Biomechanical Evaluation of a Jackhammering Task with and Without List Assist

Abstract

The construction and utility industries have relatively high levels of hazardous tasks that impose high physical demands on a worker. For the past decade these industry sectors had one of highest incident rates for non-fatal injuries (BLS, 2013). The task of operating a jackhammer presents several risk factors that promote the high rates of injuries to this industry sector. Until the introduction of the lift assist, relatively few interventions were available to make the task of operating a jackhammer safer. However, no research has been conducted to support that this device is able to make jackhammering safer. The aim of this study was to evaluate and quantify the changes of operating a jackhammer with and without a lift assist. Eight experienced jackhammer operators participated in this study. All participants were asked to use a 90lb and 60lb jackhammer once with the lift assist attachment and once without the lift assist attachment while breaking a 3'x3' concrete section. Throughout the trials, grip pressure, bilateral muscle activity, vibration, and task time were recorded. For each variable a general linear model ANOVA was with 95% confidence was performed to determine statistically significance changes. The factors of lift assist, weight, and the interaction between the two were factors in the ANOVA. The factor of subject was blocked. Results showed that using the lift assist reduced the grip pressure and muscle activity for the lifting portion of the task. During operation, using the lift assist did not result in a change of vibration amplitude on the jackhammer or dose of the exposure to the operator or affect the grip pressure needed to operate the jackhammer. However, the task time was slightly increased. This is suspected to be due to the inexperience of the operators with using the lift assist. These results support that the lift assist reduces the lifting effort/demands required of the operator, while without altering other risk factors during the jackhammering task. Reduction in the jackhammer lifting effort while using a lift assist device may lead to a reduced risk of overexertion injuries, as well as allow more diverse population of the operators to perform the task.