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It not even the end of Dec and the Feb issue of Clinical Biomechanics has appeared with this nice finding (...which we sort of new anyway, but nice to have it confirmed):
Background
The plantar fascia, which is one of the major arch-supporting structures of the human foot, sustains high tensions during weight-bearing. A positive correlation between Achilles tendon loading and plantar fascia tension has been reported. Excessive stretching and tightness of the Achilles tendon are thought to be the risk factors of plantar fasciitis but their biomechanical effects on the plantar fascia have not been fully addressed.
Methods
A three-dimensional finite element model of the human foot and ankle, incorporating geometrical and material nonlinearity, was employed to investigate the loading response of the plantar fascia in the standing foot with different magnitudes of Achilles tendon loading.
Findings
With the total ground reaction forces of one foot maintained at 350 N to represent half body weight, an increase in Achilles tendon load from (0–700 N) resulted in a general increase in total force and peak plantar pressure at the forefoot of up to about 250%. There was a lateral and anterior shift of the centre of pressure and a reduction in the arch height with an increasing Achilles tendon load as a result of the plantar flexion moment on the calcaneus. From the finite element predictions of simulated balanced standing, Achilles tendon forces of 75% of the total weight on the foot (350 N) were found to provide the closest match of the measured centre of pressure of the subject during balanced standing. Both the weight on the foot and Achilles tendon loading resulted in an increase in tension of the plantar fascia with the latter showing a two-times larger straining effect.
Interpretation
Increasing tension on the Achilles tendon is coupled with an increasing strain on the plantar fascia. Overstretching of the Achilles tendon resulting from intense muscle contraction and passive stretching of tight Achilles tendon are plausible mechanical factors for overstraining of the plantar fascia
It not even the end of Dec and the Feb issue of Clinical Biomechanics has appeared with this nice finding (...which we sort of new anyway, but nice to have it confirmed):
The research finding that the magnitude of tensile force within the plantar fascia is directly related to magnitude of tensile force within the Achilles tendon during weightbearing is a main part of a lecture that I have given numerous times, "The 10 Functions of the Plantar Fascia". This recent paper confirms the findings of two previous studies that also showed that plantar fascial tension is directly related to Achilles tendon tension (Carlson RE, Fleming LL, Hutton WC: The biomechanical relationship between the tendoachilles, plantar fascia and metatarsophalangeal joint dorsiflexion angle. Foot Ankle Intl., 21:18-25, 2000; Erdimir A, Hamel AJ, Fauth AR, Piazza SJ, Sharkey NA: Dynamic loading of the plantar aponeurosis in walking. JBJS, 86A:546-552, 2004).
I had explained this mechanical relationship between the Achilles tendon and plantar fascia by developing a mechanical model for the foot and leg in a series of Precision Intricast Newsletters in 2002 (Kirby KA: Foot and Lower Extremity Biomechanics II: Precision Intricast Newsletters, 1997-2002. Precision Intricast, Inc., Payson, AZ, 2002, pp. 139-152).
Understanding this relationship between the Achilles tendon and plantar fascia is critical to understanding the mechanical nature of many of the pathologies that are present within feet and lower extremities of our patients.
__________________
Sincerely,
Kevin
**************************************************
Kevin A. Kirby, DPM
Adjunct Associate Professor
Department of Applied Biomechanics
California School of Podiatric Medicine at Samuel Merritt College
A portion of the Clinical Biomechanics article quoted at the beginning of this thread, states:-
Interpretation
Increasing tension on the Achilles tendon is coupled with an increasing strain on the plantar fascia. Overstretching of the Achilles tendon resulting from intense muscle contraction and passive stretching of tight Achilles tendon are plausible mechanical factors for overstraining of the plantar fascia
Does the "passive stretching of the tight achilles tendon" the author refers to as a plausible mechanical factor for overstraining the plantar fascia include the general gastroc and soleus stretching we often prescribe as clinicians as part of the treatment for plantar fasciitis? If a tight or shortened achilles causes excessive load on the p.f., but passive stretching of the achilles also causes overstrain of the p.f. how do you address the issue of the problematic achilles and its effect on the p.f.?
Adam
Last edited by Berms : 5th January 2006 at 10:36 PM.
Achilles loads and load in plantar fascia
Linear Mode
