title: Muscle size, neuromuscular activation, and rapid force characteristics in elderly men and women: effects of unilateral long-term disuse due to hip-osteoarthritis.
abstract: Substantial evidence exists for the age-related decline in muscle strength and neural function, but the effect of long-term disuse in the elderly is largely unexplored. The present study examined the effect of unilateral long-term limb disuse on maximal voluntary quadriceps contraction (MVC), lean quadriceps muscle cross-sectional area (LCSA), contractile rate of force development (RFD, Delta force/Delta time), impulse (integral force dt), muscle activation deficit (interpolated twitch technique), maximal neuromuscular activity [electromyogram (EMG)], and antagonist muscle coactivation in elderly men (M: 60-86 yr; n = 19) and women (W: 60-86 yr; n = 20) with unilateral chronic hip-osteoarthritis. Both sides were examined to compare the effect of long-term decreased activity on the affected (AF) leg with the unaffected (UN) side. AF had a significant lower MVC (W: 20%; M: 20%), LCSA (W: 8%; M: 10%), contractile RFD (W: 17-26%; M: 15-24%), impulse (W: 10-19%, M: 19-20%), maximal EMG amplitude (W: 22-25%, M: 22-28%), and an increased muscle activation deficit (-18%) compared with UN. Furthermore, women were less strong (AF: 40%; UN: 39%), had less muscle mass (AF: 33%; UN: 34%), and had a lower RFD (AF: 38-50%; UN: 41-48%) compared with men. Similarly, maximum EMG amplitude was smaller for both agonists (AF: 51-63%; UN: 35-61%) and antagonist (AF: 49-64%; UN: 36-56%) muscles in women compared with men. However, when MVC and RFD were normalized to LCSA, there were no differences between genders. The present data demonstrate that disuse leads to a marked loss of muscle strength and muscle mass in elderly individuals. Furthermore, the data indicate that neuromuscular activation and contractile RFD are more affected by long-term disuse than maximal muscle strength, which may increase the future risk for falls.
authors.affiliation: Institute of Sports Medicine, Bispebjerg Hospital, University of Copenhagen, 2400 NV Copenhagen, Denmark. cs08@bbh.hosp.dk
authors.forename: C
authors.initials: C
authors.lastname: Suetta
authors.forename: P
authors.initials: P
authors.lastname: Aagaard
authors.forename: S P
authors.initials: SP
authors.lastname: Magnusson
authors.forename: L L
authors.initials: LL
authors.lastname: Andersen
authors.forename: S
authors.initials: S
authors.lastname: Sipilä
authors.forename: A
authors.initials: A
authors.lastname: Rosted
authors.forename: A K
authors.initials: AK
authors.lastname: Jakobsen
authors.forename: B
authors.initials: B
authors.lastname: Duus
authors.forename: M
authors.initials: M
authors.lastname: Kjaer
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D004576:Electromyography; D005260:Female; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D020966:Muscular Disorders, Atrophic / Q000473:pathology / Q000503:physiopathology*; D015207:Osteoarthritis, Hip / Q000473:pathology / Q000503:physiopathology*; D052097:Quadriceps Muscle / Q000473:pathology / Q000503:physiopathology*