Utility of pwc75% as an estimate of aerobic power in epidemiological and population-based studies.Med. Sci. Sports Exerc.,Vol. 31, No. 2, pp. 348-351, 1999.Purpose:Studies of physical activity often assess physical work capacity (pwc) and this is usually achieved with extrapolated estimates of maximal aerobic power (&OV0312;O2max). However, extrapolation beyond the measured values may be problematic, particularly for older subjects. On a population basis, interpolated measures of pwc may provide the same information and avoid the errors associated with extrapolated measures.Methods:This study assessed extrapolated (pwc at 150 and 170 beats·min−1heart rate (HR) and estimated &OV0312;O2max) and interpolated (pwc at 75% of maximum HR: pwc75%) measures of pwc in a population sample of 1043 men and women aged 18-78 yr. Each measure was assessed to determine whether it showed the key characteristics of measured &OV0312;O2max: a decrease with age and an increase with reported physical activity.Results:Both pwc150 and pwc170 did not decline with age, estimated &OV0312;O2max(est.&OV0312;O2max) exhibited a spurious plateau for older age groups, while pwc75% declined ∼9% per decade of age. All four pwc measures detected a significant difference (∼10-15%) between inactive and active groups classified according to a questionnaire of leisure time physical activity.Conclusions:Although the pwc75% test requires direct validation, these results suggest that it may be a useful submaximal exercise measure for epidemiological studies of aerobic power.