Effect of Surrogate Surface Compliance on the Measured Stiffness of Snowboarding Wrist Protectors

Abstract

Wrist injuries have been reported to account for 35%–45% of snowboarding injuries. Snowboarding wrist protectors are designed to limit impact forces and prevent wrist hyperextension. The absence of a standard for snowboarding wrist protectors makes it hard to identify models offering an adequate level of protection. Wrist surrogates are well suited for testing and benchmarking wrist protectors. This study investigated the effect of introducing a soft tissue simulant onto an otherwise stiff wrist surrogate on the bending stiffness of snowboarding wrist protectors. A compliant surrogate (stiff core and 3 mm thick silicone layer) and a comparable stiff surrogate were fabricated. Two snowboarding wrist protectors were tested on each surrogate, under three strapping conditions, following a bend test to ~80° wrist extension. The introduction of a compliant layer to the wrist surrogate gave higher torque values for a given wrist extension angle, increasing protector effective stiffness, relative to a rigid surrogate.

Repeatability of a bending stiffness test for snowboarding wrist protectors

“…The same bending stiffness test method as Leslie et al [14] was conducted, on three test sessions, each a week apart. The intention was not to exactly replicate the test in ISO 20320:2020, but to go beyond it, testing a wider range of loads and hence wrist angles, which could have implications for future revisions of the standard.…”

“…Such revisions could include specific requirements for strapping condition, changes to the surrogate outer surface compliance, and how they may influence the required pass criteria. While the load was not applied perpendicular to the fingers, as stipulated in ISO 20320:2020, the equivalent load was calculated [7,8,14]. The torque values specified in ISO 20320:2020 for the medium sized surrogate fall within the load range tested here, and results are extracted and presented for the conditions specified in the standard.…”

“…Recent work has reviewed the biofidelity (modelling the response of a human) of human body surrogates used for testing personal protective equipment, such as by incorporating compliant material to represent soft tissue [10][11][12][13]. The authors previous study [14] presented a 'compliant wrist surrogate', based on the geometry specified in ISO 20320:2020, consisting of a stiff core (nylon) and a 3 mm thick silicone outer layer to represent skin. The silicone outer layer increased the measured stiffness of wrist protectors in the bending stiffness test of Adams et al [7,8], relative to a comparable stiff surrogate (without silicone).…”

“…Repeatability of procedures is determined when tests are separated by time intervals, and a test-retest study has been conducted to assess the suitability of a device for measuring wrist joint angles in boxing [15] using the surrogate from EN 14120:2003. The previous work on bending stiffness testing of snowboarding wrist protectors [6][7][8]14] conducted the tests during one session and did not assess the intraoperator repeatability. Therefore, this study investigated the intra-operator repeatability of a bending stiffness test for snowboarding wrist protectors.…”

“…Therefore, this study investigated the intra-operator repeatability of a bending stiffness test for snowboarding wrist protectors. The purpose was to assess the repeatability of the bending stiffness test for both a stiff (ISO 20320:2020) and a compliant surrogate [14], with regard to test session and protector strapping condition. The hypothesise was, for a single operator, test session would not affect measured torque values of the bending stiffness test.…”