Acute Effects of High-Intensity Interval Running on Plantar Fascia Thickness and Stiffness in Healthy Adults

Plantar fascia (PF) thickness and stiffness have been linked diagnostically to plantar fasciitis. Acute changes to these properties in response to submaximal running have been noted but not yet tested in maximal effort bouts. This study assessed the acute effects of high-intensity interval running on PF thickness and stiffness in healthy adults. Sixteen participants completed 5 maximal effort 400-m sprints with a 1:1 work-to-rest ratio, followed by additional maximal effort trials until fatigue. Thickness and stiffness at the calcaneal origin were measured prerun, postrun, and 30 minutes postrun via ultrasonography and shear wave elastography, respectively. PF thickness and stiffness did not differ between right and left foot (P > .05) and between males and females (P = .067). Thickness and stiffness decreased postrun (0.43 mm, P < .001; 1.54 m·s-1, P < .001) and increased 30 minutes postrun (0.28 mm, P < .002; 1.0 m·s-1, P < .001). No significant difference was found between prerun and 30 minutes postrun thickness (P = .134), but prerun stiffness was higher than 30 minutes postrun (P = .031). These findings indicate that although high-intensity interval running altered both PF thickness and stiffness, 30 minutes of rest allowed some level of recovery in the noninjured PF tissue.