Dose of physical activity, physical functioning and disability risk in mobility-limited older adults: results from the LIFE study randomized trial

Authors: FIELDING, ROGER - Jean Mayer Human Nutrition Research Center On Aging At Tufts University; GURALNIK, JACK - University Of Maryland; KING, ABBY - Stanford University; PAHOR, MARCO - University Of Florida; MCDERMOTT, MARY - Northwestern University; TUDOR-LOCKE, CATRINE - University Of Massachusetts; MANINI, TODD - University Of Florida; GLYNN, NANCY - University Of Pittsburgh; MARSH, ANTHONY - Wake Forest University; AXTELL, ROBERT - Southern Connecticut State University; HSU, FANG-CHI - Wake Forest University; REJESKI, W. JACK - University Of Pittsburgh

Submitted to: PLOS ONE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/10/2017
Publication Date: 8/18/2017
Citation: Fielding, R.A., Guralnik, J.M., King, A.C., Pahor, M., McDermott, M.M., Tudor-Locke, C., Manini, T.M., Glynn, N.W., Marsh, A.P., Axtell, R.S., Hsu, F., Rejeski, W. 2017. Dose of physical activity, physical functioning and disability risk in mobility-limited older adults: results from the LIFE study randomized trial. PLoS One. 12(8):e0182155. https://doi.org/10.1371/journal.pone.0182155.
DOI: https://doi.org/10.1371/journal.pone.0182155

Interpretive Summary: Understanding the minimal dose of physical activity required to achieve improvement in physical functioning and reductions in disability risk is necessary to inform public health recommendations. We examined the effect of physical activity dose on changes in physical functioning and the onset of major mobility disability using data from The Lifestyle Interventions and Independence for Elders (LIFE) Study. LIFE was a multicenter single masked randomized controlled study that enrolled participants in 2010 and 2011 and followed them for an average of 2.6 years. 1,635 sedentary men and women aged 70-89 years who had functional limitations were randomized to a structured moderate intensity walking, resistance, and flexibility exercise program or a health education program. Physical activity dose was assessed by 7-day accelerometry using a device worn at the waist and a questionnaire. Outcomes included walking performance and a composite measure of physical functioning. We observed a dose-dependent effect of physical activity on physical functioning and onset of major mobility disability. That is, the more activity a participant performed the greater their improvements in walking performance and score on the composite measure of physical functioning. Relatively small increases (> 48 minutes per week) in regular physical activity participation had significant and clinically meaningful effects on these outcomes.

Technical Abstract: Understanding the minimal dose of physical activity required to achieve improvement in physical functioning and reductions in disability risk is necessary to inform public health recommendations. To examine the effect of physical activity dose on changes in physical functioning and the onset of major mobility disability in The Lifestyle Interventions and Independence for Elders (LIFE) Study. We conducted a multicenter single masked randomized controlled trial that enrolled participants in 2010 and 2011 and followed them for an average of 2.6 years. 1,635 sedentary men and women aged 70-89 years who had functional limitations were randomized to a structured moderate intensity walking, resistance, and flexibility physical activity program or a health education program. Physical activity dose was assessed by 7-day accelerometry and self-report at baseline and 24 months. Outcomes included the 400 m walk gait speed, the Short Physical Performance Battery (SPPB), assessed at baseline, 6, 12, and 24 months, and onset of major mobility disability (objectively defined by loss of ability to walk 400 m in 15 min). When the physical activity arm or the entire sample were stratified by change in physical activity from baseline to 24 months, there was a dose-dependent increase in the change in gait speed and SPPB from baseline at 6, 12, and 24 months. In addition, the magnitude of change in physical activity over 24 months was related to the reduction in the onset of major mobility disability (overall P < 0.001) (highest versus the lowest quartile of physical activity change HR 0.23 ((95% CI:0.10-0.52) P = 0.001) in the physical activity arm. We observed a dose-dependent effect of objectively monitored physical activity on physical functioning and onset of major mobility disability. Relatively small increases (> 48 minutes per week) in regular physical activity participation had significant and clinically meaningful effects on these outcomes.