Introduction Walking on vibrating floor causes a complex exposure pattern and the superimposition of walk and vibration may induce early muscular fatigue.¹ The problem is relevant is many field, as sea platform or railway transports. The present study studies the leg muscular activation and stride phases during walking under vibration to derive a muscle model in these circumstances.

Methods Subjects walked on a treadmill positioned on a 6-DOF vibrating table. Vibration was imposed at four frequencies (4, 8, 12, 16 Hz) along vertical and transversal direction. The walking speed was set at 1.25 m/s. Surface electromyography (sEMG) of four muscles was recorded. Stride phases were recorded using accelerometers and stride length was calculated. Acceleration signals were acquired in several body districts (foot, knee and hip). All measurements were related to the walking condition without the vibration.

Result Preliminary results showed that vibration does not affect stride length and step phases. The muscular activation patterns exhibit frequency related modification, in terms of sEMG bursts amplitude and timing. There is a linear correlation between 8 Hz frequency and muscular activation.

Discussion Transmitted vibration triggers a tonic vibration reflex (TVR) that is related to mechanical frequencies.² TVR is also related to the motor task because of the mechanical coupling between vibrator and biological apparatus.³ These facts could explain the modifications in leg muscle activation revealed with sEMG.

References

1. . Fattorini L, Tirabasso A, Lunghi A, Di Giovanni R, Sacco F, Marchetti E. Muscular forearm activation in hand-grip tasks with superimposition of mechanical vibrations. J Electromyogr Kinesiol2016;26:143–148.

2. . Eklund G, Hagbarth KE. Normal variability of tonic vibration reflexes in man. Exp Neurol1966;16:80–92.

3. . Fattorini L, Tirabasso A, Lunghi A, Di Giovanni R, Sacco F, Marchetti E. Muscular synchronisation and hand-arm fatigue. Int J Ind Ergon2017.