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Monday, December 5, 2011

Kinesiological Approach To Bike Fit: Cleat Position

Before I talk about the different cleat positions, it's important to understand the basic kinesiology of the body related to the cleat.  The position of the cleat can have a major effect on the ankle and knee three ways:
  1. It can affect the available range of motion.
  2. It can change the posture or alignment of these joints relative to each other.
  3. It can affect the amount of stabilization or balance required to maintain safe posture.
With that in mind, bike fit systems should begin with assessments which look for problems with flexibility, standing/ cycling posture and balance.  Afterwards, recommendations or training sessions should be performed to improve on any of the results that fell below average.  Top priority in training session should always be given to the corrective exercises which can fix the body.  No matter how perfectly the bike is set, the rider can still develop an overuse injury if the body is not aligned and trained to move efficiently.  Once improvements are made, adjustments on the bike can also be made to take advantage of the rider's new potential.

KINESIOLOGY 101: ANKLE
Since the ankle can be directly affected by the cleat, I put together a list that shows the different movements of the ankle:
  • Dorsiflexion:  Pointing the foot up.  Eversion occurs with dorsiflexion.
  • Plantarflexion: Pointing the foot down.  Inversion occurs with plantarflexion.
  • Pronation (eversion):  Foot tilts so that little toe lifts off the ground.
  • Supination (inversion): Foot tilts so that big toe lifts off the ground.
While the list and picture above shows each movement individually, the ankle doesn't simply move straight up and down or in and out.  A combination of these movements occur simultaneously.  As the ankle moves into dorsiflexion, it's normal for the foot to evert.  In plantarflexion, it's normal for the foot to invert.

KINESIOLOGY 101: KNEE
If you're sitting on a chair, you might be thinking what about foot rotation???  Well, the foot actually doesn't rotate.  Rather, the entire lower leg rotates (tibial rotation) and it only does this when the knee is bent.  When the knee is fully extended and locked, the hip rotates the upper and lower leg.  This is how the foot can appear to rotate internally or externally.  A good way to remember this is to repeat "bent, knee, locked, hip."  Better yet... try it out!

Because cycling is in a seated position and the cleat can be adjusted to affect rotation inside the pedal, it's also worth mentioning the actions of the knee.  The movements italicized are the ones most greatly affected by the cleat.  I listed the muscles which are responsible for either internal rotation or external rotation.  Notice how the muscles that perform internal and external rotation are all part of the hamstrings group.
  • Flexion
  • Extension
  • Internal Rotation: Semimembranosus, semitendinosus
  • External Rotation: Biceps femoris
Lastly, there are two types of stress on the knee which is extremely important to understand.
  • Valgus stress:  Forces that move the knee towards the midline.
  • Varus stress:  Forces that move the knee away from the midline.
vaLgus = L shape,
VARus = Knees move "var" away
Cheesy.. but it helped me remember what these terms mean!
Valgus and varus stress are forces that try to make the knee move laterally or side-to-side...  These forces are bad for the knee.  In a balanced musculature, the muscles can prevent these movements from affecting the position of the knee.  If the muscles fail to provide enough stabilization, the knee must rely more on the ligaments which protect it from forward, backward, varus and valgus stress.  The ligaments which offer protection from these forces respectively are the PCL, ACL, LCL and MCL ligaments.  Don't tear any of these!

CLEAT POSITION OPTIONS:
When making any adjustments to the cleat position, there are four types of adjustments which can be made.
  1. Fore/ Aft:  Cleat moves towards the toes or towards the heel.  Fore is any position in front of the spindle line.  Aft is any position behind the spindle line.  Most shoes or cleats will have lines to indicate the location of the spindle.
  2. Lateral/ Medial:  Cleat moves towards (medially) or away (laterally) from the bike midline.
  3. Rotation:  Cleat turns internally or externally.
  4. Tilt & Lift:  Through the use of shims, the cleat can be raised to correct leg length differences.  The cleat may also be tilted to reduce subtalar pronation or supination.
FORE/AFT
The effects of fore and aft cleat placement is a very popular topic of interest for researchers.  Surprisingly, what research has shown is that all three cleat positions are equally efficient.  When comparing oxygen cost over an hour at a high intensity, there were no differences between a forward, spindle or rear cleat position (Van Sickle and Hull 2007).  While the study didn't compare graded climbs and different postures, it's nice to know that when the rider cycles in a seated position on a relatively flat road, the aerobic system will work at the same amount with any cleat position.

The differences between cleat positions are clearer when available range of motion and balance are compared.
  • A forward cleat position is the only position that's clearly associated with injury.  When the cleat is placed forward, the ankle can move through a greater range of motion and contribute to movement.  Problems only occur when the rider drops the heel while approaching the bottom of the pedal stroke. By doing this, the achilles tendon will stretch excessively under the load created by the larger muscle groups of the upper leg/ hip. It's similar to ballistically stretching your muscles, except that instead of 10-15 repetitions, it's stretched thousands of times over the course of the ride. This injury is so common that it's now identified as a risk for developing achilles tendonitis. If you overhear any of your cycling buddies complain about "ankle" or achilles pain, be sure to let them know (FYI.. some people get offended when you critique form so be careful!).
  • If a rider's balance is poor, form will be compromised which can lead to injury.  This is more obvious when performing a one leg exercise.  In order to maintain balance, someone with poor balance will shift the knees, hip, torso and swing the arms.  If you could freeze time at any point while they try to recover balance, you'll see a body completely out of alignment. This also means that the joints are not aligned or absorbing forces evenly among the bony contact points, the cartilage and ligaments.  Instead of two menisci absorbing force, one of the menisci must do two times the work to compensate.  When the cleat is placed further forward, balance is more difficult to maintain simply because it's like standing only on the balls of your feet.  With the cleat further back, it is much easier to maintain balance.  This is the reason why I always recommend starting with an aft placement and working inch by inch (or millimeter by millimeter) to a forward position.  You'll know if your balance needs improvement because you'll experience a lot of soreness with the ankle, knee and hip stabilizing muscles- the tensor fascia latte and IT band are common places to experience soreness if balance needs improvement (this could also be caused by poor posture or pedal technique so check that too!).
Although highly related to seat height, trends show that track cyclists like the forward cleat position and time trialist like the rear cleat position.  Since track cyclists must use higher cadences, the forward position helps with producing smooth pedal strokes because the ankle has more room to dorsiflex and reduce hip flexion.  In contrast to this setup, it will be more difficult to pedal very fast and smooth with a backward cleat position, but it will be easier to apply more power from the larger muscle groups at the hips and upper leg- a reason why time trialist like this setup.

Remember that POWER = Force * Distance.  Increasing either force or distance will result in increased power.  When range of motion increases at the hip because the cleat was positioned in the back, more power can be produced because the joint will move through more degrees of motion (increased distance). Another way to increase power through improving distance is to work on flexibility.

LATERAL POSITION
Placing the pedal closer to the plane of the bicycle will improve the efficiency of your pedal stroke by reducing the forces that cause the bicycle to sway side to side.  The cleat should be set as close as possible to the bike without the feet hitting the crank arm.

ROTATION:
While many cleat manufacturers designed cleats to restrict rotation, research has found that giving the foot the freedom to rotate prevents overuse injuries such as IT band syndrome, patellofemoral syndrome, hamstring strains and calf strains.  Cleats should be set so that the foot has an equal amount of internal and external rotation from the forward position.

Here is a list of overuse injuries related to cleat rotation, saddle height/fore/aft and muscular imbalances:
  • Patellofemoral Syndrome:  
    • Excessive internal and external rotation.
    • Saddles set too low and/or far forward.
    • Muscular imbalances: Tight quadriceps & hip flexors and weak inner quadriceps & hamstrings.
  • IT band syndrome:
    • Excessive internal rotation.
    • A seat height that allows more than 150 degrees of knee extension.
    • Saddles set to far back may also cause IT band syndrome.
    • Muscular imbalances:  Weak gluteus medius and hip abductors.
  • Hamstring & Calf Strain:
    • Excessive internal rotation
    • Saddle set too high and back
    • Muscular imbalances:  Tight quadriceps and weak hamstrings. 
In a perfect world, everyone's feet would point straight ahead, but this isn't the case for most people.  Some people walk with their feet turned in or out which also changes the position of the knees.  If the cause of this isn't related to faulty bone development or permanent injury, the rider can train the feet to point forward.  The best way to correct this is through corrective and proprioceptive exercises.  Consciously trying to point the feet forward while keeping the knee in the right position is a good proprioceptive exercise to practice.

TILT & LIFT:
Before even considering a shim, it is important to determine whether or not the rider actually has everted ("pronated") or inverted ("underpronated") feet.  The first place to look is the arch.  Although not as accurate as a mat loaded with pressure sensors, moistening the bottom of a foot and stepping on paper can paint a rough picture of the arch.  After determining the rider's arch, don't assume that the ankle will be pronated just because the rider has flat feet.  Check the ankle for eversion, inversion or neutral alignment (this would have already been done with the posture assessment).

Remember that the platform of the cycling shoe is rigid and any tilting will affect the entire foot.  This means that shims will affect the position of the ankle the most, but do nothing for the arch.  So even if the ankle is aligned properly, the rider may still experience foot pain because it was never addressed.  If an arch support is needed, the proper orthotic must be used.  Another option is to tape the foot for support.  Many times, correcting the arch will also correct the ankle, so double check to see if the shim is still needed. I recommend starting at the foot (orthotics/ tape) and then moving to the ankle (shims).

Another word of caution about using shims to tilt the cleat and "correct" a pronated or supinated ankle.  As mentioned in "Kinesiology 101: Ankle", eversion accompanies dorsiflexion and inversion accompanies plantarflexion.  If a shim is used to evert the ankle, the knee may move out of alignment when the ankle is dorsiflexed.  In a similar situation, if a shim is placed to invert the ankle, it may invert too much during plantarflexion.  Too much inversion or eversion will compromise the position of the knee and put it at risk for injury.

Before deciding on the steepness of the shim, assess the rider's ankling throughout the pedal stroke.  See how much dorsiflexion and plantar flexion the rider uses on and off the saddle.  After setting the shim, reassess the rider's cycling technique to make sure the knee is aligned.

With regards to leg length discrepancies, shims are very effective.  This can make a dramatic difference in the ride because the shorter leg will never need to "reach" from the hip whenever the leg approaches full extension.  If a shim is not available, lowering the saddle is another effective solution.  Although I haven't tried it, I think it would be possible to make a flat shim from extra garage supplies lying around in the garage.

GO BACK TO MORE ON CYCLING

REFERENCES:
  1. Cosca, David, and Franco Navazio. "Common Problems in Endurance Athletes." Family Doctor. N.p., n.d. Web. 5 Dec. 2011. <familydoctor.org>.
  2. Floyd, R. T.. Manual of structural kinesiology. 17th ed. Boston: McGraw-Hill Higher Education, 2009.
  3. Holmes J.C., Pruitt A.L., Whalen N.J. Lower Extremity overuse in bicycling. Clinical Sports Medicine 1994;13:
  4. Schwellnus, MP, and EW Derman. "Common injuries in cycling: Prevention, diagnosis and management." Department of Human Biology 47.7 (2005): 14-19. Print.
  5. Timothy, Noakes, Schwellnus Martin, and Zyl Elize van. "A Review of the Etiology, Biomechanics, Diagnosis, and Management of Patellofemoral Pain in Cyclists." International Sport Medicine Journal 2.1 (2001): 1-36. Print.