Muscle quality, aerobic fitness and fat mass predict lower-extremity physical function in community-dwelling older adults.
BACKGROUND
Muscle mass, strength and fitness play a role in lower-extremity physical function (LEPF) in older adults; however, the relationships remain inadequately characterized.


OBJECTIVE
This study aimed to examine the relationships between leg mineral free lean mass (MFLM(LEG)), leg muscle quality (leg strength normalized for MFLM(LEG)), adiposity, aerobic fitness and LEPF in community-dwelling healthy elderly subjects.


METHODS
Fifty-five older adults (69.3 +/- 5.5 years, 36 females, 19 males) were assessed for leg strength using an isokinetic dynamometer, body composition by dual energy X-ray absorptiometry and aerobic fitness via a treadmill maximal oxygen consumption test. LEPF was assessed using computerized dynamic posturography and stair ascent/descent, a timed up-and-go task and a 7-meter walk with and without an obstacle.


RESULTS
Muscle strength, muscle quality and aerobic fitness were similarly correlated with static LEPF tests (r range 0.27-0.40, p < 0.05); however, the strength of the independent predictors was not robust with explained variance ranging from 9 to 16%. Muscle quality was the strongest correlate of all dynamic LEPF tests (r range 0.54-0.65, p < 0.001). Using stepwise linear regression analysis, muscle quality was the strongest independent predictor of dynamic physical function explaining 29-42% of the variance (p < 0.001), whereas aerobic fitness or body fat mass explained 5-6% of the variance (p < 0.05) depending on performance measure.


CONCLUSIONS
Muscle quality is the most important predictor, and aerobic fitness and fat mass are secondary predictors of LEPF in community-dwelling older adults. These findings support the importance of exercise, especially strength training, for optimal body composition, and maintenance of strength and physical function in older adults.
Misic
Mark M
MM
Department of Kinesiology and Community Health, University of Illinois at Urbana-Champaign, Urbana, Ill 61801, USA.
Rosengren
Karl S
KS
Woods
Jeffrey A
JA
Evans
Ellen M
EM
D015502:Absorptiometry, Photon; D000368:Aged; D000369:Aged, 80 and over; D001823:Body Composition / Q000502:physiology*; D005080:Exercise Test; D005260:Female; D005684:Gait / Q000502:physiology*; D006801:Humans; D016014:Linear Models; D035002:Lower Extremity / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D053580:Muscle Strength / Q000502:physiology*; D053581:Muscle Strength Dynamometer; D018482:Muscle, Skeletal / Q000502:physiology; D010101:Oxygen Consumption / Q000502:physiology*; D010809:Physical Fitness / Q000502:physiology*