Activity of Upper Body Muscles during Bowing and Prostration Tasks in Healthy Subjects M.K.M. Safee, W.A.B. Wan Abas, N.A. Abu Osman, and F. Ibrahim INTRODUCTION The electrical activity in the human muscles can be measured using electromyography (EMG). This allows for the measurement of the change in the membrane potential as the action potentials are transmitted along the fiber. The study of the muscles from this perspective can be valuable in providing information concerning the control of voluntary and reflexive movement. The study of muscle activity during a particular task can yield insight into which muscles are active and when the muscles initiate and cease their activities. Surface electrodes are placed on the skin over a muscle and thus are mainly used for superficial muscle [1]. With the technique of electromyography, or recording the electrical impulses generated by muscular contractions, it is possible to determine very precisely which muscle, superficial and deep, contract during a given movement. Electromyography can also provide information on the sequence in which each of several participating muscles contracts and can help in estimating the strength of contraction of each muscle [2]. There are many research findings that show the benefits of muscle contraction and muscle strength. For example, to protect and stabilize the head and neck in high Gz environments, higher neck muscle strength is needed; less muscle strength in fighter pilot may cause pain and perhaps reduced mission effectiveness [3]. Besides, more research that relate