The purpose of this study was to investigate the effects of an inclined and declined slope on kinematic properties and muscle activation magnitudes. This purpose was achieved by using a +10% grade for inclined backward walking (IBW) and -10% grade for declined backward walking (DBW) on a treadmill. Eleven participants (24.6 ± 4.1 yrs, 68.5 ± 14.6 kg, 1.7 ± 0.1 m) were recruited from the UNLV student body and were subject to a three day adaptation protocol to allow them to choose a preferred walking speed and to familiarize themselves with such a novel task. Two consecutive practice days included a trial that allowed participants to choose a preferred walking speed and practice for five minutes at each slope at that chosen speed. The third day included a final adaptation period in which the previous two walking speeds were averaged. For each slope condition, participants were allowed a three minute practice period before a thirty second data collection. The order in which participants walked on experimental slope conditions was counter balanced.

Participants walked on a motor-driven treadmill, with a 3-D motion video camera system. Participants were instrumented with surface electrodes to measure muscle (EMG) data. Joint range of motion (ROM), stride time, stride frequency, and integrated EMG were measured. One way repeated measure ANOVAs were conducted for each dependent variable using pairwise comparisons between each experimental condition and the level condition (α=.05). Results showed significant differences in ROM in the hip, knee, and ankle joint under both conditions (p < .01). Stride time exhibited differences under both experimental conditions (p < .001). Stride frequency was not significantly different at a decline (p = .391) but was at an incline (p = .003). Integrated EMG exhibited significant differences for the rectus femoris (p = .024), biceps femoris (p < .001), tibialis anterior (p = .011), gastrocnemius medialis (p < .001)) at an incline. At a decline, the rectus femoris (p < .001), tibialis anterior (p = .006), and gastrocnemius exhibited significant differences (p < .001), but the biceps femoris did not (p = .052). The results of this study suggest that inclined backward walking may be beneficial for treating physical conditions of the knee, due to the increased muscle activity induced by the slope as well as the increased knee range of motion. For hamstring overuse related injuries, both IBW and DBW have their own benefits in improving hamstring flexibility. The increase in knee ROM suggest further extensibility of the hamstrings muscles, while the added eccentric activity in DBW may also lead to increasing hamstring flexibility.