Increased motor unit potential shape variability across consecutive motor unit discharges in the tibialis anterior and vastus medialis muscles of healthy older subjects.
OBJECTIVE
To study the potential utility of using near fiber (NF) jiggle as an assessment of neuromuscular transmission stability in healthy older subjects using decomposition-based quantitative electromyography (DQEMG).


METHODS
The tibialis anterior (TA) and vastus medialis (VM) muscles were tested in 9 older men (77 ± 5 years) and 9 young male control subjects (23 ± 0.3 years). Simultaneous surface and needle-detected electromyographic (EMG) signals were collected during voluntary contractions, and then analyzed using DQEMG. Motor unit potential (MUP) and NF MUP parameters were analyzed.


RESULTS
NF jiggle was significantly increased for both the TA and VM in the old age group relative to the younger controls (P<0.05). NF jiggle was significantly higher in the TA compared to VM (P<0.05). For TA, NF jiggle was negatively correlated with MUNE, and positively correlated with S-MUP amplitude, NF count, MUP duration, MUP peak-to-peak voltage, and MUP area (P<0.05). For VM, NF jiggle was positively correlated with NF count and MUP area (P<0.05), and no significant correlations were found between NF jiggle and S-MUP amplitude, MUP duration, or MUP peak-to-peak voltage (MUNE was not calculated for VM, so no correlation could be made).


CONCLUSIONS
Healthy aging is associated with neuromuscular transmission instability (increased NF jiggle) and MU remodeling, which can be measured using DQEMG.


CONCLUSIONS
NF jiggle derived from DQEMG can be a useful method of identifying neuromuscular dysfunction at various stages of MU remodeling and aging.
Department of Anatomy and Cell Biology, Schulich School of Medicine and Dentistry, Western University, London, Ontario, Canada.
Maddison L
ML
Hourigan
School of Kinesiology, Faculty of Health Sciences, Western University, London, Ontario, Canada.
Neal B
NB
McKinnon
Department of Anatomy and Cell Biology, Schulich School of Medicine and Dentistry, Western University, London, Ontario, Canada.
Marjorie
M
Johnson
Department of Anatomy and Cell Biology, Schulich School of Medicine and Dentistry, Western University, London, Ontario, Canada; School of Kinesiology, Faculty of Health Sciences, Western University, London, Ontario, Canada.
Charles L
CL
Rice
Department of Systems Design Engineering, University of Waterloo, Waterloo, Ontario, Canada.
Daniel W
DW
Stashuk
School of Kinesiology, Faculty of Health Sciences, Western University, London, Ontario, Canada; Department of Physical Medicine and Rehabilitation, Schulich School of Medicine and Dentistry, Western University, London, Ontario, Canada; Department of Clinical Neurological Sciences, Schulich School of Medicine and Dentistry, Western University, London, Ontario, Canada. Electronic address: tim.doherty@lhsc.on.ca.
Timothy J
TJ
Doherty
D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000473:pathology / Q000502:physiology*; D004576:Electromyography / Q000379:methods / Q000639:trends*; D006304:Health Status; D006801:Humans; D008297:Male; D009046:Motor Neurons / Q000502:physiology*; D009119:Muscle Contraction / Q000502:physiology; D052097:Quadriceps Muscle / Q000473:pathology / Q000502:physiology*; D011999:Recruitment, Neurophysiological / Q000502:physiology*; D013977:Tibia / Q000502:physiology; D055815:Young Adult
Aging; Decomposition-based quantitative electromyography (DQEMG); Jiggle; Motor unit potential (MUP); Neuromuscular transmission; Skeletal muscle