Comparison of the muscle pattern variability during treadmill walking (fixed and self-pace) and overground walking of able-bodied adults

Study purpose: The purpose of the study was to understand whether treadmill walking (fixed and self-paced) exhibits sufficiently similar motor patterns to overground walking to justify its use as a rehabilitation modality in the recovery of normal walking function. The study compared the activity patterns of five lower-limb muscle groups (Hamstrings, Quadriceps, Tibialis Anterior, Gastrocnemius and Soleus) while walking on a Traditional Treadmill (FPT), a Self-Paced Treadmill (SPT) and during Overground Walking (OG). The Variance Ratio (VR), which quantifies cycle-to-cycle repeatability, was used as the primary comparator with a higher VR indicating greater variability across cycles. Eleven able-bodied adults participated (mean age 27.8 years, weight 72.3 kg, 5 female).
Major findings: The VR observed during FPT walking (0.22) was higher than both the SPT (0.18) and OG (0.20) walking but these differences were not statistically significant (F=1.23, P=0.3).
Interpretation: Counter intuitively, FPT walking created a more variable pattern of muscle activity than SPT, possibly by constraining the natural tendency to vary speed. The similarity between SPT and OG suggests this form of treadmill walking may have better training specificity than FPT walking for functional gait recovery. This possibility should be tested in future statistically powered trials including clinical populations.
Conclusion: Differences in muscle activity variability, while not statistically significant, suggests that SPT walking may offer a more specific training experience than fixed pace for gait rehabilitation.