Head movement induced by angular oscillation of the body in the pitch and roll axes.

The transmission of angular acceleration to the head of the human subject has been investigated during sinusoidal angular oscillation of the body in either pitch or roll about an axis through the upper lumbar vertebrae. The results indicated that angular acceleration of the skull was induced in all three axes of the head by both pitch and by roll motion. At frequencies below 1-2 Hz the head moved with the body, but in the frequency range 2-8 Hz the amplitude of head acceleration was augmented indicating that oscillation about a centre of rotation low in the body may induce large angular movements in this frequency range because of the linear component of acceleration delivered at the cervical vertebrae. At higher frequencies, the acceleration at the head was attenuated with an associated increase in phase lag, probably due to the absorption of input acceleration by the upper torso.