Running is one of the most common forms of physical activity that
we engage in, and it is frequently prescribed in exercise programs. As runners
increase the number of miles under their feet, they often forget that their
activity of choice places high demands on the biomechanics of the foot,
including the foot's stability of the arches. Once the demand exceeds the
capacity, we can experience an injury or a dysfunction, which can either
sideline a runner or increase their risk for injury in the future.
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| Fig. 1 Medial view of the foot and medial longitudinal arch |
A recent journal article published in the British Journal of Sports Medicine outlines the importance of foot stability to
normal foot and lower extremity function. This article draws parallels between
the concept of core stabilization around the lumbar spine and pelvis to
stabilization of the foot. Similarly to the spine, stabilization of the foot
requires functional integration between 3 subsystems: passive, active, and
neural subsystems.
Passive Subsystem – Consists of bones, ligaments, and joint
capsules that maintain the various arches of the foot. The arches unite into a
functional half dome responsible for adapting to loads during dynamic
activities (e.g., running and jumping).
Active Subsystem – Consists of the muscles and tendons that act
on the foot (intrinsic and extrinsic foot musculature). The local stabilizers
are the plantar intrinsic musculature that originate and insert on the foot.
These muscles are primarily responsible for stability within the foot during
dynamic tasks. The global movers are the muscles that originate in the lower
leg, cross the ankle and insert on the foot. They are responsible for general
foot motion and modulate the structures within the passive subsystem. This modulation
is important for key events in foot mechanics, such as transitioning from a
mobile to a rigid body during gait.
Neural Subsystem – Consists of sensory receptors in the plantar
fascia, ligaments, joint capsules, muscles and tendons involved in the active
and passive subsystems. Intrinsic foot musculature is responsible for providing
immediate sensory information about changes in the foot dome posture and may be
modulated through training to alter their sensitivity to foot dome deformation.
What does this
matter to runners?
The intrinsic foot musculature (local stabilizers) has been shown
to be more active in dynamic tasks and when additional loads are added to the
participant, as with running. With each footstep, the four layers of intrinsic
muscles act to control the degree and velocity of arch deformation. When they
are not functioning properly, the foundation becomes unstable and misaligned,
leading to abnormal movement of the foot. This may manifest in foot related
problems such as plantar fasciitis, posterior tibial tendon dysfunction, and
medial tibial stress syndrome (shin splints), all of which are common
pathologies in runners.
Anthropologically, the foot has evolved in response to the
increased demand of load carriage due to bipedalism. Bipedalism requires a foot
that is reasonably mobile, able to accommodate uneven surfaces (stable), and is
actively controlled. With bipedalism came the need for the human foot to
operate as a compact, rigid lever system during the latter half of stance. One
of the major adaptations of this demand was a well-defined medial longitudinal
arch defended by strong plantar tensile elements. This becomes especially
important in running because we need to be able to deform the arch to take
advantage of the spring-like characteristics of the foot, as it stores and
releases elastic energy with each foot strike.
Training the “Foot
Core”
Traditional training strategies for increasing plantar intrinsic
foot muscle endurance and control have been based around exercises that induce
to flexion, such as towel curls or marble pick-ups. However, these exercises
have been shown to involve substantial activation of the global movers
(extrinsic musculature) of the foot.
Recently, the “short foot exercise” or “foot doming” has been
shown to isolate contraction of the plantar intrinsic muscles. The foot is
shortened by using the intrinsic muscles to pull the first metatarsophalangeal
joint towards the heel (calcaneus), as the medial longitudinal arch is elevated.
It is important to establish control of intrinsic foot muscle function before
increasing capacity. Foot doming is a foundational exercise for foot and ankle
rehabilitation. Evidence has shown that 4 weeks of daily foot-doming training
reduces arch collapse in running and improves dynamic balance (15-20 reps x 2
sets, 2x/day).
The “Short-Foot”/”Foot Doming”
Exercise
Take Home Points
Runners require requisite stability and mobility of the foot to
reach optimal levels of performance and to avoid increases in injury risk. Just
as with other sports, we cannot forget the loads placed on our body by running
and, thus, must increase our capacity to meet the demand.
- The interaction between the active, passive and neural subsystems is essential for foot control and stability during static and dynamic tasks
- The plantar intrinsic foot musculature play a critical role within the active and neural subsystems, acting as local stabilizers and direct sensors of arch deformation
- Foot core training begins with targeting the plantar intrinsic muscles via foot doming/the short-foot exercise
Protect your feet runners. You only have one
pair.
References
1.
McKeon P, Hertel J, Bramble D, Davis I. The foot core system: a
new paradigm for understanding intrinsic foot muscle function. British Journal
of Sports Medicine. 2014; 49(5): 290-290.
2.
Janda V, Vavrova M, Hervenova A, et al. Sensory motor stimulation.
In: Liebenson C. ed Rehabilitation of the spine: a practitioner’s manual. 2nd
edn. Lippincott Williams & Wilkins, 2006.
3.
Sauer LD, Beazell J, Hertel J. Considering the intrinsic foot
musculature in evaluation and rehabilitation for lower extremity injuries. Athl
Train Sports Health Care 2011;3:43–7.
Danny Dulay
Strength and Conditioning Specialist
Doctor of Chiropractic Candidate
danny@catalyst-health.ca
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