Abstract
Purpose
The timeline and potential contributing factors leading up to a plantar fascia (PF) injury are still unknown. This study aimed to investigate the effects of three maximal-effort 5-kilometer (km) runs over three consecutive days on PF thickness and stiffness in healthy adults.
Methods
Sixteen recreationally active adults completed three maximal-effort 5-km runs, each separated by 24 h. At each running session, ultrasonography and shear wave elastography were used to measure PF thickness and stiffness (via shear wave velocity) near the calcaneal origin at pre-run, post-run, and 30-min post-run. Two-way (3 session x 3 timepoints) repeated measures ANOVAs were used to evaluate the effects of session and timepoints on PF thickness and stiffness.
Results
PF thickness at pre-run increased from day 1 to day 2 (P = 0.003) and from day 1 to day 3 (P = 0.003). PF thickness decreased from pre-run to post-run on day 1 (P = 0.008), day 2 (P = 0.041), and day 3 (P < 0.001), yet recovered 30-min post-run. PF stiffness decreased from pre-run to post-run on day 1 (P = 0.002), day 2 (P = 0.001), and day 3 (P = 0.001), yet had no main effects across sessions at any timepoint.
Conclusion
The increase in pre-run PF thickness across sessions highlights the importance of adequate recovery between consecutive days of running to allow the appropriate time for adaptation to repeated mechanical loading. Acute thickness and stiffness decrease at post-run demonstrates the PF’s viscoelastic behavior in response to mechanical loading. Both findings add to knowledge of PF responses to repeated running exposure.