A comparison of variability in spatiotemporal gait parameters between treadmill and overground walking conditions

• Variability in gait parameters may differ between treadmill and overground walking.
• We examined stride-to-stride variability with Poincaré analyses.
• Mean values were equivalent between treadmill and overground walking.
• Short- and long-term variability indicators were reduced on the treadmill.
• Treadmill training may induce invariant gait patterns.

Motorized treadmills are commonly used in biomechanical and clinical studies of human walking. Whether treadmill walking induces identical motor responses to overground walking, however, is equivocal. The purpose of this study was to examine differences in the spatiotemporal gait parameters of the lower extremities and trunk during treadmill and overground walking using comparison of mean and variability values. Twenty healthy participants (age 23.8 ± 1.2 years) walked for 6 min on a treadmill and overground while wearing APDM 6 Opal inertial monitors. Stride length, stride time, stride velocity, cadence, stance phase percentage, and peak sagittal and frontal plane trunk velocities were measured. Mean values were calculated for each parameter as well as estimates of short- (SD1) and long-term variability (SD2) using Poincaré analyses. The mean, SD1, and SD2 values were compared between overground and treadmill walking conditions with paired t-tests (α = 0.05) and with effect size estimates using Cohen's d statistic. Mean values for each of the gait parameters were statistically equivalent between treadmill and overground walking (p > 0.05). The SD1 and SD2 values representing short- and long-term variability were considerably reduced (p < 0.05) on the treadmill as compared to overground walking. This demonstrates the importance of consideration of gait variability when using treadmills for research or clinical purposes. Treadmill training may induce invariant gait patterns, posing difficulty in translating locomotor skills gained on a treadmill to overground walking conditions.