Relationship of Body Composition, Strength, and Asymmetry to Lower Extremity Physical Function in Women: Impact of Age and Physical Activity Level

Preserving independence in the aging population has become a public health priority; therefore, understanding factors that contribute to physical declines is critical. This study explored the relationships among body composition, strength, and lower extremity physical function (LEPF) in women varying in physical activity and age. Lower extremity asymmetries in strength and muscle mass and the relative contributions of intrinsic electrical, measured by electromyography (EMG), and mechanical, measured by mechanomyography (MMG), properties of muscle function were explored as possible determinants of declines in LEPF across the adult lifespan. One hundred four women were tested (mean +/- standard deviation; age 46.9 +/- 19.9 years, range = 20--83 years; body mass index = 23.9 +/- 4.00 kg/m2; body fat 30.6 +/- 6.9%; average daily steps 9891 +/- 4005). Body composition, including mineral free lean mass (MFLM), was measured using dual energy x-ray absorptiometry. Strength was assessed using an isokinetic dynamometer. LEPF was assessed using a 7-meter walk with and without an obstacle, an up-go speed/agility test, and a lower extremity reach test where the participant stood on one leg and reach maximally with the opposite leg in several directions. The results revealed that strength, MFLM, muscle quality, and physical activity declined; however, declines were often not significant until over 60 years of age. Body fatness increased with age. Age was the best predictor of LEPF overall; however, when age was controlled for, body fatness was the best predictor. When analyzing the data by age groups, the young women were less fat and LEPF was more strongly related to MFLM whereas the women over 40 years of age were fatter and LEPF was more closely related to fatness than MFLM. Leg asymmetries in composition or function explained a very small amount of the variability in LEPF. EMG did not differ significantly across the lifespan but MMG was significantly different among young, middle-aged, and older women. This study offers insights into the interactions between physical activity, body composition and LEPF in women across the adult lifespan to aid the design of appropriate interventions to preserve independence in late life.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Kinesiology and Community Health

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2015

Author dc:creator

• Misic, Mark Mathew

Contributors dc:contributor

• Evans, Ellen M.

• Health Sciences, Recreation

Language dc:language

eng

Identifier

(MiAaPQ)AAI3269979

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/86384