Shear wave elastography of the plantar fascia: A cross-sectional observational study in asymptomatic runners and sedentary controls.

No significant differences in plantar fascia thickness were observed between runners and sedentary controls at any measurement site.

• 56 participants were included: 38 elite runners (12 short-distance, 11 middle-distance, 15 long-distance) and 18 sedentary controls.
• All between-group comparisons for thickness yielded P > .10.
• Among runner subgroups, a difference in thickness was detected only at the left-proximal site (P = .043), with the highest values in short-distance runners.
• Proximal thickness exceeded distal thickness across all groups (P < .001).

Shear-wave elastography revealed no significant differences in plantar fascia stiffness between runners and sedentary controls at any measurement site.

• All between-group ANOVA comparisons for shear-wave velocity yielded P > .45.
• Effect sizes were small, with Hedges' g ranging from -0.07 to -0.29.
• Post hoc statistical power to detect such small effects was low, approximately 6% to 16%.
• Proximal shear-wave velocity was higher than distal shear-wave velocity (P < .001).

Plantar fascia stiffness was consistently higher at the proximal site than at the distal site across all participants.

• This proximal-greater-than-distal pattern was statistically significant (P < .001) for both thickness and shear-wave velocity.
• At the distal site, left-sided shear-wave velocity values were higher than right-sided values (Wilcoxon, P = .032).
• Measurements were taken at proximal (~1 cm from the calcaneal insertion) and distal (~6 cm) sites.

Among sedentary participants, females had higher proximal shear-wave elastography values than males, but no gender effect was observed in runners.

• The gender difference in proximal SWE among sedentary individuals was statistically significant (P ≈ 0.014–0.053).
• No corresponding gender effect on SWE was detected within the runner group.
• Gender distribution did not differ between the overall runner and sedentary groups (χ2, P = .748).

Shear-wave elastography and B-mode ultrasound demonstrated good to excellent intraclass correlation coefficients for plantar fascia measurements.

• ICC for distal SWE ranged from 0.965 to 0.979, rated as excellent reliability.
• ICC for right-proximal SWE was 0.755, rated as good reliability.
• Thickness ICC values ranged from 0.765 to 0.814.
• Measurements were performed using an Acuson S2000 system (Siemens) with a 4 to 9 MHz linear array transducer.

Body mass index was lower in middle- and long-distance runners than in sedentary controls, and age differed across subgroups.

• BMI difference between middle- and long-distance runners versus sedentary controls was statistically significant (P = .042).
• Age differed significantly across subgroups (ANOVA, P = .011).
• Gender distribution did not differ between groups (χ2, P = .748).

Adaptation of the plantar fascia to chronic mechanical loading in asymptomatic elite runners may occur without macroscopic hypertrophy or increased stiffness.

• Authors conclude that 'adaptation of the PF to mechanical loading may occur without macroscopic hypertrophy or increased stiffness.'
• The study design was cross-sectional and observational, limiting causal inference.
• Participants were young and asymptomatic, and all runners were classified as elite, representing a specific population.