Acute Effects of Foot Orthoses on Muscle Mechanical Properties in Individuals With Pes Planus

Participants will first undergo baseline assessments, followed by 30 minutes of treadmill walking at a self-selected speed and 0° incline while wearing comfortable shoes without an added orthosis. Dynamic stiffness, oscillation frequency, other MyotonPRO parameters, and pain will then be reassessed (T0). Participants in the medial arch support and insole groups will rest for 30 minutes and complete a second 30-minute walk at the same speed and incline with the assigned device placed inside the shoe. Outcomes will be reassessed immediately after this walk (T1). Participants in the control group will complete the study after the first, unassisted walking condition and T0 assessment; no T1 measurement is planned for this group. MyotonPRO assessments will include the tibialis anterior, peroneus longus, and medial and lateral gastrocnemius-soleus muscle groups, following the measurement procedures specified in the ethics application.

The control group will characterize the acute response to the initial unassisted walking task. Because the approved protocol does not include a second walking condition for the control group, analyses requiring T1 will be limited to the two orthosis groups. Between-group comparisons involving all three groups will use the time points available across all groups, including baseline and T0.

Inclusion criteria

• Aged 18-30 years
• Diagnosed with unilateral or bilateral pes planus
• Willing to participate voluntarily in the study

Exclusion criteria

• History of lower-extremity injury or surgery within the past 6 months
• Diagnosis of a rheumatologic or neurological condition that may affect foot joint alignment
• Skin lesions or damage that may prevent the measurements from being performed
• Current use of an orthosis, such as an insole or wedge, to support pes planus
• Body mass index (BMI) ≥25 kg/m² or ≤18.5 kg/m²
• Unwilling to participate in the study