Part 1: THE PINKY TOE TO USE
The pinky toe is not just the smallest among other digits but significantly small in proportion to the body. So the range of motion – or the scope of voluntary movement we can exert over it – may also feel pretty limited – perhaps even more so if trying to move this little one separately from the others. But those physical, functional properties – from which one might get confused or even get tempted to ignore them all – are, in fact, closely related to the main function of the pinky toe: providing a sensory (proprioceptive) cue for an inward rolling motion of the foot and ankle, which to be performed during locomotion, such as walking, running, and jumping. And during those cyclic, alternating movements, this rolling motion occurs very quickly as it needs to be performed – reactively, reflexively – in concert with the other parts of the foot – and even further with the ankle, knee, hips, and abdomen – all of which are bent or tilted slightly forward. And also, this rolling motion (from outside to inside) is crucial for dynamic movements – which can be characterized by frequent changes in direction and intensity, such as dancing, countermovement jumps, etc. So, with its anatomical features – the pinky toe is unique enough to be viewed as a sheer reflection of its function, which makes it an integral part of the functional anatomy of the human body.
The foot is a complex functional unit to be the base of support for the human body to stand upright. In particular, the arches – a half-dome-shaped structure located in the middle portion of the foot, which needs to be supportive and elastic – can be described as a defining feature that characterizes how humans stand, walk, run, and jump. And as suggested by the name, their functional mechanisms are quite similar to how an arch (the architecture) stays balanced with its own weight – with the pressure exerted downward throughout their unique shape. However, the human body is not a static structure but an elastic, responsive organism that continuously moves for optimal functioning. And driven by their elastic, resilient nature, the arches in the foot are set to react automatically when mechanical force is applied – vertically, laterally – to its well-rounded shape through the ankle joint, which is also to roll around. So during locomotion (walking, running, jumping, etc.), the foot is down there to push the body along the outline of the arches – outward toward the pinky toe and then inward toward the big toe – the very natural way we stay balanced during movement.
The pinky toe finally comes into play when the foot and ankle roll outward – the initial phase of bipedal locomotion – rolling along the base of the arches, ultimately toward the pinky toe. This outward motion of the foot and ankle is called supination, but it can only be performed properly with other parts, such as the trunk, the hips, the knee, and the ankle – all bent or tilted slightly forward. Otherwise, the pinky toe would barely touch the ground. So, located at the outer edge of the foot, the pinky toe is meant to touch the ground first among other toes, withstanding the impact force and reactively rolling inward – from which the foot gets ready to push the body off with the big toe. This natural mechanism is more apparent when it comes to running or jumping – where the impact force is greater than walking – which can be even more easily examined by doing so barefoot on the floor or the ground.