Effect of a Simultaneous Mental Arithmetic Task to a MMH Lifting Task on Muscle Activity in the Trunk and Shoulders

Introduction: This study investigated the effects of concurrent mental demands on material handling tasks. Methods: Eleven subjects performed a material handling task with and without cognitive loads while lifting a 5 kg box to three different destination heights. The cognitive load was created by having participants perform a concurrent math task while lifting the box. The study measured the muscle activity in trunk and shoulder muscles. Results: The study found that, in select muscles, the cognitive load conditions led to longer lift times and increased cumulative muscle activity, but lower peak muscle activity. Conclusion: These findings suggest that lifting tasks with a concurrent cognitive load could lead to greater cumulative muscle activity, increasing the risk of muscular fatigue during manual material handling tasks.