Upper Extremity Muscle Activity During Geared Manual Wheelchair Mobility

It is estimated 248,000 people have a spinal cord injury (SCI) that significantly affects their daily life activities [1]. Many individuals in this population use manual wheelchairs to assist them in propulsion and activities of daily living [2]. However, manual wheelchairs often lead to an increase in shoulder pain and injuries [3]. The aim of this study was to evaluate the biomechanical effects of a new, geared manual wheel for users with SCI. We seek to better understand the upper extremity biomechanics and muscle activity during manual wheelchair mobility.Ten (10) able-bodied individuals ages 18- 30 (5 females, 5 males) participated in this study. A Breezy manual wheelchair (Sunrise Medical LLC) was used by participants with both standard wheels and Easy Push (IntelliWheels, Inc.) geared wheels. The geared wheels have a gear ratio of 1:1.6. Participants propelled on level, tile flooring and up an ADAcompliant wheelchair ramp (4.8 degree slope).. Delsys Trigno wireless surface electrodes were placed on the anterior deltoid, pectoralis major and infraspinatus muscles of the participant\u27s dominant side to measure muscle activity. Electromyography (EMG) signals were normalized by subject specific maximum voluntary contractions (MVCs) and used to quantify peak and integrated muscle activity during a wheelchair stroke cycle.The results indicated that peak and integrated shoulder muscle activity decreased when using geared wheels compared to that of standard wheels. The notable decrease in shoulder muscle activity during geared manual wheelchair mobility demonstrates potential benefits for geared manual wheels. Reduction in peak EMG and muscle energy may ultimately lead to decreased resultant shoulder joint forces and a reduction in secondary musculoskeletal injuries, such as rotator cuff tears [4]. Further investigation is underway with a larger population of individuals with spinal cord injury