Edward Archer of the University of South Carolina's Arnold School of Public Health said the study was a follow-up to a controversial study published earlier this year that demonstrated in 2010, women spent 25 percent more time engaged in leisure-time computer use and watching TV than cooking, cleaning and doing laundry combined.
Archer, an epidemiologist and exercise scientist, said the new study examined 45-year trends in maternal activity in two groups: mothers with younger children at age 5 and younger, and those with older children -- ages 6-18.
During the 45-year span of the study, mothers with younger children reported a decline in physical activity of almost 14 hours per week, or 2 hours per day, from 44 hours per week in 1965 to less than 30 hours by 2010. This substantial decline in activity led to a decrease in energy expenditure of 225 calories per day, or 1,573 calories per week, Archer said.
Mothers with older children experienced an average decline of more than 11 hours per week, decreasing from 32 hours per week in 1965 to less than 21 hours in 2010. This led to a reduction in energy expenditure of 177 calories per day, or 1,238 calories/week. This means mothers in 2010 would have to eat 175-225 less calories per day to maintain their weight than mothers in 1965, Archer explained.
Mothers with older children reported an average increase in sedentary behaviors from 18 hours in 1965 to 25 hours in 2010; while mothers with young children increased sedentary behaviors from 17 hours per week to nearly 23 hours per week.
Non-employed mothers had approximately twice the declines in physical activity and much larger increases in sedentary behaviors than employed mothers. For example, non-employed mothers with younger children reported a decline in physical activity of 14 hour per week compared with a 5-hour-per-week decline for employed mothers.
The data were from American Heritage Time Use Study, which consists of more than 50,000 diary days spanning 1965-2010. Physical activity was defined as the aggregate time engaged in general child care and playing with children, preparing meals, post-meal cleanup, housework, as well as participating in sports and exercise.
"The confluence of our results and other research suggests that inactivity has increased significantly over the past 45 years and may be the greatest public health crisis facing the world today," Archer said in a statement.
The findings were published in Mayo Clinic Proceedings.