Neuromuscular function and adaptation are often evaluated by comparing a patient's kinematic (movement) and kinetic (forces and moments) gait patterns with those obtained from healthy individuals. A feature of many patients' gait is a much slower than normal walking speed. It is important when interpreting a patient's data to distinguish which variations from normal are due solely to differences in walking speed and which are due to neuromuscular abnormalities or adaptations other than speed. The purpose of this project is to investigate the effect of dramatically different walking speeds on the mechanics of gait. One specific objective is to determine if a """"""""quadriceps avoidance"""""""" pattern of net knee flexion-extension moments (reported in the literature for patients with anterior cruciate ligament deficiency) is demonstrated by healthy subjects at slower walking speeds. Movement and force data have been collected from 18 healthy subjects (9 male, 9 female, ages 21-37 yrs) who walked at 25%, 50%, 75%, 100%, and 125% of a normalized speed of 0.785 statures/s (? 2.5%). Speed was measured over a 2.28 m distance using two photocells and a gait speed indicator circuit. Inverse dynamics analysis was performed to calculate the net flexion-extension moments at the knee during the stance phase of gait. Two-thirds of individual subjects had knee flexion-extension moment patterns that were similar across all five walking speeds. One-third of the subjects, however, demonstrated a quadriceps avoidance strategy (net flexor moment or zero moment) in at least one trial at the slowest speed. Decreased moment amplitude was related to decreased knee flexion during the """"""""loading response"""""""" phase in early to mid stance. The subjects who produced the quadriceps avoidance pattern at the slowest speed did so by keeping the knee near full extension throughout the stance phase of gait.
