Background
Treadmill walking is emerging as a viable intervention for treating gait impairments following neurological disorders such as stroke, spinal cord injury, and Parkinson's disease. Over the last 20 years, instrumented treadmills that incorporate one or more high–fidelity force plates have emerged as a valuable measurement tool in clinical gait studies and applied research settings. Instrumented treadmills provide basic spatiotemporal gait parameters and ground reaction forces in near real–time and have been reported to have 'high' levels of reliability, with coefficients of variation (CVs) of < 10% typically reported between– and within–days for temporal gait parameters and ground reaction forces (GRF) collected with these systems.
Recently, however, a relatively new instrumented treadmill that incorporates an array of pressure transducers, rather than a force plate, has become commercially available. To date, this new system has been used to investigate fundamental control mechanisms in gait, disturbances associated with neurological disorders, including Parkinson's disease and cerebellar ataxia, and as an outcome measure to monitor the progression of ergonomic training programs, and the effectiveness of various clinical, and neuro–rehabilitation trials.
Despite the increasing use of these instrumented treadmills in clinical and research settings, however, there is limited published data regarding their measurement properties. This is surprising, given the performance characteristics and spatial resolution of similar capacitance–based pressure platforms are known to differ to those of force platforms. In one of the few studies performed to date, Faude et al. reported that CVs between–days were typically < 7% for most parameters, except for measures of temporal (25–30%) and spatial (32–36%) variability in healthy seniors (n = 20; mean age, 64.3 ± 3.2 years) when walking at a constant imposed walking speed (1.39 m.s). However, the study did not evaluate the repeatability of GRF–based parameters, which are also routinely derived by these systems.
The aim of the current investigation, therefore, was to evaluate the within– and between–day repeatability of spatiotemporal gait parameters and vertical ground reaction forces measured in a group of healthy young adults while walking at self–selected speeds on a capacitance–based treadmill system. We specifically evaluated the repeatability of basic gait parameters in young adults as recent intervention studies have used the same treadmill system as outcome measures in this cohort.