Author(s): NICHOLSON, G., HODSON-TOLE, E., PINCKNEY, M., WALKER, J., Institution: LEEDS BECKETT UNIVERSITY, Country: UNITED KINGDOM, Abstract-ID: 2678

INTRODUCTION:
Muscle fasciculations are involuntary contractions that occur in healthy individuals but clinically, their manifestation is deemed a sign of denervation. Evidence exists [1] to suggest that the number of fasciculations someone experiences might increase with age, but the time-course of these changes compared to other common measures of age-related decline (e.g. muscle mass, muscle quality) is currently unknown. The aim of this study was therefore to compare muscle fasciculations and existing markers of age-related decline across a spectrum of different age ranges.
METHODS:
Participants in young (Y: 20-30 years), middle-aged (M: 45-55 years) and older (O: 70-80 years) age ranges completed a single testing session. Following a dual energy x-ray absorptiometry (DXA) scan to assess body composition, participants completed a resting muscle fasciculation assessment of the gastrocnemius medialis using dynamic ultrasound (60 Hz) and high-density surface electromyography (1000 Hz). Isometric plantar flexion strength was assessed using an isokinetic dynamometer (200 Hz), and a stair ascent-descent and gait speed reserve (GSR) test were used to assess functional performance. Fasciculations were analysed using a validated automated identification algorithm [2] in MATLAB. Differences groups were determined using Cohens d effect sizes and were categorised as small (>0.2), medium (>0.50) large (>0.8) or very large (>1.2).
RESULTS:
Moderate-large differences in muscle fasciculations were observed between groups (Y vs M: d=0.22, Y vs O: d=0.89, M vs O: d=0.71) with O observing 40% and 31% more than Y and M, respectively, and M experiencing 7% more than Y. These differences were also underpinned by moderate-to-large differences in appendicular lean mass (Y vs M: d=0.83, Y vs O: d=1.39, M v O: d=0.91) and muscle quality index (Y v M: d=0.51, Y vs O: d=0.92: M v O: d=0.46). Differences in strength and functional performance were more pronounced, with moderate-to-very large differences being shown in plantar flexor strength (Y v M: 1.01, Y v O: 1.67, M v O: 0.82), stair ascent-descent (Y v M: d=0.56, Y v O: d=2.99, M v O: d=2.72) and GSR (Y v M: d=0.56, Y v O: d=1.31, M v O: d=0.86).
CONCLUSION:
The lower levels of strength and functional performance in older and middle-aged adults occurred alongside reductions in muscle mass and muscle quality, as well as increases in muscle fasciculations. Since automated, reliable and non-invasive methods now exist to characterise involuntary muscle activity, greater utilisation of these methods in health screening may provide deeper insights into the neurophysiology of musculoskeletal decline and enable earlier intervention.

References:
[1] Fremont J et al. (2010) Amyotrophic Lateral Sclerosis; 11: 181-186
[2] Bibbings, K et al. (2019) Ultrasound in Med & Biol; 45:1164-1175