Graded Cycling Exercise Test Research Articles

Effect of Acute Altitude Exposure on Anaerobic Threshold Assessed by a Novel Electrocardiogram-Based Method.

Background: Acute altitude has a relevant impact on exercise physiology and performance. Therefore, the positive impact on the performance level is utilized as a training strategy in professional as well as recreational athletes. However, ventilatory thresholds (VTs) and lactate thresholds (LTs), as established performance measures, cannot be easily assessed at high altitudes. Therefore, a noninvasive, reliable, and cost-effective method is needed to facilitate and monitor training management at high altitudes. High Alt Med Biol. 25:94-99, 2024. Methods: In a cross-sectional setting, a total of 14 healthy recreational athletes performed a graded cycling exercise test at sea level (Munich, Germany: 512 m/949 mbar) and high altitude (Zugspitze: 2,650 m/715 mbar). Anaerobic thresholds (ATs) were assessed using a novel method based on beat-to-beat repolarization instability (dT) detected by Frank-lead electrocardiogram (ECG) monitoring. The ECG-based ATs (ATdT°) were compared to routine LTs assessed according to Dickhuth and Mader. Results: After acute altitude exposure, a decrease in AT was detected using a novel ECG-based method (ATdT°: 159.80 ± 52.21 W vs. 134.66 ± 34.91 W). AtdT° levels correlated significantly with LTDickhuth and LTMader, at baseline (rDickhuth/AtdT° = 0.979; p < 0.001) (rMader/AtdT° = 0.943; p < 0.001), and at high altitude (rDickhuth/AtdT° = 0.969; p < 0.001) (rMader/AtdT° = 0.942; p < 0.001). Conclusion: Assessment of ATdT is a reliable method to detect performance alterations at altitude. This novel method may facilitate the training management of athletes at high altitudes.

Maximum Phonation Time as a Predictor of Lactate Threshold during Intermittent Incremental Endurance Test.

The aim of the present study was to examine whether the exercise intensity corresponding to the lactate threshold may be predicted by the Maximum Phonation Time task (MPT). Ten Greek amateur football players (age: 18.4 ± 1.0 years), performed a graded cycling exercise test to exhaustion in order to determine lactate threshold. A number of physiological variables were measured including perceived exertion, cardiopulmonary values and blood lactate. The MPT variable was correlated with all of the physiological variables. Also, a binary logistic regression analysis was used to investigate whether MPT could predict lactate threshold. The ROC analysis showed specificity to be 0.90 and sensitivity to be 0.70 (optimal screening cutoff point for MPT 9.5 seconds). The results showed an odds ratio of 1.45 indicating a 45% increase in the probability of passing the threshold for every second there was a reduction in voice duration. MPT may be used as a simple, non-invasive, inexpensive method for monitoring exercise intensity during physical exercise. Further research is needed to measure its efficacy in bigger samples and in different sports.

The Interaction Between Psychosocial Factors and Exercise-Induced Hypoalgesia in Pain-Free Nurses.

This cross-sectional study aimed to investigate whether psychosocial factors were predictive for exercise-induced hypoalgesia (EIH) in pain-free adults. A sample of 38 pain-free nurses with a mean (SD) age of 26 (6) years were included in this study. Participants completed psychosocial questionnaires prior to physical tests. Pressure pain threshold (PPT) was assessed bilaterally at the calves (local), lower back (semi-local) and forearm (remote) before and immediately after a maximal graded cycling exercise test. Separate linear mixed effects models were used to determine change in PPT before and after cycling exercise (EIH). Multiple linear regression for all psychosocial variables and best subset regression was used to identify predictors of EIH at all locations. The relative mean increase in PPT at the forearm, lumbar, calf, and globally (all sites pooled) was 6.0% (p<0.001), 10.1% (p<0.001), 13.9% (p<0.001), and 10.2% (p=0.013), respectively. Separate best subset multiple linear regression models at the forearm (predictors; Multidimensional Scale of Perceived Social Support (MSPSS) total), lumbar (predictors; MSPSS total, Pain Catastrophizing Scale (PCS) total, Depression Anxiety Stress Scale (DASS) depression), calf (predictors; MSPSS friends, PCS total), and global (predictors; MSPSS friends, PCS total) accounted for 7.5% (p=0.053), 13% (p=0.052), 24% (p=0.003), and 17% (p=0.015) of the variance, respectively. These findings confirm that cycling exercise produced EIH in young nurses and provided preliminary evidence to support the interaction between perceived social support, pain catastrophizing and EIH. Further investigation is required to better understand psychological and social factors that mediate EIH on a larger sample of adults at high risk of developing chronic musculoskeletal pain.

UBC-Nepal Expedition: Cerebrovascular Responses to Exercise in Sherpa Children Residing at High Altitude.

Understanding the process of successful adaptation to high altitude provides valuable insight into the pathogenesis of conditions associated with impaired oxygen uptake and utilization. Prepubertal children residing at low altitude show a reduced cerebrovascular response to exercise in comparison to adults, and a transient uncoupling of cerebral blood flow to changes in the partial pressure of end-tidal CO2 (PETCO2); however, little is known about the cerebrovascular response to exercise in high-altitude native children. We sought to compare the cerebral hemodynamic response to acute exercise between prepubertal children residing at high and low altitude. Prepubertal children (n = 32; 17 female) of Sherpa descent (Sherpa children [SC]) at high altitude (3800 m, Nepal) and maturational-matched (n = 32; 20 female) children (lowland children [LLC]) residing at low altitude (342 m, Canada). Ventilation, peripheral oxygen saturation (SpO2), PETCO2, and blood velocity in the middle and posterior cerebral arteries (MCAv and PCAv) were continuously measured during a graded cycling exercise test to exhaustion. At baseline (BL), PETCO2 (-19 ± 4 mmHg, p < 0.001), SpO2 (-6.0% ± 2.1%, p < 0.001), MCAv (-12% ± 5%, p = 0.02), and PCAv (-12% ± 6%, p = 0.04) were lower in SC when compared with LLC. Despite this, the relative change in MCAv and PCAv during exercise was similar between the two groups (p = 0.99). Linear regression analysis demonstrated a positive relationship between changes in PETCO2 with MCAv in SC (R2 = 0.13, p > 0.001), but not in LLC (R2 = 0.03, p = 0.10). Our findings demonstrate a similar increase in intra-cranial perfusion during exercise in prepubertal SC, despite differential BL values and changes in PETCO2 and SpO2.

Modeling Perceived Exertion during Graded Arm Cycling Exercise in Spinal Cord Injury.

RPE may be useful for exercise testing and prescription in individuals with spinal cord injury (SCI), although the roles of differentiated central and peripheral fatigue during exercise are not clear. We aimed to model differentiated RPE responses during graded arm cycling in individuals with SCI and to describe their relationship to cardiorespiratory outcomes. Thirty-six individuals with SCI (13 paraplegia and 23 tetraplegia) completed a maximal graded arm cycling exercise test to volitional exhaustion (5 W·min paraplegia; 10 W·min tetraplegia). Participants were asked to report central RPE (CRPE) and peripheral RPE (PRPE) every minute using the Borg category ratio (CR10) scale until termination of exercise. Heart rate and breath-by-breath respiratory outcomes were collected throughout the exercise test. Ventilatory threshold (VT) was assessed using the ventilatory equivalents method. Cardiorespiratory indices increased linearly during graded arm exercise. By contrast, both CRPE and PRPE responses were best fit to a quadratic model with positively accelerating growth in individuals with paraplegia (P < 0.01) and tetraplegia (P < 0.05). PRPE developed faster than CRPE in individuals with tetraplegia (P < 0.01). Individuals with paraplegia had accelerated CRPE (P < 0.05) and PRPE (P < 0.05) responses compared with tetraplegia, but not when considering only individuals who reached VT. PRPE was higher than CPRE only in the late stages (80%-100% test duration; P < 0.05) in both groups when only considering individuals who reached VT. PRPE develops faster than CRPE in individuals with tetraplegia in a nonlinear fashion, despite linear increases in cardiorespiratory responses during graded arm cycling. Although there is promise to use differentiated RPE for exercise testing and prescription within the SCI population, our results indicate that there are differences in how individuals with tetraplegia perceive peripheral versus central exertion.

The Effect of Acute Simulated Altitude on the Lactate Thresholds of Well-Trained Cyclists

PURPOSE: Endurance cyclists often race or train at altitudes ranging from 1,000-3,000 m above sea level. It is well known that peak oxygen consumption (VO2peak) and mean power output (PO) decrease with increasing altitude. However, factors such as lactate thresholds are also important for endurance performance. Research investigating the response of the lactate thresholds to acute hypoxia is however scarce. The aim of this study was to quantify and titrate the acute effect of simulated altitude on the lactate thresholds of well-trained cyclists. METHODS: Ten well-trained, non-altitude acclimatized male cyclists and triathletes completed a graded cycling exercise test in a hypobaric chamber at each of four simulated altitudes (200, 1,200, 2,200, 3,200 m). The test protocol comprised 5 x 5-min submaximal efforts (50, 100, 150, 200 and 250 W), to determine VO2, heart rate (HR) and blood lactate concentration ([La-]) responses. Following a 10 min passive rest, a 5-min maximal time-trial (5-minTT) was performed to determine peak physiological and performance responses. Combining these measures allowed a modified 2-in-1 protocol to be applied to calculate the lactate thresholds (LT1, LT2) using customized software (ADAPT). RESULTS: VO2 decreased by 5.5 ± 1.1%, 15.9 ± 1.5% and 26.3 ± 1.4% at LT1 and by 6.5 ± 1.2%, 13.4 ± 1.3% and 23.2 ± 1.8% at LT2 at 1,200, 2,200 and 3,200 m compared with 200 m respectively, P<0.05. Mean PO declined by 5.4 ± 1.1%, 17.7 ± 1.7% and 30.3 ± 1.9% for LT1 and by 5.2 ± 1.3%, 13.9 ± 1.4% and 25.7 ± 1.8% at LT2 at 1,200, 2,200 and 3,200 m compared with 200 m respectively, P<0.05. HR and [La-] at these thresholds remained unchanged. 5-minTT VO2peak and PO both followed the same pattern of decline with increasing altitude, P<0.05. CONCLUSIONS: A dose response effect of acute hypobaric hypoxia on VO2 and PO was found at both submaximal (LT1 and LT2) and maximal (5-minTT) intensities. No such effects were seen for HR or [La-] at any intensity.

Effects of Low-Frequency Vibration on Physiological Recovery from Exhaustive Exercise

Objective: This study examined the effects of low-frequency vibration on physiological recovery from exhaustive exercise. Methods: Twelve college males were recruited in this randomized crossover-designed study, and were asked to perform one of three treatments following a graded cycling exercise test: nonvibration (0 Hz, 0 mm, CON), high-amplitude vibration (8 Hz, 8 mm, HVT), or low-amplitude vibration (8 Hz, 2 mm, LVT). After the 10-min treatment, participants were asked to rest in a supine position for a 1-h recovery. The oxygen uptake, heart rate (HR), and blood lactate concentration (La) were measured during the trials. Results: The oxygen uptake during HVT were significantly higher than those in the CON and LVT (p &lt; 0.05, effect size = 1.52−1.63). The La immediately following HVT was significantly lower than that following CON (HVT vs. CON = 11.52 ± 1.85 vs. 12.95 ± 1.78 mmol•L-1, p &lt; 0.05, effect size = 1.94). Additionally, the Las following HVT and LVT at the post 30-min were significantly lower than that following the CON (HVT vs. LVT vs. CON = 4.72 ± 0.97 vs. 4.58 ± 1.06 vs. 5.98 ± 1.49 mmol•L-1, p &lt; 0.05). No significant differences were found on the HRs, or on the time and frequency domain indices of HR variability among treatments during the recovery period. Conclusion: These results indicated that vibration with low frequency (8 Hz) can facilitate the removal of metabolic by-products after exhaustive exercise, but it has little effect on the autonomic nervous modulation of HR recovery.

Cross-validation of Peak Oxygen Consumption Prediction Models From OMNI Perceived Exertion.

This study cross-validated statistical models for prediction of peak oxygen consumption using ratings of perceived exertion from the Adult OMNI Cycle Scale of Perceived Exertion. 74 participants (men: n=36; women: n=38) completed a graded cycle exercise test. Ratings of perceived exertion for the overall body, legs, and chest/breathing were recorded each test stage and entered into previously developed 3-stage peak oxygen consumption prediction models. There were no significant differences (p>0.05) between measured and predicted peak oxygen consumption from ratings of perceived exertion for the overall body, legs, and chest/breathing within men (mean±standard deviation: 3.16±0.52 vs. 2.92±0.33 vs. 2.90±0.29 vs. 2.90±0.26 L·min(-1)) and women (2.17±0.29 vs. 2.02±0.22 vs. 2.03±0.19 vs. 2.01±0.19 L·min(-1)) participants. Previously developed statistical models for prediction of peak oxygen consumption based on subpeak OMNI ratings of perceived exertion responses were similar to measured peak oxygen consumption in a separate group of participants. These findings provide practical implications for the use of the original statistical models in standard health-fitness settings.

Cardiorespiratory Fitness Suppresses Age-Related Arterial Stiffening in Healthy Adults: A 2-Year Longitudinal Observational Study.

Cardiorespiratory fitness is negatively associated with arterial stiffness, although it is unclear whether it is associated with prospective arterial stiffness changes. The authors examined cardiorespiratory fitness and arterial stiffness progression in a 2-year follow-up study of 470 healthy men and women aged 26 to 69years. Peak oxygen uptake (V˙O2peak) was measured at baseline using a graded cycle exercise test. Arterial stiffness was assessed using brachial-ankle pulse wave velocity (baPWV) at baseline and after 2years. Two-year changes in baPWV were significantly higher in patients in the lowest V˙O2peak tertile (28.8±7.6cm/s) compared with those in the highest V˙O2peak tertile (-1.4±7.5cm/s) (P=.024) and were inversely correlated with V˙O2peak (r=-.112, P=.015). Stepwise multiple regression analysis revealed that age, glucose, baPWV, V˙O2peak, and sex were independent correlates of 2-year changes in baPWV, suggesting that higher cardiorespiratory fitness is associated with age-related arterial stiffening suppression.

The oxygen uptake efficiency slope in 1411 Caucasian healthy men and women aged 20-60 years: reference values.

The oxygen uptake efficiency slope (OUES) has been proposed as an independent, reproducible and objective measure of cardiorespiratory function that does not require maximal exercise testing. Existing reference values have been published for healthy paediatric populations and healthy elderly. However, reference ranges and equations for healthy adults of working age are insufficiently documented. The aim of the present study was to establish prediction equations and to describe reference values for healthy men and women aged 20-60 years. Cross-sectional study. One thousand four hundred and eleven (877 men) healthy individuals (mean age 38.6 years; range 20-60) completed a maximal graded cycle exercise test until volitional exhaustion. Subsequently, oxygen uptake was plotted against the logarithm of total ventilation and the OUES was calculated by means of linear regression analysis. Multivariate regression analyses revealed age, sex and body surface area as statistically significant determinants of the OUES. Following this, sex-specific prediction equations for the OUES were established and cross-validated. Finally, the distribution of the OUES with age was described and reference values were established for men and women separately. This study established a comprehensive set of reference values and reference equations for the OUES for a healthy population of men and women aged between 20 and 60 years.

Cardiac output but not stroke volume is similar in a Wingate and $$ \dot{V}{\text{O}}_{{ 2 {\text{peak}}}} $$ test in young men

Wingate test (WT) training programmes lasting 2-3weeks lead to improved peak oxygen consumption. If a single 30s WT was capable of significantly increasing stroke volume and cardiac output, the increase in peak oxygen consumption could possibly be explained by improved oxygen delivery. Thus, we investigated whether a single WT increases stroke volume and cardiac output to similar levels than those obtained at peak exercise during a graded cycling exercise test (GXT) to exhaustion. Fifteen healthy young men (peak oxygen consumption 45.0±5.3mlkg(-1)min(-1)) performed one WT and one GXT on separate days in randomised order. During the tests, we estimated cardiac output using inert gas rebreathing (nitrous oxide and sulphur hexafluoride) and subsequently calculated stroke volume. We found that cardiac output was similar (18.2±3.3 vs. 17.9±2.6lmin(-1); P=0.744), stroke volume was higher (127±37 vs. 94±15ml; P<0.001), and heart rate was lower (149±26 vs. 190±12 beatsmin(-1); P<0.001) at the end (27±2s) of a WT as compared to peak exercise during a GXT. Our results suggest that a single WT produces a haemodynamic response which is characterised by similar cardiac output, higher stroke volume and lower heart rate as compared to peak exercise during a GXT.

Low-intensity Walk Training With Blood-Flow Reduction Concurrently Improved VO2peak and Muscular Function In Elderly Women

Low-intensity walk training with leg blood flow reduction (BFR-walk) has been shown to elicit a significant increase in skeletal muscle size and strength, and may also improve in aerobic capacity in young subjects. However, it is unknown if BFR-walk training would improve muscular function/ hypertrophy and aerobic capacity in older subjects. PURPOSE: To investigate the effects of BFR-walk training on MRI-measured muscle size and function as well as peak oxygen uptake (VO2peak) in the elderly women. METHODS: 18 elderly women (age, 65.7±4.3 yrs; BMI, 22.8±2.8 kg/m2) were divided into two walk training groups: BFR-walk (n=10) and control walk (n=8, CON-walk). Both groups performed 20 min treadmill walking at an exercise intensity of 45% of heart rate reserve, 4 days per week for 10 weeks. The BFR-walk group wore pressure cuff belts (5 cm wide) on the proximal part of both upper legs during training (external compression: 160-200 mmHg). MRI-measured mid-thigh muscle cross-sectional area (CSA), and also maximal isometric and isokinetic (30 and 180 deg/sec) knee extension and flexion strength (Biodex system-3) were measured before and after training. VO2peak was estimated by fitting age-predicted maximum heart rate (HRmax) value into a linear regression equation computed from the individual VO2 and HR values obtained during a graded cycle exercise test (until ∼80% HRmax). Functional ability was assessed by the Timed Up and Go test (time to walk both ways from the chair to 2.4m marker, UG-Test) and the Chair Stand test (repeated chair stand in 30 seconds, CS-Test). RESULTS: Maximum isometric (6%) and isokinetic (3∼22%) strength and thigh muscle CSA (3.3%) increased in the BFR-walk group, but not in the CON-walk group. VO2peak also increased (P<0.05), but only in the BFR-walk group (pre, 25.0±4.0; post, 27.5±5.2 ml/kg/min), however, there was a trend for improvement in the CON-walk group (pre, 26.3±3.1; post, 29.1±3.9 ml/kg/min). Similarly, functional ability improved (P<0.01) only in the BFR-walk group (10.7% for UG-Test, 20.5% for CS-Test). CONCLUSION: Our results suggest that 40-50% intensity BFR-walk training improves both muscle hypertrophy and aerobic capacity concurrently in the elderly. The improvements of functional ability were probably due in part to the increases in muscular function.

Acute High-Intensity Single-Leg Cycling Decreases Perceived Exertion Associated with Subsequent Submaximal Exercise

Previous investigators have reported that nociceptive afferent neurons innervating skeletal muscles respond to a milieu of metabolic byproducts typical of high intensity exercise. Neural inhibitory responses may be reduced following benign exposure to stimuli. PURPOSE: The purpose of this investigation was to evaluate physiological and perceptual responses to an acute trial of high intensity single-leg cycling. We hypothesized that acute exposure to high concentrations of metabolic byproducts would habituate afferent nociceptors and ultimately reduce perceived exertion associated with subsequent exercise. METHODS: Five trained cyclists (age: 27±10 yrs) performed a graded cycling exercise test (3 min; 35 watt/stage) to determine power at lactate threshold (1 mmol above baseline) before (baseline) and 48hr after acute single-leg cycling. Blood lactate, heart rate (HR), oxygen consumption (VO2), and rating of perceived exertion (RPE) were assessed during the final 30s of each stage. Following the graded exercise test each participant performed single-leg cycling at 110% of their double-leg lactate threshold power (251±38 watts). Participants cycled repeatedly at this power until volitional failure. Trials were repeated until participants had accumulated a total of 5min. Legs were exercised with a counter balanced design. Differences in dependent variables were assessed using paired t-tests. RESULTS: Compared to baseline, RPE decreased (12.2 vs. 11.4; p< 0.01) and HR decreased (150 vs. 148; p=0.05), There were no alterations in blood lactate and VO2. Peak lactate concentrations following single-leg cycling trials were 13 ± 2.2 mmol/L. CONCLUSSION: These data demonstrate that an acute exposure to an extraordinarily high perturbation of the metabolic milieu reduced perceived exertion associated with subsequent sub maximal exercise. Note that blood lactates concentrations following single-leg cycling were similar to those associated with maximal aerobic exercise but were produced within the muscles of one leg. Thus, the disturbance in homeostasis in those muscles was likely twice as large. These results may have implications for treatment of patients with inappropriately functioning nocioceptors (e.g., fibromyalgia). Supported by PEAK Graduate Student Research Grant.

Chronic physical activity mitigates cerebral hypoperfusion during central hypovolemia in elderly humans

This study sought to test the hypothesis that orthostasis-induced cerebral hypoperfusion would be less severe in physically active elderly humans (ACT group) than in sedentary elderly humans (SED group). The peak O(2) uptake of 10 SED (67.1 +/- 1.4 yr) and 9 ACT (68.0 +/- 1.1 yr) volunteers was determined by a graded cycling exercise test (22.1 +/- 1.2 vs 35.8 +/- 1.3 ml.min(-1).kg(-1), P < 0.01). Baseline mean arterial pressure (MAP; tonometry) and middle cerebral arterial blood flow velocity (V(MCA); transcranial Doppler) were similar between the groups (SED vs. ACT group: 91 +/- 3 vs. 87 +/- 3 mmHg and 54.9 +/- 2.3 vs. 57.8 +/- 3.2 cm/s, respectively), whereas heart rate was higher and stroke volume (bioimpedance) was smaller in the SED group than in the ACT group. Central hypovolemia during graded lower body negative pressure (LBNP) was larger (P < 0.01) in the ACT group than in the SED group. However, the slope of V(MCA)/LBNP was smaller (P < 0.05) in the ACT group (0.159 +/- 0.016 cm/s/Torr) than in the SED group (0.211 +/- 0.008 cm/s/Torr). During LBNP, the SED group had a greater augmentation of cerebral vasomotor tone (P < 0.05) and hypocapnia (P < 0.001) compared with the ACT group. Baseline MAP variability and V(MCA) variability were significantly smaller in the SED group than in the ACT group, i.e., 0.49 +/- 0.07 vs. 1.04 +/- 0.16 (mmHg)(2) and 1.06 +/- 0.19 vs. 4.24 +/- 1.59 (cm/s)(2), respectively. However, transfer function gain, coherence, and phase between MAP and V(MCA) signals (Welch spectral estimator) from 0.08-0.18 Hz were not different between SED (1.41 +/- 0.18 cm.s(-1).mmHg(-1), 0.63 +/- 0.06 units, and 38.03 +/- 6.57 degrees ) and ACT (1.65 +/- 0.44 cm.s(-1).mmHg(-1), 0.56 +/- 0.05 units, and 48.55 +/- 11.84 degrees ) groups. We conclude that a physically active lifestyle improves the intrinsic mechanism of cerebral autoregulation and helps mitigate cerebral hypoperfusion during central hypovolemia in healthy elderly adults.

Cardiopulmonary exercise data during quadriceps isometric contraction sustained to fatigue in children with cerebral palsy

The aims of this study were to: 1) study the cardiopulmonary responses during exhaustive isometric contraction in cerebral palsy (CP) children vs. apparently normal (AN) children 2) to study the relationship between muscle endurance and maximal O 2 uptake (peak VO 2 ) in CP children. Eight CP children (GMFC 1 to 2) and 8 AN children underwent a graded cycle exercise test and a quadriceps force and endurance assessment with cardiopulmonary measurement on an isokinetic dynamometer. During isometric contraction, muscle endurance did not differ between the groups but a higher O 2 uptake was shown in the CP group. Moreover in this group, peak VO 2 was correlated with muscle strength (R = 0.77, P < 0.05) and endurance (R = 0.68, P < 0.05). Cerebral palsy children have a higher O 2 uptake during isometric endurance testing despite a lower absolute isometric force but their quadriceps endurance is not impaired after normalization with muscle mass and time. Additionally, quadriceps strength and endurance in CP children were in relationship with their peak VO 2 . This higher O 2 uptake is probably due to coactivation and/or cocontraction during exhaustive quadriceps isometric contraction.

Aerobic-Exercise Training Improves Ventilatory Efficiency in Overweight Children

The objective of this study was to investigate the effect of an 8-week aerobic-exercise training program on ventilatory threshold and ventilatory efficiency in overweight children. Twenty overweight children (BMI > 85th percentile) performed a graded cycle exercise test at baseline and were then randomly assigned to 8 weeks of stationary cycling (n = 10) or a nonexercising control group (n = 10). Ventilatory variables were examined at ventilatory threshold (VT), which was determined via the Dmax method. After 8 weeks, significant improvements occurred in the exercise group compared with the control group for oxygen uptake at VT (exercise = 1.03 +/- 0.13 to 1.32 +/- 0.12 L/min vs. control = 1.20 +/- 0.10 to 1.11 +/- 0.10 L/min, p < .05) and ventilatory equivalent of carbon dioxide (VE/VCO2) at VT (exercise = 32.8 +/- 0.80 to 31.0 +/- 0.53 vs. control = 30.3 +/- 0.88 to 31.7 +/- 0.91, p < .05). Aerobic-exercise training might help reverse the decrements in cardiopulmonary function observed over time in overweight children.

Severe obesity associated with cardiovascular deconditioning, high prevalence of cardiovascular risk factors, diabetes mellitus/hyperinsulinemia, and respiratory compromise

ObjectiveTo determine the extent and severity of obesity-related cardiorespiratory morbidity in children with body mass index (BMI) ≥40 kg/m2.Study designCross-sectional analysis of a cohort comprised of 48 boys and girls aged 8 to 17 years with BMI ≥40 kg/m2. Cardiorespiratory fitness (graded cycle exercise test), left ventricular (LV) mass (echocardiography), blood pressure, fasting lipid profile, fasting insulin, fasting glucose, HbA1c, and pulmonary function (spirometry and sleep studies) were measured.ResultsThe cohort averaged 14.2 ± 2 years of age with mean BMI of 45.5 kg/m2. Only 2 patients had normal fitness; 37 of 48 had peak oxygen consumption <20 mL O2/minute. Hypertension was present in 10 of 48 patients. Mean lipid values were: triglycerides 103 ± 48 mg/dL, HDL cholesterol 41 ± 10 mg/dL, and LDL cholesterol 108 ± 26 mg/dL. Type II diabetes mellitus was diagnosed in 6 patients. Mean fasting insulin was 31 ± 19 μU/mL. Asthma treatment, small airways disease by pulmonary function testing, or both were present in 35 of 48 patients; upper airway obstruction was present in 7 patients. LV hypertrophy was present in 8 patients, with a mean LV mass of 43 ± 11 g/m2.7.ConclusionsChildren and adolescents with BMI ≥40 kg/m2 have substantial cardiorespiratory morbidity including severe physical deconditioning.

Severe obesity associated with cardiovascular deconditioning, high prevalence of cardiovascular risk factors, diabetes mellitus/hyperinsulinemia, and respiratory compromise

ObjectiveTo determine the extent and severity of obesity-related cardiorespiratory morbidity in children with body mass index (BMI) ≥40 kg/m2. Study designCross-sectional analysis of a cohort comprised of 48 boys and girls aged 8 to 17 years with BMI ≥40 kg/m2. Cardiorespiratory fitness (graded cycle exercise test), left ventricular (LV) mass (echocardiography), blood pressure, fasting lipid profile, fasting insulin, fasting glucose, HbA1c, and pulmonary function (spirometry and sleep studies) were measured. ResultsThe cohort averaged 14.2 ± 2 years of age with mean BMI of 45.5 kg/m2. Only 2 patients had normal fitness; 37 of 48 had peak oxygen consumption <20 mL O2/minute. Hypertension was present in 10 of 48 patients. Mean lipid values were: triglycerides 103 ± 48 mg/dL, HDL cholesterol 41 ± 10 mg/dL, and LDL cholesterol 108 ± 26 mg/dL. Type II diabetes mellitus was diagnosed in 6 patients. Mean fasting insulin was 31 ± 19 μU/mL. Asthma treatment, small airways disease by pulmonary function testing, or both were present in 35 of 48 patients; upper airway obstruction was present in 7 patients. LV hypertrophy was present in 8 patients, with a mean LV mass of 43 ± 11 g/m2.7. ConclusionsChildren and adolescents with BMI ≥40 kg/m2 have substantial cardiorespiratory morbidity including severe physical deconditioning.

Physical Fitness and Exercise Endurance Measured by Oxygen Uptake Kinetics in Patients with Type 2 Diabetes Mellitus.

Exercise testing was used to examine 38 type 2 diabetes mellitus (DM) patients without cardiovascular complications, aged 47-74 years (body mass index (BMI), 23.8 ± 1.6 kg/m 2 ), and 18 healthy volunteers, aged 45-68 years (BMI, 22.5 ± 1.5 kg/m 2 ). A graded cycling exercise test was performed, monitoring gas exchange to evaluate physical fitness and exercise endurance by oxygen uptake (V • O2) kinetics. The following results were obtained. (1) Oxygen deficit (O2deficit) and time constant (τ on) at the onset of exercise were significantly higher in subjects with type 2 DM compared with controls (p<0.01). (2) Maximum oxygen uptake (V • O2max) and maximum work load were lower by 12% and 15%, respectively (p<0.05). These data suggest a notable abnormality in the cardiopulmonary response at the onset of exercise and a lower exercise endurance in subjects with type 2 DM. These findings may reflect impaired cardiac response to exercise, although an additional defect in skeletal muscle oxygen diffusion or oxygen utilization is also possible.

Changes in the Cardiopulmonary Response to Exercise after Cardiac Transplantation in Patients Enrolled in an Early Rehabilitation Program

OBJECTIVE: To evaluate the changes in the cardiopulmonary response to exercise in the first year after cardiac transplantation in patients enrolled in a rehabilitation program in the first three months post-transplantation.METHODS: A graded cycle exercise test with mixed expired gas analysis was performed on patients with end-stage cardiac failure before and serially after cardiac transplantation at one, three and 12 months.RESULTS: Before cardiac transplantation, seven patients were fit enough to be tested. They had a low peak oxygen uptake (VO2 max) and a blunted heart rate and blood pressure response to exercise. They also displayed a restrictive pattern of ventilation during exercise. At three months following transplantation, patients (n=19) had a significantly higher VO2 max(19.9±5.3 versus 9.8±1.4 mL/kg/min, P&lt;0.05), higher peak systolic blood pressure (177±22 versus 94±18 mmHg, P&lt;0.05), greater peak minute ventilation (70±23 versus 34±5 L/min, P&lt;0.05) and lower slope of minute ventilation to carbon dioxide output (35.4±6.2 versus 45.1±6.7, P&lt;0.05) than before transplantation. The VO2 maxmeasured at 12 months post-transplant was similar to the three month value and was on average equal to 59% of the predicted value.CONCLUSIONS: These results indicate that there is a rapid and marked improvement in exercise capacity in patients following cardiac transplantation. These changes are associated with significant respiratory and cardiovascular adaptations. However, despite the marked improvement in exercise capacity, the VO2 maxof cardiac transplant recipients enrolled in an early rehabilitation program did not return to normal at 12 months after surgery.