muscle saturation index at exhaustion, were the major physiological factors related to HIIT performance. These findings provide insights into the role of the recovery phase after maximal INC exercise testing. Future research investigating a combination of INC and HIIT testing to determine training-induced performance improvement is warranted

A randomized controlled trial of enhancing hypoxia-mediated right cardiac mechanics and reducing afterload after high intensity interval training in sedentary men

Abstract Hypoxic exposure increases right ventricular (RV) afterload by triggering pulmonary hypertension, with consequent effects on the structure and function of the RV. Improved myocardial contractility is a critical circulatory adaptation to exercise training. However, the types of exercise that enhance right cardiac mechanics during hypoxic stress have not yet been identified. This study investigated how high-intensity interval training (HIIT) and moderate-intensity continuous training (MICT) influence right cardiac mechanics during hypoxic exercise A total of 54 young and healthy sedentary males were randomly selected to engage in either HIIT (3-min intervals at 40% and 80% of oxygen uptake reserve, n = 18) or MICT (sustained 60% of oxygen uptake reserve, n = 18) for 30 min/day and 5 days/week for 6 weeks or were included in a control group (CTL, n = 18) that did not engage in any exercise. The primary outcome was the change in right cardiac mechanics during semiupright bicycle exercise under hypoxic conditions (i.e., 50 watts under 12% FiO2 for 3 min) as measured by two-dimensional speckle tracking echocardiography.: After 6 weeks of training, HIIT was superior to MICT in improving maximal oxygen consumption (VO2max). Furthermore, the HIIT group showed reduced pulmonary vascular resistance (PVR, pre-HIIT:1.16 ± 0.05 WU; post-HIIT:1.05 ± 0.05 WU, p < 0.05) as well as an elevated right ventricular ejection fraction (RVEF, pre-HIIT: 59.5 ± 6.0%; post-HIIT: 69.1 ± 2.8%, p < 0.05) during hypoxic exercise, coupled with a significant enhancement of the right atrial (RA) reservoir and conduit functions. HIIT is superior to MICT in dilating RV chamber and reducing radial strain but ameliorating radial strain rate in either systole (post-HIIT: 2.78 ± 0.14 s-1; post-MICT: 2.27 ± 0.12 s-1, p < 0.05) or diastole (post-HIIT: − 2.63 ± 0.12 s-1; post-MICT: − 2.36 ± 0.18 s-1, p < 0.05). In the correlation analysis, the changes in RVEF were directly associated with improved RA reservoir (r = 0.60, p < 0.05) and conduit functions (r = 0.64, p < 0.01) but inversely associated with the change in RV radial strain (r = − 0.70, p < 0.01) and PVR (r = − 0.70, p < 0.01) caused by HIIT. HIIT is superior to MICT in improving right cardiac mechanics by simultaneously increasing RA reservoir and conduit functions and decreasing PVR during hypoxic exercise

High‐Intensity Interval Training Is Associated With Improved 10‐Year Survival by Mediating Left Ventricular Remodeling in Patients With Heart Failure With Reduced and Mid‐Range Ejection Fraction

Background This study aimed to assess the left ventricular (LV) remodeling response and long‐term survival after high‐intensity interval training (HIIT) in patients with various heart failure (HF) phenotypes during a 10‐year longitudinal follow‐up. Methods and Results Among 214 patients with HF receiving guideline‐directed medical therapy, those who underwent an additional 36 sessions of aerobic exercise at alternating intensities of 80% and 40% peak oxygen consumption (V̇$$\dot{\mathrm{V}}$$O2peak) were considered HIIT participants (n=96). Patients who did not undergo HIIT were considered participants receiving guideline‐directed medical therapy (n=118). Participants with LV ejection fraction (EF) <40%, ≥40% and <50%, and ≥50% were considered to have HF with reduced EF, HF with mid‐range EF, and HF with preserved EF, respectively. V̇$$\dot{\mathrm{V}}$$O2peak, serial LV geometry, and time to death were recorded. In all included participants, 10‐year survival was better (P=0.015) for participants who underwent HIIT (80.3%) than for participants receiving guideline‐directed medical therapy (68.6%). An increased V̇$$\dot{\mathrm{V}}$$O2peak, decreased minute ventilation carbon dioxide production slope, and reduced LV end‐diastolic diameter were protective factors against all‐cause mortality. Regarding 138 patients with HF with reduced EF (P=0.044) and 36 patients with HF with mid‐range EF (P=0.036), 10‐year survival was better for participants who underwent HIIT than for participants on guideline‐directed medical therapy. Causal mediation analysis showed a significant mediation path for LV end‐diastolic diameter on the association between HIIT and 10‐year mortality in all included patients with HF (P<0.001) and those with LV ejection fraction <50% (P=0.006). HIIT also had a significant direct association with 10‐year mortality in patients with HF with LV ejection fraction <50% (P=0.027) but not in those with LV ejection fraction ≥50% (n=40). Conclusions Reversal of LV remodeling after HIIT could be a significant mediating factor for 10‐year survival in patients with HF with reduced EF and those with HF with mid‐range EF

High-Intensity Interval Training is Associated with Improved Long-Term Survival in Heart Failure Patients

This matched-control cohort study explored the effects of high-intensity interval training (HIIT) on left ventricle (LV) dimensions and survival in heart failure (HF) patients between 2009 and 2016. HF patients who underwent the multidisciplinary disease management program (MDP) were enrolled. Non-exercising participants, aged (mean (95% confidence interval)) 62.8 (60.1&#8211;65.5) years, were categorized as the MDP group (n = 101). Participants aged 61.5 (58.7&#8211;64.2) years who had completed 36 sessions of HIIT were treated as the HIIT group (n = 101). Peak oxygen consumption (VO2peak) and LV geometry were assessed during the 8-year follow-up period. The 5-year all-cause mortality risk factors and overall survival rates were determined in the longitudinal observation. An increased VO2peak of 14&#8211;20% was observed in the HIIT group after exercise training. Each 1-mL/kg/min increase in VO2peak conferred a 58% improvement in 5-year mortality. Increased LV end-systolic diameter (LVESD) was significantly (p = 0.0198) associated with increased mortality. The 8-month survival rate was significantly improved (p = 0.044) in HIIT participants compared to non-exercise participants. HF patients with VO2peak &#8805;14.0 mL/kg/min and LVESD &lt;44 mm had a significantly better 5-year survival rate (98.2%) than those (57.3%) with lower VO2peak and greater LVESD. Both HIIT-induced increased VO2peak and decreased LVESD are associated with improved survival in HF patients