The role of intrinsic foot strengthening and activation in field sports conditioning and athlete rehabilitation.

In high performance sport there are always new ideas and
research to find the one percenters that can ultimately contribute to
performance increases and injury risk mitigation. One area that is vastly
underutilised is the role of sports & musculoskeletal podiatrists
collaborating with sports science and strength and conditioning for lower limb
programming.

There is new research coming to light regarding intrinsic
foot strengthening and the role minimisation of longitudinal arch deformation
to maximise running economy and to increase power output during gait/running
propulsion. This commentary hopes to provide insight into the practical
application of the research and realistically apply it in a field sport
setting.

In most field sports Australian Rules, Rugby league/union,
soccer etc. it seems most logical that the primary physiological task, skill,
movement patter and activity is running. Sub-skill/tasks such as jumping,
change of direction, kicking etc. depends on the sport requirements. However, a
commonly undervalued component for the primary task is the role of intrinsic
foot muscles and their key properties of strength and flexibility in running.
These muscles perform important tasks such as

  • shock absorption capabilities;
  • efficient running patterns,
  • tolerating load from both the body pushing down
    and ground reaction force pushing up,
  • the first contact to the ground initiating the
    kinetic chain
  • minimising alterations in related lower limb
    neuromuscular and joint range of motion fatigue
  • a key role in power/endurance output for
    sprinting/high speed running

Recently we have had quality research come out from Dr. Luke
Kelly (Podiatrist) who is a leading podiatrist in Australia on the topic of
intrinsic foot muscle training and also Michael Skovdal Rathleff and co. have
been producing quality information in regard to high-load strength training for
foot/ankle muscle complex. Follow their works on journal databases and there is
excellent practical pears of wisdom that can be used from their works. Some
examples include:

  • unilateral/bilateral towel calf/heel raises
    (loaded or body weight)
  • Short foot (contraction of the medial arch
    loaded or semi-wb)
  • Heel walks and calf walks
  • Foot Inversion and eversion walks
  • Heel to toe hops
  • 1,2,3 3 triple extensions barefoot
  • Triple extension onto a step
  • Skipping rope/resistance band foot activation

So in the context of not only in high performance sport, but
at sub elite and participation level there should be considerations for
intrinsic foot strengthening/activation/prehab in the overall planning of the
training year and the rehabilitation process. Handheld dynamometers and linear
force production transducers, force plates, push/pull force devices etc. can be
used to baseline testing of athlete strength and data can be used to return to
performance markers as well. As a guide in the general population young males
<65 years can pull approximately 10% of their body weight with their big toe
and females can pull approximately 5%. It is not uncommon to see 10-20%
variation from their non dominant side.

Following on from normative values there is research to
support that in vivo that the plantar intrinsic foot muscles function in
parallel to the plantar fascia. There are suggestions that increasing muscular
length and strength in the plantar intrinsic muscle layers can increase
resilience in the medial longitudinal arch and minimise deformation. This
increase in muscular length and strength can also contribute to increased ach
stiffness which is essential for efficient foot propulsion and can possible
translate to increased speed and power while maximising energy use. It’s
important to think as increasing foot intrinsic stiffness/strength can lead to
increased propulsion capabilities and increasing intrinsic foot muscle length/flexibility
can lead to increased shock absorption capabilities.

In the athlete rehabilitation setting for returning players
to performance from injuries such as plantar fascial stress pathology
(fasciitis, fasciopathy, fasciocis, structural tears), Achilles tendon
pathology, calf/MTJ strains/tears etc. it is important to either have:

  • Baseline data on their foot strength (integrate
    into pre-season screenings)
  • Record strength values as soon as possible (pain
    < 3/10)

This data can help inform rehab progressions especially
leading up to return to run strategies as well as baseline data to assist
markers for increasing speed thresholds without the risk of causing harm to
injured site during the rehabilitation continuum. Strength in the intrinsic
muscles is an important factor for the decision to return to run post injury
and having specific, valid and replicable ways of recording strength data can
help inform rehab progressions, periodise prehab/independent correctives for
prevention of future injury and overall improve athletic performance in the
context for running/sprinting an efficient energy expenditure. These overall
considerations are useful, take minimal time to implement into individual
training programs and can be a factor improvement in overall athletic
capability.

References

Menz, H., Zammit, G., Munteanu, S., & Scott, G. (2006).
Plantarflexion Strength of the Toes: Age and Gender Differences and Evaluation
of a Clinical Screening Test. Foot & Ankle International, 27(12),
1103-1108.

Kelly, Kuitunen, Racinais, & Cresswell. (2012).
Recruitment of the plantar intrinsic foot muscles with increasing postural
demand. Clinical Biomechanics, 27(1), 46-51.

Kelly, L., Cresswell, A., Racinais, S., Whiteley, R., &
Lichtwark, G. (2014). Intrinsic foot muscles have the capacity to control
deformation of the longitudinal arch. Journal of the Royal Society, Interface,
11(93), 20131188.

Kelly, L. A., Farris, D. J., Lichtwark, G. G., &
Cresswell, A. (2018). The Influence of Foot-Strike Technique on the Neuromechanical
Function of the Foot. Medicine & Science in Sports & Exercise, 50(1),
98-108.

Kelly, L., Racinais, S., & Cresswell, A. (2013).
Discharge properties of abductor hallucis before, during, and after an
isometric fatigue task. Journal of Neurophysiology, 110(4), 891-898.

Rathleff, Mølgaard, Fredberg, Kaalund, Andersen, Jensen, . .
. Olesen. (2015). High‐load strength training improves outcome in patients with
plantar fasciitis: A randomized controlled trial with 12‐month follow‐up.
Scandinavian Journal of Medicine & Science in Sports, 25(3), E292-E300.

Rathleff, M., & Thorborg, K. (2015). ‘Load me up,
Scotty’: Mechanotherapy for plantar fasciopathy (formerly known as plantar
fasciitis). British Journal of Sports Medicine, 49(10), 638-639.

Riel, H., Cotchett, M., Delahunt, E., Rathleff, M.,
Vicenzino, B., Weir, A., & Landorf, K. (2017). Is ‘plantar heel pain’ a
more appropriate term than ‘plantar fasciitis’? Time to move on. British
Journal of Sports Medicine, 51(22), 1576-1577

Riel, H., Vicenzino, B., Jensen, M., Olesen, J., Holden, S.,
& Rathleff, M. (2018). The effect of isometric exercise on pain in
individuals with plantar fasciopathy: A randomized crossover trial.
Scandinavian Journal of Medicine & Science in Sports, 28(12), 2643-2650.