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evidence suggests that muscle power (force*velocity, or rate
of performing work) is a more critical determinant of physical
functioning in older adults. Past work has not followed participants longitudinally to evaluate if lower muscle power predicts prospective falls and disability in large studies. However,
lower power is shown to predict mortality independent of
muscle strength and mass. Reliable assessment of dynamic
muscle power is feasible in older adults, including oldest old
and frail populations. Commonly used methods involve participants pushing against a fixed load (e.g., Nottingham) or
at a % of 1 repetition maximum (e.g., Keiser). Cut-points
from leg press strength, velocity, and power that predict
poor physical performance in Boston RISE participants will
be presented (Ward). Clinically important differences in leg
press power related to change in self-reported function from
randomized controlled trials in mobility-limited older adults
will be defined (Reid). Power measures that are body weight
bearing, e.g., chair rise or countermovement leg extension
(“jump”), and performed on a force plate, are not widely used
in older adults. Correlations between these force plate measures and leg press power will be presented (Winger). Jump
test methods and issues in octogenarian men from the Study
of Osteoporotic Fractures in Men (MrOS) will be described
(Strotmeyer). Dr. Caserotti (Discussant) will critically review
the current methodologic work, focusing on future research
recommendations to characterize the important role of muscle power in physical function and geriatric outcomes.
DEFINING CLINICALLY MEANINGFUL CUT-POINTS
FOR IMPAIRED MUSCLE POWER, STRENGTH, AND
VELOCITY USING PHYSICAL PERFORMANCE IN
OLDER ADULTS
R. Ward1,2,3, M.K. Beauchamp1,2, T.G. Travison2,4, L.A.
Kurlinski1,2, S.G. Leveille2,5, A. Jette3, J.F. Bean1,2, 1.
Physical Medicine and Rehabilitation, Spaulding Hospital,
Canbridge, Massachusetts, 2. Harvard Medical School,
Cambridge, Massachusetts, 3. Health and Disability
Research Institute, Boston University School of Public
Health, Boston, Massachusetts, 4. Institute for Aging
Research, Hebrew SeniorLife, Boston, Massachusetts, 5.
College of Nursing and Health Sciences, University of
Massachusetts Boston, Boston, Massachusetts
Strength and velocity, which comprise muscle power, are
key predictors of mobility decline in aging. Cut-points defining meaningful impairment of these attributes are therefore
critical in developing interventions to improve mobility.
Using data from 430 Boston RISE participants (68% female;
mean age 76.5 years), we determined cut-points for strength,
velocity, and power that maximized sensitivity/specificity in
capturing presence/absence of poor physical performance
(≤9 points on SPPB). Cut-points for men and women, respectively, were 11.33 and 8.86 N/kg for leg press strength, 1.24
and 0.93 m/s for leg press velocity, 6.15 and 3.91 watts/kg for
leg press power, and 3.07 and 2.59 watts/kg for stair climb
power. Stair climb and leg press power exhibited greatest sensitivity (64.2%-82.6%) and least specificity (60.8%-73.2%),
while velocity exhibited greatest specificity (73.2%-75.5%)
and least sensitivity (51.1%-58.9%). These results demonstrate the feasibility of isolating thresholds in neuromuscular impairment that are predictive of poor mobility in older
adults.
The Gerontological Society of America
WHAT IS A CLINICALLY MEANINGFUL CHANGE
IN LOWER EXTREMITY POWER FOR MOBILITYLIMITED OLDER ADULTS?
D. R. Kirn1, K.F. Reid1, C. Hau1, E. Phillips1,2,3, R. Fielding1,
1. Nutrition, Exercise Physiology, and Sarcopenia
Laboratory, Jean Mayer USDA Human Nutrition Research
Center on Aging at Tufts University, Boston, Massachusetts,
2. Department of Physical Medicine and Rehabilitation,
Harvard Medical School, Boston, Massachusetts, 3. Institute
of Lifestyle Medicine, Joslin Diabetes Center, Boston,
Massachusetts
Muscle power is an important predictor of physical function in older adults, however, clinically meaningful changes
in lower extremity muscle power have yet to be established
.This study estimates the minimal clinically important difference (MCID) for lower extremity power in mobility-limited
older adults. We compiled data from three resistance training study interventions. Change in lower extremity power
was anchored to change in self-reported function using the
Late-Life Disability Index. Standard error of measurement
and effect size calculations represent the distribution-based
MCID. Data from 164 subjects (mean age: 76.6±6 years;
60% female; Short Physical Performance Battery score:
7.8±1.3) was used in this analysis. Estimates for MCID of
lower extremity power output were 9-13%, and substantial change was 23%. This is the first study to establish the
MCID for lower extremity power in this population. The
MCID can be used to design and interpret clinical trials that
utilize muscle power as an outcome.
CORRELATIONS BETWEEN TASK-BASED POWER
AND LEG PRESS POWER AND STRENGTH MEASURES
IN DECOS
M. Winger1, P. Caserotti2, R. Ward3, R. Boudreau1,
T. Harris4, E.S. Strotmeyer1, 1. Epidemiology, University of
Pittsburgh Graduate School of Public Health, Pittsburgh,
Pennsylvania, 2. University of Southern Denmark, Odense,
Denmark, 3. Spaulding Rehabilitation Hospital, Boston
University, Boston, Massachusetts, 4. National Institute on
Aging, Laboratory of Epidemiology and Population Science,
Bethesda, Maryland
Task-based leg power measured under weight-bearing
conditions requires appropriate postural control and may
better predict functional ability than leg press power/strength
(externally applied force). Because multiple power/strength
measures are rarely done simultaneously, these correlations are unknown. Pearson correlations (adjusting for age,
sex, race, height and stratified by sex) between force plate
power (chair rise; jump) and leg press power (Nottingham;
Keiser)/strength (Keiser) measures were classified as weak
(r<0.4), moderate (r=0.4-0.6) or strong (r>0.6) (all p<0.05)
for N=47 DECOS participants (age=78.9±5.8 years; 53%
women). Chair rise power/kg had moderate correlations
with Nottingham power/kg (r=0.60) (strong for women)
and Keiser strength/kg (r=0.46) (weak for men) and strong
correlation with Keiser power/kg (r=0.70). Jump power/
kg had moderate correlation with Nottingham power/kg
(r=0.58) (weak for men) and strong correlations with Keiser
strength/kg (r=0.65) (moderate for men) and Keiser power/
kg (r=0.75). Task-based power measures may be alternates
for leg press strength/power measures in older adults.