Monday, December 5, 2011

Kinesiological Approach To Bike Fit: Cleat Position

CLEAT POSITION:  There are four types of adjustments which can be made to a cleat.
  1. Fore/ Aft:  
    • FORE:  Positioning the cleat forward allows the ankle to move more freely, allowing for a smoother pedal stroke.  The trade-off is that this requires more ankle stability, calf strength and puts the rider at risk of developing quad dominance.
    • AFT:  This position limits ankle motion.  This provides added stability to the ankle, allowing the calves to rest, but makes the rider prone to bouncy pedal strokes.  When switching from a forward cleat position to a rearward position, a lower saddle position is needed to compensate for decreased plantarflexion.
  2. Lateral/ Medial:  The goal is to spread weight evenly across the foot side-to-side.
    • LATERAL:  Shifts weight towards the outside of the foot (small toe side).
    • MEDIAL:  Shifts more weight onto the medial side of the foot (big toe side).  Limits the maximum amount of external rotation available before the heel strikes the crank arm.
  3. Rotation:
    • EXTERNAL:  Since the drive side foot sits further away from center, this side typically needs more external rotation to increase glute activation.
    • INTERNAL:  Aside from causing the knee to strike the top tube, greater internal rotation tends to increase adductor and quadricep activation.
  4. Tilt/ Lift:  Lifts are used to correct leg length discrepancies.  Tilt shims are typically used for riders with ankle or foot instability.
BIKE FIT NEVER ENDS
Now that you know how cleat position can impact your performance, don't set it and forget it!  If you worked hard to gain ankle mobility and strength, don't forget to put your newly acquired abilities to use by adjusting your cleat position to harness your new powers!

TEST YOUR ANKLE MOBILITY
The amount of freedom you have in your cleat position is determined largely by your ankle mobility.  I listed each motion and the normal range of motion for each movement.

  • Dorsiflexion (25 degrees):  Point the foot up.  Eversion naturally occurs with dorsiflexion.
  • Plantarflexion (45 degrees): Point the foot down.  Inversion naturally occurs with plantarflexion.
  • Pronation (Eversion 20 degrees):  Foot tilts so that the small toe lifts off the ground.
  • Supination (Inversion 45 degrees): Foot tilts so that big toe lifts off the ground.
KNEE MOBILITY
  • Flexion (120 degrees):  If you have tight quads, the ankles must be more flexible to compensate for this restriction.  If they're not, the pelvis will tilt side to side to compensate.
  • Extension (0 degrees):  Reaching negative numbers simply means that your knees hyperextend.
  • Internal Rotation:  Tight hamstrings, specifically the semimembranosus and semitendinosus will cause the foot the internally rotate.
  • External Rotation:  Tight hamstrings, specifically the biceps femoris will cause the foot to externally rotate.  
Additionally, there are two types of undesireable knee movements that can occur in your pedal stroke.
  • Valgus stress:  Forces that move the knee towards the midline.  Tight adductors.
  • Varus stress:  Forces that move the knee away from the midline.  Tight hip external rotators.
vaLgus = L shape,
VARus = Knees move "var" away
Cheesy.. but it helped me remember what these terms mean!
WORK ON MOBILITY
Remember that POWER = Force * Distance.  Working on mobility and flexibility increases the distance variable, which basically means MORE power for minimal work.  There's no better reason to spend more training time on stretching!

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. 
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.

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.