Transmission of fore-and-aft floor vibration to the spine and head of standing people

In this work, sixteen standing male participants were subjected to fore-and-aft sinusoidal vibration with peak magnitude and frequency in the range 0.44–4.431 ms-2 and 2–6 Hz, respectively. The fore-and-aft (Tx,x), lateral (Tx,y) and vertical (Tx,z) transmissibilities to the first dorsal vertebra (T1), eighth dorsal vertebra (T8), twelfth dorsal vertebra (T12), fourth lumbar vertebra (L4) and the head were measured. Large inter-participant variability was observed in the transmissibilities at all locations. Nevertheless, peaks in the range 3–4.5 Hz were identified at all locations implying a whole-body resonance in this frequency range. The response was found dominant in the mid-sagittal plane as Tx,y showed low values. Below 4.5 Hz, Tx,x increased with moving from caudal to cranial locations of the upper body. However, at higher frequencies, the opposite trend was observed. The results can be used for developing models that may help understand how vibration affects health and comfort.