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Greetings.

A search for plantar fasciitis therapy reveals ubiquitous advice on stretching the plantar fascia (PF) specifically and more generally the gastroc group of muscles. Yet I cannot find the rationale for doing so, what are we expecting will happen by stretching (other than the much quoted reduction of pain and increase in function)? I see one reference that a max of 14.91% elongation by application of tension was achieved in cadaver studies. And so....?

The article goes on to conclude:
"CONCLUSION: This study provides a mechanical explanation for enhanced outcomes in recent clinical trials using plantar fascia tissue-specific stretching exercises and lends support to the use of ankle and MTP joint dorsiflexion when employing stretching protocols for nonoperative treatment in patients with chronic proximal plantar fasciitis."
(The influence of foot position on stretching of the plantar fascia. Flanigan RM, Nawoczenski DA, Chen L, Wu H, Digiovanni BF. Foot Ankle Int. 2007 ul;28(7):815-22.)


Another study (Foot & Ankle International/Vol. 24, No. 3/March 2003; Amit Gefen) describes an in vivo attempt to measure PF elongation, again with around 11% elongation of the PF (max).
Table 1:
Body characteristics of subjects, and the mean ± SD of
lengths, strains and stiffness values for their plantar fascia.
Subject I Subject II
Age [Years] 27 35
Weight [Kg] 58 60
Fascia’s Length at Arch-Contact [mm] 112 ±1.5 115 ±1.5
Fascia’s Length at Toe-Off [mm] 125 ±2.0 128 ±1.5
Maximal Deformation [mm] 13 ±2.0 13 ±1.5
Maximal Strain [%] 11.6 ±1.8 11.3 ±1.3
Average Stiffness of Fascia [N/mm] 112 ±7 225 ±9
(Underlined is subject two data, table format did not work).
It was demonstrated that the fascia elongates more rapidly during weight acceptance and midstance of the contact phase of barefoot walking. A slower elongation during push-off and toe-off follows the initially rapid deformation..... During the contact phase of walking, both the collagen and elastic fibers change from a wavy to a straight configuration as stress is applied. Having a lower modulus of elasticity compared to collagen, the elastic fibers contribute their
structural support in early extension of the fascia (around midstance), while the stretching of collagen produces restraining effects on the elongation occurring at the late extension phase (toward push-off and toe-off).

So, given that plantar fasciosis/opathy is recognized as a traction stress injury, what is the function of applying further stress through traction? Certainly studies (good and bad) support changes in the VAS score for increased comfort but why/how?

Brendan