Filter frequency selection for manual wheelchair biomechanics

Area of Science:

• Biomechanics
• Rehabilitation Engineering
• Spinal Cord Injury Research

Background:

• Manual wheelchair propulsion is crucial for mobility in spinal cord injury (SCI) but can cause upper-limb pain and inefficiency.
• Biomechanics offers insights into optimizing wheelchair use and mitigating associated issues.

Purpose of the Study:

• To determine the frequency content of hand motion during wheelchair propulsion at different speeds.
• To identify optimal filter frequencies for cleaning wheelchair motion data.
• To provide signal-to-noise ratio (SNR) data for wheelchair kinematics.

Main Methods:

• Participants: Manual wheelchair users with SCI-induced paraplegia.
• Procedure: Propelled wheelchairs on a dynamometer at 0.9 m/s and 1.8 m/s.
• Data Collection: Motion data captured at 60 Hz using an infrared marker-based system.

Main Results:

• No useful signal power was detected above 6 Hz for wheelchair propulsion at analyzed speeds; often, useful power was below 4 Hz.
• Mean SNR ranged from 21.8 dB to 91 dB, highest in the forward (x) direction and lowest in the medial-lateral (z) direction.
• Frequency content resembles that of human gait.

Conclusions:

• Manual wheelchair propulsion kinematic data should be low-pass filtered at approximately 6 Hz for speeds up to 1.8 m/s.
• Existing literature likely uses appropriate filtering frequencies.
• Findings aid in refining biomechanical analysis of wheelchair use.