title: Calf muscle-tendon properties and postural balance in old age.
abstract: We tested the hypothesis that compromised postural balance in older subjects is associated with changes in calf muscle-tendon physiological and mechanical properties. Trial duration and center of pressure (COP) displacements were measured in 24 younger (aged 24+/-1 yr), 10 middle-aged (aged 46+/-1 yr), and 36 older (aged 68+/-1 yr) healthy subjects under varying levels of postural difficulty. Muscle-tendon characteristics were assessed by dynamometry, twitch superimposition, and ultrasonography. In tandem and single-leg stances, trial duration decreased (<or=65% lower, P<0.001) and COP displacements increased (<or=90% higher, P<0.05) with age. Muscle strength, size, activation capacity, and tendon mechanical properties decreased with age by 55, 13, 13, and 36-48%, respectively (P<0.05). Regressions with these parameters and balance indexes were significant (P<0.05) for single-leg and tandem (0.69<r2<0.90) postures only, indicating that the age-related changes in muscle-tendon characteristics may explain the majority of the variance in balance performance during tasks more difficult than habitual bipedal stance.
authors.affiliation: Institute for Biophysical and Clinical Research into Human Movement, Manchester Metropolitan University, Hassall Rd., Stoke-on-Trent, ST7 2HL UK. g.pearson@mmu.ac.uk
authors.forename: Gladys L
authors.initials: GL
authors.lastname: Onambele
authors.forename: Marco V
authors.initials: MV
authors.lastname: Narici
authors.forename: Constantinos N
authors.initials: CN
authors.lastname: Maganaris
mesh_terms: D000058:Accidental Falls; D000328:Adult; D000368:Aged; D000375:Aging / Q000502:physiology*; D001696:Biomechanical Phenomena; D005246:Feedback / Q000502:physiology; D005260:Female; D006801:Humans; D007866:Leg / Q000033:anatomy & histology / Q000502:physiology; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000000981:diagnostic imaging* / Q000503:physiopathology; D004856:Postural Balance / Q000502:physiology*; D012044:Regression Analysis; D013710:Tendons / Q000000981:diagnostic imaging* / Q000503:physiopathology; D013997:Time Factors; D019415:Torque; D014463:Ultrasonography