You would be hard-pressed to have a session with a physiotherapist, exercises specialist or personal trainer and not, at some point, have core strength or core stability come up. Cue eye roll. The truth is it is widely shown to be extremely important in rehabilitation, athletic training and pretty much any activity of daily living Sulowska et al (2018).
“Stability of the core influences the mobility of distal body parts and the pattern of energy generation and transfer from proximal to distal segments.” (Read that again).
I was on an advanced lower limb physiotherapy course pre-COVID19 and the instructor referenced a school of thought (growing in its support by current research) that the intrinsic or small muscles of the arch of the foot are being called the core of the foot. Their job is to maintain the longitudinal medial arch of the foot much like the abdominal and spinal muscles maintain proper midline/spine mechanics. Sulowska et al (2018) reviewed literature which “indicates a relationship between the plantar short foot muscles and proximal segments with the functional of the body”. They further found support that the strength of these muscles is important for gait speed, step count and postural control. So, if you are going to pound the pavement by running, it could be argued that you would want your interface with you and the ground, your feet, to be firing at all cylinders properly.
The authors of the article I reviewed basically identify the importance of good foot and lower leg strength as having an influence on the joints and muscles above. As a physiotherapist, I almost always give glute, hip, quad and hamstring strengthening to runners for self-care/performance enhancement and the muscles of the feet should be thought of as equally important.
The aim of the Sulowska (2018) study was to “evaluate the influence of exercises of the plantar short foot muscles on the performance of lower extremities in long-distance runners”. They concluded that the inclusion of such types of exercise in the daily program for runners may improve energy transfer through body segments, increase the strength and values of generated power. The study has admitted limitations and looked at 47 runners aged 21-45 years who ran regularly for a range of 20-100 km per week.