Monthly Archives: July 2011

Proprio-what? a deeper look at balance and stability

Yesterday’s post got lots of comments; I’d like to post a bit more here to help folks understand this concept a bit deeper. Why does this idea about balance matter at all to runners? Midstance is basically single leg standing balance. However there is a difference between “reactive balance” and “proprioceptive control.”

Let’s define a few terms here:

Strength – relates to the cross-sectional area of a given tissue. This is related to the muscle’s ability to generate force. Bigger muscle, bigger force. Simple.

Proprioception: there are 3 primary things we use for balance.

  1. Vestibular  (inner ear) – If you are standing still, inner fluid is still. If you turn your head suddenly, the inner ear fluid swirls and this information goes to your brain to help determine acceleration and change in position.
  2. Somatosensory – You “feel” the ground. You have sensory receptors in your skin which allow you to feel something – light and deep pressure, vibration, heat, cold, etc. This sensation goes a long way to improve your tactile feedback to help you remain stable.
  3. Vision – We use our eyes to orient our head and trunk and let us know which way is “up”.

Note- you do have other reflexes that play a role here, but these are the primary ones that have the greatest effect.

If these 3 systems “agree” then you are using your body as best you can to achieve control in stance. So let’s look at examples of how these can change. If you are on a merry go round, your eyes see you are spinning, your somatosensory feels the body turning, and your vestibular system says you are spinning. Everything is fine. If you stop, your eyes and somatosensory system say you have stopped, but your inner ear fluid is still swirling – signals don’t agree….. and you become dizzy.

So why is it harder to close your eyes in single leg balance? Most folks are visual dominant. They rely highly on their eyes to find their position in space. The problem with this is that it’s “slow.” You need to see information, process it in the visual part of your brain, then send a signal to the part of your brain that control motion (motor cortex) to make a correction. Somatosensory information is very very fast. There is a direct relay between the sensory and motor reflexes both inside and outside the brain – resulting in fast rapid “micro-corrections” of position. Let’s use an example.

If you look at skiers, surfers, skateboarders, white water paddlers – they all have something in common – they need to make positional corrections VERY quickly – faster than they can see visually and adjust. They get good feedback about the position of their body from their hard ski edge (transferred up through a very stiff plastic boot), or the rail of the surf board (transferred through their bare feet). Each and every time they practice their sport they are refining their position sense by “feeling” where the body is. They consistently train and improve their somatosensory system.

Research shows that the somatosensory system is highly trainable. Its best done frequently in small doses. Instead of trying to balance on one leg for 10 min each night, its better to do it 20x’s a day for 30 seconds. Yes, you CAN improve your balance….by practicing.  Not your “I’m-rocking-back-and-forth-like-a-weeble-wobble” re-active balance, but your “proactive balance.” Proactive balance means “I know what to do to keep my body stable – I can micro-correct to improve my stability.” Think about spreading your toes out wide to maximize the width of your foot. Try to push your big toe down – not curling, just down as you keep it straight. This will improve your muscles firing inside your foot. I’ll make a deal with you – if you work on your single leg balance every day, you’ll find not only will you be able to stand with eyes closed, but also be able to begin to rotate left and right with your eyes closed. The goal is to reduce your dominance on vision and improve your use and perception of “feel.” It works!

OK – so let’s now look at this with respect to running. I’m going somewhere with this I promise – I’m building a case for you. There is a ton of research that supports the idea that firm surfaces offer better “feel” to the individual and thus better balance control. Soft surfaces mute the feedback to the person and result in poor stability in stance. The goal is to maximize your level of active stability control that your body can produce.

If I am in the clinic working with a patient, I always work them in barefoot, and will use all kinds of rocker/wobble/rolling boards to do this. All of these are FIRM and HARD surfaces. Even though the foot is moving, the contact between the ground and the foot is solid. The person gets good feel for what is happening. I am not a proponent of foam pads to work on balance. Why? Foam pads let you cheat and roll off to the outside of the foot. They don’t mandate that you activate the big toe. They don’t train “pro-active control.”

Let’s take this idea and now apply is to footwear and the entire rationale for you reading this post. What is traditional footwear? – It’s got an elevated heel, a wider lever arm than your foot, and a big marshmellow stuck underneath. This marshmallow allows your weight to shift to the outside of the foot. The heel-higher-than-the-forefoot provides a “rocker” in front of the shoe that you can simply roll off of. It lets you “cheat” by conforming to your foot. A lot of runners have gotten used to this.  Their feet have become weaker as the shoe does more of the work.

When we look at minimal footwear or barefoot running, this foam pad is gone completely or reduced significantly.  Suddenly, you can’t cheat. You have to actively use the muscles inside the foot to stabilize. The absence or reduced cushioning in the shoe allows you to get better “feel”  - why do so many proponents of barefoot and minimalist running claim that they feel “free” or like they’ve “been released”…….? It’s simple – your foot gets more information from the surface you are on when you don’t have a big piece of compressible foam in the between. More information  = better muscle activation.

I see a hand up in the audience.

Q: So I’ve been running for years and I still can’t stabilize with my eyes closed. What gives?

A: closing eyes might be slightly overkill, but you know what? – Almost every standardized assessment for balance testing has an eyes-closed component to assess just what we mentioned above (the 3 things that impact proprioception). So if you have good balance with eyes closed, I know that you are good in this regard and not going to ask you to add this into your training program. It allows the examiner to differentiate how well you use different skills that affect balance. If the eyes closed part is the issue, and this is connected to faulty foot and ankle mechanics during running, it give me more information as to what your limiters are as a runner.

Q:  So I’ve been running for years, and I still can’t stand on one leg – even with my eyes open. What gives?

A:  There is no research to show that your poor balance will result in injury, but there is research to show that those with a number of lower extremity injuries do have poor balance. Further, I’ll be happy to say that those with poor single leg balance almost always have some very interesting finding in our lab – they usually have altered forces around the ankles which results in abnormal stresses to the lower leg and foot. Improving your single leg balance is a way work on prevention. I’d much rather you not get hurt and keep enjoying your runs, than not. Maybe you are one of the lucky ones who has run for years without injury – awesome! However, research shows that 82% of you runners will be hurt at some point. Both personally and professionally, I’d rather see you in the 18% of those who are not.

Less From Your Shoes, More From Your Feet

There has been a lot of interest lately in the transition to minimal footwear. Am I going to get hurt? How long does this transition take? Is this really better for me? Will my old shoes take it personally? Last year at this time, there were 6 minimal shoes on the market. This year there are 64. It’s a hot market, and folks are taking notice. While shoes are nice to talk about, let’s not forget that it’s the runner in the shoe that plays an active role in this equation. Shoes don’t run by themselves!

The recent article by Giuliani et. al. has raised some concerns.2 They highlight 2 cases of stress fractures in 2 different runners who transition to minimal footwear. The switch to minimal footwear can be dramatic. You get more “feel” since the squishy midsole is reduced or gone. You get a lower differential from your rear foot to your forefoot. These 2 factors change a) the position of the foot (Heel isn’t higher than the forefoot in full contact) and, b) the demand of the runner to stabilize the foot inside the shoe. In short, with less “stuff” in between you and the ground, you need your body to do a bit more, and get accommodate to a bit more as well.

Ever hear about the experiment with pre-K kids with the cookies? They put a kid in a room with cookie on the table and tell him/her that they can eat the cookie and they’ll get one cookie. BUT, if they don’t eat the cookie, they’ll get 2 cookies later (yea!). The tester walks out of the room and the kids go into panic mode when sitting in front of this stellar, delicious cookie. Most eat the single cookie for instant gratification.  They fail to see the merits of waiting patiently for a better result.

What in the world do cookies have to do with running shoes? A lot. The switch to minimal footwear can pay off in the long run, but you need ensure you’ve got what it takes for a successful transition. Obviously any time you make a change to your body, there is an adaptation period that needs to occur.  A lot of “experts” say that it will take 6 months to a year to fully transition to a minimal shoe. I’d like to think that this is overly cautious, and like to discuss why using the anatomy. We’ve found great success using the following 3 criteria for runners looking to run with “less”.

1. Mobility: Traditional running shoes have about a 10-13mm drop from the heel to the forefoot. This creates a “rocker” effect in the shoe. Take a look at a shoe from the side and you’ll see that the curve from the ball of the foot to the tip of the toe rises up. Since your foot is flat, you need to ensure that you have enough mobility (called dorsiflexion) of the big toe to allow the foot to roll over. Additionally, since the heel is higher in a traditional running shoe (think a small high heel) the heel chords are used to operating in a shortened position. You need to ensure that you’ve got the mobility needed to allow the heel chords to operate form their slightly lengthened position. So what to you test?

    • Ankle mobility (heel chords) – you need to be able to dorsiflex (cock the foot up towards the shin) about 25 degrees. Lack of mobility here means you’ll need to stretch the calf and Achilles.
    • Plantar facsia mobility – with the ankle in about 5 degrees of dorsiflexion, you need to have 30 degrees of dorsiflexion at the big toe. If you don’t have this, you can’t roll over the toes, and will be forced to spin off of the forefoot.

2. Single-leg Standing Balance: normal balance has been identified as standing on single leg for 30 seconds
with a still upper body and full foot contact. Since the midstance phase of running is essentially a single leg squat, it is essential that the runner is able to maintain the foot in contact. A triangle between the inside ball of the foot (1st MTP), end of the big toe (distal phalanx of the 1st ray), and outside ball of the foot (5th MTP) should be seen. When in single leg stance, the muscles in the foot need to be “pro-active” not “re-active”. If you are wobbling your foot back and forth when standing on one foot, you’ve got some room to improve your “proprioception” – or sense of where and what you’re your foot is doing during contact. The most successful way to improve single leg balance is to perform it frequently (15-20 times a day) for small doses (30 seconds each).

3. Ability to isolate the Flexor Hallucis Brevis: a key factor that distinguishes humans from primates is our medial longitudinal arch. This arch is actively stabilized by the flexor hallicus brevius (FHB). While standing, try to drive the big toe (1st MTP) into the ground (plantar flexion) while slightly elevating (dorsiflexing) the lesser toes. Make sure not to roll the ankle in or out. This test enables screening of muscles inside the foot that stabilize the arch. The FHB can be easily distinguished from the longus (FHL), as the FHL crosses another joint in your big toe (1st IP joint), resulting in your big toe curling. Spend some time getting to know your foot. Aim to drive the big toe down while lifting the little toes (without curling the big toe!), and lift the big toe up while driving the little toes down. It’s the best way to work on coordination of muscles that actively stabilize the foot in stance. It’s your foot – control it! If you can do this, it’s a sign that you can keep the rear foot stable on the forefoot when the body sees the greatest amount of pronation (which is just slightly after midstance and AFTER the heel is off of the ground by the way.)1 Midstance is when forces are highest throughout the body- about 2.5x’s your body weight. You need the internal strength to be able to respond to these forces to keep things in alignment.

When your foot “works” it can actively stabilize the transfer of forces through the foot. If you don’t pass these 3 tests, no worry  -get to work on improving your limitations. Pay a visit to your local PT if you need help with specific exercises and stretches to improve.  If you lack mobility, research shows it takes 10-12 weeks to gain significant improvements. So stretching for 2 weeks likely won’t be enough for most folks. Improving tissue length can take some time. If your limitations are in the balance aspect, you’ll be amazed how quickly this improves if you simply practice practice practice. Typically, about 2 weeks yields a significant improvement. Finally, strength gains take about 6-8 weeks to achieve. So if you really have trouble isolating your foot muscles, this could take a bit to get them stronger – but you can always improve the strength of your muscles!  Passing these 3 tests doesn’t mean that you should go run a marathon in your new minimal shoes on day 1, but we’ve seen that folks who master these have little to no problem making the transition. I’ll note here that these tests are not new in my mind. I’d like all runners  – even those who run in traditional shoes – to pass these tests. Its that when the “stuff” under your foot is less, these traits are that much more important.

So invest some time to improve your foot – Because it’s always better to have 2 cookies instead of one!  Shoes make a difference, but it’s the runner in the shoe that you’ve got control over.

References:

Dicharry, JM., Franz, JR., Della Croce, U., Wilder, RP., O’Riley, P., Kerrigan, DC. Differences in Static and Dynamic Measures in Evaluation of Talonavicular Mobility in Gait. J Orthop Sport Phys Ther 2009;39(8):628-634

Giuliani J, Masini B, Alitz C, Owens BD. Barefoot-simulating Footwear Associated With Metatarsal Stress Injury in 2 Runners. Orthopedics. 2011 Jul 7;34(7)