Friday, March 2, 2001
EMG activity from the plantarflexors was recorded during walking in 10 subjects (six men, four women) without ankle pathology. Four walking conditions were examined: normal walking, immobilized (cam walker) in neutral plantarflexion, immobilized with a ½" heel lift, and immobilized with a 1" heel lift. In the immobilized ankle, the addition of a 1" heel lift was sufficient to minimize plantarflexor activity during walking.
EMG activity relative to plantarflexor torque was determined for each subject during isometric contractions at 25 percent, 50 percent, 75 percent and 100 percent of maximal voluntary contraction (MVC). EMG activity during walking was calculated as a percentage of MVC based on the EMG-torque relationship during graded isometric contractions.
During normal walking the plantarflexor torque was estimated to be 30±12 percent (SD) of MVC, compared with 21±15 percent MVC for immobilization in neutral (p < 0.01), 17±15 percent MVC with the addition of a ½" heel lift (p < 0.01) and 12±12 percent MVC with the addition of a 1" heel lift (p < 0.01).
The 1" heel lift resulted in less than 10 degrees plantarflexion in all subjects. When the ankle is immobilized, stress on the Achilles tendon is determined by the degree of plantarflexion and the contractile activity of the plantarflexors. In the immobilized ankle, the addition of a 1" heel lift was sufficient to minimize plantarflexor activity during walking.
Investigators are Kenneth H. Akizuki, MD; Eric J. Gartman, BA; Barton Nisonson, MD; and Malachy P. McHugh, PhD, all of the Nicholas Institute of Sports Medicine and Athletic Trauma at Lenox Hill Hospital, New York, N.Y.; and Simon Ben-Avi, PhD, Cooper Union School of Engineering, New York, N.Y.
|2001 Academy News March 2 Index C|
Last modified 15/February/2001 by IS