title: What is a Clinically Meaningful Improvement in Leg-Extensor Power for Mobility-limited Older Adults?
abstract: BACKGROUND
  Muscle power is a key predictor of physical function in older adults; however, clinically meaningful improvements in leg-extensor muscle power have yet to be identified. The purpose of this study is to establish the minimal clinically important improvement (MCII) and substantial improvement (SI) for leg-extensor power and muscle contraction velocity in mobility-limited older adults.
  
  
  METHODS
  Data were extracted from three randomized trials of leg-extensor muscle power training interventions (3- to 6-month duration). Measurements of leg-extensor power and velocity were obtained using dynamic bilateral leg press at 40% and 70% of the one-repetition maximum. Anchor-based MCIIs were calculated using selected items extracted from the Late Life Function and Disability Instrument. Standard error of measurement and effect size methods were used to calculate the distribution-based MCII.
  
  
  RESULTS
  Data from 164 participants (mean age: 76.6 ± 5.6 years; Short Physical Performance Battery score: 7.8 ± 1.3) were used in this analysis. The respective MCII and SI estimates for 40% leg-extensor power were 18.3 (9%) and 30.5 (15%) W, and 23.1 (10%) and 41.6 (18%) W for 70% leg-extensor power. The respective MCII and SI estimates for 40% average velocity were 0.03(7%) and 0.08(18%) m/s, and 0.02(6%) and 0.05(15%) m/s for 70% average velocity.
  
  
  CONCLUSIONS
  This is the first study to establish a clinically meaningful improvement of leg-extensor power (9%-10%) and velocity (6%-7%) in mobility-limited older adults. These findings should be used to aid in the design and interpretation of clinical trials and interventions that target improvements in muscle power in this high-risk population.
authors.affiliation: Nutrition, Exercise Physiology, and Sarcopenia Laboratory, Jean Mayer USDA Human Nutrition Research Center on Aging, Tufts University, Boston, Massachusetts.
authors.forename: Dylan R
authors.initials: DR
authors.lastname: Kirn
authors.affiliation: Nutrition, Exercise Physiology, and Sarcopenia Laboratory, Jean Mayer USDA Human Nutrition Research Center on Aging, Tufts University, Boston, Massachusetts.
authors.forename: Kieran F
authors.initials: KF
authors.lastname: Reid
authors.affiliation: Nutrition, Exercise Physiology, and Sarcopenia Laboratory, Jean Mayer USDA Human Nutrition Research Center on Aging, Tufts University, Boston, Massachusetts.
authors.forename: Cynthia
authors.initials: C
authors.lastname: Hau
authors.affiliation: Nutrition, Exercise Physiology, and Sarcopenia Laboratory, Jean Mayer USDA Human Nutrition Research Center on Aging, Tufts University, Boston, Massachusetts. Department of Physical Medicine and Rehabilitation, Harvard Medical School, Boston, Massachusetts. Institute of Lifestyle Medicine, Joslin Diabetes Center, Boston, Massachusetts.
authors.forename: Edward M
authors.initials: EM
authors.lastname: Phillips
authors.affiliation: Nutrition, Exercise Physiology, and Sarcopenia Laboratory, Jean Mayer USDA Human Nutrition Research Center on Aging, Tufts University, Boston, Massachusetts. roger.fielding@tufts.edu.
authors.forename: Roger A
authors.initials: RA
authors.lastname: Fielding
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006801:Humans; D007866:Leg; D008297:Male; D051346:Mobility Limitation; D009119:Muscle Contraction / Q000502:physiology; D053580:Muscle Strength / Q000502:physiology*; D018482:Muscle, Skeletal / Q000503:physiopathology; D017063:Outcome Assessment, Health Care; D020127:Recovery of Function / Q000502:physiology*; D055070:Resistance Training
keywords: Clinically important improvement; Exercise; Muscle; Physical performance; Power