Background Q-Motor provided reliable quantitative endpoints in TRACK-HD and several clinical trials. Finger tapping was the most sensitive assessment of disease progression and to detect treatment effects. Recently a foot tapping test was introduced to expand Q-Motor to the lower extremity. However, subjects had difficulties to properly lift the foot from the force sensor.

Aims To assess the feasibility of using a novel foot tapping apparatus that requires subjects to lift their foot properly.

Methods Two novel setups were constructed with the force sensor above the foot, one using a rigid (G1), one with a non-rigid bar (G2) to carry the sensor. Both setups were compared with the old setup carrying the sensor underneath the foot (G3). 6 healthy controls were asked to perform the foot tapping task on each setup on 4 consecutive days. They tapped with the foot on the force sensor as fast as possible for 10 seconds with 5 repetitions at each foot.

Results The ‘Tap-Speed-Inter-Onset-Interval-Mean-Foot’ is the main endpoint of foot tapping. It is the average time between the start of each successive tap. A density plot showed normally distributed data only for G2 and G3, thus G1 was not analyzed further. The data showed that the new inverted test setup (G2) provided less variability and better reproducibility over time.

Conclusions The novel foot tapping task is feasible and provided more reliable data. The new setup with the non-rigid bar merits further exploration in upcoming studies and should be tested in a larger cohort of subjects over longer periods.