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How often have you heard the claim that foot orthoses are "crutchs" and should not be used as they weaken muscles etc etc .... ... well...:
Quote:
Foot orthoses use does not affect muscle strength
Craig Payne & Gerard Zammit
Department of Podiatry, School of Human Biosciences, La Trobe University, Melbourne, Australia
Foot orthoses are widely used in clinical practice to treat pathologies associated with what is assumed to be excessive pronation of the rearfoot. However it is not uncommon to come across unsupported statements in the lay press or from alternative health practitioners that foot orthotics or foot supports should not be used as they will, for example “act as a crutch” or “weaken the muscles that support the arch”. As there is no data on the effects of foot orthotics use on muscle strength, the aim of this project was to determine toe plantarflexion strength in subjects prior to the use of foot orthoses and again after 4 weeks of use.
Subjects were recruited from a teaching clinic who were issued with foot orthoses for symptoms that were assumed to be due to excessive pronation of the foot. The force required to plantarflex the toes of the left foot was measured using a specially designed platform. Subjects stood on a raised platform which was at a hinged part at the level of the lesser metatarsophalangeal joints, but not at the first metatarsophalangeal joint. The hinged part was held level by a force gauge. Subjects were instructed to maximally plantarflex the toes against the platform, while the examiner held their hand over the metatarsal heads to prevent them being elevated. The force gauge measured the plantarflexor force in Newton’s. The subjects were asked to lean against the wall behind them, so as not to lean forward or bend the knee when plantarflexing the lesser toes. Previous work had shown this testing method to be reliable. This test was considered to measure the strength of the intrinsic muscles and the flexor digitorum longus muscles. The test was conducted 5 times, with the mean used for the analysis. The trial was repeated at the 4 week review of the foot orthoses. The Wilcoxon signed ranks text was used to analyse the difference.
Sixteen subjects were recruited (mean age: 44.5 (±16.3); 5 male; 11 female). The mean follow up was 4.5 (±0.8) weeks. The mean plantarflexion strength of the lesser toes at baseline was 37.3 (±14.9)N and at follow-up it was 40.2 (±16.3)N (p=0.23)
This study has shown that there was no decrease in muscle strength after the use of foot orthoses for 4 weeks, giving no reason to be concerned with unsupported statements that foot orthoses can weaken muscles.
The results need to be interpreted in the context of the relatively short follow-up of 4.5 weeks and it may have been too soon to detect any weakness, however, the trend was for an increase in strength (but not statistically significant), perhaps suggesting that a longer follow up may not have shown any weakness developing.
__________________
Craig Payne
Department of Podiatry
La Trobe University
Melbourne, Australia http://www.latrobe.edu.au/podiatry
__________________________________________________ ___________________________________ God put me on this earth to accomplish a certain number of things - right now I am so far behind, I will never die.
The views expressed above are those of the author and not that of La Trobe University This is where I am, where are you?
Last edited by Admin : 5th March 2005 at 10:38 PM.
My reply is anecdotal and relates to what I have seen in myself after wearing orthotics for just over 20 years (since I was 22 y.o.). I have a flexible flatfoot and notice that each new pair of orthotics I get (and for that matter, each set of casts) has a noticeably "higher" arch. There is however no corresponding increase in the weight bearing, unsupported view of my foot. This could account for the inaccurate observation that my foot is "weak". A lay person with no understanding of biomechanics and intrinsic bone structure could incorrectly deduce that my flat, kind of floppy foot is weak as a result of the orthotics. I feel quite the opposite, that the orthotics hold my foot in a rectus postion allowing the muscles to accomodate to a corrected position. The bone structure sadly does not follow suit and my foot pronates still when unsupported.
How often have you heard the claim that foot orthoses are "crutchs" and should not be used as they weaken muscles etc etc .... ... well...:
Craig:
Nice study. It would be interesting also to test the plantarflexion strength of the 1st MPJ, instead of just the lesser MPJs. I have never thought that foot orthoses weaken the foot muscles, even though this is a common question that lay-people have of orthoses. I do believe that foot orthoses decrease the muscle activity in many muscles of the foot, but improves their efficiency so that they are not working as hard but are accomplishing more for the foot.
The medial arch supporting mechanism of the foot involves the extrinsic muscles, intrinsic muscles, plantar aponerosis and other plantar ligaments. If the muscles are weaker, then they will have a decreased ability to support the arch of the foot. However, I truly doubt that an orthosis will cause actual weakness of the foot as long as the patient is staying physically active while wearing the orthoses. In addition, I am sure that in many cases, if the orthoses allow the patient's pain to resolve so that they can become more physically active, the muscle strength may actually increase as a result of wearing foot orthoses.
__________________
Sincerely,
Kevin
**************************************************
Kevin A. Kirby, DPM
Adjunct Associate Professor
Department of Applied Biomechanics
California School of Podiatric Medicine at Samuel Merritt College
Its also reminds of all those claims re strengthening intrinsc muscles can be used to elevate arch and stop the foot pronating ... so you don't need foot orthoses ..... that claims gets my Homer doh! award:
The intrinsic muscles don't even start to fire until the heel is coming off the ground :p - don't matter how strong they are, its toooooooooo late :p .....doh!
__________________
Craig Payne
Department of Podiatry
La Trobe University
Melbourne, Australia http://www.latrobe.edu.au/podiatry
__________________________________________________ ___________________________________ God put me on this earth to accomplish a certain number of things - right now I am so far behind, I will never die.
The views expressed above are those of the author and not that of La Trobe University This is where I am, where are you?
Last edited by Admin : 6th March 2005 at 12:34 AM.
The intrinsic muscles don't even start to fire until the heel is coming off the ground :p - don't matter how strong they are, its toooooooooo late :p .....doh!
Craig:
Root et al show that the lumbricales are active from early midstance to mid-propulsion, the interosseous muscles are active from late midstance to nearly toe-off, the abductor hallucis muscle is active from late midstance to toe-off, the adductor hallucis is active from late midstance to toe-off, the flexor hallucis brevis is active from the middle of midstance to toe-off, the flexor digitorum brevis and transverse pedis muscles are active from heel-off to toe-off, and the quadratus plantae is active from forefoot loading to mid-propulsion (Root, M.L., W.P. Orien and J.H. Weed: Normal and Abnormal Function of the Foot. Clinical Biomechanics Corporation, Los Angeles, CA, 1977, pp. 224-252). Therefore, Root et al show that nearly all the plantar intrinsics are active before heel off, with some of them active before the middle of midstance.
Do you disagree with Root et al in their assessment of the muscle function of the plantar intrinsics? I would be interested in any research you have that the plantar intrinsics are only active after heel-off.
__________________
Sincerely,
Kevin
**************************************************
Kevin A. Kirby, DPM
Adjunct Associate Professor
Department of Applied Biomechanics
California School of Podiatric Medicine at Samuel Merritt College
Here's an interesting article on the arch supporting function of the plantar intrinsics that I came across. The authors stated, "The results support the idea that the intrinsic pedal musculature supports the medial longitudinal arch, in addition to the bone structure and ligaments."
Quote:
Intrinsic pedal musculature support of the medial longitudinal arch: an electromyography study.
J Foot Ankle Surg 2003 Nov-Dec;42(6):327-33 (ISSN: 1067-2516)
Fiolkowski P; Brunt D; Bishop M; Woo R; Horodyski M
Gemini Research Consulting, Gainsville, FL 32606, USA. pfiolkowski@yahoo.com.
Much of the work describing support of the medial longitudinal arch has focused on the plantar fascia and the extrinsic muscles. There is little research concerning the function of intrinsic muscles in the maintenance of the medial longitudinal arch. Ten healthy volunteer adults served as subjects for this study, which was approved by the University Investigational Review Board. The height of the navicular tubercle above the floor was measured in both feet while subjects were seated with the foot in a subtalar neutral position and then when standing in a relaxed calcaneal stance. Subtalar neutral was found by palpating for talar congruency. Recordings of muscle activity from the abductor hallucis muscle were performed while the subjects maintained a maximal voluntary contraction in a supine position by plantarflexing their great toes. An injection of lidocaine (1% with epinephrine) was then administered by a Board-certified orthopedic surgeon in the region of the tibial nerve, posterior and inferior to the medial malleolus. Measurements were repeated and compared by using a paired t test. After the nerve block, the muscle activity was 26.8% of the control condition (P =.011). This corresponded with an increase in navicular drop of 3.8 mm. (P =.022). The observation that navicular drop increased when the activity of the intrinsic muscles decreased indicates that the intrinsic pedal muscles play an important role in support of the medial longitudinal arch.
__________________
Sincerely,
Kevin
**************************************************
Kevin A. Kirby, DPM
Adjunct Associate Professor
Department of Applied Biomechanics
California School of Podiatric Medicine at Samuel Merritt College
Do you disagree with Root et al in their assessment of the muscle function of the plantar intrinsics? I would be interested in any research you have that the plantar intrinsics are only active after heel-off.
I said:
Quote:
until the heel is coming off the ground
- I did not mean the heel "off" the ground - I meant late midstance - I was not meaning heel off -- to use Howard D's terminology, I meant the time when the heel starts to unweight - thats different to heel off. I agree totally with waht Root et al said with the timing ---- we are saying the same thing.
As the timing of muscle firing is mid to late midstance, then having those muscles strengthened to stop a foot pronating is too late - hence the doh! award to those that claim it.
Quote:
Intrinsic pedal musculature support of the medial longitudinal arch: an electromyography study. J Foot Ankle Surg 2003 Nov-Dec;42(6):327-33 (ISSN: 1067-2516)
I read that when it came out - they tested the EMG of the plantar intrinsic muscles and made all their claims about what they do when the subjects were standing!!! - that equates to midstance in the gait cycle, when the instrinsics don't even fire until after then in gait!
__________________
Craig Payne
Department of Podiatry
La Trobe University
Melbourne, Australia http://www.latrobe.edu.au/podiatry
__________________________________________________ ___________________________________ God put me on this earth to accomplish a certain number of things - right now I am so far behind, I will never die.
The views expressed above are those of the author and not that of La Trobe University This is where I am, where are you?
I said:- I did not mean the heel "off" the ground - I meant late midstance - I was not meaning heel off -- to use Howard D's terminology, I meant the time when the heel starts to unweight - thats different to heel off. I agree totally with waht Root et al said with the timing ---- we are saying the same thing.
Craig:
Glad to hear that we are saying the same thing regarding the temporal patterns of plantar intrinsic muscle activity.
However, I will respectfully disagree with you that strengthening of the plantar intrinsics don't have the potential to limit subtalar joint (STJ) pronation. The plantar intrinsics probably have little effect on STJ pronatoin in the first half of stance phase but will probably have a significant effect during late midstance at reducing STJ pronation and reducing flattening of the medial longitudinal arch. Most of the plantar intrinsics are active in late midstance. Late midstance is the time when these muscles are needed most to stiffen the medial longitudinal arch against the increasing magnitudes of ground reaction force that occur during this phase of walking gait.
I would be very surprised if muscular activation of the plantar intrinsics during the late midstance phase of gait doesn't help create a forefoot plantarflexion moment and a STJ supination moment which would tend to resist medial arch collapse and STJ pronation.
__________________
Sincerely,
Kevin
**************************************************
Kevin A. Kirby, DPM
Adjunct Associate Professor
Department of Applied Biomechanics
California School of Podiatric Medicine at Samuel Merritt College
As the timing of muscle firing is mid to late midstance, then having those muscles strengthened to stop a foot pronating is too late - hence the doh! award to those that claim it.
Craig:
A few more thoughts on this topic. The plantar intrinsics are mostly firing when the forefoot is receiving more ground reaction force (GRF) and when the plantar heel is receiving less GRF (by the way, I don't mind the term "unweighting of the heel" but the term "heel coming off the ground" is very misleading and I don't think should be used).
If one were to model these forces along with the vertical compression force from the tibia on the talus along with the tensile force in the Achilles tendon, it would be obvious that the time during gait when there was the greatest forefoot dorsiflexion moments (i.e. arch flattening moments) would be the period from middle of midstance to heel lift (i.e. late midstance).
With this fact in mind, then it makes complete sense that the plantar intrinsics are firing when they are needed most, when the forefoot dorsiflexion moments are increasing with a tendency to flatten the medial longitudinal arch (MLA) in late midstance. If the foot is trying to resupinate in late midstance or prevent further pronation in late midstance, then it may very much need the contributions from the plantar intrinsics to prevent pronation or accelerate supination in late midstance. Now, these muscles are not very strong or big, but they definitely are not firing "too late" to limit subtalar pronation and MLA collapse in late midstance.
Think of an example of a foot without intrinsic muscles such as the "intrinsic minus foot". It is theoretically possible that these feet may develop Charcot arthropathy in the midfoot possibly as a consequence of these plantar intrinsics not providing good forefoot plantarflexion moment during late midstance, that would tend to decrease the dorsal interosseous compression forces across the midfoot during late midstance.
Therefore, I'm fighting here for those little guys: the plantar intrinsics.
__________________
Sincerely,
Kevin
**************************************************
Kevin A. Kirby, DPM
Adjunct Associate Professor
Department of Applied Biomechanics
California School of Podiatric Medicine at Samuel Merritt College
Think of an example of a foot without intrinsic muscles such as the "intrinsic minus foot".
In those with diabetes, most "intrinsic minus feet" develop into a cavus foot due to the clawing of the toes from lack of plantarflexion on proximal phalanx!!!, so a weakness of the "arch muscles" does not appear to be a cause of a pronated foot.
__________________
Craig Payne
Department of Podiatry
La Trobe University
Melbourne, Australia http://www.latrobe.edu.au/podiatry
__________________________________________________ ___________________________________ God put me on this earth to accomplish a certain number of things - right now I am so far behind, I will never die.
The views expressed above are those of the author and not that of La Trobe University This is where I am, where are you?
In those with diabetes, most "intrinsic minus feet" develop into a cavus foot due to the clawing of the toes from lack of plantarflexion on proximal phalanx!!!, so a weakness of the "arch muscles" does not appear to be a cause of a pronated foot.
Craig:
Here's some interesting research in that regard. I tend to agree with these researchers that a decrease in plantar intrinsic muscles in the intrisinsic minus foot may lead to postural instability. I still think it could lead to Charcot arthropathy.
By the way, I thought the appearance of the cavus foot in the "intrinsic minus foot" was not actually due to a raising of the osseous structures of the longitudinal arches but rather due to the lack of soft tissue in the plantar arch, thus giving it the appearance of a cavus deformity.
Quote:
Intrinsic muscle atrophy and toe deformity in the diabetic neuropathic foot: a magnetic resonance imaging study.
Diabetes Care 2002 Aug;25(8):1444-50 (ISSN: 0149-5992)
Bus SA; Yang QX; Wang JH; Smith MB; Wunderlich R; Cavanagh PR
Center for Locomotion Studies, Penn State University, University Park, Pennsylvania, USA.
OBJECTIVE: The objectives of this study were to compare intrinsic foot muscle cross-sectional area (CSA) in patients with diabetic polyneuropathy and nondiabetic control subjects and to examine the association between intrinsic muscle CSA and clawing/hammering of the toes in neuropathic feet. RESEARCH DESIGN AND METHODS: High-resolution T2-weighted fast spin-echo images and parametric T2 multiple spin-echo images were acquired using multiple spin-echo magnetic resonance imaging (MRI) of frontal plane sections of the metatarsal region of the foot in a sample of eight individuals with diabetic polyneuropathy and eight age- and sex-matched nonneuropathic nondiabetic control subjects. The configuration of joints of the second toe was obtained using a three-dimensional contact digitizer. RESULTS: Remarkable atrophy was found in all the intrinsic muscles of neuropathic subjects as compared with nondiabetic control subjects. Quantitative T2 analysis showed a 73% decrease in muscle tissue CSA distally in the neuropathic subjects. Muscle comprised only 8.3 +/- 2.9% (means +/- SD) of total foot CSA compared with 30.8 +/- 3.9% in control subjects. No significant differences were found between the groups in the metatarso-phalangeal and proximal and distal interphalangeal joint angles of the second ray. Moreover, clawing/hammering of the toes was found in only two of eight neuropathic subjects. CONCLUSIONS: Although sensory neuropathy is often emphasized in considerations of diabetic foot pathology, our results show that the consequences of motor neuropathy in the feet are profound in people with diabetes. This has implications for foot function and may play a significant role in postural instability. However, intrinsic muscle atrophy does not necessarily appear to imply toe deformity.
__________________
Sincerely,
Kevin
**************************************************
Kevin A. Kirby, DPM
Adjunct Associate Professor
Department of Applied Biomechanics
California School of Podiatric Medicine at Samuel Merritt College
Hi I am currently doing some post grad research ( UTS) on the foot, posture and Pilates exercise .I am interested in the research : do foot orthoses weaken arch muscle , and would like to read the whole paper. Could you tell me where I could access it? and any other related research.
One of my interests is the MLA and the intrinsic foot muscles both as postural "stance muscles" as well as assisting in propulsion during gait. I am curious about the discussion on intrinsic foot muscles as I successfully teach exercises that improves strength, flexibility and endurance for the whole body (including feet), would n't it be good to teach exercises for the feet to improve 'late mid stance' MLA control?
Sincerely
Penny
I am interested in the research : do foot orthoses weaken arch muscle , and would like to read the whole paper. Could you tell me where I could access it?
Sorry, we have not yet got to publishing this yet ... its on the ever expanding "to do" pile.
__________________
Craig Payne
Department of Podiatry
La Trobe University
Melbourne, Australia http://www.latrobe.edu.au/podiatry
__________________________________________________ ___________________________________ God put me on this earth to accomplish a certain number of things - right now I am so far behind, I will never die.
The views expressed above are those of the author and not that of La Trobe University This is where I am, where are you?
Do foot orthoses weaken "arch" muscles?
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