The consequences of motor unit remodelling for motor control
Research type
Research Study
Full title
The consequences of motor unit remodelling for motor control: an important factor in the loss of mobility with old age.
IRAS ID
152903
Contact name
Jamie McPhee
Contact email
Sponsor organisation
Manchester Metropolitan University
Clinicaltrials.gov Identifier
152903 , NIHR CRN Portfolio
Duration of Study in the UK
1 years, 9 months, 1 days
Research summary
Research summary:
Motor neurons carry the electrical signals generated by the brain through to muscles to control our voluntary movements. Large muscles can have hundreds of motor neurons and each innervates hundreds of muscle fibres (known as a motor unit). This arrangement helps to precisely control movements. In order to change the strength of a movement (e.g. to run faster), the brain can activate more motor units within any given muscle or it can more strongly activate each motor unit.
It was noticed in the 1970s that elderly people had fewer motor units controlling their muscles. Very little research has since looked into this problem. We believe that loss of motor units during normal ageing will decrease muscle size as well as fine motor control such as writing or balancing and may affect whole body movements like walking or correcting a trip.
It is easy to measure the electrical signals that control muscles by using electromyography (EMG). Small metal contacts (electrodes) are placed on the skin covering the muscle (surface EMG, or sEMG) or a very thin needle electrode ( 26 gauge, and smaller than a blood sampling needle) is introduced into the muscle (intramuscular EMG, or iEMG). EMG reveals how hard the muscles are working and estimates the total number of motor units, their size (i.e. how many fibres are controlled by each motor neuron) and how often they are activated.
In healthy, independent living volunteers we will use iEMG and sEMG to examine differences between young and elderly men in size and number of motor units of muscles controlling the arms and legs. Results will be assessed in relation to the size and strength of the muscles and bones, movements such as walking, balancing and picking up objects and blood samples will be collected to examine mechanisms of neuronal cell loss.Lay summary of study results:
We found that substantial loss and remodelling (attachment of orphaned muscle fibres to surviving motor units) occurs in older age. We found that motor unit remodelling is more pronounced in active than inactive people, although motor unit loss is similar, therefore remodelling may contribute to preservation of muscle mass and function in older age in more active individuals.REC name
North West - Greater Manchester West Research Ethics Committee
REC reference
15/NW/0426
Date of REC Opinion
12 Jun 2015
REC opinion
Favourable Opinion