Utility of pwc75% as an estimate of aerobic power in epidemiological and population-based studies

Studies of physical activity often assess physical work capacity (pwc) and this is usually achieved with extrapolated estimates of maximal aerobic power (VO2max). 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.

This study assessed extrapolated (pwc at 150 and 170 beats x min(-1) heart rate (HR) and estimated VO2max) 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 VO2max: a decrease with age and an increase with reported physical activity.

Both pwc150 and pwc170 did not decline with age, estimated VO2max (est.VO2max) exhibited a spurious plateau for older age groups, while pwc75% declined approximately 9% per decade of age. All four pwc measures detected a significant difference (approximately 10-15%) between inactive and active groups classified according to a questionnaire of leisure time physical activity.

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.