Investigation of the Effect of Foot Muscle Fatigue on the Foot Sole and Tendon Structural Properties

In healthy individuals, fatigue in the foot muscles increases the load and stress on the feet. The extrinsic muscles of the foot, which investigators aimed to create fatigue in this study, are closely related anatomically and functionally to the plantar fascia and Achilles tendon. Considering that fatigue or weakness of the foot extrinsic muscles is an important risk factor for foot-ankle pathologies, it is important to reveal the relationship with the plantar fascia and Achilles tendon in healthy sedentary individuals and to determine mechanical properties of the feet of the participants to prevent possible foot injuries. Therefore, the aim of this study is to show the acute effects of fatigue in the extrinsic muscles of the foot on the viscoelastic properties of the plantar fascia and Achilles tendon. The study was completed with 19 people who met the inclusion criteria. Before starting the study, the dominant foot of the participants was determined, physical activity level was determined, foot posture index and foot posture were evaluated, navicular height and fall distance of the foot were measured, m.gastrocnemius shortness was measured with the Silfverskiöld test, flexibility was evaluated with a baseline sitting bench, tendon and fascia measurements were made with the MyotonPRO device. After the measurements, the participant was trained to perform the heel raise exercise. When the exercise was completed, the participant's foot Myoton measurements were repeated. One week later, pre-exercise Myoton measurement was performed, then the participant was trained for the foot adduction exercise. When the exercise was completed, the participant's foot Myotone measurements were repeated. In another week, pre-exercise Myotone measurement was performed, then heel raising and foot adduction exercises were performed sequentially. When the exercise was completed, the participant's foot Myoton measurements were repeated.

This study was carried out on healthy, sedentary male individuals between the ages of 18-35. In the power analysis to estimate the sample size, Usgu et al. (2020), it was determined that there should be a minimum of 17 observations in each group, with a statistical power level of 82.2% and a significance level of 5%. The study was completed in 3 groups in line with the selected exercises. Firstly, 42 young individuals were included in the study. However, after the preliminary evaluation, 23 individuals who did not meet the inclusion criteria and did not provide continuity to the study were excluded from the study. This study was completed with 19 healthy male individuals with a mean age of 21.37(SD 2.21) years.

Eligibility Criteria:
Inclusion Criteria:

* Agreeing to participate in the study voluntarily
* Being a healthy, sedentary male individual between the ages of 18 and 35
* Being in categories 1 and 2 according to the International Physical Activity Survey (UFAA)
* Having a normal Body Mass Index (BMI) (18.5 kg/m2 ≤ BMI ≤24.9 kg/m2)
* Having a neutral foot posture (\<6 points in the Foot Posture Index)

Exclusion Criteria:

* Refusing to participate in the study or wanting to leave the study
* Having a history of previous surgery in the lower extremity
* Being diagnosed with a musculoskeletal disease
* Having any chronic disease (hypertension, diabetes, cardiovascular disease, osteoporosis, rheumatism, etc.)
* Having a skin lesion in the area to be measured
* Significant weakness in the lower extremity gross muscle test
* Any limitation in the normal range of motion of the lower extremity
* Having any deformity in the foot (pes planus, pes cavus, hallux valgus)
* Navicular drop distance ≥10 mm
* Limitation in the range of motion of the 1st metatarsophalangeal joint (hallux rigidus-limitus)