Abstract
The aim of this study is to elucidate passengers' postural maintenance methods and exercise loads. In a small marine craft, participants were either sitting or standing. In the laboratory, participants were sitting, standing, or performing step tests. Ship motion and participants' postural motions were quantified in the root mean square value of linear and angular acceleration which were measured at the head and waist of each participant, and on the floor of the craft. Participants' muscular activities were quantified in integrated electromyogram (EMG) of soleus, vastus lateralis, lumbar paraspinals and cervical paraspinals muscles. Participants' exercise loads were calculated by dividing the energy expenditure measured in each condition by the value measured in the sitting condition. Participants' postural motions were rotational motions, and were large when their integrated EMG was large. Participants' exercise loads were similar to that during stepping tests. Thus, rotational postural motions were generated at the head and waist of passengers because of muscular activities to maintain standing posture against floor heave motion, and their exercise loads were low intensity.
