Decreased plantar sensation is associated with a number of changes in gait characteristics which have been shown to increase the likelihood of tripping and falls. Older adults often experience age-related sensory loss in the plantar surface of their feet, which can predispose them to falls leading to injury or psychological declines. Previous research has shown how gait can be altered by decreasing plantar sensitivity, however, to date the relationship between plantar cutaneous mechanoreceptors and muscles of the leg has not been quantified. Observing this relationship will provide insight into how the body adapts to changes in walking terrain and other instabilities during gait in order to prevent tripping or falling.

Twenty-one (10 male, 11 female) healthy young adults were recruited from the university population (mean age= 22, SD=3.37). Each participant completed 10 normal walking and 20 randomized uneven terrain walking trials on a 10m walkway. Participants were equipped with 8 electromyography (EMG) electrodes on the left and right legs, and wore standardized shoes containing size-matched pressure sensors. Uneven terrain conditions were induced using wooden wedges placed in the walking path. Uneven terrain conditions were in the 1) anterior, 2) posterior, 3) lateral and 4) medial directions in order to assess a variety of plantar pressure situations.

A significant negative correlation was found between loading rates under the contralateral great toe and the magnitude of tibialis anterior during normal walking in both short and long latency periods, as well as in conditions 2 (posterior), 3 (lateral) and 4 (medial). A significant positive correlation was found between the loading rates under the ipsilateral heel and the magnitude of the tibialis anterior activity in normal walking, condition 2 (posterior) and condition 3 (lateral) in the short and long latency response periods. Conditions 3 (lateral) and 4 (medial) showed altered muscle activity in the tibialis anterior in order to respond faster to the medial-lateral perturbations and to increase the surface area in contact with the walking surface for improved cutaneous input Condition 1 (anterior) showed a significant positive correlation between tibialis anterior magnitude and contralateral great toe loading as the COM was slowed due to the upward slope and a stronger push off was required. Alternatively, condition 2 (posterior) showed increased tibialis anterior activity, thought to be required to maintain a slowed dorsiflexion on a downward slope to prevent tripping and maintain a comfortable COM speed.

This study provides evidence of a relationship between plantar cutaneous mechanoreceptors and the magnitude of muscle activity in the tibialis anterior during gait This quantifiable relationship can be used in future research to determine gait abnormalities, as well as in the development of walking aids to better support the body and provide the appropriate input for stability. These results may also be directly transferable to the further development of footwear and insoles to improve plantar sensation in the elderly population and those with plantar sensory loss.