Understanding the effect of finger–ball friction on the handling performance of rugby balls

Finger friction with leather and seam of new and used softballs with and without rosin powder

The purpose of this study was to investigate the friction of finger against polyurethane-coated leather and seam surfaces of new and used softballs. The effects of seam alignment (across and along the seam) and chalk/rosin powder application were also investigated. The coefficient of static friction (COF) was evaluated on 14 college female softball players who rubbed the pad of their index finger on a test surface fixed on a biaxial force plate. The mean COF of the new leather was 1.04, and those of the seam were 1.16 for the across condition, and 1.07 for the along condition. The leather-seam difference in COF was significant. The used ball's leather and seam had lower COF than those of the new ball. The seam alignment difference did not reach the level of significance. For both new and used balls, the application of chalk/rosin powder to the finger reduced COF, and the reduction was greater on the leather than on the seam. It was concluded that the outer cover of softballs, and especially the seam portions, is equipped with reasonably high friction under natural finger condition. The friction is reduced in used balls and with the use of chalk/rosin powder.

Effects of Rosin Powder Application on the Frictional Behavior Between a Finger Pad and Baseball

Rosin powder, which is composed of magnesium carbonate powder and pine resin, is often used as a grip-enhancing agent in baseball pitching. However, the effect of rosin powder on friction at the baseball-human finger interface remains unclear. This study aimed to investigate the effect of rosin powder on the friction coefficient between a baseball and a finger using sliding friction tests. Ten young adult males participated in this study who were asked to slide the index finger of their dominant hand over the leather skin of a baseball adhered to the force sensor, which was not a real baseball pitching situation. Our findings suggest that rosin powder application stabilizes friction under both dry and wet conditions; that is there was less dependence of the friction coefficient on the normal force and less variation in the friction coefficient among individuals. For most participants, the friction coefficient was not necessarily increased by the presence of rosin powder at the finger pad-leather sheet interface under dry conditions. However, under wet conditions, rosin powder application increased the friction coefficient compared with the non-powdered condition in the large normal force condition, indicating the efficacy of rosin powder as a grip-enhancing agent.

Engineered Skin Tissue Equivalents for Product Evaluation and Therapeutic Applications

The current status of skin tissue equivalents that have emerged as relevant tools in commercial and therapeutic product development applications is reviewed. Due to the rise of animal welfare concerns, numerous companies have designed skin model alternatives to assess the efficacy of pharmaceutical, skincare, and cosmetic products in an in vitro setting, decreasing the dependency on such methods. Skin models have also made an impact in determining the root causes of skin diseases. When designing a skin model, there are various chemical and physical considerations that need to be considered to produce a biomimetic design. This includes designing a structure that mimics the structural characteristics and mechanical strength needed for tribological property measurement and toxicological testing. Recently, various commercial products have made significant progress towards achieving a native skin alternative. Further research involve the development of a functional bilayered model that mimics the constituent properties of the native epidermis and dermis. In this article, the skin models are divided into three categories: in vitro epidermal skin equivalents, in vitro full-thickness skin equivalents, and clinical skin equivalents. A description of skin model characteristics, testing methods, applications, and potential improvements is presented.