Foot Strengthening with the Short Foot Exercise (SFE)

Plantar Fasciitis is one of the most common musculoskeletal conditions we treat here at Forster Tuncurry Sports Podiatry. Every patient will have an individualised treatment plan, however there is one exercise that we find almost all of our patients respond to. The Short Foot Exercise (SFE).

You would not believe how many patients I have had walk (or more often than not, hobble) through my door who’ve seen therapist after therapist and have not once been prescribed ANY foot strengthening exercises!

(calf stretches and rolling your foot on a tennis ball or frozen bottle don’t count here)

There are a number of reasons that I introduce foot strengthening exercises early on in the treatment regimes for my patients, especially those suffering plantar fasciitis.
The biggest reason? They work!

If structure & function isn’t your thing and you just want to know how to perform the SFE skip to the end.

Strengthening exercises are in an entirely different realm to stretching exercises and manual therapies (foam rolling etc).
Strengthening exercises involve muscular contraction to increase the strength, endurance and size of skeletal muscles.

If something is weak stretching and massaging isn’t going to fix the problem!

There are a handful of foot strengthening exercises that I prescribe depending on which structures I want to load and how I want to load them. Today we are only looking at one, the SFE.

Now let me be clear from the start, the SFE is not the golden bullet for everyone with plantar fasciitis.

Why?

As with the complex nature of musculoskeletal conditions there are multiple factors that contribute to an individual’s presentation of the condition.

Depending on a person’s individual risk/contributing factors, the level of response to various treatment interventions will vary. To make this a bit clearer let’s throw in some visuals.

In the picture below let’s imagine we have 8 contributing factors for a condition, and three different people presenting with the same condition. Person 1 (left), person 2 (middle) and person 3 (right) all have contributing factor 1 present. As contributing factor 1 makes up a greater portion of the contributing factor for person 1 we can assume that an intervention geared towards that factor will likely create a greater treatment response than persons 2 and 3.

If weakness of the intrinsic muscles are not a significant contributing factor to your presentation of plantar fasciitis then they will likely not produce significant results. However, if weakness of the intrinsic muscles are contributing to your plantar fasciitis symptoms then there’s a good chance that they’re going to help you a lot.

Before we get too far ahead I think a quick revision (or other cases a quick introduction) of the plantar fascia is a good idea.

The plantar aponeurosis (PA) originates from the calcaneus and consists of medial, central and lateral portions. Depending on the literature the terms plantar fascia and plantar aponeurosis can be used interchangeably. Other literature describes the central portion as aponeurosis, and the medial & lateral portions as fascia.

At its distal end the central portion/PA divides in to five bands that attach to the fibrous digital sheaths and sesamoid bones of the hallux. The fibrous digital sheaths are located on the plantar surface of the toes and hold the long digital flexor tendons in place (1). Other literature reports the insertion of the five distal bands of the plantar fascia attach through the plantar plates to the proximal phalanges (2).

 

Here’s where things get a little more involved. Now enter the intrinsics…

Both micro- and macroscopic studies of the foot have identified that the plantar fascia is firmly attached to the abductor hallucis, flexor digitorum brevis and abductor digiti minimi muscles. Along with covering the plantar surface of these muscles the fascia also creates an array of inter- and intramuscular septae separating the muscles, and serves as the origin and insertion to many of the muscle fibres (8).

So logic should be starting to kick in here… If the plantar fascia & superficial intrinsic foot muscles are physically connected it would stand to reason that they at least share some functions…?

Correct

Both the intrinsic muscles of the foot and the plantar fascia contribute to preventing flattening of the medial longitudinal arch and the stabilisation of the arches of the foot during and resupination of the midtarsal and subtalar joints during propulsion (5, 6).
Now as we are discussing structures sharing responsibilities it is time to introduce the third cog in this wheel. Also playing a large role in arch stability and load-bearing function of the foot are the plantar ligaments of the foot (4).

To further explain the interrelationship between these structures, Dr Kevin Kirby – one of the top podiatry biomechanical minds, describes the load-bearing structures of the foot as the longitudinal arch load-sharing system (LALSS).

The LALSS sees the three load bearing structures working in synergy to share the load-bearing forces within the plantar arch, and to maintain the height & stability of the longitudinal arch. Should one of these structures fail we would see an increase in load-bearing forces placed on the remaining structures (6).

Applying this model to the structural triad, weakness of intrinsic foot muscles would result in increased loads being placed on the plantar ligamentous structures and the plantar fascia. Weakness of the plantar fascia would result in increased loads being placed on the intrinsics and the ligamentous structures and so on.

At this stage we don’t know what the causal relationship between weakness of the intrinsic muscles and plantar fasciitis is. Meaning;

Q: Does weakness of the intrinsics cause plantar fasciitis?
Q: Does plantar fasciitis cause weakness of the intrinsics?

A: We don’t know!

Thanks to the study by Cheung, R.T.H. et al. published in 2016 what we do know is that runners with chronic plantar fasciitis had a decrease in muscle volume compared to healthy asymptomatic runners.

Regardless of what came first, if there is a weakness identified it would stand to reason that incorporating intrinsic strengthening exercises in to a treatment regime would be warranted?

A few of the more common exercises for treating plantar fasciitis include;
Calf stretches
Rolling the plantar fascia on a frozen bottle/tennis ball/golf ball etc
Toe curls
Yes sometimes they work, but for the dozen or more new patients I see each month with heel pain they haven’t worked.

So here we have it, the Short Foot Exercise. Enjoy!

Aside from clinically observing that the SFE tends to produce more positive and consistent results with my patients, there is also a bit of research backing up its position at the top of the ladder. Jung, Do-Young et al. (2011) found that the SFE achieved greater EMG activity of the Abductor Hallucis (AbdH) muscle in both seated and standing positions compared to the toe curl (TC) exercise. Leading to the SFE being a more superior exercise for increasing strength of the AbdH.

In a clinical setting it is pretty difficult to test the functional strength of the intrinsic muscles so we have to be a little savvy with out clinical reasoning.

  • We know that the intrinsics and plantar fascia are two of the three structures that create the LALSS and that disruption of one will increase mechanical load on the other structures.
  • We know that the plantar fascia and intrinsic foot muscles are physically connected.
  • We know that studies of those runners with chronic plantar fasciitis vs healthy controls the ones suffering plantar fasciitis all displayed atrophy of the intrinsic muscles.
  • We know that the SFE results in greater EMG muscle activity of the Abductor Hallucis muscle than the toe curl exercise.
The Short Foot Exercise (SFE)
  • You will perform this exercise one foot at a time
  • Begin exercise seated (as you progress and find the exercise becoming easier you can start performing the SFE standing)
  • Ensure heel and ball of foot remains in contact with ground the entire time
  • Try to keep toes straight (ie: don’t allow them to flex/curl downward when performing movement)
  • Visualise the heads of the metatarsals and try to draw them back towards your heel
  • Hold contraction for 2-5 seconds. Gradually work up to holds of up to 10 or more seconds

    Image sourced from: denverfitnessjournal.com/the-short-foot-exercise-for-stronger-feet/

 

Sets & Reps

Some people may experience a few foot cramps in the initial stages of performing this exercise.
Depending on how you tolerate the exercise you can implement it one of the two ways I prescribe this to my patients.

Reps for time or a designated number of sets & reps.

Sets for time

Sets for time would see you performing As Many Reps As Possible (AMRAP) in 30 seconds. This is usually easier for those new to this exercise. Here we are after quality of movement over quantity of reps.
Repeat 10 x per day

Sets & Reps

5 sets x 10 reps (holding contraction for 2-5 seconds each rep)
Rest for a period of no less than 60 seconds between performing exercise.


 


References

(1) “Anatomyexpert: Fibrous Sheaths Of Digits Of Foot – Structure Detail”. Anatomyexpert.com. N.p., 2017. Web. 15 Mar. 2017.

(2) Chen, Da-wei et al. “Anatomy And Biomechanical Properties Of The Plantar Aponeurosis: A Cadaveric Study”. PLoS ONE 9.1 (2014): e84347. Web.

(3) Cheung, R.T.H. et al. “Intrinsic Foot Muscle Volume In Experienced Runners With And Without Chronic Plantar Fasciitis”. Journal of Science and Medicine in Sport 19.9 (2016): 713-715. Web.

(4) Huang, Ching-Kuei et al. “Biomechanical Evaluation Of Longitudinal Arch Stability”. Foot & Ankle International 14.6 (1993): 353-357. Web.

(5) Jung, Do-Young et al. “A Comparison In The Muscle Activity Of The Abductor Hallucis And The Medial Longitudinal Arch Angle During Toe Curl And Short Foot Exercises”. Physical Therapy in Sport 12.1 (2011): 30-35. Web.

(6) Kirby, K. “Understanding Ten Key Biomechanical Functions Of The Plantar Fascia | Podiatry Today”. Podiatrytoday.com. N.p., 2016. Web. 15 Mar. 2017.

(7) Pavan, P. G. et al. “Investigation Of The Mechanical Properties Of The Plantar Aponeurosis”. Surgical and Radiologic Anatomy 33.10 (2011): 905-911. Web.

(8) Stecco, Carla et al. “Plantar Fascia Anatomy And Its Relationship With Achilles Tendon And Paratenon”. Journal of Anatomy 223.6 (2013): 665-676. Web.


Talysha Reeve B.App.Sc.(Podiatry) – GradCertClinRehab – Cert IV Fitness


 

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