Evaluation of aging effects on muscle efficiency during isometric contractions using HD-SEMG technique

Léà Scapucciati, a Biomedical Engineering student at the University of Technology of Compiègne, France, is one of the students involved in the student exchange program between Sorbonne Universites and the University of Waterloo. As part of the exchange program, Léà is currently working in the Engineering Bionics Lab of Dr. Ning Jiang, who is a Centre for Bioengineering and Biotechnology Member, as well as an Assistant Professor in the Department of Systems Design Engineering.

Professor Jiang is an assistant professor and researcher in the department of Systems Design Engineering. His main research interests include biological signal processing and analysis with the use of electroencephalograms (EEGs), electrocardiograms (ECGs) and electromyographies (EMG); electrical monitoring methods used to record activity of the brain, heart and skeletal muscle. Other application areas of his work include the fields of balance, motor control, biomechanics, rehabilitation, mHealth, eHealth, and fall prevention. In his current lab, Professor Jiang utilizes his interest in EMGs to explore the effects of aging on muscle efficiency during isometric contractions.

Aging is known to be associated with a degenerative loss of muscle tissue, otherwise known as sarcopenia. Sarcopenia is primarily caused by a loss of muscle fibers, resulting in diminished muscle function, decreased strength, and a high incidence of falls among the elderly¹.

Using a BIODEX machine to perform strength tests, and a high-density electromyogram (HD-SEMG) to record muscle fiber use and activation, Professor Jiang’s lab seeks to analyze and compare the differences in muscle activity between the young and old. Data is collected through a three-step process. First, participants find out their maximum strength by pulling with the BIODEX machine as hard as possible. Then, participants work at either 20, 40 or 60 percent of their maximum strength in a random order, and perform isometric contractions for 15 seconds. Following, participants perform the fatigue test, where they hold a contraction at 20% of their maximum strength for as long as they can. The HD-SEMG is then used to measure muscle activity in order to determine which parts of the muscles older persons use when performing a specific action, in comparison to the parts used by younger persons.

Léà notes that a surprising outcome of the pre analysis of the data was that older people are better at performing the fatigue test than younger people. “As we age, our muscles have less ‘fast’ fibres and more ‘slow’ fibres… Older people can hold a contraction at 20% of their maximum strength for as long as 15 minutes, whereas younger people can only hold a contraction at 20% of their maximum strength for about 4 to 5 minutes,” Léà recalls.

When asked about future applications of their findings, Léà comments that Professor Jiang’s research is a long term project with its overall aim being to improve the mobility and quality of life of older people. Léà also states that information derived from the study could be used to determine what exercises would best work for older people to prevent or prolong muscle atrophy.