The aim of this thesis was to examine the mechanical work performed by different joints in the human body and correlate it with the metabolic energy. The motivation behind this objective was to understand human performance at sea during long maritime activities. Long-duration ship activities aggravate the chances of various motion disorders including motion-induced fatigue, motion sickness, sopite syndrome, and nausea. These disorders have been considered as major biodynamic barriers that reduce efficiency of crewmembers and ship operators during navigational tasks. Therefore the methodology of this research included implementing a mathematical model of the human body to calculate the mechanical work expended while maintaining balance. This will aid in understanding the performance of humans during such tasks and also help in formulating strategies to improve the efficiency of human performance. Experimental data from human subjects were collected on a ship motion simulator under twelve different deck motion conditions associated with four sea states and three ship headings relative to the principal wave direction for a typical frigate. Data were collected using a motion capture system, foot pressure sensors, a load cell, and a metabolic analyzer. The mechanical work performed by the human body and different body joints were calculated through the developed ninety-six degree of freedom mathematical model. The variation of metabolic levels with sea severity was investigated and a mechanical work-metabolism correlation was performed. Direct comparison of mechanical work with metabolic energy was done. Also, the variation of ground reaction axial force and other biological factors were calculated. The results signified that metabolic levels increase as the sea severity increases. Also, the work-energy variables were highly correlated which indicated that muscle contraction and ATP utilization increase for postural maintenance activities. In addition, distribution of mechanical work across 14 body joints showed different activation patterns are follwed by lower extremity joints (i.e., ankle, knee, and hip) with changing ship motion. The results of this research provide significant information towards understanding of the impact of ship motion on human performance which will lead to improvements in operational planning and ultimately safety of shipboard personnel.
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