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When responding to emergency operations, firefighters must wear a range of personal protective clothing (PPC) and equipment (PPE) to maintain their safety. Indeed, in some environments, such as those where high heat and smoke exist self-contained breathing apparatus’ (SCBA) and structural clothing ensembles are vital to a firefighters’ ability to undertake work. When PPC and PPE are combined, the weight added to the ambulating individual can exceed 23kg in addition to tools or equipment required to complete any given work task. When at work, firefighters are tasked with occupation specific, repetitive movement patterns that can include climbing stairs, alighting from fire appliances and negotiating obstacles. It is therefore likely that, when combined with the requirement to carry significant loads, the repetitive nature may be predisposing firefighters to significant repeated loading, which may lead to increased risk of developing chronic injuries.

For firefighters to work safely in hot and unstable terrain, in addition to firefighting PPE, they wear structural firefighting boots (referred to as Type 2). Boots in this category are required to have protection against penetration and heat, along with toe protection in the form of hard toe caps. These design requirements, while providing necessary thermal and impact protection, add weight while concurrently reducing the flexibility of the boot. Another significant design requirement is that a boot-shaft that terminates above the line of the ankle joint, to increase stability and reduce the incidence of ankle injuries and provide firefighting specific protection. Specifically, boot design standards (ISO) require boots to have a minimum shaft height. For example, for size 45 boots and above, a shaft no shorter than 192mm is needed.

During landing movements, such as alighting from a fire appliance, ground reaction forces (GRFs) are transferred from the distal to the proximal extremities. Specifically during landing, forces are absorbed and dissipated through the ankle, knee and then hip-joint in sequence. This is generally referred to as the kinetic chain and alterations to this will change the body’s natural ability to attenuate forces. When landing without restriction to the ankle joint, such as when barefoot, the foot is generally in plantar flexion (toe down). When the ankle is restricted, thus not allowing for plantar flexion on landing, a heel-toe landing (HTL) technique occurs. A HTL landing pattern has been associated with greater vertical GRFs. This then results in increased compressive forces in the soft tissue and joints surrounding the hip and knee joints. It is widely believed that chronic exposure to such forces may lead to lumbar instabilities resulting in lower lumbar and lower body injuries.

Soft tissue injuries, both acute and chronic, in the lower body and lower lumbar region of the spine are reported as being the leading cause of disability and early retirement in firefighters. Thus, it is intuitive to expect that, in addition to work specific movement patterns, an interaction between boot design and injury may be occurring. In research undertaken into non-firefighting boots, such as ski-boots and ice-skates, which share common design features at the ankle joint, reduced range of motion has been observed at both the ankle and the knee joint. As such, we hypothesised that firefighting boots with designs that restrict the ankle joints may elicit similar reductions in range of motion in firefighters when they complete landing tasks. Furthermore, as a consequence, boots may increase the risk of suffering an injury to the lower body or lumbar region as a result of alterations to the kinetic chain.