Do you know where your rocker is?

At 1st pass, some articles may seem like a sleeper, but there can be some great clinical pearls to be had. I recently ran across one of these. It was a presentation from the  42nd annual American Academy of Orthotists and Prosthetists meeting in Orlando, March 2016 entitled “ Shifting Position of Shoe Heel Rocker Affects Ankle Mechanics During Gait”. The title caught my eye.

They looked at ankle kinematics while keeping the toe portion of rocker constant at 63% of foot length, angled at 25 degrees and shifting the base of a rockered shoe from 1cm behind the medial malleolus, directly under it and 1cm anterior to it. Knee and hip kinematics did not differ significantly, however ankle range of motion did.

The more forward the ankle rocker, the less plantarflexion but more ankle dorsiflexion at midstance. So, the question begs, why do we care? Lets explore that further…

  • Think about the “average” heel rocker in a shoe. It largely has to do with the length of the heel and heel flare (base) of the shoe. The further back this is (ie; the more “flare”) the more plantar flexion at heel strike and less ankle dorsiflexion (and thus ankle rocker, as described HERE) you will see. Since loss of ankle dorsiflexion (ie: rocker) usually means a loss of hip extension (since these 2 things should be relatively equal during gait (see here), and that combination can be responsible for a whole host of problems that we talk about here on the blog all the time. Picking a shoe with a heel rocker based further forward (having less of a flare) would stand to promote more ankle dorsiflexion.
  • Having a shoe with a greater amount of “drop” from heel to toe (ie: ramp delta) is going to have the same effect. It will move the calcaneus forward with respect to the heel of the shoe and effectively move the rocker posteriorly.
  • Lastly, look a the shape of the outsole of the shoe. The toe drop is usually clear to see, but does it have a heel rocker (see the picture above)?

These are  a few examples of what to look for in a clients shoe when examining theirs or making a recommendation, depending on whether you are trying to improve or decrease ankle rocker. We can’t think of why you would want to decrease ankle rocker, but with conditions like rigid hallux limitus, where the person has limited or no dorsiflexion of the great toe, you may want to employ a rockered sole shoe. We would recommend one with the rocker set more forward.

This is apparently a growing thing, INTERVAL walking. Oy. We are not particular fans at this point, nothing exciting or earth shattering at this point (other than the concerns we hi light below) but we will look into it more.
What you need to see, and be aware of, is that this is what happens when you wear a shoe that has too soft a rear foot. At heel strike, instead of progressing forward into the mid and forefoot, the rear foot of the shoe deforms and forces you into more HEEL rocker, sustained heel rocker. If you stay in heel rocker too long, you won’t progress forward into ANKLE rocker (ankle dorsiflexion). This often causes knee hyperextension. If you have a good trained eye, you will see both of these things, prolonged heel rocker and never any ankle rocker/ankle dorsiflexion. IT is like the ankle in this video is frozen at 90 degrees the entire time, train your eye to see this absense of ankle rocker. This will cause premature heel rise and premature posterior compartment contraction which can cause premature forefoot loading. This is what happens when the heel of the shoe is too soft. A perfect example of “more cushion” is not always better. IT can be a liability as well. Remember the angry revolution over the MBT shoe and its mushy rear foot?. Same principle, same risks and concerns. Welcome to round two of the same old problems ????? Maybe. you decide. To be clear, this is a comment on the shoes being used, the technique is , well, perhaps interesting. That is all we are willing to comment on at this point until we look into it more. Look at the heel and ankle mechanics during the slow mo clips.
Sorry Ben Greenfield. We are not impressed, as of yet. We like your podcast Ben, you are doing us all a great service, but this one is promoting some potential problems that people need to know about.
Start with our “Shuffle Walk”. Google search it under the Gait Guys. That is a good start.

– Dr. Allen

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Gait Cycle Basics: Part 3

As Promised: The Rockers…

According to Perry, progression of gait over the supporting foot depends on 3 functional rockers

heel rocker: the heel is the fulcrum as the foot rolls into plantar flexion. The pretibial muscles eccentrically contract to decelerate the foot drop and pull the tibia forward

 

ankle rocker: the ankle is the fulcrum and the tibia rolls forward due to forward momentum. The soleus eccentrically contracts to decelerate the forward progression of the tibia over the talus. Ankle and forefoot rocker can be compromised by imbalances in strength and length of the gastroc/soleus group and anterior compartment muscles.

 

forefoot rocker: tibial progression continues and the gastroc/soleus groups contract to decelerate the rate of forward limb movement. This, along with forward momentum, passive tension in the posterior compartment muscles, active contraction of the posterior compartment and windlass effect of the plantar fascia results in heel lift.

Now see if you can pick out the rockers in today’s video.

The Gait Guys… We are everywhere!!