The Impact of Aging and Hand Dominance on the Passive Wrist Stiffness of Squash Players: Pilot Study (Preprint)

Abstract

Background: Passive joint stiffness can influence risk of injury and the ability to participate in sports and activities of daily living. Yet little is known about how passive joint stiffness changes over time with intensive repetitive exercise, particularly when performing unilateral activities using the dominant upper limb.Objective: We investigated the difference in passive wrist quasi-stiffness between the dominant and non-dominant upper limb of competitive squash players, compared these results to a previous study on young unskilled subjects, and explored the impact of aging on wrist stiffness.Methods: Seven healthy, right-side dominant male competitive squash players were recruited and examined using the Massachusetts Institute of Technology Wrist-Robot. Subjects were between 24-72 years old (mean=43.7, SD=16.57) and had a mean of 20.6 years of squash play experience (range=10-53 years, SD=13.85). Torque and displacement data was processed and applied to two different estimation methods, the fitting ellipse and the multiple regression method, to obtain wrist stiffness magnitude and orientation.Results: Young squash players (mean 30.75, SD 8.06 years) demonstrated a stiffer dominant wrist, with an average ratio of 1.51, compared to an average ratio of 1.18 in young unskilled subjects. The older squash players (mean 64.67, SD 6.35 years) revealed an average ratio of 0.86 (i.e., the non-dominant was stiffer than the dominant wrist). There was a statistically significant difference between the magnitude of passive quasi-stiffness between the dominant and nondominant wrist of the young and older squash player groups (P < .004). Conclusions: These study results are novel and contribute to our understanding of the likely long-term effect of highly intensive, unilateral sports on wrist quasi-stiffness and the aging process; repetitive exercise may increase quasi-stiffness in the young while preserving flexibility of the aging wrist.