# Doctor, when can I drive? – Influence of muscle weakness of dorsal flexors and plantar flexors from the ankle joint on driving ability

## TL;DR

This study examines how weakness in ankle muscles affects driving performance, using a simulator to test emergency braking and stop-and-go scenarios.

## Contribution

The study experimentally evaluates the impact of simulated dorsiflexion and plantarflexion weakness on driving performance using a driving simulator.

## Key findings

- Dorsiflexion weakness significantly prolonged brake pedal activation during emergency braking.
- Plantarflexion weakness increased acceleration use and safety distance in stop-and-go traffic.
- Dorsiflexion weakness also reduced speed and safety distance in stop-and-go scenarios.

## Abstract

Dorsiflexion (DF) and plantarflexion (PF) weakness are among the most commonly observed muscle strength impairments of the lower extremities. This may be due to spinal conditions, peripheral nerve damage, trauma or multiple other reasons. The personally used automobile remains the most commonly used mode of individual transportation in Germany. However, it is unclear whether and to what extent DF or PF weakness affects the ability to drive safely. This study aimed to experimentally assess the impact of DF and PF weakness on driving ability.

Twenty healthy licensed drivers with an annual mileage of > 5000 km participated in this experimental study. A custom-made orthosis was applied to the right leg to simulate both DF and PF weakness. Participants completed two driving simulator scenarios: an emergency braking maneuver (EBM) and stop-and-go traffic (StGo) under controlled conditions and with different levels of strength impairment (3/5 and < 3/5). Driving performance parameters were recorded and statistically analyzed using SPSS 29.

DF weakness significantly prolonged brake pedal activation during EBM (2238 ms vs. 2046 ms; p < 0.02), while PF weakness had no significant effect. In StGo, PF weakness led to significantly more frequent acceleration use (1.4 vs. 1.05; p < 0.02) and increased safety distance (30.3 m vs. 24.8 m; p < 0.01). DF weakness resulted in more frequent acceleration use, lower speed, and a reduced safety distance (21.9 m vs. 24.8 m; p < 0.05).

PF weakness primarily affects fine motor control in StGo, while DF weakness significantly impacts both EBM and StGo. Compensation mechanisms should be further investigated.