This randomized crossover clinical study aims to investigate the immediate effects of plantar fascia release combined with foot exercises on Functional Movement Screen sub-scores in physically active young adults with pes planus.

Participants aged 18-35 years with pes planus, determined by the Navicular Drop Test, will complete two different intervention protocols in a randomized order. Protocol A will include foot-core exercises combined with plantar fascia stretching. Protocol B will include the same foot-core exercises and plantar fascia stretching, with the addition of plantar fascia myofascial release. Each participant will receive both interventions on separate sessions, with a 24-hour washout period between sessions.

Functional movement quality will be assessed using two Functional Movement Screen subtests: Deep Squat and Hurdle Step. These tests will be performed before and after each intervention session to evaluate acute changes in movement performance.

The main hypothesis of the study is that plantar fascia myofascial release combined with foot-core exercises and plantar fascia stretching will produce greater immediate improvements in Functional Movement Screen Deep Squat and Hurdle Step scores compared with foot-core exercises and plantar fascia stretching alone.

This study is planned as a randomized crossover interventional clinical study designed to evaluate the acute effects of plantar fascia release combined with foot exercises on functional movement quality in young adults with pes planus.

Pes planus is associated with reduced medial longitudinal arch support and excessive pronation, which may influence lower extremity alignment, load transfer, postural control, and functional movement patterns. Foot-core exercises aim to activate and strengthen the intrinsic muscles of the foot that support the medial longitudinal arch. Plantar fascia stretching and myofascial release may improve the flexibility and mechanical properties of the plantar fascia and may contribute to improved ankle and lower extremity movement capacity. Therefore, combining active foot stabilization exercises with plantar fascia interventions may provide an immediate effect on movement quality.

The study will include physically active young adults aged 18-35 years with pes planus. Pes planus will be determined using the Navicular Drop Test. Physical activity level will be assessed using the International Physical Activity Questionnaire. After eligibility screening and written informed consent, participants will complete two different intervention protocols in a randomized order.

The crossover design will allow each participant to receive both intervention protocols and serve as their own control. A 24-hour washout period will be provided between the two intervention sessions to minimize possible carryover effects. In each session, Functional Movement Screen subtests will be assessed before the intervention. The assigned intervention protocol will then be applied, followed by a one-hour waiting period. After this waiting period, the Functional Movement Screen subscores will be repeated to determine the immediate effect of the intervention.

Protocol A will consist of foot-core exercises combined with plantar fascia stretching. The foot-core exercise program will include short foot exercise, towel curl, toe spread, great toe extension, and reverse tandem walking. Plantar fascia stretching will be performed using a plantar fascia-specific stretching technique.

Protocol B will consist of the same foot-core exercises and plantar fascia stretching, with the addition of plantar fascia myofascial release. Myofascial release will be applied manually along the plantar fascia, from the calcaneal region toward the metatarsal heads, with controlled pressure and within the participant's tolerance.

Functional movement quality will be evaluated using the Deep Squat and Hurdle Step subtests of the Functional Movement Screen. These tests were selected because they reflect lower extremity mobility, stability, balance, and movement control, which may be influenced by foot posture and plantar fascia mobility.

The primary aim of the study is to compare the immediate effects of the two intervention protocols on Functional Movement Screen Deep Squat and Hurdle Step scores. The study hypothesis is that the protocol including plantar fascia myofascial release, plantar fascia stretching, and foot-core exercises will result in greater immediate improvement in Functional Movement Screen subscores compared with foot-core exercises and plantar fascia stretching alone.

All assessments and interventions will be performed face to face in a clinical setting by trained physiotherapists. Procedures will be conducted according to standardized instructions, and participant safety and comfort will be monitored throughout the study.

Inclusion Criteria:

• Being between 18 and 35 years of age
• Voluntarily agreeing to participate in the study and providing written informed consent
• Having pes planus according to the Navicular Drop Test result
• Having the cognitive ability to understand and perform the Functional Movement Screen (FMS) test instructions
• Being classified as sufficiently physically active according to the International Physical Activity Questionnaire (IPAQ), defined as at least 1,500 MET-min/week of vigorous-intensity activity or at least 3,000 MET-min/week of moderate-intensity activity
• Having no history of lower-extremity surgery within the previous 6 months
• Having no history of lower-extremity injury or disability within the previous 6 months
• Agreeing to complete the study protocol over two days

Exclusion Criteria:

• Having a history of ankle sprain, particularly recurrent ankle sprains
• Presence of hallux valgus deformity
• Presence of hammer toe deformity
• Presence of generalized ligamentous laxity
• Having a history of systemic disease, such as rheumatic, neurological, or metabolic disorders
• Presence of ongoing lower-extremity pain
• Having any orthopedic or neurological condition that may prevent the safe performance of the Functional Movement Screen tests

The outcomes assessor will be blinded to the intervention sequence. Participants and care providers cannot be blinded due to the nature of the exercise and manual therapy interventions.