Flatfoot condition: etiological foundations, risk factor analysis, therapeutic interventions, and the biomechanical role of resistance training in podiatric rehabilitation

The anatomically sound human foot does not make contact with the ground across its entire plantar surface; rather, it relies on a tripod support system formed by the calcaneal tuberosity, the first metatarsal head, and the fifth metatarsal head. Bridging these bony landmarks are the dynamic foot arches: the medial longitudinal, lateral longitudinal, and transverse arches. Pes planus (flat foot) is a structural deformity characterized by the collapse or absence of these physiological arches. Clinically, it presents as longitudinal flat foot (medial arch collapse) or transverse flat foot (forefoot splay). Arch collapse severely compromises dynamic shock absorption.

The etiology of flat feet is multifactorial, categorized into congenital and acquired forms. Congenital pes planus arises from tarsal coalitions or generalized ligamentous laxity. The far more prevalent acquired form results from dynamic insufficiency of the supporting musculoligamentous structures. Primary predisposing factors include: overweight and obesity placing excessive compressive loads upon the plantar fascia, sedentary lifestyles, ill-fitting footwear (high heels, restrictive narrow toe-boxes, stiff soles), prolonged static standing occupations, posterior tibial tendon dysfunction (PTTD), and post-traumatic ankle injuries.

The compromise of natural plantar shock absorption generates pathogenic forces ascending the entire kinetic chain. Ground impact forces induce excessive foot pronation, triggering compensatory knee valgus, internal femoral rotation, and anterior pelvic tilt. Consequently, patients experience chronic plantar fasciitis, calcaneal spurs, patellofemoral pain syndrome, early hip osteoarthritis, and chronic lumbosacral spinal strain. Furthermore, transverse arch flattening inevitably precipitates severe painful forefoot metatarsalgia, intractable plantar callosities, and hallux valgus deformities.

Management of flexible pes planus centers on conservative protocols designed to strengthen intrinsic and extrinsic foot musculature and restore postural balance. Evidence-based physical therapy includes targeted exercises for the tibialis posterior and anterior, myofascial release of the plantar fascia with massage balls, barefoot ambulation on textured natural surfaces (sand, grass), and toe-gripping drills. Custom dynamic orthotic insoles, crafted from computerized pedobarographic scans, provide corrective structural arch support and calcaneal realignment. In overweight individuals, nutritional weight reduction is mandatory to alleviate mechanical overload.

Individuals with flat feet need not avoid resistance training, but compound axial-loading movements (such as squats and deadlifts) demand strict biomechanical precision. Allowing foot arches to collapse under heavy barbell loads drives dynamic knee valgus, dramatically elevating injury risk to menisci and cruciate ligaments. Prior to loading, athletes should execute the 'short foot' exercise (Janda's short foot maneuver), actively doming the medial longitudinal arch while anchoring the first metatarsal head. Squatting in soft, pillowed running shoes must be avoided in favor of rigid, flat-soled lifting shoes or barefoot grounding.