Footwear Science: Forefoot Arch Support
By Chief Editor Matt Klein
Some of the more common questions I get regarding footwear is whether an individual has enough arch support or how much stability a shoe has. While stability can come from a variety of places, the footwear industry generally describes stability by how much denser medial midsole material there is in the shoe. This is also called posting and most companies add stability in the heel and midfoot as that is the only place they seem to think stability is needed to control pronation. Pronation is generally described as the collapse of the medial longitudinal arch. The problem with that thinking is that the forefoot is an important component of the medial longitudinal arch.
There are three arches of the foot. There is a medial longitudinal arch,
transverse metatarsal arch (at the base of the metatarsals) and a lateral longitudinal arch. The medial longitudinal arch is what is most
commonly discussed with regards to pronation. While the midfoot is stabilized a great deal by the posterior tibialis
(more so than the intrinsic foot muscles), the forefoot is heavily influenced and stabilized by
fibularis longus, abductor hallucis and some of the intrinsic foot
muscles. If these muscles are weak,
there can be some issues as the biomechanics of the joints can be compromised. They are very important for stabilizing the
first metatarsal of the foot, which makes up the front half of the medial
longitudinal arch. The position of this
bone affects how the great toe functions, which in turn affects how the
forefoot rocker works.
During the gait cycle, the forefoot is
extremely important for the propulsive or toe-off phases of gait. As you transition from foot flat or the
midstance of gait to the forefoot, the first metatarsal needs to stay in a
plantarflexed position. That means that
front half needs to be able to stay down so the first MTP joint
(metatarsophalangeal joint) maintains contact with the ground. When the first metatarsal is plantarflexed,
the first MTP joint functions as it should, meaning that the first toe is able
to dorsiflex or extend at least 60 degrees for normal gait (+70 degrees from
some sources for running). The extension
of the great toe engages the plantar fascia and the Windlass Mechanism, which
acts to stabilize the entire foot. This
provides a stable base at both the forefoot and the rest of the foot for a
powerful toe-off during the terminal stance phase of gait (aka propulsive) over
the first MTP joint. This is also called
the forefoot rocker and is extremely important for maintaining forward moment
during gait as well as properly utilizing the calf muscles.
With instabilities in the forefoot, you may see a collapse of the
various arches. As pronation is a
triplanar motion, meaning that it is comprised of three motions including
dorsiflexion, abduction and eversion, the first metatarsal will dorsiflex or
raise up during a collapse. When the
first metatarsal dorsiflexes as the forefoot collapses, the first MTP joint becomes
limited due to pulling on the plantarfascia and other ligamentous
structures. Thus, the first toe is
limited in extension or dorsiflexion making it very difficult to roll off that
important joint, comprising the forefoot rocker. The human body will attempt to compensate
around this in many ways. Many people
will avoid the first MTP joint, instead rolling off the lateral metatarsal
joints. This places a great deal of stress
on the 4th and 5th MTP joints, which are prone to stress
fractures due to the smaller shape compared to the medial forefoot. The more common compensation is to evert the foot to roll off
the medial side of the first toe, placing excessive force on the medial side of
the first MTP joint. This causes some
problems. This compensation further promotes
collapse of the medial longitudinal arch as it changes to progression angle of
the foot, causing an increase in eversion. Rolling off the medial aspect of the first MTP joint also pushes the
first toe laterally, since the body will compensate for a lack of extension motion in another plane of motion, in this case adduction of the hallux (this
eventually leads to hallux valgus or bunions).
Finally, the calf muscles may not engage as well due to the lack of a
fully functional forefoot rocker, which may limit the maintenance of forward
moment and cause further compensations at the knee, hip, pelvis and even low
back.
Classic Pronation. Image from Craig Payne at Running Research Junkie
The first MTP and first metatarsal are stabilized by the fibularis
longus and abductor hallucis and should be strengthened to try to naturally
maintain and stabilize the normal function of these joints and structures. I will have a full post on this in the
future. From a footwear standpoint,
there is potential to assist these muscles and joints but most footwear
companies do not typically offer stability in the forefoot to help maintain
these important functions. As mentioned
earlier, most footwear companies will put posting or firmer midsole material at
the medial heel and midfoot. The idea is
to slow down pronation in those areas.
The problem is that you then leave the forefoot naked and without
assistance. As with other areas of the
foot you can stabilize the forefoot with medial posting, somewhat through
medial sole flare and to a degree through the proper execution of toe
spring.
The full length stability is one of the
few ways companies provide stability in the forefoot as seen in the Nike
Odyssey 2.
Forefoot posting is a rare feature in the running shoe industry
but there are a few shoes out there with this feature. The first shoes I saw with this were the
early Adidas Adizero Mana 1 (with a small heel and forefoot posts) as well as
the New Balance 801s in the early 2000s.
There were several Asics Japan racing shoes that had forefoot posting,
but those seem to have died out for the most part. The Newton Distance S had a forefoot post but
that shoe has been discontinued for some time.
The current shoes that have some kind of stability up front are mostly
those that posting that extends the full length of the shoe. This includes the Nike Odyssey, the Skechers
GOrun Forza, the Asics GT-3000 series, the New Balance Vongo, the Hoka Gaviota and the Hoka Arahi. Although I have not tested it myself, the
Adidas Tempo 9 is supposed to have forefoot only stability per Sam Winebaum at
RoadTrailRun. So this is a somewhat rare feature in the footwear industry. It may not be as rare with a certain shoe
coming out from Skechers that Sam Winebaum has a great video introduction of
HERE (coming early 2018). This shoe
executes forefoot stability very well and I am looking forward to discussing it
more in the future.
Medial
forefoot sole flare in the Saucony Ride 10
Another way to try to stabilize the forefoot is through forefoot
medial sole flare. I have discussed sole
flare previously HERE, but again the medial protrusion of the sole may serve to
slow the inward roll of the foot to some degree. This is a increasingly common feature of both (supposedly) stability and neutral shoes.
Saucony is one company that tends to do this frequently and this is
something you will typically see more in trainers. Racing shoes do not typically have this as
companies are trying to save as much weight as possible, so the soles will tend
to be narrower.
Toe Spring and extended stability into the
forefoot as seen with the Hoka Arahi.
Finally we have toe spring, which may be somewhat surprising. I have discussed toe spring previously as
well (HERE) and the point of it is to create an artificial forefoot
rocker. For those that have lost the
mobility of their first MTP joint, toe spring is great to help the foot roll
over the forefoot without excessive pressure up front. Hoka tends to do this very well, but I prefer
what they call the Late Stage Metarocker, which can be found in the Gaviota and
Arahi. This appears to save the toe spring
until you hit the metatarsal joints, may be more natural. I have had problems with many Hoka shoes due
to the extensive early toe spring, but the more natural placement late toward the
toes may engage the foot better the shoes that have earlier spring. This will create a certain degree of
stability by helping to maintain forward momentum of the foot rather than
allowing it to deviate into other planes of motion. This mimics the extension of the first toe
and to some degree the plantarflexion of the first ray that is normally needed for
forefoot stability. I tend to prefer the upward curve of the sole under the toes be less than at the outsole. Excessive toe spring can also create problems
if stiff toes are held in extension as that may place excessive strain on the
plantar fascia. So make sure the shoes
keep your foot in a more neutral position than what the spring does (this was a
problem in the early versions of the Adidas Boston Boost).
Terminal stance phase of gait.
So while forefoot stability is not commonly utilized in running shoes, this should shed some light not only on some shoes that may help with this but also some other ways you can stabilize this area. As I mentioned earlier, I will have a post on how to strengthen the muscles responsible for stabilizing the forefoot as that should be your priority. However, people may have biomechanical issues that may be assisted with some of these shoe attributes. I need to emphasize that posting, sole flare, toe spring all assist the foot. A shoe should not force the foot to do things as that may cause problems.
Hopefully as footwear companies began to expand out their understanding of stabilizing the foot, we will see more shoes with stability in the forefoot. I am glad to see less shoes with extreme stability as light stability is usually what most people need (with those with specific biomechanical or genetic based issues being an exception) in addition to extensive strength and mobility work. However, given the forefoot is a extremely important part of the foot for both stability and propulsion, a wider range of shoes with stability there can only help.
Thanks for reading.
*As always, my views are my own. My blog should not and does
not serve as a replacement for seeking professional medical care. I have
not evaluated you in person, am not aware of your injury history and personal
biomechanics, thus am not responsible for any injury that you may incur from
the performance of the exercises on this blog. This blog is meant for
educational purposes only. If you are currently injured or concerned
about an injury, please see your local physical therapist.
References
Neumann, D. (2012). Kinesiology of the Musculoskeletal
System: Foundations for Rehabilitation - Second Edition. St. Louis, MI:
Mosby Elsevier
Noakes, T. (2003). Lore of Running - Fourth Edition. Champaign,
Il: Human Kinetics
Perry, J. (1992). Gait Analysis: Normal and Pathological
Function. Thorafare, NJ: SLACK Incorporated.
Richards, C., Magin, P., Callister, R. (2009). Is your
prescription of distance running shoes evidence based? British Journal
of Sports Medicine: 43(3): 157-158. doi: 10.1136/bjsm.2009.058453
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