Muscle size, neuromuscular activation, and rapid force characteristics in elderly men and women: effects of unilateral long-term disuse due to hip-osteoarthritis

• Published in: Journal of applied physiology (1985) 2007-03, Vol.102 (3), p.942-948
• Main Authors: Suetta, C, Aagaard, P, Magnusson, S. P, Andersen, L. L, Sipila, S, Rosted, A, Jakobsen, A. K, Duus, B, Kjaer, M
• Format: Article
• Language: English
• Subjects: Aged; Aged, 80 and over; Aging; Arthritis; Biological and medical sciences; Effects; Electromyography; Female; Fundamental and applied biological sciences. Psychology; Humans; Isometric Contraction - physiology; Male; Middle Aged; Muscular Disorders, Atrophic - pathology; Muscular Disorders, Atrophic - physiopathology; Muscular system; Older people; Osteoarthritis, Hip - pathology; Osteoarthritis, Hip - physiopathology; Quadriceps Muscle - pathology; Quadriceps Muscle - physiopathology
• ISSN: 8750-7587; 1522-1601
• DOI: 10.1152/japplphysiol.00067.2006

1 Institute of Sports Medicine, Bispebjerg Hospital, University of Copenhagen, 2 Institute of Sports Science and Clinical Biomechanics, University of Southern Denmark, and 3 National Institute of Occupational Health, Copenhagen, Denmark; 4 Department of Health Sciences, University of Jyväskylä, Jyväskylä, Finland; and Departments of 5 Radiology and 6 Orthopedics, Bispebjerg Hospital, University of Copenhagen, Copenhagen, Denmark Submitted 19 January 2006 ; accepted in final form 10 November 2006 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, force/ time), impulse ( force d t ), 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. aging; rate of force development; neural activity; muscle activation Address for reprint requests and other correspondence: C. Suetta, Institute of Sports Medicine, Copenhagen, Bisp