This study aimed to investigate forearm fatigue during grinding and methods to decrease this with handle design. The present master thesis is divided into three articles. The literature regarding this topic is limited and in order to present aim and goals clear it was it necessary to divide it into three articles.
Each article has its own aim, yet all three build upon each other. Study one purpose: Understanding the influence of grinding direction on forearm fatigue. Study two purpose: Tests different handle diameters grinding backwards. Study 3 purpose: A technical note explaining how to develop custom-fitted handles for individuals.
Forearm fatigue is measured using time to fatigue, maximum voluntary contraction and surface electromyography for all three studies.
Study one found indications of forearm fatigue being more severe during backwards grinding than forward grinding. These indications are based on statistically significant difference in time to fatigue and MVC. In addition, sEMG shows the same signs but nothing of statistical significance. Preceding with newfound knowledge from study one ‘the optimal handle diameter’ is established in study two. The optimal handle diameter (32 mm) is based solely on backwards grinding. The 32 mm handle results in less forearm fatigue in relation to time to fatigue and MVC. Finally, study three (technical note) is a description of method to custom-fit individualized handles using 3D scanning and printing. Study one and two as well as related grip strength studies work as the foundation for the developed method in the technical note.