Torque variability of the plantar flexors in people with Huntington's disease

Torque steadiness can be impaired in people with Huntington's disease (HD) and worsen with disease advancement. However, existing studies have several methodological oversights. Studies have used absolute torque targets, which do not account for differences in maximal torque capacity between people. Furthermore, despite its known influence on torque steadiness, previous studies in HD have not controlled for visual feedback. This study evaluated torque variability at relative intensities with and without visual feedback between people with prodromal HD and healthy controls.

Twenty-four people with prodromal HD and twenty-seven age- and sex-matched healthy controls were recruited for this study. Torque variability was evaluated, with and without visual feedback, in the right plantar flexors at 10% and 30% of each participant's maximum voluntary isometric contraction (MVIC). Measures of disease burden included the CAG age product, diagnostic confidence level and Unified Huntington's Disease Rating Scale - Total Motor Score.

Significant differences in torque variability were observed, though not in overall MVIC, between people with prodromal HD and healthy controls. Significantly higher torque fluctuations were observed for both groups when visual feedback was removed. No associations were observed between torque variability and disease burden in people with prodromal HD. Torque variability measurements showed higher reliability in healthy controls.

People with prodromal HD exhibited greater torque variability than healthy controls. Torque variability worsened for both groups when visual feedback was removed. These findings support further investigation into the utilisation of torque variability measurements as markers of disease progression in people with prodromal HD.