This document outlines a study protocol to: 1) Determine if the nociceptive withdrawal reflex (NWR) is modulated by different gait initiation postures. 2) Evaluate if differential accelerometry can be used to measure the reflex response. The study will stimulate four locations on the foot and record EMG and accelerometry data from the leg muscles during five sessions with 60 total stimuli across different standing postures. The results will show if accelerometry can measure the NWR and conclude if the reflex is modulated by gait initiation posture.

1. Detection and quantification of
the withdrawal reflex with
accelerometer based sensors in
healthy volunteers
Study I – Protocol
Miguel A. Richard

2. Aim experiment.
1.If the NWR is modulated by gait
initiation postures?
2.Is the differential accelerometry
signal usable for measure the reflex
response?

3. Posture and NWR
The positions to simulate are:
1)Standing 50%
2)Heel contact, with 80% of the body
weight on the right foot, GI. Start RL
3)Toe off, with 20% of the body
weight on the right foot, GI. Start LL

4. Posture and NWR
•To obtain a natural posture the
subject will receive visual feedback.
•The feedback consists on a square
moving, following the COP.
•The square changes its color
according the body load on the
platform.

6. Evoking the NWR
Locations:
• The third metatarsophalangeal
• The medial arch
• The plantar side of calcaneus
• The posterior side of calcaneus.
Reference electrode: the dorsal side the foot.
Stimulation:
•train of 5 electrical stimuli at 15 Hz.
•the train consist of 5, 1 ms pulses at 200 Hz.
Intensity: equal pain intensity on all sites.

7. Session
Each session:
• 4 stimulation on the 3 postures.
The subject must complete a total of 5
sessions.
This adds a total of 60 stimuli for
evoking the NWR.
Time duration expected: 3hs.

8. Outcomes
•EMG: Tibialis anterios, soleos,
vastus lateralis and biceps
femoralis, rigth leg.
•Differential acelerometry.
•Kinematics from ankle and knee
(back-up)

9. Results
•Viability of use diferential
accelerometry to measure the
NWR.
•A conclusion about if the NWR is
modulated by the posture in gait
initiation positions.

10. Question?
Send to : oka@hst.auu.dk

11. The Beginning