Older adults with limited mobility may lower their risk of heart attack and coronary death for every minute of physical activity, according to research published February 2015 in the Journal of the American Heart Association.
"Reducing time spent being sedentary even by engaging in low-intensity activities could have important cardiovascular benefits for older adults with mobility limitations," said Thomas W. Buford, Ph.D., senior author of the study and director of the Health Promotion Center of the University of Florida Institute on Aging in Gainesville, Florida.
In the Lifestyles Interventions and Independence for Elders Study (LIFE), researchers measured movement with accelerometers in 1,170 people ages 74-84 at eight centers across the United States who had physical limitations but could walk 400 meters (about 1,312 feet).
Accelerometer readings of fewer than 100 counts a minute were considered sedentary periods. Anything more was deemed physical activity:
• readings of 100-499 suggested exercise like slow walking or light housekeeping, and
• 500 indicated moderate walking or similarly intensive activities.
Using factors such as age, cholesterol levels and blood pressure, the researchers calculated participants' predicted 10-year risk of heart attack or coronary death and found:
• For every 25-30 minutes a participant was sedentary per day, his/her predicted risk was 1 percent higher.
• Physical activity in the 100-499 counts/minute range was linked to higher HDL ("good") cholesterol levels in people with no history of heart disease.
• Participants on average spent only an hour or less with physical activity readings at or above 500.
Generally, most physical activity recommendations suggest that adults should engage in higher intensity activities -- readings around 2,000 counts a minute -- to improve or maintain health. But that level might not be realistic for sedentary older adults with limited mobility, researchers said.
"In the past, much of the emphasis was placed on engaging in structured physical exercise," Buford said. "It is becoming increasingly evident, however, that encouraging individuals to just reduce the amount of time they spend being sedentary may have important cardiovascular benefits."
Because study participants were active in a narrow range of intensity, researchers aren't sure if intensity doesn't matter.
"The idea is that, even if you exercise for an hour in the morning, if you go and sit for eight hours the rest of the day you may have health risks that are independent of the fact you exercised," Buford said. "This stresses the need for regular intervals of low-level movement and to avoid sitting for excessive stretches of time."
The American College of Sports Medicine and American Heart Association's 2007 recommendations on physical activity in older adults includes adjusting intensity for individual fitness levels and incorporating exercises for flexibility, balance and strength.