To Shim or Not to Shim?

As a coach and professional bike fitter I always here this question “should I shim”? The answer to that question depends on what are you trying to accomplish. I would have to say 90% of the time shimming is like putting a band-aid on the problem. Putting a shim in the shoe or on the cleat is a cheap way to say “hey you are messed up, but I don’t know how to fix you”.

The coach/bike fitter who puts a shim on his/her athlete is like the Joe gym rat. You can be Joe gym rat who each time goes to the gym puts on a weight belt before lifting weights. The belt becomes a crutch and Joe gym rat ends up with weaker core muscles, which promotes muscle imbalances, and weak stabilizers. The same thing happens when you put a shim in the shoe or on the cleat.

Think about this your athlete spends maybe 20% to 40% of their time on the bike. This leaves the athletes with the rest of their day spent in sandals or regular shoes. Do you believe that fixing their gait on the bike is going to fix their gait when they are off the bike? Think again this leaves the athlete with more muscle imbalances and probably some long term injuries. Say you shim your athlete, and he/she is doing really well on the bike. As you watch them walk off the bike they tend to have their knees turn out or turn in while they walk. Now you have a bigger problem. You need to fix their biomechanics not only on the bike, but off the bike as well. Your athlete becomes an accident waiting to happen.

I would consider these coaches, bike fitters, or doctors who shims as someone who treats the symptoms and not the problem. As a coach or bike fitter you need to be proactive and address both the on the bike issues and off the bike issues. You have probably seen this when you go to a doctor for an injury and he gives medicine for the pain, but never addresses the causes only the symptoms. Do you want to be the coach, bike fitter, or doctor that fixes things or the one that gives a band-aid?

There is a small percent of people who are born with flat or club feet. Those who were born with club feet or flat feet probably will need to use shims. Although, those that were not born with flat feet and currently experience flat feet symptoms this is due to a muscle imbalance. Flat feet are muscle imbalances of probable overactive peroneal complex, lateral gastrocnemius, bicep femoris, and TFL. The probable underactive muscles are the anterior tibialis, posterior tibialis, medial gastrocnemius, and glute medius. Performing an Optimal Corrective Program by foam rolling and static stretching overactive muscles and activating the underactive muscles with will help create an arch back in your athlete’s feet. If you are the athlete and say and don’t believe you can get an arch back in your feet. I ask you to try this; stand up tall, and then contract your glutes like you were going to squeeze a penny between your glutes (butt). If you look down your arch in your feet has reappeared. If your athlete has feet problems he/she probably will have other compensations in the knee, lumbo-pelvic hip complex, and the upper body.

Some great tips or cues to watch for while you athlete is in the gym:

  • Pretend his/her pelvis is a bucket of water. If the bucket tilts forward (anterior) or back (posterior) when performing an exercise water will pour out. Make sure he/she keeps their pelvic in neutral alignment.
  • Watch how your athlete walks and sits. This can help you determine probable overactive and underactive muscle imbalances
    To learn more about Optimal Corrective Program check out the Kinetic Loop Training System workshop on Muscles imbalances or our Optimal Bike Fitting Technique visit

To learn more about shimming or not to shim contact Michael Lovegren at Kinetic Loop Training System. We provide professional coaching, bike fitting, movement assessments, and educational classes. Visit to learn more.

By Mike Lovegren, M.S. Biomechanics 
Kinetic Loop Training Systems

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