Backward walking at three levels of treadmill inclination: an electromyographic and kinematic analysis.

Backward walking on a treadmill is a common tool for lower extremity rehabilitation in the clinical setting. The purpose of this study was to evaluate the adaptations in the gait cycle produced by walking backward on a treadmill at 0, 5, and 10% inclination. Sixteen healthy adult subjects (14 females, two males), mean age of 23.19 +/- 3.02, participated. Joint positions for hip, knee, and ankle were measured during a complete gait cycle. Values were time matched with average electromyographic (EMG) activity (surface electrode) of the rectus femoris, hamstrings, gastrocnemius, and anterior tibialis during each subphase of gait (initial contact, midstance, heel-off, and midswing). Values of joint position and average EMG were compared over the three treadmill conditions. Subjects walked for approximately 1 minute at 4.0 km/h. A simple repeated measures analysis of variance (p < .05) with a Duncan post hoc test was used to analyze for changes. Significant changes occurred in the joint positions of the knee and ankle at initial contact (ankle increased from 9.81 +/- 5.06 degrees to 13.08 +/- 3.68 degrees; knee increased from 30.94 +/- 5.25 degrees to 42.42 +/- 4.08 degrees) as the treadmill was raised from 0 to 10%. Significant changes occurred for average EMG activity for each muscle studied over the three treadmill conditions. The greatest changes occurred in the gastrocnemius at initial contact (increase from 189.76 +/- 44.29% to 293.09 +/- 79.16%) between the 0 and 10% conditions. The results of this investigation confirm that backward walking up an incline may place additional muscular demands on an individual.(ABSTRACT TRUNCATED AT 250 WORDS)