Sequence and onset of whole-body coordination when turning in response to a visual trigger: Comparing people with Parkinson's disease and healthy adults

•We examined whole-body coordination when turning in people with PD (PwPD).•Contrary to common belief, head movement preceded eye movement in all subjects.•We found longer overall latencies for PwPD from head to second foot moving.•For PwPD, differences were found for disease severity, age group and gender.•Significant differences were found in the lower part of the body (pelvis and feet).

Turning round is a routine everyday activity that can often lead to instability. The purpose of this study was to investigate abnormalities of turning among people with Parkinson's disease (PwPD) through the measurement of sequence of body segments and latency response. Participants were asked to turn 180° and whole-body movements were recorded using CODAmotion and Visio Fast eye tracking equipment. Thirty-one independently mobile PwPD and 15 age-matched healthy controls participated in the study. We found that contrary to common belief, the head preceded movement of all other body segments (eyes, shoulders, pelvis, first and second foot). We also found interaction between group and body segment (P = 0.005), indicating that overall, PwPD took longer to move from head to second foot than age-matched healthy controls. For PwPD only, interactions were found between disease severity and body segment (P < 0.0001), between age group and body segment (P < 0.0001) and between gender and body segments (P < 0.0001). For each interaction, longer time periods were noted between moving the first foot after the pelvis, and moving the second foot after the first, and this was noted for PwPD in Hoehn and Yahr stage III-IV (in comparison to Hoehn and Yahr stage I-II); for PwPD who were under 70 years (in comparison with 70 years or over); and for ladies (in comparison with men). Our results indicate that in PwPD and healthy elderly, turning-on-the-spot might not follow the top-to-bottom approach we know from previous research.