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NEW FINDINGS: What is the central question of this study? Ischaemic preconditioning is a novel pre-exercise priming strategy. We asked whether ischaemic preconditioning would alter mitochondrial respiratory function and pulmonary oxygen uptake kinetics and improve severe-intensity exercise performance. What is the main finding and its importance? Ischaemic preconditioning expedited overall pulmonary oxygen uptake kinetics and appeared to prevent an increase in leak respiration, proportional to maximal electron transfer system and ADP-stimulated respiration, that was evoked by severe-intensity exercise in sham-control conditions. However, severe-intensity exercise performance was not improved. The results do not support ischaemic preconditioning as a pre-exercise strategy to improve exercise performance in recreationally active participants. ABSTRACT: We examined the effect of ischaemic preconditioning (IPC) on severe-intensity exercise performance, pulmonary oxygen uptake ( V ̇ O 2 ${\dot V_{{{\rm{O}}_{\rm{2}}}}}$ ) kinetics, skeletal muscle oxygenation (muscle tissue O2 saturation index) and mitochondrial respiration. Eight men underwent contralateral IPC (4 × 5 min at 220 mmHg) or sham-control (SHAM; 20 mmHg) before performing a cycling time-to-exhaustion test (92% maximum aerobic power). Muscle (vastus lateralis) biopsies were obtained before IPC or SHAM and ∼1.5 min postexercise. The time to exhaustion did not differ between SHAM and IPC (249 ± 37 vs. 240 ± 32 s; P = 0.62). Pre- and postexercise ADP-stimulated (P) and maximal (E) mitochondrial respiration through protein complexes (C) I, II and IV did not differ (P > 0.05). Complex I leak respiration was greater postexercise compared with baseline in SHAM, but not in IPC, when normalized to wet mass (P = 0.01 vs. P = 0.19), mitochondrial content (citrate synthase activity, P = 0.003 vs. P = 0.16; CI+IIP, P = 0.03 vs. P = 0.23) and expressed relative to P (P = 0.006 vs. P = 0.30) and E (P = 0.004 vs. P = 0.26). The V ̇ O 2 ${\dot V_{{{\rm{O}}_{\rm{2}}}}}$ mean response time was faster (51.3 ± 15.5 vs. 63.7 ± 14.5 s; P = 0.003), with a smaller slow component (270 ± 105 vs. 377 ± 188 ml min-1 ; P = 0.03), in IPC compared with SHAM. The muscle tissue O2 saturation index did not differ between trials (P > 0.05). Ischaemic preconditioning expedited V ̇ O 2 ${\dot V_{{{\rm{O}}_{\rm{2}}}}}$ kinetics and appeared to prevent an increase in leak respiration through CI, when expressed proportional to E and P evoked by severe-intensity exercise, but did not improve exercise performance.

Premature birth is associated with endothelial and mitochondrial dysfunction, and chronic oxidative stress, which might impair the physiological responses to acute altitude exposure. We assessed peripheral and oxidative stress responses to acute high-altitude exposure in preterm adults compared to term born controls. Post-occlusive skeletal muscle microvascular reactivity and oxidative capacity from the muscle oxygen consumption recovery rate constant (k) were determined by Near-Infrared Spectroscopy in the vastus lateralis of seventeen preterm and seventeen term born adults. Measurements were performed at sea-level and within 1 h of arrival at high-altitude (3375 m). Plasma markers of pro/antioxidant balance were assessed in both conditions. Upon acute altitude exposure, compared to sea-level, preterm participants exhibited a lower reperfusion rate (7 ± 31% vs. 30 ± 30%, p = 0.046) at microvascular level, but higher k (6 ± 32% vs. −15 ± 21%, p = 0.039), than their term born peers. The altitude-induced increases in plasma advanced oxidation protein products and catalase were higher (35 ± 61% vs. −13 ± 48% and 67 ± 64% vs. 15 ± 61%, p = 0.034 and p = 0.010, respectively) and in xanthine oxidase were lower (29 ± 82% vs. 159 ± 162%, p = 0.030) in preterm compared to term born adults. In conclusion, the blunted microvascular responsiveness, larger increases in oxidative stress and skeletal muscle oxidative capacity may compromise altitude acclimatization in healthy adults born preterm.

Bláfoss, R, Rikardo, J, Andersen, AØ, Hvid, LG, Andersen, LL, Jensen, K, Christensen, PM, Kvorning, T, and Aagaard, P. Effects of resistance training cessation on cycling performance in well-trained cyclists: an exploratory study. J Strength Cond Res 36(3): 796-804, 2022 - Supplementary (i.e., concurrent) resistance training can enhance cycling performance among competitive cyclists. However, a lack of knowledge exists about the retention (decay profile) in mechanical muscle function and cycling performance after concurrent resistance and endurance training. The present exploratory intervention study investigated the effect of 6 weeks of resistance training cessation when preceded by 8 weeks of concurrent resistance and endurance training on mechanical muscle function and cycling performance in 9 male well-trained competitive cyclists (Vo2max = 66 ± 7 ml·min-1·kg-1). Cyclists performed periodized resistance training targeting leg and core muscles for 8 weeks as a supplement to their normal endurance (cycling) training. This was followed by 6 weeks of endurance training only (retention period) leading up to the start of the competitive season. Maximal leg extensor power, isometric leg extensor strength (maximal voluntary contraction [MVC]), rate of force development (RFD), and long-term cycling performance (2-hour submaximal cycling at 55% of Wmax), followed by 5-minute max cycling were evaluated. After 8 weeks of concurrent resistance and endurance training, leg extensor power, MVC, and RFD increased by 12, 15, and 17%, respectively while mean power output (W) during 5-minute max cycling increased by 7% (p < 0.05). Training-induced gains in MVC and 5-minute max cycling power were retained after 6-week cessation of resistance training (p < 0.05). These findings indicate that competitive cyclists can focus on cycling training alone for at least 6 weeks leading up to competition without losing attained gains in maximal muscle strength and cycling performance achieved by preceding periods of concurrent resistance training.

Purpose Intensity domains are recommended when prescribing exercise. The distinction between heavy and severe domains is made by the critical speed (CS), therefore requiring a mathematically accurate estimation of CS. The different model variants (distance versus time, running speed versus time, time versus running speed, and distance versus running speed) are mathematically equivalent. Nevertheless, error minimization along the correct axis is important to estimate CS and the distance that can be run above CS (d′). We hypothesized that comparing statistically appropriate fitting procedures, which minimize the error along the axis corresponding to the properly identified dependent variable, should provide similar estimations of CS and d′ but that different estimations should be obtained when comparing statistically appropriate and inappropriate fitting procedure. Methods Sixteen male runners performed a maximal incremental aerobic test and four exhaustive runs at 90, 100, 110, and 120% of their peak speed on a treadmill. Several fitting procedures (a combination of a two-parameter model variant and regression analysis: weighted least square) were used to estimate CS and d′. Results Systematic biases (P d′, even when comparing two statistically appropriate fitting procedures, though negligible, thus corroborating the hypothesis. Conclusion The differences suggest that a statistically appropriate fitting procedure should be chosen beforehand by the researcher. This is also important for coaches that need to prescribe training sessions to their athletes based on exercise intensity, and their choice should be maintained over the running seasons.

Purpose: To investigate the effect of sex and load carriage on cardiorespiratory responses to high intensity exercise in male and female soldiers. Methods: Soldiers (9 women, 9 men) performed a graded treadmill test until exhaustion with no load (NL) and combat-gear with body armor (CG). Cohen's d effect sizes, paired t-tests and ANOVA were used to study differences between conditions. A mixed linear regression model analyzed the relationship between heart rate (HR) and oxygen uptake (V̇O2) with load and between sexes. Results: Wearing CG resulted in, for both sexes, a decreased time to exhaustion (−11 min), lower V̇O2peak (L/min) ES = 0.56; VO2peak (mL//kg/min) ES = 2.44, both p < 0.001, a net decrease in minute ventilation (ES = 3.53) and no change in HRmax. No sex-difference were present except for absolute V̇O2peak. The VO2 and HR relationship showed a cardiorespiratory reduction wearing CG vs. NL. Added load was equal between sexes, although female soldiers' CG relative to body mass was higher (25%) than male soldiers’ (20%), p < 0.01. Conclusion: Wearing CG reduces soldiers’ cardiorespiratory capacity and exercise performance level, although the reduction cannot be explained solely based on the added load of CG, instead CG seems to restrict the capacity to fully ventilate. No sex differences were found in relative cardiorespiratory responses to wearing CG compared to NL.

Oxygen uptake (V̇o 2 ) at exercise onset is determined in part by acceleration of pulmonary blood flow ([Formula: see text]). Impairments in the [Formula: see text] response can decrease exercise tolerance. Prior research has shown that voluntary respiratory maneuvers can augment venous return, but the corollary impacts on cardiac function, [Formula: see text] and early-exercise V̇o 2 remain uncertain. We examined 1) the cardiovascular effects of three distinct respiratory maneuvers (abdominal, AB; rib cage, RC; and deep breathing, DB) under resting conditions in healthy subjects (Protocol 1, n = 13), and 2) the impact of pre-exercise DB on pulmonary O 2 transfer during initiation of moderate-intensity exercise (Protocol 2, n = 8). In Protocol 1, echocardiographic analysis showed increased right ventricular (RV) cardiac output and left ventricular (LV) cardiac output (RVCO and LVCO, respectively), following AB (by +23 ± 13 and +18 ± 15%, respectively, P < 0.05), RC (+23 ± 16; +14 ± 15%, P < 0.05), and DB (+27 ± 21; +23 ± 14%, P < 0.05). In Protocol 2, DB performed for 12 breaths produced a pre-exercise increase in V̇o 2 (+801 ± 254 mL·min -1 over ∼6 s), presumably from increased [Formula: see text], followed by a reduction in pulmonary O 2 transfer during early phase exercise (first 20 s) compared with the control condition (149 ± 51 vs. 233 ± 65 mL, P < 0.05). We conclude that 1) respiratory maneuvers enhance RVCO and LVCO in healthy subjects under resting conditions, 2) AB, RC, and DB have similar effects on RVCO and LVCO, and 3) DB can increase [Formula: see text] before exercise onset. These findings suggest that pre-exercise respiratory maneuvers may represent a promising strategy to prime V̇o 2 kinetics and thereby to potentially improve exercise tolerance in patients with impaired cardiac function.NEW & NOTEWORTHY We demonstrate that different breathing maneuvers can augment both right and left-sided cardiac output in healthy subjects. These maneuvers, when performed immediately before exercise, result in a pre-exercise "cardiodynamic" increase in oxygen uptake (V̇o 2 ) associated with a subsequent reduction in the "cardiodynamic" V̇o 2 normally seen during early exercise. We conclude that pre-exercise breathing maneuvers are a plausible tool worthy of additional study to prime V̇o 2 kinetics and improve exercise tolerance in patients with cardiovascular disease.

Introducao A presenca de bloqueio do ramo esquerdo (BRE) na aparente ausencia de outra doenca cardiaca suscita questoes e preocupacoes a respeito da estratificacao de risco de eventos ou sintomas cardiovasculares subsequentes. – Estima-se que a deteccao de BRE em adultos assintomaticos, inclusive em atletas, varie entre 0,1% e 0,8%, o que muito provavelmente corresponde a doencas cardiacas estruturais, e nao a respostas fisiologicas ao exercicio. – Por outro lado, alguns estudos demonstraram que o risco de morte dos pacientes [...]

PURPOSE: The clinical relevance of abnormal exercise testing (ET) results (at least 0.1 mV ST segment depression measured during exercise or recovery in three consecutive beats) in athletes without obstructive coronary artery disease (CAD) is not well understood. It is unknown whether this phenomenon reflects a physiological adaptation to sport or a truly ischemic response and a concomitant attenuated stroke volume (SV) response. The aim of this study was to investigate if athletes with abnormal ET results without obstructive CAD showed signs of an attenuated SV response using cardiopulmonary ET parameters.METHODS: A total of 78 male master athletes with abnormal ET results without obstructive CAD underwent cardiopulmonary ET. ΔO2 pulse/Δwork rate (WR), ΔV˙O2/ΔWR, and Δheart rate (HR)/ΔWR were assessed and compared with data from 78 male master athletes with normal ET results, matched for age, sports characteristics, and exercise capacity.RESULTS: The ΔO2 pulse/ΔWR ratio beyond anaerobic threshold in athletes with abnormal ET results was lower than that in athletes with normal ET results (0.73 ± 0.41 vs 1.12 ± 0.54, respectively, P < 0.001). The ΔV˙O2/ΔWR ratio was also lower in athletes with abnormal ET results (0.9 ± 0.2 vs 1.0 ± 0.3, respectively, P = 0.041). Furthermore, these athletes showed a greater increase in HR in the last 2 min of exercise (ΔHR/ΔWR ratio: 1.19 ± 0.5 vs 0.80 ± 0.6, P < 0.001).CONCLUSION: Athletes with abnormal ET results without obstructive CAD showed an attenuated O2 pulse slope, decreased ΔV˙O2/ΔWR ratio, and increased ΔHR/ΔWR ratio beyond anaerobic threshold when compared with athletes with a normal ET result. These results support the hypothesis that at least a part of the athletes with an abnormal ET in absence of obstructive CAD have an attenuated SV response at high-intensity exercise.

PURPOSE. Recent evidence suggests that the smaller retinal vessels are significantly involved in the regulation of retinal blood flow and that this regulation may differ among the macular area and the retinal periphery. An alternative to studying blood flow regulation in smaller retinal vessels that are difficult to resolve is to assess the metabolic consequences of changes in the microcirculation using oximetry. METHODS. In 20 normal persons aged (mean ± SD, range) 30.1 ± 3.8 (24-37) years, the oxygen saturation and diameter of retinal arterioles and venules to the macular area and the retinal periphery were studied before and during an increase in the arterial blood pressure induced by isometric exercise. RESULTS. The isometric exercise increased the mean arterial blood pressure by (mean ± SEM) 10.0 ± 1.1 mm Hg but induced no significant changes in the diameter of the arterioles (P = 0.83). The isometric exercise had no significant effect on the oxygen saturation in the arterioles supplying the macular area and the retinal periphery (P > 0.42 for both comparisons). However, there was a significant increase in the oxygen saturation in venules draining the retinal periphery to reduce the oxygen extraction from (mean ± SEM) 36.0% ± 2.3% to 30.6% ± 2.1% (P = 0.002) but no significant change in the preexisting low oxygen extraction in the macular area that changed from (mean ± SEM) 18.2% ± 3.0% to 16.2% ± 1.9% (P = 0.37). CONCLUSIONS. Minor changes in the arterial blood pressure can induce changes in retinal rheology with significant regional variation. The finding may help explain regional variations in manifestations of retinal vascular disease such as hyperpermeability in the macular area and capillary occlusion in the retinal periphery.

We evaluated the cardiometabolic effects of a 15-week combined exercise programme, implemented in sports clubs, for 50–70-year-olds with low aerobic fitness. In a randomized controlled trial, 45 participants (26 women) with low fitness were randomly assigned (2:1-ratio) to a training group (TG, n = 30) or inactive control group (CG, n = 15). TG had 15 weeks with one weekly 90-min supervised group-based session in a recreational sports club with combined aerobic exercise and strength training and were encouraged to perform home-based training 30 min/wk. Evaluations of relative VO2max (mLO2/min/kg), blood pressure, resting heart rate (HR), echocardiography, peripheral arterial tonometry, body composition, lipid profile and HbA1c were performed at 0 and 15 wks. Average HR during supervised training was 113 ± 13 bpm (68.6 ± 7.0%HRmax), with 4.3 ± 6.6% spent >90%HRmax. At 15-wk follow-up, intention-to-treat analyses revealed no between-group difference for VO2max/kg (0.4 mLO2/min/kg, 95%CI −0.8–1.5, P = 0.519; −3 mL/min, 95%CI −123–118, P = 0.966) or other cardiovascular outcomes (all P > 0.05). Compared to CG, total fat mass (−1.9 kg; 95%CI −3.2 to −0.5, P = 0.005), total fat percentage (−1.3%, 95%CI −2.2 to −0.3, P = 0.01) and total/HDL cholesterol ratio (P = 0.032) decreased in TG. Regular adherence to supervised training was high (81%), but 0% for home-based exercise. In conclusion, the group-based supervised training was associated with high adherence and moderate exercise intensity, whereas insufficiently supported home-based training was not feasible. Together, 15 wks of combined exercise training did not improve aerobic fitness or affected cardiovascular function in 50–70-yr-olds with low aerobic fitness, whereas some positive effects were observed in metabolic parameters. Highlights Combined exercise training implemented in a sports club elicited moderate aerobic intensity in 50-70-year-old untrained individuals. Supervised group-based training had high adherence whereas unsupported home-based training had very low adherence. 15 weeks of low-frequency combined moderate intensity exercise training improved lipid profile and fat mass, but had no effect on cardiovascular fitness.

Objectives: To investigate to which extent disability, psychological and pain-related factors are associated with the outcomes of an isometric trunk muscle strength test and a cardiopulmonary exercise test in persons with chronic nonspecific low back pain (CNSLBP). Design: Cross-sectional study. Setting: REVAL Rehabilitation Research Center (Hasselt, Belgium). Participants: Persons with CNSLBP. Main outcome measures: Questionnaires concerning disability, patient specific functioning, kinesiophobia, perceived stress, pain intensity, and central sensitization were recorded. Outcomes of an isometric trunk strength test (maximum back and abdominal torque) and cardiopulmonary exercise test (VO(2)max) were assessed. Multivariate linear regression models determined factors explaining outcome variance. Results: Data of 101 persons (39 males, mean age: 44.2y (SD = 9.6)) was assessed. Neither disability, nor psychological, nor pain-related factors were associated with the assessments. Variance in back muscle strength (R-2 = 0.44, F = p < 0.01), abdominal muscle strength (R-2 = 0.68, F = p < 0.01), and aerobic capacity (R-2 = 0.76, F = p < 0.01) could only be explained through the included demographics covariates (age, gender, weight). Conclusion: This study highlighted the lack of biopsychosocial factors in explaining variance in outcomes of abdominal and back strength, and aerobic capacity in persons with CNSLBP with characteristics as depicted in the current sample. This information supports the valid interpretation of the outcomes of these assessments. (C) 2020 Published by Elsevier Ltd.

Le test de course en navette de 20m reste l’épreuve cardiorespiratoire de terrain de référence chez les enfants et adolescents (Tomkinson et al., 2017), y compris obèses (Castro-Pineiro et al., 2011; Quinart et al., 2014). Néanmoins, derniers parviendraient difficilement à atteindre réaliser une perfor- mance maximale aérobie valide lors d’une épreuve incrémentale de course (Breithaupt et al., 2012). La présence de nombreuses phases de freinage-réaccélération (PFR) du test navette pourrait accentuer cette difficulté et expliquer la sous-estimation du pic de VO2 chez le jeune obèse (Quinart et al, 2014). Par ailleurs, l’intérêt d’un protocole intermittent de type 15-15 n’a été démontré chez l’adolescent obèse que pour des vitesses supérieures à 7 km.h 1 (Rey et al., 2016 ; Thivel et al., 2017) qui ne sont pas adaptées aux obésités sévères (Klijn et al., 2007). Ainsi, nous avons supposé qu’une évaluation de l’impact énergétique et psychologique des PFR permettrait d’identifier la principale cause d’abandon à un test de type navette chez l’adolescent obèse. Nous avons mesuré l’impact des phases de freinage- relance (PFR) et de courtes périodes de récupération (15-15) sur la consommation en oxygène (VO2) et la perception de l’effort (RPE) d’adolescents sévèrement obèses lors de trois exercices incrémentaux de marche dont la vitesse était comprise entre 3 et 6 km.h 1. 19 adolescents sévèrement obèses âgés de 15.2 ± 1.5 ans (IMC = 39.7 ± 5.9) ont complété le protocole. La présence de 2 PFR par minute n’a pas augmenté significativement la VO2 ni la RPE en comparaison avec un exercice continu contrôle. Pendant le protocole 15-15, nous avons observé une diminution moyenne de 17 à 26% de la VO2 (p

Background: Atrial fibrillation (AF) is associated with increased mortality in heart failure (HF) patients. Objective: To evaluate whether the risk of AF patients can be precisely stratified by relation with cardiopulmonary exercise test (CPET) cut-offs for heart transplantation (HT) selection. Methods: Prospective evaluation of 274 consecutive HF patients with left ventricular ejection fraction ≤ 40%. The primary endpoint was a composite of cardiac death or urgent HT in 1-year follow-up. The primary endpoint was analysed by several CPET parameters for the highest area under the curve and for positive (PPV) and negative predictive value (NPV) in AF and sinus rhythm (SR) patients to detect if the current cut-offs for HT selection can precisely stratify the AF group. Statistical differences with a p-value

ObjectivesGuidelines for exercise intensity prescription in Cardiac Rehabilitation (CR) are inconsistent and have recently been discussed controversially. We aimed (1) to compare training intensities between European CR centres and (2) to assess associations between training intensity and improvement in peak oxygen consumption (V˙O2) in elderly CR patients.MethodsPeakV˙O2, heart rate and work rate (WR) at the first and second ventilatory thresholds were measured at start of CR. Training heart rate was measured during three sessions spread over the CR. Multivariate models were used to compare training characteristics between centres and to assess the effect of training intensity on change in peakV˙O2.ResultsTraining intensity was measured in 1011 out of 1633 EU-CaRE patients in 7 of 8 centers and the first and secondary ventilatory threshold were identified in 1166 and 817 patients, respectively. The first and second ventilatory threshold were found at 44% (SD 16%) and 78% (SD 9%) of peak WR and 78% (SD 9%) and 89% (SD 5%) of peak heart rate, respectively. Training intensity and session duration varied significantly between centres but change in peakV˙O2over CR did not. Training above the first individual threshold (β 0.62, 95% confidence interval [0.25–1.02]) and increase in training volume per hour (β 0.06, 95%CI [0.01–0.12]) were associated with a higher change in peakV˙O2.ConclusionWhile training intensity and volume varied greatly amongst current European CR programs, changes in peakV˙O2were similar and the effect of training characteristics on these changes were small.

Recreational team handball is an intermittent high-intensity exercise mode with physiological demands in the range of those found to enhance health and physical fitness of sedentary adults. We examined the effects of a short-term team handball-based training programme on physical fitness and metabolic and cardiovascular health of sedentary 33-55-year-old former male team handball players. Twenty-four participants were divided into team handball (THG; n=15) and control groups (CG; n=9) and evaluated at baseline and postintervention. During 12 weeks, THG performed 2-3 60-min recreational team handball matches weekly (average: 2.2 ± 0.7), and CG maintained an inactive lifestyle. Average heart rate (HR) during matches was 80 ± 7%HRmax, with peak values of 91 ± 6%HRmax. A time-by-group interaction was shown in aerobic performance (p=0.016), postural balance (p=0.019), maximum oxygen uptake (VO2max) (p=0.023), resting HR (pp=0.048), and fasting blood glucose (p=0.052) in favor of THG. THG improved aerobic performance (80%, p2max (14%, p p=0.018). Decreases in resting HR (16%, p p=0.015) and increases in HDL cholesterol (11%, p=0.002) were found in THG. Recreational team handball practice shows positive physical fitness and health-related adaptations, with high attendance, which may contribute to the reduction of the risk of developing lifestyle diseases.

Objective To evaluate the effect of quadriceps functional electrical stimulation (FES)-cycling on exertional oxygen uptake ( V ˙ o 2 ) compared with placebo FES-cycling in patients with chronic obstructive pulmonary disease (COPD). Design A randomized, single-blind, placebo-controlled crossover trial. Setting Pulmonary rehabilitation department. Participants Consecutive patients (N=23) with COPD Global Initiative for Chronic Obstructive Lung Disease stage 2, 3, or 4 (mean forced expiratory volume during the first second, 1.4±0.4L [50.3% predicted]) who had recently begun a respiratory rehabilitation program. Intervention Two consecutive 30-minute sessions were carried out at a constant load with active and placebo FES-cycling. Main Outcome Measures The primary outcome was mean V ˙ o 2 during the 30-minute exercise session. The secondary outcomes were respiratory gas exchange and hemodynamic parameters averaged over the 30-minute endurance session. Lactate values, dyspnea, and perceived muscle fatigue were evaluated at the end of the sessions. Results FES-cycling increased the physiological response more than the placebo, with a greater V ˙ o 2 achieved of 36.6mL/min (95% confidence interval [CI], 8.9–64.3mL/min) ( P =.01). There was also a greater increase in lactate after FES-cycling (+1.5mmol/L [95% CI, .05–2.9mmol/L]; P =.01). FES-cycling did not change dyspnea or muscle fatigue compared with the placebo condition. Conclusions FES-cycling effectively increased exercise intensity in patients with COPD. Further studies should evaluate longer-term FES-cycling rehabilitation programs.

Purpose The present study investigated the effects of periodic carbohydrate (CHO) restriction on endurance performance and metabolic markers in elite endurance athletes. Methods Twenty-six male elite endurance athletes (maximal oxygen consumption (VO 2max), 65.0 mL O 2·kg -1·min -1) completed 4 wk of regular endurance training while being matched and randomized into two groups training with (low) or without (high) CHO manipulation 3 d·wk -1. The CHO manipulation days consisted of a 1-h high-intensity bike session in the morning, recovery for 7 h while consuming isocaloric diets containing either high CHO (414 ± 2.4 g) or low CHO (79.5 ± 1.0 g), and a 2-h moderate bike session in the afternoon with or without CHO. VO 2max, maximal fat oxidation, and power output during a 30-min time trial (TT) were determined before and after the training period. The TT was undertaken after 90 min of intermittent exercise with CHO provision before the training period and both CHO and placebo after the training period. Muscle biopsies were analyzed for glycogen, citrate synthase (CS) and β-hydroxyacyl-coenzyme A dehydrogenase (HAD) activity, carnitine palmitoyltransferase (CPT1b), and phosphorylated acetyl-CoA carboxylase (pACC). Results The training effects were similar in both groups for all parameters. On average, VO 2max and power output during the 30-min TT increased by 5% ± 1% (P < 0.05) and TT performance was similar after CHO and placebo during the preload phase. Training promoted overall increases in glycogen content (18% ± 5%), CS activity (11% ± 5%), and pACC (38% ± 19%; P < 0.05) with no differences between groups. HAD activity and CPT1b protein content remained unchanged. Conclusions Superimposing periodic CHO restriction to 4 wk of regular endurance training had no superior effects on performance and muscle adaptations in elite endurance athletes.

Purpose: Cardiorespiratory fitness (CRF) is regarded a clinical vital sign, and accurate reference values for all age groups are essential. Little data exist on CRF and cardiorespiratory function in older adults. The aim of this study was to provide normative values for CRF and cardiorespiratory function in older adults, including people with history of cardiovascular diseases (CVD). Methods: In total, 1537 (769 women) participants age 70 to 77 yr underwent clinical examinations and cardiopulmonary exercise tests. Peak oxygen uptake (V˙ O2peak), ventilation (V˙ Epeak), expiration of carbon dioxide (VV˙ CO2peak), breathing frequency (BFpeak), tidal volume (VTpeak), oxygen pulse (O2 pulsepeak), ventilatory efficiency (EqV˙ O2peak and EqV˙ CO2peak), and 1-min HR recovery were assessed. Results: Men compared with women had higher V˙ O2peak (31.3 T 6.7 vs 26.2 T 5.0 mLIminj1 Ikgj1 ), BFpeak (41.8 T 8.0 vs 39.7 T 7.1 breaths per minute), VTpeak (2.3 T 0.5 vs 1.6 T 0.3), O2 pulsepeak (16.4 T 3.2 vs 11.3 T 2.0), V˙ CO2peak (2.9 T 0.2 and 1.9 T 0.1 LIminj1 ), V˙ Epeak (96.2 T 21.7 vs 61.1 T 21.6 LIminj1 ), EqV˙ O2peak (38.0 T 6.9 vs 35.1 T 5.6), and EqV˙ CO2peak (33.5 T 5.7 vs 31.9 T 4.5). Women and men with CVD had lower V˙ O2peak (14% and 19%), peak HR (5% and 6%), V˙ Epeak (8% and 10%), VTpeak (7% and 4%), and lower EqV˙ CO2peak (4% and 6%) compared with their healthy counterparts, respectively. Compared with healthy women and men, 1-min HR recovery was 12% and 16% lower for women and men with CVD. Conclusions: This study represents the largest reference material on directly measured CRF and cardiorespiratory function in older men and women, with and without CVD. This novel information will help researchers and clinicians to interpret data form cardiopulmonary testing in older adults. Copyright 2017 The Author(s). Published by Wolters Kluwer Health, Inc. on behalf of the American College of Sports Medicine. This is an open-access article distributed under the terms of the Creative Commons Attribution-Non Commercial-No Derivatives License 4.0 (CCBY-NC-ND), where it is permissible to download and share the work provided it is properly cited.

OBJECTIVE Long before clinical complications of type 1 diabetes (T1D) develop, oxygen supply and use can be altered during activities of daily life. We examined in patients with uncomplicated T1D all steps of the oxygen pathway, from the lungs to the mitochondria, using an integrative ex vivo (muscle biopsies) and in vivo (during exercise) approach. RESEARCH DESIGN AND METHODS We compared 16 adults with T1D with 16 strictly matched healthy control subjects. We assessed lung diffusion capacity for carbon monoxide and nitric oxide, exercise-induced changes in arterial O2 content (SaO2, PaO2, hemoglobin), muscle blood volume, and O2 extraction (via near-infrared spectroscopy). We analyzed blood samples for metabolic and hormonal vasoactive moieties and factors that are able to shift the O2-hemoglobin dissociation curve. Mitochondrial oxidative capacities were assessed in permeabilized vastus lateralis muscle fibers. RESULTS Lung diffusion capacity and arterial O2 transport were normal in patients with T1D. However, those patients displayed blunted exercise-induced increases in muscle blood volume, despite higher serum insulin, and in O2 extraction, despite higher erythrocyte 2,3-diphosphoglycerate. Although complex I– and complex II–supported mitochondrial respirations were unaltered, complex IV capacity (relative to complex I capacity) was impaired in patients with T1D, and this was even more apparent in those with long-standing diabetes and high HbA1c. O2max was lower in patients with T1D than in the control subjects. CONCLUSIONS Early defects in microvascular delivery of blood to skeletal muscle and in complex IV capacity in the mitochondrial respiratory chain may negatively impact aerobic fitness. These findings are clinically relevant considering the main role of skeletal muscle oxidation in whole-body glucose disposal.

Purpose: This study aimed to develop a prediction model for peak oxygen uptake (O 2peak ) in children with spina bifida (SB), considering peak workload (W peak ), peak heart rate, age, sex, anthropometric measures, walking level, physical activity level, and level of the lesion. Methods: Data of 26 participants with SB performing a graded arm crank test were used to develop the prediction model. An unrelated data set of participants with SB was used for validation. Results: The following equation was developed to predict O 2peak of participants with SB: O 2peak (mL/min) = 194+18 × W peak -110 × sex (adjusted R 2 = 0.933, SEE = 96 mL/min). Bland-Altman analysis showed a nonsignificant mean difference between the measured and predicted values of O 2peak (-0.09 L/min) and limits of agreement of-0.4036 and 0.2236 L/min. Conclusions: The prediction model shows promising results; however, further validation using the same protocol is warranted before implementation in clinical practice.

Objective: Preoperative functional evaluation is central to optimizing the identification of patients with non-small cell lung cancer (NSCLC) who are candidates for surgery. The minute ventilation/carbon dioxide output (VE/VCO2) slope has proven to be a predictor of surgical complications and mortality. Pulmonary rehabilitation programs (PRPs) could influence short-term outcomes in patients with COPD undergoing lung resection. Our objective was to evaluate the effects of a PRP on the VE/VCO2 slope in a cohort of patients with COPD undergoing lung resection for NSCLC. Methods: We retrospectively evaluated 25 consecutive patients with COPD participating in a three-week high-intensity PRP prior to undergoing lung surgery for NSCLC, between December of 2015 and January of 2017. Patients underwent complete functional assessment, including spirometry, DLCO measurement, and cardiopulmonary exercise testing. Results: There were no significant differences between the mean pre- and post-PRP values (% of predicted) for FEV1 (61.5 ± 22.0% vs. 62.0 ± 21.1%) and DLCO (67.2 ± 18.1% vs. 67.5 ± 13.2%). Conversely, there were significant improvements in the mean peak oxygen uptake (from 14.7 ± 2.5 to 18.2 ± 2.7 mL/kg per min; p < 0.001) and VE/VCO2 slope (from 32.0 ± 2.8 to 30.1 ± 4.0; p < 0.01). Conclusions: Our results indicate that a high-intensity PRP can improve ventilatory efficiency in patients with COPD undergoing lung resection for NSCLC. Further comprehensive prospective studies are required to corroborate these preliminary results. RESUMO Objetivos: A avaliação funcional pré-operatória é fundamental para otimizar a seleção dos pacientes para cirurgia torácica para tratamento do CPCNP. Uma alta inclinação VE/VCO2 se mostrou um preditor de complicações cirúrgicas e de aumento da mortalidade. Programas de reabilitação pulmonar (PRP) demonstraram aumentar os parâmetros funcionais e os desfechos de curto prazo em pacientes com DPOC submetidos à ressecção pulmonar. O impacto dos PRP na inclinação VE/VCO2 não foi totalmente investigado. Métodos: Avaliamos retrospectivamente 25 pacientes com DPOC consecutivos submetidos aos efeitos de um programa de reabilitação pulmonar de alta intensidade (PRP) na inclinação VE/VCO2. Resultados: Não foram observadas variações significativas nos principais parâmetros espirométricos após o programa de reabilitação de três semanas (pré-reabilitação VEF1 versus pós-reabilitação VEF1 %prev: 61,5 ± 22,0% para 62,0 ± 21,1%, ns; pré-reabilitação DLCO para pós-reabilitação DLCO %prev: 67,2 ± 18,1% para 67,5 ± 13,2%, ns). Por outro lado, o pico de VO2 e a inclinação VE/VCO2 melhoraram significativamente após PRP (pico de VO2 pré-reabilitação para pico de VO2 pós-reabilitação: 14,7 ± 2,5 para 18,2 ± 2,7 mL/kg/min, p < 0,0000001; inclinação pré-reabilitação VE/VCO2 para pós-reabilitação inclinação VE/VCO2: 32,0 ± 2,8 para 30,1 ± 4,0, p

Item does not contain fulltext AIMS: In cardiac hypertrophy (CH) and heart failure (HF), alterations occur in mitochondrial enzyme content and activities but the origin and implications of these changes for mitochondrial function need to be resolved. METHODS AND RESULTS: Right ventricular CH or HF was induced by monocrotaline injection, which causes pulmonary artery hypertension, in rats. Results were compared with saline injection (CON). NAD(P)H and FAD autofluorescence were recorded in thin intact cardiac trabeculae during transitions in stimulation frequency, to assess mitochondrial complex I and complex II function, respectively. Oxygen consumption, mitochondrial morphology, protein content, and enzymatic activity were assessed. NAD(P)H autofluorescence upon an increase in stimulation frequency showed a rapid decline followed by a slow recovery. FAD autofluorescence followed a similar time course, but in opposite direction. The amplitude of the early rapid change in NAD(P)H autofluorescence was severely depressed in CH and HF compared with CON. The rapid changes in FAD autofluorescence in CH and HF were reduced to a lesser extent. Complex I-coupled respiration showed an approximately 3.5-fold reduction in CH and HF; complex II-coupled respiration was depressed two-fold in HF. Western blot analyses revealed modest reductions in complex I protein content in CH and HF and in complex I activity in supercomplexes in HF. Mitochondrial volume density was similar, but mitochondrial remodelling was evident from changes in ultrastructure and fusion/fission indices in CH and HF. CONCLUSION: These results suggest that the alterations in mitochondrial function observed in right ventricular CH and HF can be mainly attributed to complex I dysfunction.

This cohort study examines the frequency, timing, risk factors, and outcomes associated with oxygen desaturation in infants with acute bronchiolitis and initially normal oxygen saturation., Key Points Question What are the frequency, timing, risk factors, and outcomes associated with oxygen desaturation in infants with acute bronchiolitis and initially normal oxygen saturation? Findings In this cohort study of 239 infants, desaturation occurred in most infants, regardless of whether they were hospitalized or discharged home. A more severe initial clinical presentation was the only risk factor associated with desaturation, but desaturation was not a risk factor associated with rehospitalization. Meaning These findings suggest that desaturation in acute bronchiolitis was frequent, especially for infants with a more severe clinical presentation, but it was not a risk factor associated with rehospitalization., Importance Little is known about the natural course of oxygen desaturation in acute bronchiolitis. Information on risk factors associated with desaturation as well as the time to desaturation in infants with bronchiolitis could help physicians better treat these infants before deciding whether to hospitalize them. Objective To prospectively determine the frequency of desaturation in infants with bronchiolitis, along with the time to desaturation and risk factors associated with desaturation, and to compare infants who were hospitalized with those discharged home and evaluate risk factors for rehospitalization. Design, Setting, and Participants This cohort study was conducted during the 2017 to 2018 and 2018 to 2019 respiratory syncytial virus seasons in a tertiary care pediatric emergency department in Switzerland. Included individuals were 239 otherwise-healthy infants aged younger than 1 year, diagnosed with acute bronchiolitis and oxygen saturation of 90% or more on arrival. Data were analyzed from July 2019 to October 2020. Exposures After receiving triage care, study participants admitted to the emergency department were equipped with a pulse oximeter to continuously record oxygen saturation (Spo2 levels), regardless of subsequent hospitalization or discharge home. Main Outcomes and Measures The primary outcome was desaturation (ie, Spo2 .99). Conclusions and Relevance These findings suggest that rates of desaturation in infants with acute bronchiolitis were high and similar between infants who were hospitalized and those discharged home. A more severe initial clinical presentation was the only risk factor associated with desaturation. However, for infants discharged home, desaturation was not a risk factor associated with rehospitalization.

The aim was to evaluate changes in peripheral and cerebral oxygenation, cardiorespiratory, and performance differences, as well as neuromuscular fatigue across multiple levels of blood flow restriction (BFR) during a repeated cycling sprint test to exhaustion (RST). Participants performed three RST (10-sec maximal sprints with 20-sec recovery until exhaustion) with measurements of power output and V̇O 2peak as well as oxygenation (near-infrared spectroscopy) of the vastus lateralis and prefrontal cortex. Neuromuscular fatigue was assessed by femoral nerve stimulation to evoke the vastus lateralis. Tests were conducted with proximal lower limb bilateral vascular occlusion at 0%, 45%, and 60% of resting pulse elimination pressure. Total work decreased with BFR (52.5 ± 22.9% at 45%, 68.6 ± 32.6% at 60%, P 2peak (12.6 ± 9.3% at 45%, 18.2 ± 7.2% at 60%, compared with 0%, P

Objective: Evaluate the interaction between high-intensity inspiratory muscle training (IMT) and aerobic exercise on physical capacity, respiratory muscle strength, peripheral muscle strength, and quality of life of patients who underwent coronary artery bypass grafting (CABG). Methods: Twenty-four patients underwent CABG were randomized into two groups. During 36 sessions, one group received IMT associated with aerobic exercise and the other group received only aerobic exercise. Primary outcome was the distance in the six-minute walk distance (6MWD) test. Secondary outcomes included respiratory muscle strength, peripheral muscle strength, and quality of life. Measures were taken at the baseline, at the 12th session, the 24th session, and 36th session. Results: Baseline characteristics were similar between the groups. There was no statistically significant difference between the two groups in any outcome [6MWD - P=0.935; peak oxygen consumption (PeakVO2) - P=0.853; maximal inspiratory pressure (MIP) - P=0.243; maximal expiratory pressure (MEP) - P=0.268; sitting-rising test (SRT) - P=0.212], but there was interaction in MIP (P=0.000) and all outcomes improved in the two groups (6MWD - P=0.000; PeakVO2 - P=0.000; MIP - P=0.000; MEP - P=0.000; SRT - P=0.000). Conclusion: There was an improvement of all outcomes in both groups, but IMT was not able to provide additional benefits. The use of this combination should be used with caution to not generate higher costs in the rehabilitation process of these patients.

The aim of this paper was to develop a model from experimental data allowing a prediction of the cardiopulmonary responses to steady-state submaximal exercise in varying gravitational environments, with acceleration in the G(z) axis (a (g)) ranging from 0 to 3 g. To this aim, we combined data from three different experiments, carried out at Buffalo, at Stockholm and inside the Mir Station. Oxygen consumption, as expected, increased linearly with a (g). In contrast, heart rate increased non-linearly with a (g), whereas stroke volume decreased non-linearly: both were described by quadratic functions. Thus, the relationship between cardiac output and a (g) was described by a fourth power regression equation. Mean arterial pressure increased with a (g) non linearly, a relation that we interpolated again with a quadratic function. Thus, total peripheral resistance varied linearly with a (g). These data led to predict that maximal oxygen consumption would decrease drastically as a (g) is increased. Maximal oxygen consumption would become equal to resting oxygen consumption when a (g) is around 4.5 g, thus indicating the practical impossibility for humans to stay and work on the biggest Planets of the Solar System.

Introduction: We investigated the effects of aerobic and resistance exercise in patients with chronic inflammatory demyelinating polyneuropathy (CIDP). Methods: Eighteen CIDP patients treated with subcutaneous immunoglobulin performed 12 weeks of aerobic exercise and 12 weeks of resistance exercise after a run-in period of 12 weeks without exercise. Three times weekly the participants performed aerobic exercise on an ergometer bike or resistance exercise with unilateral training of knee and elbow flexion/extension. Primary outcomes were maximal oxygen consumption velocity (VO 2-max) and maximal combined isokinetic muscle strength (cIKS) of knee and elbow flexion/extension. Results: VO 2-max and muscle strength were unchanged during run-in (−4.9% ± 10.3%, P = 0.80 and −3.7% ± 10.1%, P = 0.17, respectively). Aerobic exercise increased VO 2-max by 11.0% ± 14.7% (P = 0.02). Resistance exercise resulted in an increase of 13.8% ± 16.0% (P = 0.0004) in cIKS. Discussion: Aerobic exercise training and resistance exercise training improve fitness and strength in CIDP patients. Muscle Nerve 57: 70–76, 2018.

AIM: The aim of this study was to investigate the effect of an acute small ethanol (EtOH) dose (0.5 ml EtOH/kg fat-free mass, combined with carbohydrate) in a drink on endurance performance of trained cyclists. METHODS: Thirteen well-trained male cyclists took part in this study. A 60-min cycling endurance performance test (time trial) was performed in a calorimetric chamber after drinking an EtOH (30 +/- 1.8 ml) or a non-EtOH control (C) drink. RESULTS: Overall, EtOH induced a significant decrease in the average cycling power output (PO) (EtOH: 233 +/- 23 W versus C: 243 +/- 24 W, P < 0.01). The time course of mechanical PO showed an early decrease during the EtOH trial as compared to C (P < 0.01). Due to the lower PO, oxygen consumption, carbon dioxide production and glucose oxidation were significantly lower (P < 0.05) as compared to C. Relative to PO, heart rate response and ratings of perceived exertion (RPE) were increased by EtOH as compared to C (P < 0.05). In contrast, EtOH did not influence gross work efficiency, glycaemia and blood lactate concentration. CONCLUSIONS: These results show that the acute low dose of EtOH decreased endurance performance. An increase of cardio-vascular strain and psychobiological mechanisms may explain this decrease of endurance performance.

Purpose: This study aimed to develop a prediction model for peak oxygen uptake (O 2peak ) in children with spina bifida (SB), considering peak workload (W peak ), peak heart rate, age, sex, anthropometric measures, walking level, physical activity level, and level of the lesion. Methods: Data of 26 participants with SB performing a graded arm crank test were used to develop the prediction model. An unrelated data set of participants with SB was used for validation. Results: The following equation was developed to predict O 2peak of participants with SB: O 2peak (mL/min) = 194+18 × W peak -110 × sex (adjusted R 2 = 0.933, SEE = 96 mL/min). Bland-Altman analysis showed a nonsignificant mean difference between the measured and predicted values of O 2peak (-0.09 L/min) and limits of agreement of-0.4036 and 0.2236 L/min. Conclusions: The prediction model shows promising results; however, further validation using the same protocol is warranted before implementation in clinical practice.

The mechanisms controlling skeletal muscle oxygen consumption (V(o)₂) during exercise are not well understood. We determined whether first-order control could explain V(o)₂kinetics at contractions onset (V(o)₂(on)) and cessation (V(o)₂off)) in single skeletal muscle fibres differing in oxdidative capacity, and across stimulation intensities up to V(o)₂(max). Xenopus laevis fibres (n = 21) were suspended in a sealed chamber with a fast response P(o)₂ electrode to measure V(o)₂ every second before, during and after stimulated isometric contractions. A first-order model did not well characterize on-transient V(o)₂ kinetics. Including a time delay (TD) in the model provided a significantly improved characterization than a first-order fit without TD (F-ratio; P < 0.05), and revealed separate 'activation' and 'exponential' phases in 15/21 fibres contracting at V(o)₂(max) (mean ± SD TD: 14 ± 3s). On-transient kinetics (τV(o)₂(on)) was weakly and linearly related to V(o)₂(max) (R² = 0.271, P = 0.015). Off-transient kinetics, however, were first-order, and τV(o)₂(off) was greater in low-oxidative (V(o)₂max < 0.05 nmol mm⁻³s⁻¹ than high-oxidative fibres (V(o)₂(max > 0.10 nmol mm ⁻³ s⁻¹; 170 ± 70 vs. 29 ± 6 s, P < 0.001). 1/ τV(o)₂(off) was proportional to V(o)₂(max) (R² = 0.727, P < 0.001), unlike in the on-transient. The calculated oxygen deficit was larger (P < 0.05) than the post-contraction volume of consumed oxygen at all intensities except V(o)₂(max). These data show a clear dissociation between the kinetic control of V(o)₂at the onset and cessation of contractions and across stimulation intensities. More complex models are therefore required to understand the activation of mitochondrial respiration in skeletal muscle at the start of exercise.

Background Polycystic ovary syndrome (PCOS) is often associated with an increased waist circumference and with lower cardio-respiratory fitness as a consequence of obesity, which may be improved by physical activity. Objective To investigate the effect of high-intensity aerobic training combined with group counselling sessions on anthropometry and cardio-respiratory fitness in women with PCOS. Design Seventeen sedentary, overweight women with PCOS were randomized in a cross-over design to 16 weeks of intervention: eight weeks high-intensity aerobic exercise was followed by eight weeks of group counselling (n = 8) or vice versa (n = 9). Fourteen of the women completed the tests. Main outcome measures Waist circumference, body mass index and maximal aerobic capacity (VO 2max) were measured at baseline, cross-over and post-intervention. Results There was a decrease in waist circumference (119.9 vs. 106.5 cm) and body mass index (34.9 vs. 34.4 kg/m 2) and an increase in VO 2max (2554.9 vs. 2807.9 mL/min) during the intervention period (t = 16 weeks, n = 14), all p < 0.05. Weight loss tended to be highest in the group which started with group counselling (2.9 vs. 0.6 kg, t = 16 weeks, n = 14, p = 0.055). Conclusion Exercise in groups followed by counselling or vice versa had beneficial effects on waist circumference, weight, and VO 2max in women with PCOS. Future studies should examine possible beneficial effects of combined group counselling and exercise on weight loss and adherence to exercise protocols among women with PCOS.

Precise determination of the effect of muscle temperature (Tm) on mitochondrial oxygen consumption kinetics has proven difficult in humans, in part due to the complexities in controlling for Tm-related variations in blood flow, fiber recruitment, muscle metabolism, and contractile properties. To address this issue, intracellular Po2(PiO2) was measured continuously by phosphorescence quenching following the onset of contractions in single Xenopus myofibers ( n = 24) while controlling extracellular temperature. Fibers were subjected to two identical contraction bouts, in random order, at 15°C (cold, C) and 20°C (normal, N; n = 12), or at N and 25°C (hot, H; n = 12). Contractile properties were determined for every contraction. The time delay of the PiO2response was significantly greater in C (59 ± 35 s) compared with N (35 ± 26 s, P = 0.01) and H (27 ± 14 s, P = 0.01). The time constant for the decline in PiO2was significantly greater in C (89 ± 34 s) compared with N (52 ± 15 s; P < 0.01) and H (37 ± 10 s; P < 0.01). There was a linear relationship between the rate constant for PiO2kinetics and Tm( r = 0.322, P = 0.03). Estimated ATP turnover was significantly greater in H than in C ( P < 0.01), but this increased energy requirement alone with increased Tmcould not account for the differences observed in PiO2kinetics among conditions. These results demonstrate that PiO2kinetics in single contracting myofibers are dependent on Tm, likely caused by temperature-induced differences in metabolic demand and by temperature-dependent processes underlying mitochondrial activation at the start of muscle contractions.

Objectives: The prevalence of chronic heart failure and a reduced ejection fraction (CHF-REF) has increased over the last decade. The cardiopulmonary exercise test (CPET) is an established tool for managing these patients. For patients who are administered beta-blockers, its predictive value is debated. The aim of this study was to assess the prognostic values of several parameters in patients with CHF-REF who were on beta-blockers. Study design: 390 patients with CHF-REF underwent CPET after cardiac rehabilitation and were followed for two years. Results: The primary endpoints were all-cause mortality, cardiac- related mortality and major cardiovascular events (hospitalization for HF, heart transplantation and acute coronary syndrome or arrhythmia). The mean beta-blockers dosage was 68.9% of the target dose. The two-year mortality rate was 13%, while the mean age of the population was 57.1 years. In addition, most of the patients were men (85.5% vs. 14.5%). The resting LVEF was 35.7+-9.4 and the maximal oxygen uptake (peak VO2) was 19.5 ml/kg/min. The peak VO2, VE/ VCO2 slope and circulatory power were significant predictors of risk. The prognosis was better when the initial linear VE/VCO2 slope was lower than 30, and the final steeper VE/ VCO2 slope was lower than 32. There was no difference between the two slopes. The oxygen uptake efficiency slope, oxygen uptake, heart rate recovery, VE/VCO2/VO2 index and ventilatory threshold had no prognostic value. Conclusion: The peak VO2, circulatory power and VE/VCO2 slope were prognostic indicators for patients with CHF-REF who were on beta-blockers.

PURPOSE: This study aimed to examine the metabolic responses and pacing strategies during the performance of successive sprint time trials (STTs) in cross-country skiing.METHODS: Ten well-trained male cross-country skiers performed four self-paced 1300-m STTs on a treadmill, each separated by 45 min of recovery. The simulated sprint time trial (STT) course was divided into three flat (1°) sections (S1, S3, and S5) involving the double poling subtechnique interspersed with two uphill (7°) sections (S2 and S4) involving the diagonal stride subtechnique. Treadmill velocity and V˙O2 were monitored continuously, and gross efficiency was used to estimate the anaerobic energy supply.RESULTS: The individual trial-to-trial variability in STTs performance time was 1.3%, where variations in O2 deficit and V˙O2 explained 69% (P < 0.05) and 11% (P > 0.05) of the variation in performance. The first and the last STTs were equally fast (228 ± 10 s) and ~1.3% faster than the second and the third STTs (P < 0.05). These two fastest STTs were associated with a 14% greater O2 deficit (P < 0.05), whereas the average V˙O2 was similar during all four STTs (86% ± 3% of V˙O2max). Positive pacing was used throughout all STTs, with significantly less time spent on the first than second course half. In addition, metabolic rates were substantially higher (~30%) for uphill than for flat skiing, indicating that pacing was regulated to the terrain.CONCLUSIONS: The fastest STTs were characterized primarily by a greater anaerobic energy production, which also explained 69% of the individual variation in performance. Moreover, the skiers used positive pacing and a variable exercise intensity according to the course profile, yielding an irregular distribution of anaerobic energy production.

This prospective study aimed to characterize the changes in blood lactate concentration and blood oxygen saturation in patients during the immediate postoperative period of cardiac surgery with extracorporeal circulation.Blood samples were collected from 35 patients in a rapid and random order from the arterial line and from the proximal and distal port of a pulmonary artery catheter.The results showed no statistically significant differences between the blood oxygen saturation in the right atrium (72% ± 0.11%) and the blood oxygen saturation in the pulmonary artery (71% ± 0.08%). The blood lactate concentration in the right atrium was 1.7mmol/L ± 0.5mmol/L, and the blood lactate concentration in the pulmonary artery was 1.6mmol/L ± 0.5mmol/L (p0.0005).The difference between the blood lactate concentration in the right atrium and the blood lactate concentration in the pulmonary artery might be a consequence of the low blood lactate concentration in the blood from the coronary sinus, as it constitutes an important substrate for the myocardium during this period. The lack of differences between the blood oxygen saturation in the right atrium and the percentage of blood oxygen saturation in the pulmonary artery suggests a lower oxygen extraction by the myocardium given a lower oxygen consumption.Caracterizar as modificações na concentração sanguínea do lactato e da saturação de oxigênio em pacientes no pós-operatório imediato de cirurgia cardíaca com circulação extracorpórea.Foram coletadas amostras de sangue de 35 pacientes, de forma rápida e aleatória, do acesso arterial e das portas proximal e distal de um cateter pulmonar.Não foram verificadas diferenças estatisticamente significantes entre saturação de oxigênio no átrio direito (72% ± 0,11%) e na artéria pulmonar (71% ± 0,08%). A concentração sanguínea de lactato no átrio direito foi de 1,7mmol/L ± 0,5mmol/L, enquanto na artéria pulmonar esta concentração foi de 1,6mmol/L ± 0,5mmol/L (p0,0005).A diferença entre as concentrações sanguíneas de lactato no átrio direito e na artéria pulmonar pode ser consequência da baixa concentração de lactato no sangue do seio coronário, já que o lactato é um importante substrato para o miocárdio durante este período. A ausência de diferenças entre saturação sanguínea de oxigênio no átrio direito e na artéria pulmonar sugere extração de oxigênio mais baixa pelo miocárdio, em razão do menor consumo de oxigênio.