Dynamic Soft Tissue Artifacts during Impulsive Loads: Measurement Errors Vary With Wearable Inertial Measurement Unit...

Area of Science:

• Biomechanics
• Sensor Technology
• Human Movement Analysis

Background:

• Inertial Measurement Units (IMUs) are widely used to measure human movement.
• Soft tissue artifacts (STAs) can introduce significant errors in IMU-based motion capture.
• Dynamic STAs, particularly during impulsive loads, are not well understood.

Purpose of the Study:

• To characterize and model IMU errors caused by dynamic soft tissue artifacts during impulsive loading.
• To investigate the influence of sensor mass on these dynamic STAs.
• To explore potential mitigation strategies for IMU measurement errors.

Main Methods:

• 10 participants were instrumented with IMUs on the dominant leg.
• Ankle IMU data was cross-validated against vertical force measures for reference vertical accelerations.
• Shank-mounted IMUs (posterior and anterior) were used to quantify dynamic STAs, with varying sensor masses.

Main Results:

• Posterior and anterior IMUs overestimated peak vertical accelerations (gains of 2.18 and 1.55, respectively).
• Oscillation duration and natural frequency of post-impact signals varied with sensor mass, fitting an underdamped second-order system model.
• Low-pass filtering reduced acceleration overestimation but also attenuated reference measures.

Conclusions:

• Dynamic STAs introduce transient, substantial IMU measurement errors.
• These errors may not be fully resolved by conventional low-pass filtering.
• Dynamic STAs can be modeled as an underdamped second-order system, potentially enabling material property estimation of soft tissues.