Comparison of estimates of population levels of physical activity using two measures

Objective: To compare estimates of population levels of 'adequate activity' for health benefit in different age and sex groups using two different mea sures kilocalories (kcals) and Mets.mins. Methods: 10,464 mid-age women (47-52 years) from the second survey of the A ustralian Longitudinal Study on Women's Health (ALSWH, 1998) and 2,500 men and women (18-75 years) from the 1997 Active Australia national survey, ans wered questions about physical activity. Kcals and Mets.mins were calculate d from self reported time spent in walking, moderate and vigorous activity, and self-reported body weight. 'Adequate activity' was defined as a minimu m of 800 kcals or 600 Mets.mins. Results: There were differences in the estimates of 'adequate activity' usi ng the two methods among women participants in both surveys, but not among the male participants in the Active Australia survey. A significant proport ion of the women in both surveys (6.4% of the ALSWH women and 8.5% of the A ctive Australia women, mean weight 60 kg) were classified as 'inactive' whe n the kcals method was used despite reporting levels of activity commensura te with good health. Fewer than 1% (mean weight 105 kg) were classified as 'active' using kcals when reporting lower than recommended levels of activi ty. Agreement between the two methods was better among men; only 3% were mi sclassified because of low or very high weight. Conclusions: The Mets.mins method of estimating 'adequate' activity assesse s physical activity independently of body weight and is recommended for use in future population surveys, as it is less likely to under-estimate the p revalence of physical activity in women. Implications: Women and men aged 4 5-59 and women aged >60 should be the target of specific health promotion s trategies to increase population levels of physical activity.