Effect of limb surrogate surface compliance on the impact response of wrist protectors

Objectives To investigate the effect on the impact response of wrist protectors by incorporating a soft tissue simulant on to a wrist surrogate made of stiff material. The effect of protector strapping condition was also investigated. Design and methods A compliant and a stiff surrogate were made, based on the wrist geometry specified in ISO 20320:2020 for the “Limitation of wrist extension” test. Two styles of wrist protectors (short, long) were tested on each limb surrogate, subject to a ∼31 ​J impact. Six protectors of each style were tested, with two of each at each strapping condition (loose, moderate, tight) on each surrogate (stiff, compliant) (24 combinations). Example temporal force and wrist angle and force vs. wrist angle plots are presented for comparison between conditions. Results When protectors were on the compliant surrogate, peak impact force was 55–68% lower (short 3.1 vs. 6.8 ​kN, long 2.7 vs. 8.3 ​kN). The time to reach this peak force was ∼4 ​ms (12%) longer, than for the stiff surrogate. Protector strapping condition had no clear effect for the stiff surrogate, with the wrist extending to its limit for all tests. Strapping protectors tighter on the compliant surrogate tended to decrease the maximum wrist angle and peak force. Conclusions With results being sensitive to surrogate design and strapping condition, these both need to be clearly reported in future work impact testing wrist protectors, with implications for certification tests within standards.