Determining validity of the PALite and ODFS PACE activity logger for measuring step count in healthy adults

Determining adherence with orthoses is important for clinicians prescribing devices. Measuring orthotic use often relies on patient recall which has poor agreement with objective measures. Measuring step count whilst wearing an orthosis could help objectively quantifying adherence. The Odstock Drop Foot Stimulator (ODFS) Pace, used in foot drop, has an integral activity logger which provides data on step count. The PALite, an accelerometer, measures step count and can be fixed to an ankle foot orthoses (AFO). Both have the potential to provide objective measures of adherence; however, their validity for this purpose has not been determined.

To determine the validity of the PALite and ODFS Pace activity logger in measuring total step count, by exploring their level of agreement.

A convenience sample of sixteen healthy volunteers, aged 18-65, were recruited from Glasgow Caledonian University (GCU). Participants walked continuously for 5 min on a treadmill at three walking speeds; normal (1.3ms^-1), slow (0.4 ms^-1) and fast (1.7-2.0 ms^-1), wearing both the PALite and ODFS Pace. All walks were video recorded, viewed by 2 raters, and observed step count was determined by a click counter. Step count from both devices was validated against observed step count using video recording. The level of agreement between the three methods was established.

There was no significant difference between the 3 methods of measuring step count at any walking speed (normal, p = 0.913; slow, p = 0.938; fast, p = 0.566). Good levels of agreement for both devices with observed step count at all 3 walking speeds, with mean percentage differences being between -1.2 and 2.1 % (maximum upper and lower levels of agreement = 19.5 and -18.8 %) was detected.

Clinicians could consider both devices to objectively measure step count with people who are prescribed foot drop orthoses, thus quantifying orthotic use.