Diacutaneous Fibrolysis (FD) is a physiotherapy technique based on Cyricax's transverse massage. Kurt Ekman, its creator, observed that Cyriax's deep transverse massage was intended to achieve a mechanical effect on the tissues, but this had a series of disadvantages such as the difficulty in penetrating between tissue septa due to the large surface area of the finger tips, as well as its soft consistency in the face of adhesions or fibrosis.

Hypothesis: Adding FD to the gastrocnemius and plantar fascia to a primary care treatment protocol will produce a decrease in the stiffness (viscoelastic property) of the plantar fascia, an increase in length, width, height and a decrease in the plantar arch, as well as an increase in the length of the gastrocnemius greater than not adding it in subjects with plantar fasciitis.

Data collection. Once the participant has passed the selection criteria and signed the informed consent form, the measurements of the anthropometric variables and classification of the foot with the Foot Posture Index will be carried out. Subsequently, the dependent variables will be collected, starting with active and passive gastrocnemius flexibility, followed by measurements with the anthropometric foot measurement platform (foot length, arch height in loading and unloading, arch height index, foot width in loading and unloading, windlass force at 20º, 40º and maximum, myotonometry measurements (tone, stiffness, elasticity, relaxation and creep) and pain. Once the initial variables have been recorded, the first patient intervention will be carried out according to the assigned group. A total of 8 sessions will be carried out over 4 weeks (2 sessions per week). The variables of this study will be collected at the beginning of the study and at the end of the 8 intervention sessions (1 month).

Intervention "Protocol The usual protocol that the health service guidelines for this pathology will be carried out. The protocol consists of calf stretching exercises, plantar fascia, proprioception exercises, ultrasound, magnet therapy and gait re-education and proprioceptive exercises. The average intervention lasts between 30-45 minutes.

"Protocol "+FD Participants in this group will additionally receive 15 minutes of the treatment technique.

The FD intervention will be carried out with the same duration and protocol for all participants.

The intervention protocol will be: Start with the point of maximum tension between the two muscle bellies of the calf and hamstring (Reverse hook). Then work on the peroneus longus lateralis and soleus. Then the external calf muscle belly and soleus and the internal calf muscle belly and soleus. Then work on the tendon of the flexor hallucis proprio of the big toe and the inner edge of the Achilles tendon and peroneus longus. Then treatment of the peroneus longus with the peroneus brevis. Scraping of the insertion of the Achilles tendon, hooking of the internal and external part of the plantar fascia. Finally, longitudinal friction of the plantar fascia.

The participant will be in prone position with a support on the front of the leg with the foot off the stretcher. The physiotherapist will be in a standing position next to the participant. The procedure will be to palpate the different intermuscular septa and grooves and then perform the FD phases with the hook (supplementary transverse traction).

Diacutaneous Fibrolysis (FD) is a physiotherapy technique based on Cyricax's transverse massage. Kurt Ekman, its creator, observed that Cyriax's deep transverse massage was intended to achieve a mechanical effect on the tissues, but this had a series of disadvantages such as the difficulty in penetrating between tissue septa due to the large surface area of the finger tips, as well as its soft consistency in the face of adhesions or fibrosis.

To overcome these difficulties, Ekman designed hooks that allowed, according to Ekman himself, to treat areas located in depth. The hooks used in the current FD are metallic, curved at both ends, which allow working more specifically in depth and transversally to the tissue without slipping on the skin, focusing the mechanical effect and reducing the stress on the physiotherapist.

Its mechanical effect is described as the elimination of areas of fibrosis, trying to recover physiological sliding between tissue planes, and although there is little scientific evidence on the mechanical effects of FD, several authors have described clinical modifications in passive muscle resistance to stretching or gains in joint movement. These modifications suggest a tendon mechanical adaptation as suggested by Lévenez, Guissard and Duchateau. A cutaneous circulatory effect is also described and is the most visible effect achieved with instrumental soft tissue mobilisation techniques. In addition, Burnotte and Duby, observed that venous return was improved with FD in several pathologies, although the mechanism is unknown. Histamine released after FD application is thought to be responsible for these effects. Neurophysiological effects were observed by Veszely et al. in the application of FD to the triceps suralis, in which neuromodulatory effects were observed 30 minutes after application, with a decrease in tendon reflexes. A neuromuscular effect has now also been described in response to tensomiography and myotonometry with a decrease in tone and stiffness of the triceps suralis muscle in asymptomatic subjects, which was maintained 30 minutes post-intervention.

The relationship of the gastrocnemius with the plantar fascia and this with the maintenance of the plantar arch is well known. The gastrocnemius, with the continuation of the Achilles tendon, modulates the tension of the plantar aponeurosis. As the tension of the triceps suralis increases, so does the tension of the plantar fascia. This is very important for weight-bearing transition during gait. The direction of the tendons of the extrinsic muscles of the foot shows their ability to provide dynamic support and control of the longitudinal and transverse components of the plantar arch. The global movements will provide both absorption and propulsive capacity during dynamic activities.

Plantar fasciitis is one of the most common foot disorders, being the leading cause of heel pain in primary care and accounting for 80% of all heel pain. Plantar fasciitis is a common injury caused by repetitive traction of the origin of the plantar fascia on the distal calcaneus.

In clinical practice, the gastrocnemius approach is commonly used to treat plantar fascia and Achilles problems. FD is one of the techniques used for these treatments; however, no studies have been found on its clinical effects or the effects of this technique on the plantar arch.

Hypothesis: Adding FD to the gastrocnemius and plantar fascia to a primary care treatment protocol will produce a decrease in the stiffness (viscoelastic property) of the plantar fascia, an increase in length, width, height and a decrease in the plantar arch, as well as an increase in the length of the gastrocnemius greater than not adding it in subjects with plantar fasciitis.

Data collection. Once the participant has passed the selection criteria and signed the informed consent form, the measurements of the anthropometric variables and classification of the foot with the Foot Posture Index will be carried out. Subsequently, the dependent variables will be collected, starting with active and passive gastrocnemius flexibility, followed by measurements with the anthropometric foot measurement platform (foot length, arch height in loading and unloading, arch height index, foot width in loading and unloading, windlass force at 20º, 40º and maximum, myotonometry measurements (tone, stiffness, elasticity, relaxation and creep) and pain. Once the initial variables have been recorded, the first patient intervention will be carried out according to the assigned group. A total of 8 sessions will be carried out over 4 weeks (2 sessions per week). The variables of this study will be collected at the beginning of the study and at the end of the 8 intervention sessions (1 month).

Intervention "Protocol The usual protocol that the health service guidelines for this pathology will be carried out. The protocol consists of calf stretching exercises, plantar fascia, proprioception exercises, ultrasound, magnet therapy and gait re-education and proprioceptive exercises. The average intervention lasts between 30-45 minutes.

"Protocol "+FD Participants in this group will additionally receive 15 minutes of the treatment technique.

The FD intervention will be carried out with the same duration and protocol for all participants.

The intervention protocol will be: Start with the point of maximum tension between the two muscle bellies of the calf and hamstring (Reverse hook). Then work on the peroneus longus lateralis and soleus. Then the external calf muscle belly and soleus and the internal calf muscle belly and soleus. Then work on the tendon of the flexor hallucis proprio of the big toe and the inner edge of the Achilles tendon and peroneus longus. Then treatment of the peroneus longus with the peroneus brevis. Scraping of the insertion of the Achilles tendon, hooking of the internal and external part of the plantar fascia. Finally, longitudinal friction of the plantar fascia.

The participant will be in prone position with a support on the front of the leg with the foot off the stretcher. The physiotherapist will be in a standing position next to the participant. The procedure will be to palpate the different intermuscular septa and grooves and then perform the FD phases with the hook (supplementary transverse traction).

Inclusion Criteria:

• Age over 18 years
• Medical diagnosis of plantar fasciitis.
• Sign the informed consent for participation in the study.

Exclusion Criteria:

• Present pathology in the lower limbs other than plantar fasciitis, which may alter the assessments.
• History of orthopaedic injuries in the last 6 months that may influence correct standing.
• Use of corrective insoles due to plantar arch problems.
• Skin lesions in the region of application that prevent the application of the technique.