Flexor Hallucis Longus (FHL) & Flexor Digitorum Longus (FDL)

This course describes the anatomy and integrated function of the flexor hallucis longus and flexor digitorum longus muscles (a.k.a. hallucis longus and digitorum longus muscles, flexor hallucis and digitorum muscles, FHL and FDL muscles). These muscles are likely composed primarily of type II fibers (based on the composition of the peroneus longus, hallucis brevis, and digitorum brevis muscles). They are located deep to the soleus in the posterior compartment of the lower leg, the flexor hallucis longus tendon, and flexor digitorum longus tendon course behind the medial malleolus, through the tarsal tunnel, and invest into the plantar surfaces of the toes. These muscles cross and contribute to ankle (talocrural) plantar flexion and inversion, transverse tarsal joint flexion and supination, the FHL contributes to great toe flexion, and the FDL to metatarsophalangeal joint flexion of toes 2-5. This course also describes the role of the FHL and FDL in ankle and foot arthrokinematics, fascial integration, postural dysfunction, and subsystem integration. Sports medicine professionals (personal trainers, fitness instructors, physical therapists, massage therapists, chiropractors, occupational therapists, athletic trainers, etc.) must be aware of these deep compartment muscles of the lower leg and foot for detailed analysis of human movement, and the development of sophisticated exercise programs and therapeutic (rehabilitation) interventions. Further, this course is essential knowledge for future courses discussing injury prevention and physical rehabilitation including tendinopathy (a.k.a. hallucis longus tendon inflammation, flexor hallucis longus tendonitis, FHL tendon dysfunction, FHL & FDL tendonitis, etc.), as well as foot ankle dysfunctions (e.g. posterior ankle pain, hallux rigidus, tarsal tunnel syndrome, plantar nerve pain, plantar fasciitis, Achille’s tendonitis, shin splints, etc.) and FHL and FDL exercises and techniques (e.g. long toe flexor muscle or plantar flexor muscle release, mobilizations, lengthening and integration techniques).

Brookbush Institute’s most recommended techniques for the Toe Flexors (see videos below):

• Release: Calf Complex Static Release
• Manual Release: Flexor Hallucis Longus & Flexor Digitorum Longus Static Manual Release
• Manual Manipulation: Talonavicular and Cuneonavicular Joint Manipulation
• Lengthening: Slant Board Calf Stretch

Caption: Cadaver Disscection of the Flexor Hallucis Longus and Flexor Digitorum Longus