A sample of convenience of participants was recruited from a physical therapy clinic and community by advertising through posters and social networks from December 2021 to December 2022. The inclusion criteria were as follows: adults aged 18 to 39 years who had asymptomatic bilateral flexible flatfoot with a navicular drop (ND) greater than 10 mm (Cote et al., 2005 (link)) and a body mass index of 18.5–22.9 kg/m2. Participants were excluded if they had undergone lower extremity surgery or had a history of trauma or accidents to the lower extremities, lower extremity deformities, or neurological conditions affecting the lower extremities.
The sample size was calculated using the IBM SPSS Statistics ver. 28.0 (IBM Co., Armonk, NY, USA) in order to detect a 1.5-mm difference in ND between groups (Alam et al., 2019 (link)). A total sample of 52 participants (26 per group) was required for a statistical power of 0.90, an alpha level of 0.05, and a drop-out allowance of 10%.
The sample size was calculated using the IBM SPSS Statistics ver. 28.0 (IBM Co., Armonk, NY, USA) in order to detect a 1.5-mm difference in ND between groups (Alam et al., 2019 (link)). A total sample of 52 participants (26 per group) was required for a statistical power of 0.90, an alpha level of 0.05, and a drop-out allowance of 10%.
