Editorial
Skin Hardness of the Foot Sole and Weight Bearing Reduce the Perceptual Representation of the Sole Mechanosensitivity Altering Posture Control
Yves Jammes* and Jean Paul Weber
Department of Physiology, Hospital European Marseille, France
*Corresponding author: Yves Jammes, Department of Physiology, Hospital European Marseille, France
Published: 18 Dec 2017
Cite this article as: Jammes Y, Weber JP. Skin Hardness
of the Foot Sole and Weight Bearing
Reduce the Perceptual Representation
of the Sole Mechanosensitivity Altering
Posture Control. Clin Surg. 2017; 2:
1819.
Editorial
The cutaneous mechanoreceptors of the foot sole detect the changes in the application of
mechanical loads on the plantar surface during gait and standing, and contribute to controlling the
standing balance and postural reflexes in healthy subjects [1]. Electrophysiological human studies
reported the presence of both slow (Merkel and Ruffini corpuscles) and fast (Meissner and Pacinian
corpuscles) adapting mechanoreceptors [2]. The Merkel and Meissner corpuscles are located at
the dermal-epidermal junction, whereas the Ruffini and Pacinian corpuscles are only present in
the deeper dermal layers. The vibration frequency can selectively activate either the Merkel disks
and Ruffini corpuscles (25 Hz) or the Meissner and Pacinian corpuscles (150 Hz). These cutaneous
afferents project on the somatosensory cortex leading to a perceptual representation. The perceptual
thresholds for the foot sole mechanosensitivity were expected to correlate with the hardness of the
skin and also to the counterforce exerted on the foot sole when bearing heavy loads.
In a recent study [3], we examined the vibration sensitivity of three plantar location of different
hardness, the fifth metatarsal head having often the highest one. The mean Shore values were for the
1st -2nd, and 5th metatarsal heads, and the heel were 30 +/- 4, 60 +/- 3 and 50 +/- 2. The Stevens power
function (Ψ=k* Φn) allowed to obtain regression equations between the estimate (Ψ) of the vibratory
stimuli and their physical magnitude (Φ).We found that the vibration threshold was significantly
higher at the level of the 5th metatarsal head and the heel for both the 25 Hz and 150 Hz frequencies.
After skin abrasion, the vibration sensitivity was significantly higher at both vibration frequencies.
Thus, skin hardness affects the foot sole mechanosensitivity and could alter the control of posture
during standing and walking.
Heavy backpacks are used by firefighters and soldiers. Majumdar et al. [4] showed that soldier
load carriage affects the kinematics of gait. Also carrying a military backpack increased the postural
sway during standing [5]. Unpublished observations by our team revealed that weight bearing when
standing upright or walking reduced the vibration sensitivity of the heel and metatarsal heads and
increased the surface and lateral deviation of the center of pressure measured by posturography.
Thus, skin hardness and bearing of heavy loads affect the foot sole’s sensitivity and posture control.
This strongly suggests first, that foot care by podiatrist is relevant to improve posture control and
second, that the efficient completion of tasks by soldiers which is of operational relevance could be
affected by bearing heavy loads.
References
- Maurer C, Mergner T, Bolha B, Hlavacka F. Human balance control during cutaneous stimulation of the plantar soles. Neurosci Lett. 2001;302(1):45-8.
- Kennedy PM, Inglis JT. Distribution and behaviour of glabrous cutaneous receptors in the human foot sole. J Physiol. 2002;538:995-1002.
- Jammes Y, Viala M, Dutto W, Weber JP, Guieu R. Skin hardness and epidermal thickness affect the vibration sensitivity of the foot sole. Clin Res Foot Ankle. 2017;5:245.
- Majumdar D, Pal MS, Majumdar D. Effects of military load carrying on kinematics of gait. Ergonomics. 2010;53:782-91.
- Heller MF, Challis JH, Sharkey NA. Changes in postural sway as a consequence of wearing a military backpack. Gait Posture. 2009;30(1):115-7