Distance runners are defined as running with more than 20km per week for more than 2 years. All recruited participants have > 1 year of plantar fasciitis. The diagnosis were made based on clinical symptoms and the thickness of plantar fasciitis > 4.0mm at the medial tubercle of heel by ultrasound imaging.~Arm 1: The purpose of this arm of the study is to determine if a 8-week targeted foot muscle exercise regimen, instructed with real-time ultrasound, affect the intrinsic foot muscle size, symptomatic relief, and foot function improvement of distance runners with plantar fasciitis. 32 participants will be recruited in this arm.~Arm 2: This group will not engage in any training, but will serve as a comparator for the intervention arm.
A reduction of intrinsic foot muscle sizes has been identified in patients with chronic plantar fasciitis. Weaker intrinsic foot muscles has been suggested to decrease the medial longitudinal arch height and subsequently increase extra tensile stress in the plantar fascia, resulting in the chronicity of the condition. Therefore, it is speculated that atrophic intrinsic foot muscles may be a significant risk factor of developing chronic plantar fasciitis. The purpose of this study is to investigate the effect of an 8-week targeted intrinsic foot muscles exercise regimen on the intrinsic foot muscle size, symptomatic relief, and foot function improvement in long-distance runners with chronic plantar fasciitis.