Intrinsic Foot Muscle Strengthening: A Comparison of Short Foot and Toe Curl Exercises

How important is foot posture? Think about this question… what are your thoughts? I guarantee that the majority sports physiotherapists would be aware of the impact of foot posture on the lower limb kinetic chain. Thus, you sports physiotherapists would be aware of the predisposition to many overuse injuries that poor foot posture will give your athletes. No arguments there (I hope).

This link between foot posture (read: over-pronation) and overuse conditions has been well established in the literature. These conditions include the commonly seen plantar fasciitis (Pohl et al, 2009), Achilles tendinopathy (Ryan et al, 2009), and patellofemoral pain syndrome (Powers et al, 1995). This has lead to the practice in the sports medicine world of attempting to strengthen the musculature responsible for restricting and/or controlling foot (over)pronation. This article discusses the thinking behind these clinical decisions and research regarding the optimal exercise choice.

WHAT INTRINSIC FOOT MUSCLES ARE THE MOST IMPORTANT?

Whilst the various intrinsic foot muscles, including the flexor digitorum brevis and interosseous muscles, contribute to arch support during gait (Mann and Inman, 1964) the abductor hallucis receives considerable attention. This is because EMG studies have shown that abductor hallucis contracts to support the medial longitudinal arch and control pronation during static stance (Headlee et al, 2008). Interestingly, navicular drop will increase when the abductor hallucis is fatigued. Therefore, it has been suggested that strengthening and thus improving the endurance of these intrinsic foot muscles in athletes may reduce over-pronation, and the subsequent pathologies. Sounds logical, doesn’t it?

WHAT EXERCISES BEST STRENGTHEN THESE INTRINSIC MUSCLES?

A recent EMG study evaluated the muscle activation of abductor hallucis during two exercises used commonly in clinical practice; Short Foot and Toe Curl Exercises, shown in the videos below if you are not familiar with them (Jung et al, 2011).

The study participants randomly performed the two exercises in seated and single-leg stance positions. The authors then assessed the EMG muscle activity of abductor hallucis (%MVC) and the medial longitudinal arch angle under all 4 test conditions.

The authors found that the short foot exercise in single leg stance produced the best results with 73.2%MVC and a reduction in the medial longitudinal arch angle (or raise in navicular height).  This is compared to 17.5%MVC for Toe Curls in single-leg stance. Therefore, the authors recommend the short foot exercise performed in single-leg stance to elicit maximum abductor hallucis muscle activity. Unfortunately, EMG muscle activity in the other intrinsic foot musculature was not measured and cannot be commented on.

THE EXERCISES IN QUESTION

Short Foot Exercise


Toe Curl Exercise


TAKE HOME MESSAGES AND CLINICAL IMPLICATIONS

  • Abductor Hallucis is important for preventing excessive navicular drop and subsequent over-pronation
  • The ‘Short Foot’ exercise elicits greater Abductor Hallucis EMG activity when compared to ‘Toe Curl’ exercises
  • The ‘Short Foot’ exercise produces a smaller medial longitudinal arch angle, which correlates to higher navicular position, when compared with the ‘Toe Curl’ exercise
  • Single leg stance elicits higher EMG activity than seated posture when performing short foot exercise.
  • The effect of strengthening these intrinsic foot muscles has solid theoretical applications however the efficacy of this for injury prevention or management has not been scientifically examined.

Do you utilise exercises to improve dynamic foot posture? What exercises do you love? Be sure to let me know in the comments or catch me on Facebook or Twitter

If you require any sports physiotherapy products be sure check out PhysioSupplies (AUS) or MedEx Supply (Worldwide)

REFERENCES

Headlee DL, Leonard JL, Hart JM, Ingersoll CD, & Hertel, J. (2008). Fatigue of the plantar intrinsic foot muscles increases navicular drop. Journal of Electromyography and Kinesiology, 18, 420-425.

Jung DY, Kim MH, Koh EK, Kwon OY, Cynn HS, Lee WH. (2011) 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;30-35

Mann R & Inman VT. (1964). Phasic activity of intrinsic muscles of the foot. Journal of Bone and Joint Surgery (Am), 46, 469-481.

Pohl MB, Hamill J & Davis IS. (2009). Biomechanical and anatomic factors associated with a history of plantar fasciitis in female runners. Clinical Journal of Sport Medicine, 19, 372-376.

Powers CM, Maffucci R & Hampton S. (1995). Rearfoot posture in subjects with patellofemoral pain. Journal of Orthopaedic and Sports Physical Therapy, 22(4), 155-160.

Ryan M, Grau S, Krauss I, Maiwald C, Taunton J & Horstmann T. (2009). Kinematic analysis of runners with Achilles mid-portion tendinopathy. Foot & Ankle International, 30, 1190-1195.

Comments

  1. Do some reading around barefoot running/walking. Much more functional way to strengthen intrinsic foot muscles. The evidence isnt amazing but the results speak for themselves

    • Hi Joe,

      Thanks for your comment. I would agree with your anecdotal evidence, particularly when performed on more challenging surfaces such as on sand. Challenging and some good results!

  2. You do realise that during gait, that the intrinsic muscles do not fire until the heel is starting to come off the ground, so I fail to see how strengthening them is going to help foot pronation as that is too late in the gait cycle to have an effect. Have a look at any muscle chart for the timing of teh firing of the muscles.

    You do realise that a weakness in the intrinsic muscles actually causes a high arched foot? Think about the ‘intrinsic minus’ foot that occurs in diabetic neuropathy and the high arched cavus foot that happens in Charcot-Marie-Tooth Disease as the intrinsic muscles area affected first.

    Doing the exercises and strengthening the muscles is probably a good idea, but they are not going to affect foot pronation/

    • Hi Peter,

      Thanks for the input, its great to have the perspective of a podiatrist.

      I agree that many muscle charts show the firing of intrinsic foot musculature late in the propulsion phase of the gait cycle. I have found some early EMG studies that show the firing of the intrinsic mass much earlier in the gait cycle i.e. as early as 15% in the patient with a pronated foot (Mann and Inman, 1964). This, it is proposed, is to attempt to increase the support of the longitudinal medial arch. Furthermore, the firing of the intrinsic muscles during the running cycle is presumably quite different, and they may therefore provide more dynamic support to the medial longnitudinal arch.

      The ‘intrinsic minus’ foot is also an interesting concept, thankyou for mentioning it. Some recent studies into the pathogenesis of the pes cavus foot in CMT patients suggest that the jury is still out regarding the role of intrinsic foot atrophy, and suggests that muscular imbalances may be more to blame. Check out this article from Brain: http://brain.oxfordjournals.org/content/129/7/E50.full

      At the end of the day, many clinicians prescribe these exercises in clinical practice, and I would like to think they are now aware of the muscle activation they are eliciting… not just prescribing by recipe. Do you use these exercises in your clinical practice? I would love to know your thoughts.

      Thanks again!

      Reference: Mann, R., & Inman, V. T. (1964). Phasic activity of intrinsic muscles of the foot. Journal of Bone and Joint Surgery (Am), 46, 469e481.

  3. I suffer from flat feet and have been under the impression that custom orthotics were the only solution.

    In the past year I have started foot exercises, such as trying to drag a small weight using my toes. Then, after discussion with a specialist, I have been also performing elastic exercises.

    Initially I was performing exercises pushing the toes away from the foot, like the last part of a calf raise. Then I was told that lateral strength was more important, pulling the foot towards the other leg and then the opposite direction.

    I find the short foot exercise hard to do, even though I can toe curl 5kg for 20 reps!

    Great stuff, keep up the good work.

    • Have those exercises helped your flat foot? Or do you still need orthotics?

      I recently acquired flat foot and have a lot of pain in my ankels when walking. it started out with plantar fasciattis and then Achilles tendinitis.

      I am doing PT right now and some of these exercises are what I am doing now. Just started last week.

  4. We use lots of running drills, walking A, pistons etc as well as lateral walking and grapevine, all with a mid foot strike for athletes…this combined with extrinsic muscle strength, tib post and soleus particularly.

  5. Dear admin,

    As a medical student, I am very much interested in this topic and what you mentioned about it earlier. as a matter of fact I am trying to write a presentation about the arch of the foot and will be very happy if you provide me with the names of any more references, the once that talk about internsic foot muscles EMG and strengthening to decrease the rear foot pronation.

    Thank you very much and I am sure your work is appreciated by many people.

    Tamkat

  6. My 10yo son had Kohlers Disorder when he was 6 and it took two years for the navicular bone to grow back to what we think is normal size. Since then he had has issue with balance and in and out of PT for it. But no one noticed, I just did that he pronates with out shoes, and pretty badly in his Hockey skates. He’s been skating for 3 years. I thought he would get stronger. He also complains of ankle pain sometimes in what we call the bad foot. Is the pronation a cause from the Kohlers . He does however pronate also on the right foot, not as bad.

  7. Hi I need some foot exercises for forefoot equinus and bunions, causing me lots of pain. Have been given orthotics but not helping that much. Only problem is that I have hypermobility and I am wondering if this is exacerbating my pain or preventing orthotics from working etc. have been to biomechanics, podiatrist surgery consultant, orthotics and podiatrist, none have been much help or perhaps don’t understand my pain levels which are unbearable sometimes! Any suggestions would be welcome.

    • Lorraine – I feel your pain, I have been diagnosed w/ hyper pronation and am on orthotic set 2 w/ no help. I’ve been told these 2 sets of orthoics are excelelnt and I should not be having any pain. I’ve tried it all, I now have Posterior Tendon tendonitis as well.

      I am not sure what else to do, but it’s difficult to walk or stand for long times. i am tiny bit overeight so I am trying to lose weight but I don’t have weakness in my feet. So not sure if strenghtening the rest of the foot will help.

  8. Reading the comments of Mr Peter Bird above I wonder if he has considered the role that the contralateral foot plays in the placement of ,and subsequent weight transference onto, the reference foot and of the role that the contralateral intrisics play in this .

  9. The short foot exercise is lovely. I’d been doing toe curls on the advice of a physical therapist and actually injured the joints below my pinkie toe. This other exercise causes no pain and I think may help my fasciitis. It’s very generous of you to make the video demonstration. Thanks!

  10. I would really appreciate any information anyone here can share with me. I have a right foot that I got a hairline stress fracture in between my second and third toe. I want to know how to help this issue my feet have. I was told that this bone is weak in both feet and so thats why I already have an ingrown corn on the bottom of my feet on this same bone. now a hairline fracture. How do I strengthen this bone in both of my feet ?

  11. I was recently told by a podiatrist that to stay pain-free I would have to use orthotics indefinitely, due to hypermobility of my joints. However, having come across the barefoot approach, I couldn’t understand how putting an orthotic into shoes that prevent proper functioning of the foot and gait could really be a solution to anyone’s problems. So I’ve started on a course of sensory motor exercise, focusing on single stance short foot work. The results after four weeks are a revelation. I can feel muscles engaging and working that I haven’t felt before and periods of time spent walking in my new ‘barefoot’ shoes have been free of symptoms I previously got when walking without arch supports. I now believe that it’s not just about ‘weak arches’; it’s a whole system of alignment and muscle use. Can’t believe my podiatrist sent me away with orthotics and no reference to the short foot exercise!

    • That is an awesome story and great result Catherine – thank you for the feedback. More anecdotal evidence for the value of intrinsic muscle strengthening.

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