Saturday, January 2, 2010

The Shim

Last year I had a Retül bike fit done at Gear West in Long Lake, Minnesota. It did wonders for my cycling last year.

At the time of the fit, my left knee was hardly traveling at all. By traveling, I mean that the knee was basically pumping up and down in a straight vertical line. But the right knee was a different story.

My right leg is shorter. We're not talking inches here, just enough to throw a person off and lead to some mechanic issues. Long story short, we added a shim underneath my right shoe cleat and right away the difference could be felt.

I rode with this single cleat shim for all of last season and it seemed fine. But this fall I started to have some pain in my right knee and some pain in the right hip. When I got on the windtrainer, I noticed the knee seemed to be traveling again and my hip seemed to be stretching. So, I went back in this last week and we added in a thicker shim.

The results were immediate. After three rides my pains have all but subsided. My right leg feels as strong as my left. It's all about mechanics. And sometimes all it takes is a little time to figure it out and something as simple as a piece of plastic that costs less than $1.

So let's dig into mechanics and injuries a bit. Cycling creates a tremendous demand on the lower extremities since they are responsible for producing a majority of the energy imparted to the bike. The high reactive forces created between the foot and the pedal produce loads that often adversely affect the joints and muscles of the legs and feet, leading to overuse injuries.

The incidence of lower extremity injury in cycling is high. One study of over 500 recreational cyclists reported 85 percent of the cyclists experienced one or more overuse injuries, 36 percent of which required medical treatment.

The main causes of overuse injuries in cyclists include a poorly fitting bicycle, musculoskeletal imbalances and training errors. Cycling is very repetitive. During one hour of cycling, a rider may average up to 5,000 pedal revolutions. The smallest amount of malalignment, whether it is anatomic or equipment-related, can lead to dysfunction, impaired performance and injury. In order to evaluate and treat a cycling athlete properly, the clinician needs a basic understanding of bicycle fitting, the proper selection of cycling shoes and foot orthoses (if indicated), and how anatomic factors and training errors contribute to these overuse injuries.

More often than not, iliotibial band syndrome is the result of over-training, a tight iliotibial band, varus alignment of the lower extremity, internal tibial torsion, overpronation or incorrect seat height. It is often accompanied by trochanteric bursitis and is characterized by pain and point tenderness over the greater trochanter. Iliotibial band syndrome can also produce symptoms at the knee joint or its insertion site on the tibia. Management of this condition consists of iliotibial band stretching, ice massage, nonsteroidal antiinflammatory drugs, orthoses and cleat and/or saddle adjustment.

Patella femoral pain, chondromalacia and infrapatella tendinitis are common problems in cyclists. Patella femoral pain is often referred to as biker’s knee and is associated with patella malalignment, increased Q angle, valgus foot and leg alignment, overpronation, a saddle that is too low or forward, poor cleat adjustment or alignment. Treatment includes correcting the mechanical factors related to the bicycle; improving foot alignment with foot orthoses or medial wedging between the shoe and cleat; and ensuring proper stretching of the vastus medialis.

Patella tendinitis presents with pain at the proximal or distal pole of the patella that increases with the extension of the knee, especially against resistance. The mechanical factors usually associated with patella tendinitis are incorrect seat height and improper saddle fitting. This condition can also result from valgus leg alignment, internal tibial torsion and overpronation while pedaling.

In addition to correcting the mechanical and foot/leg alignment factors, cyclists should decrease the intensity of rides and the resistance they are pedaling against by using lower gears and higher cadence until decreased symptoms permit a return to increased training.

Achilles tendinitis and plantar fasciitis are overuse injuries that can be caused by training errors or riding with the seat height too low. Biomechanical conditions contributing to these injuries include overpronation and a leg length discrepancy. Plantar fasciitis may also be caused by old or worn out biking shoes. The shank or rigid sole of the biking shoe becomes more pliable, causing excessive flex in the shoe and strain on the plantar fascia.

Achilles tendinitis is marked by pain in the Achilles tendon and occasionally the insertion. Patients have increased pain when toeing off or standing on their toes and pedaling. Plantar fasciitis usually presents with pain at the plantar fascia insertion of the medial calcaneus.

Treatment and management of these conditions consist of therapeutic exercise including stretching, ice massage and NSAIDs. Both conditions benefit from the use of foot orthoses and night splints. In the case of a leg length discrepancy, one should first correct any existing overpronation, proceed to fit the bike to the long leg and then address the short leg with orthoses or shim between the shoe and cleat. The thickness of the shim should be less than the measured discrepancy. The cyclist can aid recovery by decreasing riding time and intensity. Riding at a higher cadence with low resistance may also help.

Hope that helps if anyone is experiencing any bike related pain. I highly recommend a proper bike fitting, such as the Retül bike fit.

1 comment: said...

Thanks for this! My right leg is shorter as well and I'm hoping the shim will help!