Following thorough evaluation at rest, 265 of 400 current or ex-shipyard workers rode a cycle ergometer with equal work increments each minute to exhaustion while continuous multiple noninvasive cardiorespiratory measures and intermittent intra-arterial blood pressure and blood gas measures were made. Seventy-seven men, with a mean age of 54, including some who were smokers, obese, or hypertensive, were judged to have normal cardiorespiratory systems based on history, physical, electrocardiogram during rest and exercise, chest X-ray, pulmonary function tests, and exercise performance. Their responses to exercise are given. It was unusual to find at maximal exercise a breathing reserve less than 11 L/min, arterial PO2 less than 80 mm Hg, alveolar-arterial PO2 difference greater than 38 mm Hg, arterial-end tidal PCO2 difference greater than 1 mm Hg, respiratory frequency greater than 60, or a dead space/tidal volume ratio greater than 0.28. The normal anaerobic threshold/maximal O2 uptake ratio exceeded 40%. With maximal exercise, the intra-arterial systolic and diastolic pressures rose an average of 68 and 13 mm Hg, respectively. For predicting maximal oxygen uptake and oxygen pulse in an overweight man, we find it preferable to use age and height rather than age and weight.

Twelve normal men performed 1-min incremental exercise tests to exhaustion in approximately 10 min on both treadmill and cycle ergometer. The maximal O2 uptake (VO2 max) and anaerobic threshold (AT) were higher (6 and 13%, respectively) on the treadmill than the cycle; the AT was reached at about 50% of VO2 max on both ergometers. Maximal CO2 output, heart rate, and O2 pulse were also slightly, but significantly higher on the treadmill. Maximal ventilation, gas exchange ratio, and ventilatory equivalents for O2 and CO2 for both forms of exercise were not significantly different. To determine the optimum exercise test for both treadmill and cycle, we exercised five of the subjects at various work rate increments on both ergometers in a randomized design. The treadmill increments were 0.8, 1.7, 2.5, and 4.2%/min at a constant speed of 3.4 mph, and 1.7 and 4.2%/min at 4.5 mph. Cycle increments were 15, 30, and 60 W/min. The VO2 max was significantly higher on tests where the increment magnitude was large enough to induce test durations of 8-17 min, but the AT was independent of test duration. Thus, for evaluating cardiopulmonary function with incremental exercise testing by either treadmill or cycle, we suggest selecting a work rate increment to bring the subject to the limit of his tolerance in about 10 min.

Obesity, because it alters the relationship between the lungs, chest wall, and diaphragm, has been expected to alter respiratory function. We studied 43 massively obese but otherwise normal, nonsmoking, young adults with spirometry, lung volume measurement by nitrogen washout, and single-breath diffusing capacity for carbon monoxide (DLCO). Changes in respiratory function were of two types, those that changed in proportion to degree of obesity--expiratory reserve volume (ERV) and DLCO--and those that changed only with extreme obesity--vital capacity, total lung capacity, and maximal voluntary ventilation. When compared with commonly used predicting equations, we found that mean values of subjects grouped by degree of obesity were very close to predicted values, except in those with extreme obesity in whom weight (kg)/height (cm) exceeded 1.0. In 29 subjects who lost a mean of 56 kg, significant increases in vital capacity, ERV, and maximal voluntary ventilation were found, along with a significant decrease in DLCO. Because most subjects fell within the generally accepted 95% confidence limits for the predicted values, we concluded that obesity does not usually preclude use of usual predictors. An abnormal pulmonary function test value should be considered as caused by intrinsic lung disease and not by obesity, except in those with extreme obesity.

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