Dr Sean Horan1,2, Mr Blayne Arnold1, Dr Benjamin Weeks1,2, Dr Justin Kavanagh1,2
1School of Allied Health Sciences, Griffith University, Gold Coast, Australia, 2Menzies Health Institute Queensland, , Australia
Introduction: Skeletal muscle mass increases over the first three decades of life, declines steadily through middle age, and more rapidly in older age. Sarcopenia describes a condition of significant loss of muscle mass in conjunction with reduced strength and function. While the changes in mass, strength and function across the lifespan are well-documented, little is known of the underlying mechanisms. This work sort to examine the neuromotor mechanisms that underpin changes in muscles mass and function in older men.
Methods: Twenty-one older men (74.8 ±4.9yrs; height: 174.4 ±6.5cm; 84.3 ±11.4kg) and 10 younger men (26.4 ±4.2yrs; height: 178.8 ±7.8cm; 75.9 ±11.1kg) were recruited. Muscle and fat mass were determined by DXA (Norland XR-800, USA). Functional performance was examined with isometric knee extension, timed-up-and-go (TUG), 5-times sit-to-stand (5TSTS), and self-selected gait speed. Neuromotor measures included Level of Voluntary Activation (LoVA; 20%, 40%, 60% 80%, MVC) during a plantar flexion task, using tibial nerve stimulation. Plantar and dorsi flexor force were recorded, as well as muscle activity using EMG.
Results: Three older men were classified with pre-sarcopenia based on DXA-derived measures of appendicular lean mass (<6.8kg/m2). No differences in LoVA were observed between young men, older men, and older men with pre-sarcopenia (YM: 20%=17.6, 40%=50.7, 60%=82.9, 80%=93.8, 100%=96.7; OM: 20%=20.5, 40%=56.3, 60%=81.3, 80%=93.1, 100%=95.5; PS: 20%=23.7, 40%=58.0, 60%=81.9, 80%=93.9, 100%=96.1). Although not significant, pre-sarcopenic men achieved the lowest dorsi flexor (YM=40.5N; OM=33.0N; PS=25.1N), plantar flexor (YM=154.5N; OM=106.7.0N; PS=70.8N), and knee extensor forces (YM=841.7N; OM=509.2N; PS=361.0N). No differences in functional performance measures were observed.
Discussion: These preliminary findings suggest that older men with pre-sarcopenia maintain functional abilities and demonstrate similar levels of voluntary muscle activation to healthy men despite apparent deficits in strength. Recruitment is ongoing and further work will examine neuromotor characteristics in response to fatigue and muscle inhibition.
Acknowledgements: This work was supported by a Physiotherapy Research Fellowship from the Health Innovation, Investment, and Research Office, Queensland Health.
Sean Horan is a Senior Lecturer at Griffith University on the Gold Coast, Queensland. Sean teaches musculoskeletal physiotherapy into both the undergraduate and postgraduate physiotherapy programs at Griffith. His key research areas of interest include the neuromotor mechanisms underlying the development of sarcopenia; the development of exercise interventions aimed at slowing or reversing the effects of osteoporosis; and the examination of the effects of surgical and physical activity interventions on paediatric muscuolskeletal conditions of the feet and lower limbs.