Cardiopulmonary exercise test indices of respiratory buffering before and after aerobic exercise training in women with pulmonary hypertension: Differentiation by magnitudes of change in six-minute walk test performance.

While aerobic exercise training (AET) has generally been shown to improve 6-min walk test (6MWT) distance (6MWD) in patients with pulmonary hypertension (PH), a substantial number of patients appear to adapt differently, with minimal or even negative changes in 6MWT distance being reported. PURPOSE: To compare post-aerobic exercise training adaptations in cardiorespiratory functional capacity across three groups of patients with PH: those with high (HI), low (LI) and negative (NEG) post-training increases in 6MWD. METHODS: Participants were 25 females (age 54 ± 11 years; BMI 31 ± 7 kg/m2) who completed a vigorous, 10-week, thrice weekly, supervised treadmill walking exercise program. Cardiopulmonary exercise tests (CPET) and 6MWT were completed before and after training. Ten of the 25 participants were classified as HI (range = 47-143 m), 11 were classified as LI (range = 4-37 m) and 4 were classified as NEG (range = -17 to -53 m). RESULTS: Peak CPET duration, WR and time to anaerobic threshold (AT) were significantly higher (p < 0.05) after training in both the LI and HI groups but not in the NEG group. There was a significant improvement in VE/VCO2 (p = 0.042), PETCO2 (p = 0.011) and TV (p = 0.050) in the HI group after training, but not in the NEG or LI group. CONCLUSION: These findings suggest that sustained ventilatory inefficiency and restricted respiratory buffering may mediate exercise intolerance and impede the ability to adapt to exercise training in some patients with PH.

Influence of training on biomechanics of wheelchair propulsion.

A quasi-experimental longitudinal design was used to compare pre- and posttraining biomechanical and physiological characteristics of wheelchair propulsion in manual wheelchair users (MWCU) across fresh and fatigue states. An instrumented wheelchair ergometer, 3D motion analysis, and computerized open-circuit spirometry were used to collect joint kinetics and kinematics, handrim kinetics, propulsion temporal characteristics, and oxygen uptake pre- and posttraining during a submaximal exercise test to exhaustion. Each subject (n = 19) participated in a specific intervention program of supervised therapeutic exercise (strengthening, stretching, and aerobic exercise) for 6 weeks. Pre- and posttraining measurements were compared with the use of ANOVA with repeated measures. Significant training effects included increased exercise loads for all strengthening activities, decreased stroke frequency, increased maximum elbow extension angle, increased trunk and shoulder flexion/extension range of motion (ROM), increased handrim propulsive moment, increased wrist extension moment, and increased power output. Results suggest that this training program increased biomechanical economy (as defined by propulsive moment) without increasing shoulder or elbow joint stresses.

Reliability of cardiorespiratory measurements during wheelchair ergometry.

The purpose of this research was to evaluate the stability of measures of heart rate (HR) and oxygen uptake (VO2) during repeated 30-minute bouts of constant work-rate wheelchair ergometry. Ten able-bodied subjects (seven male; three female) completed three sequential, single-stage wheelchair ergometer propulsion tests, to exhaustion, at least 48 hours apart, to determine the reliability of measurements of HR and VO2. Power output was determined as the resistance required to elicit 75% of the peak V02 attained during a peak graded exercise wheelchair ergometer test, at a propulsion velocity of three miles per hour and a flywheel roll distance of 6.32 meters. The HR and VO2 measurements were averaged over the last 30 seconds of the first (T1) and second (T2) thirds of the tests and at volitional exhaustion (T3). Significant differences were not observed at any of the data points except for HR at exhaustion. The HR at exhaustion was lower for the third test than for the second test. Intraclass correlation coefficients for HR (R=0.92, 0.95, and 0.86) and VO2 (R=0.95, 0.96, and 0.97) were high across the three tests, at all of the data points, respectively. Coefficients of variation were generally low. The results of this study indicated that, with the exception of HR during exercise sustained longer than approximately 30 minutes, VO2 and HR measurements can be made with high reliability during sustained wheelchair ergometer propulsion.

Functional aerobic impairment in adolescents seropositive for HIV: a quasiexperimental analysis.

OBJECTIVE: To determine the degree to which cardiorespiratory insufficiency limits physical performance in adolescents seropositive for human immunodeficiency virus (HIV). DESIGN: Quasiexperimental, case series design. SETTING: Rehabilitation physiology laboratory. PARTICIPANTS: Seventeen adolescents (12 women, 5 men; age, 18 +/- 2 yr; weight, 74.7 +/- 19.3 kg; height, 170 +/- 9 cm) with HIV infection (viral load, 22,043 +/- 55,869 copies/mL; CD4 count, 499 +/- 210/mL) who were free of comorbid conditions limiting treadmill performance. MAIN OUTCOME MEASURES: Spirometric measurements of oxygen uptake and anaerobic threshold obtained from a peak exercise treadmill test using the modified Bruce protocol. RESULTS: Measured peak oxygen consumption (VO2) was 42% +/- 19% lower than expected (p < .025), suggesting a significant functional aerobic impairment (FAI) or peak VO2 less than 73% of expected values. Peak VO2 was only slightly higher (p < .05) than the oxygen uptake requirements for the most intense activities of daily living (ADL). Anaerobic threshold was only slightly higher (p < .05) than minimum ADL intensities. CONCLUSIONS: Cardiorespiratory insufficiency and FAI limited the ability to perform even low levels of physical activity in these adolescents with mild HIV seropositivity. Disability identified by quantification of FAI may affect implementation of the American with Disabilities Act and public health policy.

Oxygen uptake during peak graded exercise and single-stage fatigue tests of wheelchair propulsion in manual wheelchair users and the able-bodied.

OBJECTIVE: To determine if a single-stage, submaximal fatigue test on a wheelchair ergometer would result in higher than expected energy expenditure. DESIGN: An experimental survey design contrasting physiologic responses during peak graded exercise tests and fatigue tests. SETTING: A rehabilitation science laboratory that included a prototypical wheelchair ergometer, open-circuit spirometry system, and heart rate monitor. PARTICIPANTS: Nine able-bodied non-wheelchair users (the NWC group: 6 men and 3 women, mean +/- SD age 30 +/- 7yrs) and 15 manual wheelchair users (the WC group: 12 men and 3 women, age 40 +/- 9yrs, time in wheelchair 16 +/- 9yrs). No subject had any disease, medication regimen, or upper body neurologic, orthopedic, or other condition that would limit wheelchair exercise. MAIN OUTCOME MEASURES: Peak oxygen uptake (VO2) for graded exercise testing and during fatigue testing, using a power output corresponding to 75% peak aerobic capacity on graded exercise test. RESULTS: In the WC group, VO2 at 6 minutes of fatigue testing was not significantly different from peak VO2. In the NWC group, VO2 was similar to the expected level throughout fatigue testing. CONCLUSION: Energy expenditure was higher than expected in the WC group but not in the NWC group. Fatigue testing may provide a useful evaluation of cardiorespiratory status in manual wheelchair users.

Exercise intensity: its effect on the high-density lipoprotein profile.

OBJECTIVE: To determine the effect of aerobic exercise intensity on the active subfraction of serum high-density lipoprotein (HDL) concentration. DESIGN: A randomized control, before-and-after investigation that tested the hypothesis that high-intensity exercise training would result in improvements in serum concentrations of HDL subfraction 2 (HDL2) greater than those accompanying moderate-intensity training. SETTING: Exercise tests were completed in a hospital stress testing laboratory, and cholesterol analyses were performed in a university research laboratory. Exercise training was performed in the community at a site determined by the subject. SUBJECTS: Subjects were 25 healthy female employees of a teaching hospital. INTERVENTION: Maximum treadmill tests and serum cholesterol profiles were assessed in 25 women before and after a 12-week aerobic walking regimen; 12 women in a high-intensity exercise group (HIG) walked at a target heart rate of 80% and 13 women in a moderate-intensity exercise group (MIG) walked at a heart rate of 60% of their heart rate reserve for a distance of 2 miles three times weekly. MAIN OUTCOME MEASURES: The main dependent variable was HDL2; other measures of the HDL profile were total HDL and HDL3. Peak oxygen uptake (VO2) was also evaluated as a dependent variable to ensure a general aerobic adaptation resulted from the exercise regimen. Measures were analyzed as pretraining to posttraining change scores and absolute values using independent and dependent t tests as appropriate. Statistical significance was assigned atp < .05. RESULTS: Total HDL was 32.3+/-8.5mg/dL before and 40.3+/-10.6mg/dL after training in the MIG and 31.6+/-6.2mg/dL before and 38.2+/-12.0mg/dL after training in the HIG. HDL2 was 14.2+/-5.7mg/dL before and 18.5+/-6.9mg/dL after training in MIG. HDL2 was 13.0+/-6.2mg/dL before and 19.6+/-8.9mg/dL after training in the HIG. Total HDL and HDL2 increased significantly in both groups as a result of exercise training, and intragroup differences were not observed. HDL3 was not affected by exercise training. Training resulted in significant increases in peak VO2 in both MIG and HIG (29.0+/-5.0 to 31.9+/-5.4mL/kg/min in the MIG and 30.7+/-5.2 to 33.5+/-6.3mL/kg/min in the HIG). Intergroup differences in change scores for peak VO2, HDL, and HDL2 were not observed. CONCLUSION: The results and analyses did not support the hypothesis that the HIG would acquire increases in HDL2 profile beyond those observed for the MIG. Moderate-intensity training was sufficient to improve the HDL profile, and high-intensity training appeared to be of no further advantage as long as total training volume (total walking distance per week) was constant.

Nonprescription chlorpheniramine maleate and submaximal exercise responses.

OBJECTIVE: To determine if a single, over-the-counter dose of the H1 antagonist chlorpheniramine maleate (CM) alters total peripheral resistance (TPR) and oxygen uptake (VO2) during submaximal exercise. DESIGN: The study was a prospective, longitudinal, double-blind, random crossover analysis of the cardiovascular and respiratory responses to a single bout of moderately intense exercise. SETTING: Exercise tests were conducted in an exercise laboratory equipped with expired gas analysis and bioelectrical impedance cardiographic monitoring capabilities. PARTICIPANTS: Subjects were 18 (9 men, 9 women) volunteers (age=29.5+/-3.6yrs; weight=70.7+/-1.1kg), free from exercise-limiting pathology and rhinitis. INTERVENTION: Each subject completed a maximal exercise tolerance test on the cycle ergometer followed by two randomly ordered submaximal exercise tests at a power output of 50% of the peak power attained on the maximal test: the first, 2 hours after ingesting 4mg of CM, the second, 2 hours after ingesting a placebo. The submaximal exercise tests lasted 20min and data were recorded at 5, 10, 15, and 20min of exercise during both the CM and placebo tests. Tests were completed approximately 48 hours apart. RESULTS: Average VO2 was 1,488+/-367mL/min for the CM test and 1,477+/-351mL/min for the placebo test. TPR was 12.3+/-7.4PRU for the CM and 11.3+/-4.5PRU for the placebo tests. Analysis of variance revealed that these scores were statistically similar. CONCLUSION: A single over-the-counter dose of CM does not alter TPR or VO2 during submaximal exercise.

Exercise training and severe caloric restriction: effect on lean body mass in the obese.

The purpose of this study was to investigate the effects of exercise intensity on the body composition of obese subjects during severe caloric restriction. Forty obese subjects (33 women, 7 men; 41 +/- 7.7 years; 106 +/- 26kg; body fat > 25% men, > 30% women) on a commercially prepared OPTIFAST 420kcal/day supplemented fast were randomized into groups that exercised at target heart rates corresponding to 40% and 60% of the heart rate reserve (HRR) at the start of the program. Training volume was similar for both groups at approximately 300kcal per session three times per week for 12 weeks. Body weight, body fat, and lean weight were similar for both exercise intensity groups at week one. Overall, body weight decreased by 15.3 +/- 6.7 kg (p < or = .05), and body fat decreased by 14.9 +/- 5.0 kg (p < or = .05) for the 40 subjects, whereas lean weight remained unchanged. No significant differences in body weight, body fat, or lean weight were observed between the two groups. The results of the current study indicated that while on a supplemented 420-kcal/day fast, exercise at 40% and 60% of the HRR affected body composition similarly when total training volume was held constant at 900kcal/week. Lean weight remained unchanged and accompanied a 14.9 +/- 5.0-kg decrease in body fat, which may have resulted when the volume of exercise (ie, 900kcals/wk) was factored into the exercise prescriptions. These results suggest that exercising at 60% of the HRR offers no advantages for body composition changes over those obtained from exercising at 40% of HRR when the total volume of exercise training is controlled.

Arm and leg cycle cross-training effect on anaerobic threshold and heart rate in patients with coronary heart disease.

It has been suggested that the anaerobic threshold (AT) represents a minimal intensity for eliciting an exercise training adaptation. Thirteen men (age = 66 +/- 9; weight = 81 +/- 13kg) and two women (age = 58 +/- 21; weight = 70 +/- 3kg) with coronary heart disease (CHD) trained for 12 weeks to determine the effect of an exercise regimen composed of three- to six-minute intervals of alternating arm and leg cycling (cross-training) on AT. The patients cross-trained for a total of 30 minutes per session, three days per week. Maximal cycle ergometer tests with breath by breath ventilatory gas analyses were performed before and after training. Peak oxygen uptake increased by 8.9% and peak power output increased (p < .05) by 28.3%, whereas resting heart rate (HR) decreased (p < .05) by 9.6% as a result of the cross-training regimen. Cross-training did not effect a significant change in AT but HR at AT was decreased by 6.3% (p < .05). Arm and leg cross-training produced a physiological adaptation and may have reduced the HR threshold for effective exercise training.

Cardiovascular responses and anaerobic threshold for bicycle and arm ergometer exercise.

Cardiovascular responses occurring at the anaerobic threshold (AT) were compared during intermittent bicycle and arm ergometry in eight healthy college students. Arm and bicycle tests used time-matched, discontinuous protocols (three-minute work stages alternated with three-minute rest intervals). Anaerobic threshold was determined by plotting expired minute volume (Ve) on oxygen consumption (VO2) and expressed as the percentage of the respective peak VO2 at which the deflection occurred. Analysis of variance revealed AT was similar for arm and bicycle tests. Absolute VO2 at AT was higher for bicycle than for arm ergometer exercise (p less than .05). Heart rate (HR) and rate pressure product (RPP) were higher for bicycle than for arm ergometry at AT (p less than .05). Moreover, a similarity in percent maximum RPP and percent maximum VO2 was observed at AT for arm ergometry, whereas percent maximum RPP was higher than percent maximum VO2 at AT for bicycle ergometry. Because AT has been suggested as an appropriate intensity of exercise for conditioning, it was concluded that a sufficient level of exercise intensity can be elicited at a lower percentage of the cardiovascular reserve for arm than for bicycle ergometer exercise.

Variations in cardiovascular response accompanying differences in arm-cranking rate.

Arm ergometry may be the only means of exercise testing for persons who cannot perform treadmill or bicycle ergometer testing. To determine the effects of arm-cranking rate on cardiovascular responses, ten healthy college students underwent maximal graded exercise testing on the arm ergometer. Each subject completed randomly ordered tests using 30-, 60-, and 70-rpm cranking rates at least seven days apart. Analysis of variance (ANOVA) indicated that both peak heart rate (HR) and rate pressure product (RPP) increased significantly with increases in cranking rate across the three tests (p less than .05). Peak systolic blood pressure (SBP) and oxygen uptake (VO2) for the 60- and 70- rpm tests was significantly higher than for the 30-rpm test (p less than .05). Peak work rate (WR) was significantly higher for the 70-rpm than for the 30-rpm test (p less than .05). Because RPP is an accepted index of myocardial oxygen consumption, the results indicated that the metabolic load on the heart was increased by increments in the cranking rate. The increases in RPP occurred as a function of the combined increases in HR and SBP as rpm increased from 60 to 70. Since increases in WR and VO2 did not occur as rpm increased from 60 to 70, the rise in HR and RPP may have occurred in response to factors other than the total-body oxygen demand.