Inertial measurement units worn on the dorsum of the foot and proximal to the ankle can provide valid slip recovery measures

Abstract

Background

Slips are a leading cause of injury among older adults. Slip recovery measures are often captured using optoelectronic motion capture (OMC) systems that can be costly and typically require a laboratory setting. Inertial measurement unit (IMU) systems show promise as a lower cost, portable, and wearable form of motion capture.

Question

Can IMUs worn on the dorsum of the feet and proximal to the ankles be used to capture valid slip recovery measures?

Methods

Thirty older adults (ages 65–80; 18 females) were exposed to a laboratory slip while wearing OMC markers, IMUs on the dorsum of the feet, and IMUs proximal to the ankles. To evaluate the concurrent validity of IMU-based slip recovery measures using the OMC-based measures as our standard, we determined whether the IMU-based slip recovery measures differed between falls and recoveries, and evaluated the strength of correlation between IMU-based measures and OMC. We also defined the difference between foot IMU-based and OMC-based slip recovery measures to be the system offset, and compared the system offset variance between participant-placed IMUs and researcher-placed IMUs.

Results

All IMU-based and OMC-based slip recovery measures differed between falls and recoveries (p ≤ 0.008), and all IMU-based measures exhibited strong correlation (r ≥ 0.94) with OMC-based measures. The system offset variance was larger when foot IMUs were participant-placed than when researcher-placed for anterior-posterior slip distance (p = 0.032), but not other slip recovery measures (p ≥ 0.054).

Significance

IMUs worn on the dorsum of the feet and proximal to the ankle can provide valid slip recovery measures in a laboratory setting. This includes IMUs placed by participants on the dorsum of the feet that might be needed for the long-term monitoring of these measures by participants outside the laboratory setting.