Evaluation of Forearm Muscle Fatigue from Operating a Motorcycle Clutch

Motorcycle riding is a hobby commonly enjoyed by Americans with nearly 8.5 million registered motorcycles in the US [1]. Motorcycle manufacturers have enjoyed consistent increases in sales throughout the first decade of the 21st century [2], an indication that the sport is gaining avid new riders each year. An important consideration as sales increase is the demographics of the riders themselves. Consistent with the US population, the median age of motorcycle riders has significantly increased in recent years [2]. In fact, the percent of total riders over age 40 has increased from 21.3% in 1985 to 53.0% in 2003 [2]. Thus, a concern arises when hand controls, such as those employed to operate a motorcycle, repeatedly require excessively high force levels over long periods of time during a recreational ride. Exposure to such high repetition-high force tasks has been linked to muscle fatigue, loss of productivity and an increased incidence of musculoskeletal disorders [3]. Indeed, recent studies have demonstrated the accumulation of muscle fatigue in the right forearm muscles attributed to motorcycle brake use [4]. Therefore, the need for a precise evaluation of motorcycle hand controls is needed as they relate to fatigue or injury to maintain safety on the roadway. Specifically, if controls such as the motorcycle clutch were redesigned to require lower force levels at adequate grip spans, it could improve the safety by minimizing fatigue.