The foot is more than a spring: human foot muscles perform work to adapt to the energetic requirements of locomotion

Abstract

The foot has been considered both as an elastic mechanism that increases the efficiency of locomotion by recycling energy, as well as an energy sink that helps stabilize movement by dissipating energy through contact with the ground. We measured the activity of two intrinsic foot muscles, flexor digitorum brevis (FDB) and abductor hallucis (AH), as well as the mechanical work performed by the foot as a whole and at a modelled plantar muscletendon unit (MTU) to test whether these passive mechanics are actively controlled during stepping. We found that the underlying passive viscoelasticity of the foot is modulated by the muscles of the foot, facilitating both dissipation and generation of energy depending on the mechanical requirements at the centre of mass (COM). Compared to level ground stepping, the foot dissipated and generated an additional -0.2 J kg 21 and 0.10 J kg 21 (both p , 0.001) when stepping down and up a 26 cm step respectively, corresponding to 21% and 10% of the additional net work performed by the leg on the COM. Of this compensation at the foot, the plantar MTU performed 30% and 89% of the work for step-downs and step-ups, respectively. This work occurred early in stance and late in stance for stepping down respectively, when the activation levels of FDB and AH were increased between 69 and 410% compared to level steps (all p , 0.001). These findings suggest that the energetic function of the foot is actively modulated by the intrinsic foot muscles and may play a significant role in movements requiring large changes in net energy such as stepping on stairs or inclines, accelerating, decelerating and jumping.

Ankle and midtarsal joint quasi-stiffness during walking with added mass

“…Conversely, standing arch height has been shown to affect leg quasi-stiffness (Powell, Queen & Williams, 2016) and ankle quasi-stiffness (Powell et al, 2014) where a higher arch is related to greater stiffness. Finally, there is a substantial body of evidence which shows that activation of intrinsic foot muscles play an important role in resisting deformation of the arch during loading (Kelly et al, 2014), influencing energy storage and return from the surrounding elastic structures (Kelly et al, 2019) and adapting to various locomotion demands (Riddick, Farris & Kelly, 2019). Despite preliminary understanding of how midtarsal stiffness may be modulated, there is limited investigation of how the ankle/foot complex quasi-stiffness changes across varied dynamic tasks (e.g., walking with altered force demand or terrain).…”

New insights into intrinsic foot muscle morphology and composition using ultra-high-field (7-Tesla) magnetic resonance imaging.

“…The distinguishing contribution of the intrinsic foot muscles, compared to passive structures, is the ability to modulate the energetic function of the foot to respond to changing demands (e.g. acceleration and deceleration, surfaces and footwear) [1,3].…”

The necessity to use microsurgical methods and intraoperative monitoring during pathology in tarsal tunnel. Technical report

“…There are several such cases of surgeries during the 20-year period described in the literature, but intraoperative monitoring techniques and microsurgery are still only an option. Due to the anatomical relationship, nerve vascular supply [12][13][14][15] and muscle functions innervated by the tibial nerve, related to the support, foot arch, and effect on the movement pattern [16,17]. The surgical technique should use methods of microsurgical dissection and intraoperative neurophysiological monitoring in order to ensure safe surgery.…”

“…These involve short and strong muscles, which are divided into three groups: medial, lateral, and intermediate eminence. A disturbance of the functions, disruption of innervation of these muscles, makes normal walking and sporting activities impossible [10,[16][17][18].…”

“…The application of direct stimulation in an operation field according to the suggested parameters using a bifurcated/fork probe makes it possible to precisely determine the trajectory of the nerve fibres. Due to the motor innervation range of the tibial nerve and by maintaining the patient's physical activity [16,17], we should guarantee modern, intraoperative monitoring of neurological functions. The purpose of the suggested procedure included in the protocol, is the elimination of neurological complications that are the consequences of the performed surgery.…”