Incremental Exercise Test Research Articles

Energetic Contributions Including Gender Differences and Metabolic Flexibility in the General Population and Athletes

Metabolic flexibility includes the ability to perform fat and carbohydrate oxidation, as well as oxidative capacity, which is associated with mitochondrial function, energetic contributions, and physical health and performance. During a session of graded incremental exercise testing (GIET), we investigated metabolic flexibility, the contributions of three energy systems, and performances of individuals with different metabolic characteristics. Fifteen general population (GP; n = 15, male n = 7, female n = 8) and 15 national-level half-marathon and triathlon athletes (A; n = 15, male n = 7, female n = 8) participated in this study. During GIET, heart rate (HR), oxygen uptake (O2mean and CO2mean), metabolic equivalents (METs) in O2mean, and blood glucose and lactate concentrations (La−) were measured. Furthermore, jogging/running speeds (S) at specific La−, fat and carbohydrate oxidations (FATox and CHOox), and energetic contributions (oxidative; WOxi, glycolytic; WGly, and phosphagen; WPCr) were calculated. The percentages of HRmax, relative O2mean, CO2mean, and METs in O2mean were all lower in A than they were in GP. FATox values were lower in GP than in A, while CHOox and La− were higher in GP than in A. Negative correlations between La− and FATox were also observed in both groups. Contributions of WOxi, WGly, and WPCr were higher in GP than in A during GIET. Moreover, values of WGly, and WPCr were significantly lower and higher, respectively, in male GP than in female GP. Furthermore, S at specific La− were higher in A than in GP. It is suggested that an individualized low-intensity recovery exercise program be established, to achieve increased metabolic flexibility and oxidative capacity (aerobic base), such as public health improvements and a greater volume of higher exercise intensities; this is the type of exercise that elite athletes worldwide mostly perform during their training period and progression. This may prevent cardiac/metabolic diseases in GP.

Respiratory and functional tests in the assessment and prognosis of patients with chagas disease

Chagas disease causes an important impact on cardiorespiratory system, functional and working capacity of the patient. Performing a functional assessment on these individuals becomes essential, since the impact of physical limitation is an important factor that is related with other life domains, such as risk of cardiovascular events in a brief period and risk of death. The goal of this work was to perform a literature review to present the evaluative and prognostic value of main valid respiratory and functional tests in patients with Chagas disease, as well as their applicability and reproducibility. A literature search was performed from 1981 to 2020 in Scielo, Pubmed/Medline, Science Direct, Scopus and Web of Science databases. Only complete studies published in English, Portuguese or Spanish were analyzed which specifically discussed the respiratory and functional tests used in patients with Chagas disease. In total, 544 articles were retrieved of which 35 were eligible. The main functional tests approached were Cardiopulmonary Exercise Testing, Incremental Exercise Testing and Six-Minute Walk Test. Several studies show themselves as useful markers for predicting quality of life, mortality and functional impairment, in addition to other patients’ characteristics. Several tests can be used to assess the respiratory and functional impact to patients’ health, as well as its relationship with important domains of their lives. KEY WORDS: Chagas disease; Chagas cardiomyopathy; exercise test; respiratory function tests; prognosis.

Cardiorespiratory fitness and left ventricular function in breast cancer survivors a decade after Epirubicin treatment

Abstract Background Anthracyclines are effective chemotherapeutic agents commonly used in breast cancer (BC) treatment. Cardiotoxicity is a serious adverse effect of anthracyclines, but knowledge of long-term cardiac effects is limited. To our knowledge, no prior study has investigated both cardiorespiratory fitness assessed by peak oxygen consumption (V̇O2 peak) and left ventricular (LV) function in long-term follow up of BC survivors (BCS) treated with anthracyclines. Purpose To assess long-term adverse effects of Epirubicin on cardiorespiratory fitness and LV function in BCS. Methods The CAUSE-trial is an ongoing study comparing exercise effects in BCS of stage I-III BC recruited from the Cancer Registry of Norway and controls with no cancer diagnosis. We present preliminary results from the baseline assessments in this trial. BCS (n=93) treated with Epirubicin between 2008 and 2013 were compared to age-matched controls (n=11). V̇O2 peak was assessed by incremental treadmill cardiopulmonary exercise test and LV function by echocardiography. Results At baseline, BCS were 58±7 years old and had received a cumulative dose of 339±85 mg/m2 Epirubicin 11±1 years before examination. There was no difference in V̇O2 peak between BSC and controls. LV ejection fraction was lower in BCS compared to controls assessed by 2D (57±3% vs. 59±2%, p=0.01) and 3D echocardiography (57±3% vs. 61±4%, p=0.006). LV global longitudinal strain was also lower (in absolute value) in BCS compared to controls (−20.6±1.3% vs. −22.0±1.3%, p=0.002). There was no difference in global work index and efficiency between BCS and controls. Conclusion Our findings indicate no difference in cardiorespiratory fitness between BCS and controls a decade after Epirubicin treatment. Systolic LV function was slightly lower in BCS compared to controls. Importantly, systolic LV function in BCS was within normal range, and the difference is probably not of clinical importance. There was no difference in myocardial work between BCS and controls. Funding Acknowledgement Type of funding sources: Public Institution(s). Main funding source(s): The Cancer Registry of Norway

Comparison of Ventilatory and Blood Lactate Thresholds in Elite Soccer Players

Despite a long research history, the lactate threshold continues to be a widely controversial field. Notwithstanding the controversies and influence of multiple determinants, the estimation of lactate threshold in sports has been considered one of the essential parameters in the prescription of training intensity, load monitoring, and perfor- mance prediction. The study aimed to compare the anaerobic ventilatory and lactate thresholds as determined by different methods in elite soccer players. The study consisted of twenty-five division 1 elite soccer players. The players were separated into two groups based on their run times on the treadmill. Group 1 (age 24.38±7.33 years, height 180.33±7.03 cm, weight 75.53±7.68 kg) consisted of players who completed more than 17 minutes on the treadmill, while group 2 (age 25.11±6.07 years, height 182.11±10.03 cm, weight 79.72±7.54 kg) consisted of those who completed less than 17 minutes. The players completed an incremental maximal cardiopulmonary exercise testing from which ventilatory thresholds were determined. Furthermore, measurements of blood samples were obtained every 3 minutes after completing each stage of the test, with a total of 141 measurements completed. Multivariate tests indicated no significant differences in the speeds calculated with ventilatory and lactate thresh- old methods. These findings suggest that the anaerobic ventilatory threshold (VT2) can be used as an alternative to the invasive lactate threshold measurements. Therefore, identifying a threshold point without utilizing an inva- sive procedure enhances the potential application of the VT2 or respiratory compensation point.

Exercise Intolerance in Untreated OSA: Role of Pulmonary Gas Exchange and Systemic Vascular Abnormalities

Reduced exercise capacity has been reported previously in patients with OSA hypopnea syndrome (OSAHS), although the underlying mechanisms are unclear. What are the underlying mechanisms of reduced exercise capacity in untreated patients with OSAHS? Is there a role for systemic or pulmonary vascular abnormalities? This was a cross-sectional observational study in which 14 patients with moderate to severe OSAHS and 10 control participants (matched for age, BMI, smoking history, and FEV1) underwent spirometry, incremental cycle cardiopulmonary exercise test (CPET) with arterial line, resting echocardiography, and assessment of arterial stiffness (pulse wave velocity [PWV] and augmentation index [AIx]). Patients (age, 50 ± 11 years; BMI, 30.5 ± 2.7kg/m2; smoking history, 2.4 ± 4.0 pack-years; FEV1 to FVC ratio, 0.78 ± 0.04; FEV1, 85 ± 14%predicted, mean±SD for all) had mean ± SD apnea hypopnea index of 43 ± 19/h. At rest, PWV, AIx, and mean pulmonary artery pressure (PAP) were higher in patients vscontrol participants (P< .05). During CPET, patients showed lower peak work rate (WR) and oxygen uptake and greater dyspnea ratings compared with control participants (P< .05 for all). Minute ventilation (V·E), ventilatory equivalent for CO2 output (V·E/V·CO2), and dead space volume (VD) to tidal volume (VT) ratio were greater in patients vscontrol participants during exercise (P< .05 for all). Reduction in VD to VT ratio from rest to peak exercise was greater in control participants compared with patients (0.24 ± 0.08 vs0.04 ± 0.14, respectively; P= .001). Dyspnea intensity at the highest equivalent WR correlated with corresponding values of V·E/V·CO2 (r= 0.65; P= .002), and dead space ventilation (r= 0.70; P= .001). Age, PWV, and mean PAP explained approximately 70%of the variance in peak WR, whereas predictors of dyspnea during CPET were rest-to-peak change in VD to VT ratio and PWV (R2= 0.50; P< .001). Patients with OSAHS showed evidence of pulmonary gas exchange abnormalities during exercise (in the form of increased dead space) and resting systemic vascular dysfunction that may explain reduced exercise capacity and increased exertional dyspnea intensity.

Effect of individual characteristics and aerobic training on the %HRR-%V̇O2R relationship

ABSTRACT This study aimed to assess if, during incremental exercise, considering individual characteristics can make the relationship between the percentages of heart rate (HRR) and oxygen uptake (V̇O2R) reserve either 1:1 or more accurate. Cycle ergometer data of the maximal incremental exercise tests performed by 450 healthy and sedentary participants (17-66 years) of the HERITAGE Family Study, grouped for sex, ethnicity, age, body fat, resting HR, and V̇O2max, were used to calculate the individual linear regressions between %HRR and %V̇O2R. The mean slope and intercept of the individual linear regressions of each subgroup were compared with 1 and 0 (identity line), respectively, using Hotelling tests followed by post-hoc one-sample t-tests. Two multiple linear regressions were also performed, using either the slopes or intercepts of the individual linear regressions as dependent variables and sex, age, resting HR, and V̇O2max as independent variables. The mean %HRR-%V̇O2R relationships of all subgroups differed from the identity line. Moreover, individual linear regression intercepts (8.9 ± 16.0) and slopes (0.971 ± 0.190) changed (p < 0.001) after 20 weeks of aerobic training (13.1 ± 11.1 and 0.891 ± 0.122). The multiple linear regressions could explain only 3.8% and 1.3% of the variance in the intercepts and slopes, whose variability remained high (standard error of estimate of 15.8 and 0.189). In conclusion, the %HRR-%V̇O2R relationship differs from the identity line regardless of individual characteristics and their difference increased after aerobic training. Moreover, due to the high interindividual variability, using a single equation for the whole population seems not suitable for representing the %HRR-%V̇O2R relationship of a given subject, even when several individual characteristics are considered. Highlights The association between %HRR and %V̇O2R is not 1:1 even when individuals are grouped by age, sex, ethnicity, body composition, HRrest, and V̇O2max. Using several subject characteristics to identify the individual’s %HRR-%V̇O2R relationship does not meaningfully increase its prediction accuracy or reduce the interindividual variability of %HRR-%V̇O2R relationships Using a single equation for the whole population is not suitable for representing the relationship of a given subject; hence, individual relationships should be preferred when prescribing the intensity of aerobic exercise. The individual %HRR-%V̇O2R relationship should be periodically assessed due to the potential training induced changes in the relationship.

The mediating role of inhibitory control in the relationship between prefrontal cortex hemodynamics and exercise performance in adults with overweight or obesity

Physical inactivity has been suggested to impair physical performance, cognitive functions and facilitate weight gain. One hypothesis is that long periods of physical inactivity could impair oxygen delivery to the prefrontal cortex (PFC), impairing one's cognitive ability to inhibit unhealthy automated behaviors and, therefore, reduce exercise tolerance. The present study sought to further understand the relationship among PFC hemodynamics, inhibitory control, and exercise tolerance in individuals with low physical fitness levels who are overweight or obese. Thirty-four participants were asked to perform a series of inhibitory control tests (i.e., Stroop task) in one testing session and complete an incremental cycling exercise test with hemodynamic fluctuations of the PFC measured with functional near-infrared spectroscopy in another session. Our results indicate that exercise performance varied with PFC oxygenation. We also found that inhibitory control played a key role mediating the relationship between PFC oxygenation and exercise performance, suggesting that the cognitive ability to inhibit automated responses has an impact on exercise behavior in adults with overweight and obesity.

Effect of sleep and fatigue on cardiovascular performance in young, healthy subjects

Physical performance could be negatively affected by sleep deficiency and fatigue. The present study assesses the role of sleep quality, fatigue and motivation on cardiovascular performance (VO2peak, Wmax, and HRmax) in a sample of active young subjects.The current study is a cross-sectional design. Ninety-six university students (males 54.2%; 21.5 ± 2.9 yrs) completed an incremental exercise test on a bicycle ergometer. Sleep, fatigue, and motivation were assessed with the Pittsburgh Sleep Quality Index and two visual analogue scales, respectively. Differences in VO2peak, Wmax, HRmax, self-perceived fatigue and motivation were compared between good and bad sleepers and sleep duration >/<7.5 h, while regression analysis defined the predictors of VO2peak, Wmax, and HRmax.In the male sample, good and bad sleepers' differences were significant only for self-perceived fatigue (p = 0.04). The female sample showed no statistically significant differences between good and bad sleepers and different sleep durations. In the male sample, linear regression analysis showed a significant inverse correlation between Wmax and the PSQI score (-0.4, p = 0.004). The stepwise regression model indicated that sleep (β = -0.3, p = 0.02) was a significant predictor of VO2peak in males accounting for 20% of the variance, whereas physical performance seems more affected by fatigue (β = -0.4, p = 0.03) in females. In conclusion, chronic inadequate and self-reported sleep quality seems to be one of the factors compromising cardiovascular performance in males.

Influence of sex and presence of cardiovascular risk factors on relations between cardiorespiratory fitness and cerebrovascular hemodynamics.

Cerebral hemodynamics and pulsatility are important mechanisms of cerebrovascular and brain health. Cardiorespiratory fitness may improve cerebrovascular pulsatility in healthy females, but not in males. Whether cardiovascular disease (CVD) risk factors modify sex-specific associations of fitness with cerebral hemodynamics and vascular contributors to cerebral hemodynamics is unknown. We assessed V̇o2peak and cerebrovascular hemodynamics in 157 adults without (42 ± 13 yr, BMI 24.5 ± 2.7 kg/m2), and 66 adults with modifiable CVD risk factors (54 ± 8 yr, BMI 29.9 ± 4.0 kg/m2). Intracranial [middle cerebral artery (MCA) pulsatility index (PI), mean velocity, conductance, and pulsatile damping] and extracranial hemodynamics [carotid artery wave transmission/reflection, PI, pulse wave velocity (PWV)-β, and carotid-femoral PWV] were assessed via transcranial Doppler/ultrasound and tonometry. Cardiorespiratory fitness was assessed via V̇o2peak during an incremental exercise test. Multiple regression was used to assess contributions of V̇o2peak to cerebrovascular outcomes after adjustment for relevant covariates. V̇o2peak was inversely associated with MCA PI among females (β = -0.39, P = 0.01) but not males (β = -0.16, P = 0.25) without CVD risk factors. V̇o2peak was positively associated with MCA PI among females (β = 0.44, P = 0.01) and not associated in males with CVD risk factors (β = -0.06, P = 0.079). V̇o2peak was beneficially associated with vascular contributors to cerebral hemodynamics but had sex-specific associations with carotid stiffness and pulse pressure in females without CVD risk factors only. These results suggest that sex-specific associations between fitness and cerebral pulsatility among females without CVD risk factors may relate to the differential effects of fitness on carotid stiffness and pulse pressure. In addition, the presence of modifiable CVD risk factors may influence the protective relations of fitness on cerebrovascular hemodynamics.NEW & NOTEWORTHY We identify beneficial associations between cardiorespiratory fitness and lower carotid stiffness and pulse pressure as potential mechanisms underlying sex-specific associations of fitness and cerebral pulsatility in females without modifiable risk factors. Greater fitness is beneficially associated with conductance, pulsatile damping, and forward wave energy among adults without risk factors; however, associations are attenuated among adults with modifiable risk factors. These data suggest sex and risk factors may alter cerebrovascular sensitivity to cardiorespiratory fitness.

Effects Of Astaxanthin On Aerobic Capacity And Antioxidant Enzymes For Team Sport Athletes

PURPOSE:Frequent competition can cause oxidative stress, leading to fatigue and a decrease in aerobic capacity. Antioxidant supplementation are commonly consumed to minimize exercise-induced oxidative stress, with the intention of enhancing recovery and improving performance. Thus, this study aims to determine 4 weeks supplement of astaxanthin on aerobic capacity, the recovery of blood lactic acid and antioxidant enzymes activity in team sports athletes during season training. METHODS:Twenty team sport varsity athletes (basketball: n = 10, football: n = 10) were randomly assigned in double-blind fashion to one of two treatment groups. The astaxanthin group (AST, n = 10) was supplemented 12 mg of astaxanthin for 4 weeks, and the placebo group was supplemented with olive oil capsules of the same dose. The incremental exercise test was performed before and after the supplementation, respectively. Fingertip blood was collected at 3, 6 and 9 min after exercise, blood lactic acid were analysed that day and calculated removal rate. Fasting venous blood was collected before and 12 h after incremental exercise test, and the activity of SOD, CAT and GSH-Px were measured. Performance indicators comparisons were made using independent sample T test and paired sample T test. Antioxidant enzymes activity comparisons were made using two-way ANOVA repeated measures. RESULTS:There were no significant changes in exhaustion time and VO2max in AST group, while the exhaustion time (17.22 ± 1.64 vs 15.53 ± 1.70 min P < 0.01) and VO2max (49.14 ± 4.41 vs 44.57 ± 3.87 ml/min/kg, P < 0.05) in PLA group were significantly decreased; The blood lactic acid removal rate had no significant change in two groups(P > 0.05);There was no significant change in the activity of antioxidant enzymes before exercise, but both the CAT (7.93 ± 0.83 vs. 2.91 ± 0.55 U/ml, P < 0.05)and GSH-Px(181.40 ± 9.49 vs. 155.39 ± 8.03 U/ml, P < 0.05) activity recovered more quickly at 12 h after exhaustive exercise than 0-week in AST group. CONCLUSIONS:4 weeks of training during the season can lead to a decline in aerobic capacity in team sport athletes, but intake of astaxanthin can help speed up CAT and GSH-Px activity recovery after exhaustive exercise, then enhancing recovery and improving performance. Supported by Herbalife Winter Sports Nutrition Research Center

Apport de l’hélium dans la réhabilitation respiratoire de patients BPCO sévères

Out of the 53 patients included, 45 were randomly assigned to two groups: Heliox (n= 23) and Air (n= 22). Patients were assessed with spirometry under air and heliox, incremental exercise test, constant workload (80% Wmax) exercise test and weekly 6-minute walk test. The two groups went through fifteen 30-minute retraining sessions in the overall framework of an identical pulmonary rehabilitation program. There was no significant difference in endurance improvement (Heliox: +52.5 sec, Air:+114sec, median value). FEV1 improvement under heliox exceeding 10% identified a group of 20 patients as "helium responders", who improved their endurance time by a median of 135sec compared to 50sec for the "non-responders" (non-significant difference). In patients with severe COPD, use of Heliox in exercise retraining did not produce significantly improved endurance. On the other hand, "helium responders" showed more FEV1 improvement than non-responders. Improved FEV1 under heliox should therefore be used in future studies as an inclusion criterion.

Left Ventricular Inotropic Response To An Exertional Challenge After Sympathetic Decentralization In Humans

Purpose: Cardiac sympathetic decentralization is a phenomenon in which supraspinal sympathoadrenal control to the heart is deprived. Dysfunction of the sympathetic nervous system is known to contribute to blood pressure abnormalities, arrhythmias, diminished heart rate variability, restricted peak heart rate, and decreased venous return and stroke volume. Cardiac inotropic insufficiency as a result of sympathetic dysfunction has been less frequently studied. This study aimed to characterize the change in left ventricular (LV) inotropicity from rest to a severe exercise challenge in the sympathetically decentralized heart using complete spinal cord injury (cSCI) as a model. Methods: We present two male cases with cSCI (age: 45 and 30 years, BMI 21.8 and 29.5 kg/m2) and compared them with two male sedentary otherwise healthy individuals (age: 43 and 29 years, BMI 29.2 and 25.6 kg/m2). Subjects underwent an incremental arm-ergometer exercise (iAEE) test to peak volitional exhaustion. All indices of LV inotropicity and hemodynamic loading conditions were assessed at rest, during iAEE and at peak iAEE using bioimpedance cardiography (PhysioFlow® Enduro, Manatec, France). LV inotropic response was characterized by observing the response of the acceleration index (dZ/dt2) in all subjects. Results: dZ/dt2 was observed to be impaired in subjects with cSCI compared to the healthy control counterparts (baseline: 0.39 and 0.44 vs .41 and 0.48; peak; 0.55 and 1.073. vs 0.96 and 0.97, respectively). Concomitant differences in the heart rate (HR) and cardiac output (Q) responses to maximal exercise between the cSCI and control subjects were also observed. HR baseline: 57 and 73 vs 97 and 63 bpm; peak: 123 and 99 vs 176 and 151 bpm, respectively. Q baseline: 4.38 and 6.04. vs 6.93 and 5.35 L/m; peak: 11.3 and 10.3 vs 17.06 and 13.94 L/m, respectively. Conclusions: A dichotomy in both the inotropic and chronotropic responses to exercise was apparent in the subjects with decentralizing cSCI. This preliminary data could underscore a critical dependency on heterometric autoregulation for mechanizing increases in cardiac function response to exercise in complete high-level SCI.

Cortisol response under low intensity exercise during cognitive-behavioral therapy is associated with therapeutic outcome in panic disorder-an exploratory study.

Patients with Panic Disorder (PD) show an abnormal stress-induced functioning of the Hypothalamic-Pituitary-adrenal (HPA)-axis. Different protocols for stress induction are of rather low relevance for the psychotherapeutic treatment. In practice, interoceptive exposure is often realized as Low Intensity Exercise (LIE), as compared to an incremental cycle exercise test to exhaustion. Currently, it is not known, whether LIE displays an effective interoceptive stressor 1.) leading to a significant anxiety induction; 2.) a comparable HPA- and Sympathetic-Adreno-Medullar (SAM)-axis response in both patients and healthy controls; 3.) stress responses under LIE are associated with treatment outcomes. N = 20 patients with PD and n = 20 healthy controls were exposed to ten minutes of LIE on an exercise bike. LIE was applied as part of the interoceptive exposure, during an intensive Cognitive-Behavioral Therapy (CBT) in a day clinic. Heart rate was monitored and salivary cortisol samples collected. Before and after the LIE, state anxiety/ arousal were assessed. In order to evaluate psychopathology, the Panic and Agoraphobia Scale, Mobility Inventory, Agoraphobic Cognitions Questionnaire and Body Sensations Questionnaire were applied, before (T1) and after five weeks (T2) of an intensive CBT. LIE led to a significant and similar heart rate increase in both groups. Cortisol decreased over time in both groups, especially in male patients. A higher psychopathology before, and after CBT, was associated with a significantly lower cortisol response under LIE. In the present study, LIE led to a divergent stress response: while there was a significant heart rate increase, cortisol decreased over time, particularly in male patients. A lower reactivity of the HPA-axis seems to be associated with a lower treatment outcome, which may affect extinction based learning. The findings suggest, that interoceptive stimuli should be designed carefully in order to be potent stressors.

Enjoyment And Tolerance Of Exercise Intensity In Objectively Versus Subjectively Regulated Interval Exercise In Older Adults

High-intensity interval exercise (HIIE) has led to significant improvements in fitness in healthy and clinical populations, including older adults. Recent evidence suggests that treadmill based HIIE using subjectively regulated HIIE may be more practically applicable to the real world and generates a similar training load for older adults to heart rate regulated HIIE. According to the guidelines of the American College of Sports Medicine, information regarding exercise enjoyment and individual preference for and tolerance of exercise intensity should be considered when developing and modifying exercise prescriptions for successful exercise adherence. PURPOSE: To examine the associations of preference for and tolerance of exercise intensity with physiological performance and perceptual outcomes during single sessions of HIIE using either subjectively (SUB) or objectively (OBJ) prescribed exercise in a treadmill in apparently healthy older adults. METHODS: Fourteen participants (71 ± 9 yrs) completed the Physical Activity Enjoyment Scale to measure exercise enjoyment and Preference for and Tolerance of the Intensity of Exercise Questionnaire to measure Preference (PREF) and Tolerance (TOL). Participants underwent an incremental exercise test on a treadmill in order to prescribe the OBJ session. This was followed by two randomly assigned HIIE sessions wherein the intensity of the exercise was prescribed and regulated by either heart rate (OBJ) or ratings of perceived exertion (RPE; SUB). The HIIE bouts consisted of 10 cycles of 1-min intervals at 80-90% and 30-40% HRpeak and at 8-9 and 3-4 RPE values for the OBJ and SUB sessions, respectively. Oxygen consumption (VO2), speed, and incline were measured during the OBJ and SUB sessions. RESULTS: Enjoyment was positively associated with speed during the OBJ (r = .60, p = .02) and SUB (r = .84, p < .01) sessions, incline during the OBJ (r = .60, p.03) session, and VO2 during the SUB (r = .73, p < .01) session. PREF was not significantly associated with any of the outcomes. TOL was negatively associated with incline during the SUB session (r = -.51, p = .05). CONCLUSIONS: Enjoyment and TOL scores, through associations with speed and VO2 in subjectively-regulated HIIT sessions, may be important for personalizing and modifying exercise prescriptions in older adults.

Predicting maximal lactate steady state from lactate thresholds determined using methods based on an incremental exercise test in beagle dogs: A study using univariate and multivariate approaches

The reliability of four lactate threshold (LT) methods to estimate the maximal lactate steady state (MLSS), defined as the highest intensity that can be maintained without plasma lactate ([La−]) accumulation over time, was determined in Beagle dogs. Six male Beagle dogs performed a standardized incremental exercise test on a treadmill when plasma lactate ([La−]) measurements were performed. The LTs for predicting MLSS, were determined by visual inspection (LTV), using a bi-segmented linear regression model (LTBI), or using a polynomial function on the [La−]/velocity ratio (LTP) by considering the vertices of the curve and calculating the point that yields the maximal distance from a curve representing [La−] as a function of velocity to the line formed by the two endpoints of the curve (LTDMAX method). The agreement was assessed using Bland-Altman plots and ordinary least products (OLP) regression among the velocities corresponding to the LTs identified using different methods (VLTv, VLTBI, VLTP, and VLTDMAX) and the velocity corresponding to the MLSS (VMLSS). A principal component (PC) analysis approach was performed to detect the degree of co-relatedness among the variables. The mean ± SD [La−] at MLSS was 1.03 ± 0.24 mM. VMLSS had a lower mean bias with VLTv, followed by VLTBI. The VLTDMAX underestimated MLSS. VLTv and VLTBI had the lowest limits of agreement with the VMLSS. The VLTP and VLTDMAX showed relatively high limits of agreement with MLSS. VLTv, VLTBI, and VMLSS had more collinearity and were dominantly aligned with the second component (PC2). VLTv and VLTBI can be used as simple methods to objectively determine aerobic fitness in Beagle dogs.

Right ventricular-pulmonary arterial coupling impairment and exercise capacity in obese adults.

BackgroundObesity-related exercise intolerance may be associated with pulmonary vascular and right ventricular dysfunction. This study tested the hypothesis that decreased pulmonary vascular reserve and right ventricular (RV)-pulmonary arterial (PA) uncoupling contributes to exercise limitation in subjects with obesity.MethodsSeventeen subjects with obesity were matched to normo-weighted healthy controls. All subjects underwent; exercise echocardiography, lung diffusing capacity (DL) for nitric oxide (NO) and carbon monoxide (CO) and an incremental cardiopulmonary exercise test. Cardiac output (Q), PA pressure (PAP) and tricuspid annular plane systolic excursion (TAPSE) were recorded at increasing exercise intensities. Pulmonary vascular reserve was assessed by multipoint mean PAP (mPAP)/Q relationships with more reserve defined by lesser increase in mPAP at increased Q, and RV-PA coupling was assessed by the TAPSE/systolic PAP (sPAP) ratio.ResultsAt rest, subjects with obesity displayed lower TAPSE/sPAP ratios (1.00 ± 0.26 vs. 1.19 ± 0.22 ml/mmHg, P < 0.05), DLCO and pulmonary capillary blood volume (52 ± 11 vs. 64 ± 13 ml, P < 0.01) compared to controls. Exercise was associated with steeper mPAP-Q slopes, decreased TAPSE/sPAP and lower peak O2 uptake (VO2peak). The changes in TAPSE/sPAP at exercise were correlated to the body fat mass (R = 0.39, P = 0.01) and VO2peak (R = 0.44, P < 0.01).ConclusionObesity is associated with a decreased pulmonary vascular and RV-PA coupling reserve which may impair exercise capacity.

Effect of caffeine intake on fat oxidation rate during exercise: is there a dose-response effect?

The effect of caffeine to enhance fat utilisation as fuel for submaximal aerobic exercise is well established. However, it is unknown whether this effect is dose dependent. The aim of this study was to investigate the effect of 3 and 6mg of caffeine per kg of body mass (mg/kg) on whole-body substrate oxidation during an incremental cycling exercise test. In a double-blind, randomised, and counterbalanced experiment, 18 recreationally active males (maximal oxygen uptake [VO2max] = 56.7 ± 8.2mL/kg/min) performed three experimental trials after ingesting either 3mg/kg of caffeine, 6mg/kg of caffeine or a placebo (cellulose). The trials consisted of an incremental exercise test on a cycle ergometer with 3-min stages at workloads from 30 to 80% of VO2max. Energy expenditure, fat oxidation rate, and carbohydrate oxidation rate were continuously measured by indirect calorimetry. During exercise, there was significant effect of substance (F = 7.969; P = 0.004) on fat oxidation rate. In comparison to the placebo, the rate of fat oxidation was higher with 3mg/kg of caffeine at 30, 40, 50 and 70% of VO2max [all P < 0.050, effect sizes (ES) from 0.38 to 0.50] and with 6mg/kg of caffeine at 30, 40, 50, 60 and 70% of VO2max (all P < 0.050, ES from 0.28 to 0.76). Both 3mg/kg (0.40 ± 0.21g/min, P = 0.021, ES = 0.57) and 6mg/kg of caffeine (0.40 ± 0.17g/min P = 0.001, ES = 0.60) increased the maximal rate of fat oxidation during exercise over the placebo (0.31 ± 0.15g/min). None of the caffeine doses produced any significant effect on energy expenditure or heart rate during exercise, while both caffeine doses reduced perceived fatigue at 80% of VO2max (all P < 0.050, ES from 0.71 to 1.48). The effect of caffeine to enhance fat oxidation during submaximal aerobic exercise is of similar magnitude with 3 and 6mg of caffeine per kg of body mass. Thus, a dose of 3mg of caffeine per kg of body mass would be sufficient to enhance fat utilisation as fuel during submaximal exercise.

Firefighter salivary cortisol responses following rapid heat stress

This research evaluated the impact of rapid heat stress on the rate of salivary cortisol appearance. We hypothesized that rapid heat stress would result in an increased rate of salivary cortisol appearance. Fourteen adult male participants performed an incremental exercise test to a termination criterion (volitional maximum, core temperature = 39.5 °C, or a 2-h time maximum time) with or without firefighting gear in a laboratory with an ambient temperature of 25-26 °C. Salivary cortisol was collected at each 0.5 °C increase in core temperature. We observed a significant increase (p ≤ 0.01) in the rate of cortisol appearance when the subjects were wearing the firefighting gear; no change was observed without firefighting gear. Our results demonstrate that rapid heat stress and the resulting physiological stress cause a rapid increase in the rate of salivary cortisol appearance. Our results also support previous research demonstrating that cortisol is a sensitive strain metric of heat intolerance.

Effects of Different Durations at Fixed Intensity Exercise on Internal Load and Recovery-A Feasibility Pilot Study on Duration as an Independent Variable for Exercise Prescription.

Duration is a rarely investigated marker of exercise prescription. The aim of this study was to test the feasibility of the methodological approach, assessing effects of different duration constant-load exercise (CLE) on physiological responses (internal load) and recovery kinetics. Seven subjects performed an incremental exercise (IE) test, one maximal duration CLE at 77.6 ± 4.8% , and CLE’s at 20%, 40%, and 70% of maximum duration. Heart rate (HR), blood lactate (La), and glucose (Glu) concentrations were measured. Before, 4, 24, and 48 h after CLE’s, submaximal IE tests were performed. HR variability (HRV) was assessed in orthostatic tests (OT). Rating of perceived exertion (RPE) was obtained during all tests. CLE’s were performed at 182 ± 27 W. HRpeak, Lapeak, , and RPEpeak were significantly higher in CLE’s with longer duration. No significant differences were found between CLE’s for recovery kinetics for HR, La, and Glu in the submaximal IE and for HRV or OT. Despite no significant differences, recovery kinetics were found as expected, indicating the feasibility of the applied methods. Maximum tests and recovery tests closer to CLE’s termination are suggested to better display recovery kinetics. These findings are a first step to prescription of exercise by both intensity and duration on an individual basis.

Cardiorespiratory Optimal Point Is a Submaximal Exercise Test Variable and a Predictor of Mortality Risk: THE BALL STATE ADULT FITNESS LONGITUDINAL LIFESTYLE STUDY (BALL ST).

The cardiorespiratory optimal point (COP) is the minimum ventilatory equivalent for oxygen. The COP can be determined during a submaximal incremental exercise test. Reflecting the optimal interaction between the respiratory and cardiovascular systems, COP may have prognostic utility. The aim of this investigation was to determine the relationship between COP and all-cause mortality in a cohort of apparently healthy adults. The sample included 3160 apparently healthy adults (46% females) with a mean age of 44.0 ± 12.5 yr who performed a cardiopulmonary exercise test. Cox proportional hazards models were performed to assess the relationship between COP and mortality risk. Prognostic peak oxygen uptake (V˙ o2peak ) and COP models were compared using the concordance index. There were 558 deaths (31% females) over a follow-up period of 23.0 ± 11.9 yr. For males, all Cox proportional hazards models, including the model adjusted for traditional risk factors and V˙ o2peak , had a positive association with risk for mortality ( P &lt; .05). For females, only the unadjusted COP model was associated with risk for mortality ( P &lt; .05). The concordance index values indicated that unadjusted COP models had lower discrimination compared with unadjusted V˙ o2peak models ( P &lt; .05) and V˙ o2peak did not complement COP models ( P ≥ .13). Cardiorespiratory optimal point is related to all-cause mortality in males but not females. These findings suggest that a determination of COP can have prognostic utility in apparently healthy males aged 18-85 yr, which may be relevant when a maximal exercise test is not feasible or desirable.