Evaluating the Effectiveness of Estimating Cumulative Loading Using Linear Integration Method

Abstract

Exposure to cumulative loading is a significant risk factor in the development of musculoskeletal disorders (MSD). To better understand the dose-response relationship, it is critically to quantify the cumulative exposure. Different integration methods have been used in estimating cumulative loading (force or torque). The general objective of the integration methods has been to sum the independently calculated task exposure. Each task was calculated by multiplying the magnitude of the task loading times the task duration which is the “area under the loading curve”. An assumption of this linear integration model is that long-time exposure to low forces will result in a similar level of damage as relatively short time exposure to high forces. To evaluate the effectiveness of this model, three loading groups of eccentric exercise with the same “area under the loading curve” were performed by thirty participants (ten in each group). Maximum isometric voluntary contractions (MIVC) and relaxed elbow angle (REA) were collected before, immediately after, and 2, 4, 8 days after the exercise. The REA and MIVC changes after the eccentric exercise were significantly impacted by the loading group. It suggests that estimating cumulative loading using linear integration method may underestimate the impact of high force loading in terms of cumulative muscle damage.