Acute effects of long‐distance running on mechanical and morphological properties of the human plantar fascia

Abstract

Long‐distance running (LDR) can induce transient lowering of the foot arch, which may be associated with mechanical fatigue of the plantar fascia (PF). However, this has not been experimentally tested in vivo. The purpose of this study was to test our hypothesis that LDR induces transient and site‐specific changes in PF stiffness and morphology and that those changes are related to the lowering of the foot arch. Ten male recreational long‐distance runners and 10 untrained men were requested to run overground for 10 km. Before and after running, shear wave velocity (SWV: an index of soft tissue stiffness) and thickness of PF at three different sites from its proximal to distal end were measured using supersonic shear imaging and B‐mode ultrasonography. Foot dimensions including the navicular height were measured using a three‐dimensional foot scanner. SWV at the proximal site of PF and navicular height was significantly decreased in both groups after running, with a higher degree in untrained men (−21.9% and −14.1%, respectively) than in runners (−4.0% and −6.3%, respectively). The relative change (%Δ) in SWV was positively correlated with %Δnavicular height in both groups (r = .69 and r = .65, respectively). Multiple regression analysis revealed that %ΔSWV at the proximal site solely explained 72.7% of the total variance in %Δnavicular height. It is concluded that LDR induces transient and site‐specific decreases in PF stiffness. These results suggest that the majority of running‐induced lowering of the foot arch is attributable to the reduction of PF stiffness at the proximal site.

Track distance runners exhibit bilateral differences in the plantar fascia stiffness

“…No bilateral differences in PF thickness of runners and untrained individuals are consistent with previous findings that PF thickness was not different between recreational runners and untrained individuals 15 , and that PF thickness was not influenced by physical activity 29 . These results, together with our findings, discard the possibility of PF adaptability in terms of its thickness for reducing mechanical stress induced by distance running.…”

“…The greater load on the left foot during curve running 19 , 20 can induce an increase of mechanical stress on PF. We previously revealed that running causes a decrease in PF SWV at its proximal site 15 , and this coincides with the simulation of stress distribution along PF 11 – 13 . The bilateral differences in PF stiffness at the proximal site in runners may reflect the adaptation to such stress accumulation in this region of the left foot during track running, regardless of the lateral dominance or foot strike patterns.…”

“…The most striking finding of the present study was that track distance runners showed stiffer PF at the proximal site in their left than the right feet, unlike the untrained participants. A number of previous studies addressing running mechanics 22 , 23 and mechanical and morphological properties of the musculotendinous and fascial tissues 15 , 24 in runners have focused on unilateral leg by assuming bilateral symmetry. Our findings however suggest that asymmetry in runners is the major issue that needs to be carefully considered.…”

“…PF has higher SWV (i.e., stiffer) at the proximal site than middle and distal sites 14 , 16 . Additionally, long-distance running induced a transient decrease of SWV at the proximal site of PF while long-distance runners showing smaller changes in SWV than untrained individuals 15 , suggesting that runners had built up a more resilient PF. These findings are evidence of PF adaptability to site-specific and chronic mechanical stress, which can be reflected in its stiffness and morphology.…”

Greater Postural Sway and Tremor during Balance Tasks in Patients with Plantar Fasciitis Compared to Age-Matched Controls

“…Other studies on runners show that an increase in thickness and water content of the plantar fascia was also seen, and that it also caused a reduction in elasticity [19]. Studies on PF also show an increase in thickness of the plantar fascia, which then caused a reduction in plantar fascia elasticity [20][21][22].…”