Foot sole and ankle muscle inputs contribute jointly to human erect posture regulation

Abstract

International audience1. In order to assess the relative contribution and the interactions of the plantar cutaneous and muscle proprioceptive feedback in controlling human erect posture, single or combined vibratory stimuli were applied to the forefoot areas and to the tendons of the tibialis anterior muscles of nine standing subjects using various vibration frequency patterns (ranging from 20 to 80 Hz). 2. The variations in the centre of foot pressure, ankle angle and the EMG activities of the soleus and tibialis anterior muscles of each subject were recorded and analysed. 3. Separate stimulation of the plantar forefoot zones or the tibialis anterior muscles always resulted in whole-body tilts oppositely directed backwards and forwards, respectively, the amplitude of which was proportional to the vibration frequency. EMG activity of ankle muscles also varied according to the direction of the postural responses. However, the same vibration frequency did not elicit equivalent postural responses: in the low frequency range, tactile stimulation induced stronger postural effects than proprioceptive stimulation, and the converse was the case for the higher frequency range. 4. Under sensory conflict conditions, i.e. foot sole-flexor ankle muscle co-stimulation, the direction of the body tilts also varied according to the difference and the absolute levels of the vibration frequencies. In all cases, the resulting postural shifts always corresponded to the theoretical sum of the isolated effects observed upon vibrating each of these two sensory channels. 5. We proposed that tactile and proprioceptive information from the foot soles and flexor ankle muscles might be co-processed following a vector addition mode to subserve the maintenance of erect stance in a complimentary way

Changes in multi-segmented body movements and EMG activity while standing on firm and foam support surfaces

“…Another finding was that the complaint foam support surface increased the movements of the lower body segments, e.g., the knee and hip movements proportionally more than shoulder and head movements, see table 2. These observations are in line with several previous reports showing that changed sensory information from vision and proprioception can have a major effect on postural control and the multi-segmented body movements (Kavounoudias et al 1999;Perry et al 2000;Kavounoudias et al 2001;Blackburn et al 2003;Vuillerme et al 2005).…”

Reducing weight increases postural stability in obese and morbid obese men

“…For example, Kavounoudias et al 31 reported that vibration (high frequency and low amplitude) of skin mechanoreceptors of anterior and/or posterior areas of one or both soles yield spatially oriented whole-body tilts for which the direction depends on the foot areas stimulated. As suggested by these authors, this is a compelling evidence that cutaneous afferent messages from the main supporting zones of the feet have spatial relevance to inform the central nervous system (CNS) about the body position with respect to the vertical reference.…”

Modulation of ankle muscle postural reflexes in stroke: influence of weight-bearing load

“…Subsequently, Dietz et al (1992) and Duysens et al (2000) have argued that GTOs signal load in humans as well. In addition, cutaneous afferents from plantar mechanoreceptors in the foot have been shown to be important for postural control (Kavounoudias et al 2001) and compensatory postural reflexes elicited in response to a forward fall while standing (Do et al, 1990).…”

“…It is believed that Ib afferents from golgi tendon organs (GTOs) provide load information to the spinal cord (Dietz et al, 1992;Duysens et al, 2000). In addition to Ib afferents from GTOs, cutaneous mechanoreceptors in the sole of the foot are in an optimal location to sense limb load and have been recently shown to be important in standing balance (Kavounoudias et al, 2001). …”