One- handed Carrying on Flat and Inclined Surfaces

Abstract

Many companies rely on manual material handling (MMH) to move raw materials or products between automated processes despite the proliferation of automation. Lifting, lowering, and carrying can lead to overexertion injuries and illnesses. One-handed MMH tasks are particularly challenging and can increase the risk for musculoskeletal disorders (MSDs) that contribute to lost work time and productivity reductions. One-handed carrying is considered one of the most fatiguing and physically demanding load-carrying methods. Performing one-handed carrying tasks on inclined surfaces has not been comprehensively studied. In MMH jobs, employees must be able to perform tasks without excessive stress relative to their capability. Assessment of these jobs should consider the environmental variables that may contribute to workers' physical and mental demands. Obese individuals are more susceptible to work-related MSDs caused by load carrying than healthy individuals. Cardiorespiratory fitness measures the body's maximal ability to transport and use oxygen to perform physical work. Physiological measurements provide an objective scale to compare physical tasks concerning stress, considering individual capabilities such as body fat percentage and fitness levels. This dissertation examines one-handed carrying using psychophysical and physiological assessment approaches. The first study investigates the effect of one-handed carrying on the endurance time and physiological and psychophysical responses of participants with different body fat percentages and fitness levels. The second study compares the effect of inclined surfaces on the physiological and psychophysical responses while performing one-handed carrying tasks. Finally, the last study investigates the effects of inclined surfaces and external loads on recovery time and rest allowances. This dissertation makes a valuable contribution to the existing body of literature concerning the influence of load on endurance time during one-handed carrying. In particular, the findings reveal important discrepancies between recorded and calculated recovery time, suggesting that a new model is needed to factor in the effects of incline and loading and participants' physical characteristics for one-handed carrying tasks. These findings emphasize the impact of load on the endurance capabilities of workers and the significance of workplace safety and productivity. The dissertation also introduces an innovative methodology by utilizing a graded exercise test to evaluate the effects of one-handed carrying on endurance and recovery time during dynamic movements. This novel approach provides valuable insights that can inform future assessments of MMH.