The influence of foam surfaces on biomechanical variables contributing to postural control

The individual receptor systems of the somatosensory system include the muscle receptors, joint receptors and mechanoreceptors. This study was intended to investigate how standing on foam surfaces would change the multiple biomechanical variables associated with the functions of each of these individual receptor systems in the foot. Mechanical inputs to these receptors, including the changes in plantar pressures, ankle joint rotation and velocity, as well as postural responses from the gastrocnemius and tibialis anterior muscles, were measured during an abrupt toes-up movement of the supporting base. These measurements were compared for three different surface conditions (i.e. hard surface, 1″, and 2″ foams, respectively). A group of 15 healthy, young male subjects participated in the study. The results showed that standing on foam (or soft surface) would affect the inputs to both joint receptors and cutaneous mechanoreceptors in the foot, but not the muscle receptors in the early phase of the platform movement. Furthermore, the medium and long latency responses in the leg muscles appeared to be delayed significantly when standing on foam, while the short latency response in the gastrocnemius muscle was unchanged.