title: Accelerometer-determined physical activity, muscle mass, and leg strength in community-dwelling older adults.
abstract: The aim of this study was to describe the relationship between accelerometer-determined physical activity (PA), muscle mass, and lower-limb strength in community-dwelling older adults.
  
  
  
  Six hundred thirty-six community-dwelling older adults (66 ± 7 years) were studied. Muscle mass was measured using dual-energy x-ray absorptiometry, whilst lower limb strength was measured via dynamometry. We measured minutes/day spent in sedentary, light, moderate, and vigorous intensity activity using Actigraph GT1M accelerometers.
  
  
  
  Participants spent a median of 583(Interquartile ratio (IQR) 522-646), 225(176-271), 27(12-45) and 0(0-0) min in sedentary, light, moderate, and vigorous activity, respectively. PA intensity was positively associated with both lean mass percentage and lower limb strength in a dose-response fashion. Sedentary activity was negatively associated with lean mass percentage, but not lower-limb strength. There was a positive association between PA and appendicular lean mass in men only. There was an interaction between age and activity; as age increased, the magnitude of the association of PA with lean mass percentage decreased. Those who adhered to the Australian Department of Health PA guidelines (moderate/vigorous PA >/=150 min/week) had greater lean mass percentage, appendicular lean mass, and lower limb strength.
  
  
  
  Using accelerometer technology, both the amount and intensity of accelerometer-determined PA had an independent, dose-response relationship with lean mass percentage and lower limb strength, with the largest effect for vigorous activity. Time spent in sedentary activity was negatively associated with lean mass percentage, but was not associated with lower limb strength. The magnitude of the association between PA and lean mass percentage decreased with age, suggesting that PA programmes may need to be modified with increasing age.
authors.affiliation: Menzies Institute for Medical Research University of Tasmania Private Bag 23 Hobart Tasmania 7000 Australia; North West Regional Hospital Burnie Tasmania 7250 Australia.
authors.forename: Yi Chao
authors.initials: YC
authors.lastname: Foong
authors.affiliation: Menzies Institute for Medical Research University of Tasmania Private Bag 23 Hobart Tasmania 7000 Australia.
authors.forename: Nabil
authors.initials: N
authors.lastname: Chherawala
authors.affiliation: Menzies Institute for Medical Research University of Tasmania Private Bag 23 Hobart Tasmania 7000 Australia.
authors.forename: Dawn
authors.initials: D
authors.lastname: Aitken
authors.affiliation: Department of Medicine, School of Clinical Sciences, Faculty of Medicine, Nursing and Health Sciences Monash University Clayton Victoria 3146 Australia; NorthWest Academic Centre The University of Melbourne St Albans Victoria 3021 Australia.
authors.forename: David
authors.initials: D
authors.lastname: Scott
authors.affiliation: Menzies Institute for Medical Research University of Tasmania Private Bag 23 Hobart Tasmania 7000 Australia; Faculty of Health University of Tasmania Hobart Tasmania 7000 Australia.
authors.forename: Tania
authors.initials: T
authors.lastname: Winzenberg
authors.affiliation: Menzies Institute for Medical Research University of Tasmania Private Bag 23 Hobart Tasmania 7000 Australia.
authors.forename: Graeme
authors.initials: G
authors.lastname: Jones
keywords: Accelerometer; Muscle mass; Physical activity; Strength