Injuries of the cervical spine occur in contact sports. Generally, muscle strengthening training of the neck is performed to prevent injuries of the cervical spine. Isometric resistance training with chin-in posture exercise is recommended for strengthening the neck. However, muscle strength and electromyography(EMG)date for chin-in posture have not been reported. The purpose of this study was to validate muscle strength and EMG testing during chin-in posture. Subjects were fifteen healthy men without pathological conditions in the neck. Muscle strength date and EMG measurements were taken for maximal voluntary isometric contraction(MVIC)flexion and extension actions during normal and chin-in posture. Subjects performed MVIC using a handheld dynamometer and surface EMG was recorded sternocleidomastoid, scalenus, upper trapezius, and splenius muscles. Results of chin-in posture showed a significant increase in muscle strength and EMG of all muscles. These results indicate the beneficial effect of chin-in posture which can increase muscle strength and prevent injuries of the neck.