Paul A. McAuley

Comparison of the Ramp Versus Standard Exercise Protocols

To compare the hemodynamic and gas exchange responses of ramp treadmill and cycle ergometer tests with standard exercise protocols used clinically, 10 patients with chronic heart failure, 10 with coronary artery disease who were asymptomatic during exercise, 11 with coronary artery disease who were limited by angina during exercise and 10 age-matched normal subjects performed maximal exercise using six different exercise protocols. Gas exchange data were collected continuously during each of the following protocols, performed on separate days in randomized order: Bruce, Balke and an individualized ramp treadmill; 25 W/stage, 50 W/stage and an individualized ramp cycle ergometer test. Maximal oxygen uptake was 16% greater on the treadmill protocols combined (21.4 +/- 8 ml/kg per min) versus the cycle ergometer protocols combined (18.1 +/- 7 ml/kg per min) (p less than 0.01), although no differences were observed in maximal heart rate (131 +/- 24 versus 126 +/- 24 beats/min for the treadmill and cycle ergometer protocols, respectively). No major differences were observed in maximal heart rate or maximal oxygen uptake among the various treadmill protocols or among the various cycle ergometer protocols. The ratio of oxygen uptake to work rate, expressed as a slope, was highest for the ramp tests (slope +/- SEE ml/kg per min = 0.80 +/- 2.5 and 0.78 +/- 1.7 for ramp treadmill and ramp cycle ergometer, respectively). The slopes were poorest for the tests with the largest increments in work (0.62 +/- 4.0 and 0.59 +/- 2.8 for the Bruce treadmill and 50 W/stage cycle ergometer, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

Long-Term Effects of Changes in Cardiorespiratory Fitness and Body Mass Index on All-Cause and Cardiovascular Disease Mortality in Men The Aerobics Center Longitudinal Study

Background— The combined associations of changes in cardiorespiratory fitness and body mass index (BMI) with mortality remain controversial and uncertain. Methods and Results— We examined the independent and combined associations of changes in fitness and BMI with all-cause and cardiovascular disease (CVD) mortality in 14 345 men (mean age 44 years) with at least 2 medical examinations. Fitness, in metabolic equivalents (METs), was estimated from a maximal treadmill test. BMI was calculated using measured weight and height. Changes in fitness and BMI between the baseline and last examinations over 6.3 years were classified into loss, stable, or gain groups. During 11.4 years of follow-up after the last examination, 914 all-cause and 300 CVD deaths occurred. The hazard ratios (95% confidence intervals) of all-cause and CVD mortality were 0.70 (0.59–0.83) and 0.73 (0.54–0.98) for stable fitness, and 0.61 (0.51–0.73) and 0.58 (0.42–0.80) for fitness gain, respectively, compared with fitness loss in multivariable analyses including BMI change. Every 1-MET improvement was associated with 15% and 19% lower risk of all-cause and CVD mortality, respectively. BMI change was not associated with all-cause or CVD mortality after adjusting for possible confounders and fitness change. In the combined analyses, men who lost fitness had higher all-cause and CVD mortality risks regardless of BMI change. Conclusions— Maintaining or improving fitness is associated with a lower risk of all-cause and CVD mortality in men. Preventing age-associated fitness loss is important for longevity regardless of BMI change.

Obesity and Cardiovascular Diseases Implications Regarding Fitness, Fatness, and Severity in the Obesity Paradox

Obesity has been increasing in epidemic proportions, with a disproportionately higher increase in morbid or class III obesity, and obesity adversely affects cardiovascular (CV) hemodynamics, structure, and function, as well as increases the prevalence of most CV diseases. Progressive declines in physical activity over 5 decades have occurred and have primarily caused the obesity epidemic. Despite the potential adverse impact of overweight and obesity, recent epidemiological data have demonstrated an association of mild obesity and, particularly, overweight on improved survival. We review in detail the obesity paradox in CV diseases where overweight and at least mildly obese patients with most CV diseases seem to have a better prognosis than do their leaner counterparts. The implications of cardiorespiratory fitness with prognosis are discussed, along with the joint impact of fitness and adiposity on the obesity paradox. Finally, in light of the obesity paradox, the potential value of purposeful weight loss and increased physical activity to affect levels of fitness is reviewed.

Physical Activity and Cardiorespiratory Fitness as Major Markers of Cardiovascular Risk: Their Independent and Interwoven Importance to Health Status

The evolution from hunting and gathering to agriculture, followed by industrialization, has had a profound effect on human physical activity (PA) patterns. Current PA patterns are undoubtedly the lowest they have been in human history, with particularly marked declines in recent generations, and future projections indicate further declines around the globe. Non-communicable health problems that afflict current societies are fundamentally attributable to the fact that PA patterns are markedly different than those for which humans were genetically adapted. The advent of modern statistics and epidemiological methods has made it possible to quantify the independent effects of cardiorespiratory fitness (CRF) and PA on health outcomes. Based on more than five decades of epidemiological studies, it is now widely accepted that higher PA patterns and levels of CRF are associated with better health outcomes. This review will discuss the evidence supporting the premise that PA and CRF are independent risk factors for cardiovascular disease (CVD) as well as the interplay between both PA and CRF and other CVD risk factors. A particular focus will be given to the interplay between CRF, metabolic risk and obesity.

The obesity paradox, cardiorespiratory fitness, and coronary heart disease.

OBJECTIVE To investigate associations of cardiorespiratory fitness (CRF) and different measures of adiposity with cardiovascular disease (CVD) and all-cause mortality in men with known or suspected coronary heart disease (CHD). PATIENTS AND METHODS We analyzed data from 9563 men (mean age, 47.4 years) with documented or suspected CHD in the Aerobics Center Longitudinal Study (August 13, 1977, to December 30, 2002) using baseline body mass index (BMI) and CRF (quantified as the duration of a symptom-limited maximal treadmill exercise test). Waist circumference (WC) and percent body fat (BF) were measured using standard procedures. RESULTS There were 733 deaths (348 of CVD) during a mean follow-up of 13.4 years. After adjustment for age, examination year, and multiple baseline risk factors, men with low fitness had a higher risk of all-cause mortality in the BMI categories of normal weight (hazard ratio [HR], 1.60; 95% confidence interval [CI], 1.24-2.05), obese class I (HR, 1.38; 95% CI, 1.04-1.82), and obese class II/III (HR, 2.43; 95% CI, 1.55-3.80) but not overweight (HR, 1.09; 95% CI, 0.88-1.36) compared with the normal-weight and high-fitness reference group. We observed a similar pattern for WC and percent BF tertiles and for CVD mortality. Among men with high fitness, there were no significant differences in CVD and all-cause mortality risk across BMI, WC, and percent BF categories. CONCLUSION In men with documented or suspected CHD, CRF greatly modifies the relation of adiposity to mortality. Using adiposity to assess mortality risk in patients with CHD may be misleading unless fitness is considered.

Obesity Paradox and Cardiorespiratory Fitness in 12,417 Male Veterans Aged 40 to 70 Years

OBJECTIVE To evaluate the influence of cardiorespiratory fitness (fitness) on the obesity paradox in middle-aged men with known or suspected coronary artery disease. PATIENTS AND METHODS This study consists of 12,417 men aged 40 to 70 years (44% African American) who were referred for exercise testing at the Veterans Affairs Medical Centers in Washington, DC, or Palo Alto, CA (between January 1, 1983, and June 30, 2007). Fitness was quantified as metabolic equivalents achieved during a maximal exercise test and was categorized for analysis as low, moderate, and high (defined as <5, 5-10, and >10 metabolic equivalents, respectively). Adiposity was defined by body mass index (BMI) according to standard clinical guidelines. Separate and combined associations of fitness and adiposity with all-cause mortality were assessed by Cox proportional hazards analyses. RESULTS We recorded 2801 deaths during a mean+/-SD follow-up of 7.7+/-5.3 years. Multivariate hazard ratios (95% confidence interval) for all-cause mortality, with normal weight (BMI, 18.5-24.9 kg/m2) used as the reference group, were 1.9 (1.5-2.3), 0.7 (0.7-0.8), 0.7 (0.6-0.7), and 1.0 (0.8-1.1) for BMIs of less than 18.5, 25.0 to 29.9, 30.0 to 34.9, and 35.0 or more kg/m2, respectively. Compared with highly fit normal-weight men, underweight men with low fitness had the highest (4.5 [3.1-6.6]) and highly fit overweight men the lowest (0.4 [0.3-0.6]) mortality risk of any subgroup. Overweight and obese men with moderate fitness had mortality rates similar to those of the highly fit normal-weight reference group. CONCLUSION Fitness altered the obesity paradox. Overweight and obese men had increased longevity only if they registered high fitness.

The ventilatory threshold: method, protocol, and evaluator agreement.

To evaluate the effects of different methods of detection, exercise modes, protocols, and reviewers on oxygen uptake (VO2) at the ventilatory threshold (ATge), 17 men with heart disease (mean age 59 +/- 6 years) and six healthy men (mean age 60 +/- 11 years) underwent six exercise tests on different days. Each subject performed three treadmill tests (Bruce, Balke, and ramp) and three bicycle ergometer tests (50 W/stage, 25 W/stage, and ramp) in random order. The ventilatory threshold was determined for each of the six exercise tests by three independent, blinded reviewers by means of graphic plots of three commonly used methods of determination: (1) changes in the ventilatory equivalents for VO2 and VCO2, (2) changes in end-tidal oxygen and carbon dioxide pressures, and (3) the intersection of the slope of VCO2 and VO2 (V slope). The largest variability in the ATge was observed with changes in the exercise protocol. The greatest absolute (ml/min) and percentage differences in oxygen uptake at the ATge as a result of changes in protocol, method of determination, and observers were 336 (36%), 125 (12%), and 70 (7%), respectively. The overall intraclass correlation coefficient for VO2 at the ATge among the three reviewers was 0.60 and among the three protocols was 0.85 (p less than 0.01). The V slope method of detection had consistently good agreement among reviewers and was least affected by the protocol. The variance in the ATge (excluding intersubject and error variance) accounted for by differences in protocol, method, and reviewer was 82%, 14%, and 4%, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Contribution of Cardiorespiratory Fitness to the Obesity Paradox

Until recently, cardiorespiratory fitness (CRF) has been overlooked as a potential modifier of the inverse association between obesity and mortality (the so-called obesity paradox), observed in patients with known or suspected cardiovascular (CV) disease. Evidence from five observational cohort studies of 30,104 patients (87% male) with CV disease indicates that CRF significantly alters the obesity paradox. There is general agreement across studies that the obesity paradox persists among patients with low CRF, regardless of whether adiposity is assessed by body mass index, waist circumference, or percentage body fat. However, among patients with high CRF, risk of all-cause mortality is lowest for the overweight category in some, but not all, studies, suggesting that higher levels of fitness may modify the relationship between body fatness and survival in patients manifesting an obesity paradox. Further study is needed to better characterize the joint contribution of CRF and obesity on mortality in diverse populations.

The joint effects of cardiorespiratory fitness and adiposity on mortality risk in men with hypertension.

BACKGROUND Whether higher cardiorespiratory fitness (CRF) attenuates the mortality risk associated with higher adiposity in adults with hypertension (HTN) is poorly understood. METHODS Participants were 13,155 men (mean age, 47.7 (s.d., 9.9) years) who completed a baseline health examination and maximal treadmill exercise test during 1974-2003. All men had HTN at baseline based on resting systolic blood pressure of > or =140 mm Hg or diastolic blood pressure > or =90 mm Hg. CRF was quantified as the duration of a symptom-limited maximal treadmill exercise test, and was grouped for analysis as low (lowest 20%), moderate (middle 40%), and high (upper 40%). Distributions of body mass index (BMI), waist circumference (WC), and percent body fat (%BF) were grouped according to standard clinical guidelines. RESULTS During a mean follow-up of 12 years, 883 deaths (355 cardiovascular disease (CVD)) were recorded. Multivariate hazard ratios (HRs) (95% confidence interval) for all-cause mortality, using low-fitness as the reference group, were 0.58 (0.48-0.69) and 0.43 (0.35-0.54) for moderate-fit and high-fit groups, respectively. We observed a similar pattern for CVD mortality. High-fit/obese men had no greater risk of all-cause (1.59 (0.95-2.67)) or CVD (1.23 (0.44-3.41)) death, high-fit/abdominal-obese men had no greater risk for all-cause (1.20 (0.80-1.78)) or CVD (0.62 (0.25-1.53)) death, and high-fit/percent body fat (%BF)-obese men had no greater risk for all-cause (1.19 (0.90-1.56)) or CVD (0.86 (0.52-1.43)) death compared with their high-fit/normal counterparts. CONCLUSIONS Fitness is a powerful effect modifier in the association of adiposity to mortality in men with HTN, negating the all-cause and CVD mortality risk associated with obesity.

Fitness and Fatness as Mortality Predictors in Healthy Older Men: The Veterans Exercise Testing Study

BACKGROUND Low body mass index (BMI) and low cardiorespiratory fitness (CRF) are independently associated with increased mortality in the elderly. However, interactions among BMI, CRF, and mortality in older persons have not been adequately explored. METHODS Hazard ratios (HRs) were calculated for predetermined strata of BMI and CRF. Independent and joint associations of CRF, BMI, and all-cause mortality were assessed by Cox proportional hazards analyses in a prospective cohort of 981 healthy men aged at least 65 years (mean age [+/-SD], 71 [+/-5] years; range, 65-88 years) referred for exercise testing during 1987-2003. RESULTS During a mean follow-up of 6.9 +/- 4.4 years, a total of 208 patients died. Multivariate relative risks (95% confidence interval [CI]) of mortality across BMI groups of <20.0, 20.0-25.0, 25.0-29.9, 30.0-34.9, and > or =35.0 were 2.51 (1.26-4.98), 1.0 (reference), 0.66 (0.48-0.90), 0.50 (0.31-0.78), and 0.44 (0.20-0.97), respectively, and across CRF groups of <5.0, 5.0-8.0, and >8.0 metabolic equivalents were 1.0 (reference), 0.56 (0.40-0.78), and 0.39 (0.26-0.58), respectively. In a separate analysis of within-strata CRF according to BMI grouping, the lowest mortality risk was observed in obese men with high fitness (HR [95% CI] 0.26 [0.10-0.69]; p = .007). CONCLUSIONS In this cohort of elderly male veterans, we observed independent and joint inverse relations of BMI and CRF to mortality. This warrants further investigation of fitness, fatness, and mortality interactions in older persons.