The Influence of Altering Push Force Effectiveness on Upper Extremity Demand During Wheelchair Propulsion
By Rankin, Jeffery R.; Kwarciak, Andrew M.; Richter, W. Mark; Neptune, Richard R.; Journal of Biomechanics, Volume 43, Number 14, pages 2771-2779Publication Date: October 19, 2010
Study used forward dynamics simulations of wheelchair propulsion to determine the influence of fraction effective force (FEF), the ratio of tangential to total handrim force, on upper extremity demand by quantifying individual muscle stress, work, and handrim force contributions at different values of FEF. The study was undertaken as studies attempting to reduce upper extremity demand during wheelchair propulsion have used FEF as a guide for modifying propulsion technique, developing rehabilitation programs, and configuring wheelchairs; however, the relationship between FEF and upper extremity demand has not been well understood. Experimental data were collected from a 36 year old experienced manual wheelchair user with a height of 177.8 centimeters and a weight of 80.7 kilograms. Raw EMG data were collected from the anterior, middle, and posterior portions of the deltoid, sternal portion of the pectoralis major, biceps brachii, and medial and lateral portions of the triceps brachii. Simulations maximizing and minimizing FEF resulted in higher average muscle stresses of 23 and 112 percent, and total muscle work of 28 and 71 percent compared to a nominal FEF simulation. The maximal FEF simulation also shifted muscle use from muscles crossing the elbow to those at the shoulder, such as rotator cuff muscles, placing greater demand on shoulder muscles during propulsion. The optimal FEF value appeared to represent a balance between increasing push force effectiveness to increase mechanical efficiency and minimizing upper extremity demand. Based on study results, the authors conclude that care should be taken in using force effectiveness as a metric to reduce upper extremity demand.
Published by: Elsevier Inc. (Website:http://www.elsevier.com)
Link to text: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2963661/?tool=pmcentrez
