Quantifying Fatigue with Wearable Assistive FES Devices for the Shoulder

Annabelle P. Smith*, Ariel B. Thomas, and Valeriya Gritsenko

Rockefeller Neuroscience Institute, Department of Neuroscience, School of Medicine, West Virginia University, Morgantown, WV 26506

Presentation Category: Health Sciences (Poster Presentation #122)

Student’s Major: Music and Health

Functional Electrical Stimulation (FES) consists of using small electrical pulses administered through electrodes placed on the skin to elicit a muscle contraction. The uses for FES on people who have lost partial or all function in a muscle are boundless when considering developments made in wearable FES technology. With recent advancements in FES technology the question of muscle fatigue from wearable assistive use is still unanswered. We examined how the use of FES can impact muscle fatigue when used to assist with a reach and grasp task. Nine healthy subjects were put into a virtual task environment and instructed to reach and grasp various targets with and without FES to the shoulder. Upper limb muscle activity was recorded using wireless sensors, along with detailed tracking of kinematics. Before FES trials, subjects performed 80 control reach and grasp repetitions without stimulation. Next, stimulation was applied to the anterior and medial deltoid at amplitude levels adjusted to induce 30 degrees shoulder flexion or abduction, respectively. This stimulation was then triggered by the subject’s movement within the VR task environment to assist the shoulder in the direction of movement with each reach (160 repetitions). After the stimulation trials, the resting stimulation and control trials were repeated. Through comparisons of the degree of abduction and flexion induced by stimulation before and after trials, we saw the presence of fatigue. This could indicate a potential hurdle in the field of wearable FES technology, highlighting the potential need to adjust stimulation amplitude during extended use.

Funding: National Institute of General Medical Sciences

Program/mechanism supporting research/creative efforts: WVU's Research Apprenticeship Program (RAP) & accompanying HONR 297-level course