Evaluating the Ergonomic Benefit of a Wrist Brace on Wrist Posture, Muscle Activity, Rotational Stiffness, and Peak Shovel-Ground Impact Force During a Simulated Tree-Planting Task

Abstract

Background Tree planters are at a high risk for wrist injury due to awkward postures and high wrist loads experienced during each planting cycle, specifically at shovel-ground impact. Wrist joint stiffness provides a measure that integrates postural and loading information. Objective The purpose of this study was to evaluate wrist joint stiffness requirements at the instant of shovel-ground impact during tree planting and determine if a wrist brace could alter muscular contributions to wrist joint stiffness. Method Planters simulated tree planting with and without wearing a brace on their planting arm. Surface electromyography (sEMG) from six forearm muscles and wrist kinematics were collected and used to calculate muscular contributions to joint rotational stiffness about the wrist. Results Wrist joint stiffness increased with brace use, an unanticipated and negative consequence of wearing a brace. As a potential benefit, planters achieved a more neutrally oriented wrist angle about the flexion/extension axis, although a less neutral wrist angle about the ulnar/radial axis was observed. Muscle activity did not change between conditions. Conclusion The joint stiffness analysis, combining kinematic and sEMG information in a biologically relevant manner, revealed clear limitations with the interface between the brace grip and shovel handle that jeopardized the prophylactic benefits of the current brace design. This limitation was not as evident when considering kinematics and sEMG data independently. Application A neuromechanical model (joint rotational stiffness) enhanced our ability to evaluate the brace design relative to kinematic and sEMG parameter-based metrics alone.

Physiological and kinematic effects of a parallel rehabilitation robot (PWRR) on wrist movements

“…In addition, nearly half of wrist movement disorders without damage to muscles and the nervous system are caused by longterm immobilization [11] in the clinic, such as fractures of the upper limb [12,13] or fingers [13]. Wrist sprains and contusions are common injuries that cause damage to the corresponding wrist ligament, fascia and other tissues [14][15][16][17]. Therefore, adequate wrist function is critical for orientating and stabilizing the hand [18].…”

“…There exists a thorny problem for almost all exoskeletons mentioned above: the patients' hands must be maneuvered through a component with a closed circular structure, especially the mentioned devices integrated with the forearm. In the case of patients with hypertonia and ankylosis [4][5][6][7][16][17][18][19][20][21], this process is particularly slow and tedious. Additionally, the device should be easy to put on and take off.…”