Proper Bicycle Fit

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Proper Bicycle Fit

• Shaun K. Riebl

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Make the bike fit you, not you fitting the bike

• Easy to adjust bike NOT your body
• Long legs/short torsoshort top tube and stem
• Short legs/long torsolong top tube and stem
• Mark Hodges OTC study with elite junior cyclists
  found an increase of 8-14 of average O2
  consumption for a given workload

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Frame Size Selection (Road) Lennard Zinn

• Stand-over height dependant on slope of top
  tube (TT)
  
• Stand over bicycle and lift until touches
  portion between legs (where saddle would be)
  holding the handle bar with one hand and the
  saddle with the other
• Wheels
• Be aware of different BB heights and slopes of
  TT
  
• Mountain bikes (Burke, 2002)
• same or slightly lower because higher BB
• TT 2-4 lower than road bike
• Space between legs and TT3-6

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Zinns Frame Size Selection cont.

• Size of bicycle measured from BB up seat tube to
  TT in three ways by manufacturers
  
• Center-center
• Center to top
• Center to top of seat tube
• Knee-handlebar clearance
• Handlebar reach and drop
• Not hitting elbows while pedaling
• Comfort
• Adjust stem
• Pedal overlap (aka toe overlap) make sure
  front tyre cannot be hit by foot while turning

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Zinns Frame Size Selection cont.-Break out the
tape measure and calculator

• Inseam book or broomstick in-between thighs,
  where saddle would be
  
• Mark top of stick or book on wall and measure
  from ground up
  
• Inseam Torso
• Sternal notch and pencil-measure from floor to
  mark on wall made by pencil
  
• Arm length 45 (degrees) abducted AC joint to
  ulnar notch _at_ wrist
  

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Zinns Frame Size Selection cont.-Break out the
tape measure and calculator

• Size of the Bike-Calculation time!
• Subtract 27.5 to 32cm (10.8-12.6) from inseam to
  provide seat-tube length (center to top)
  
• Sloping TT requires shorter seat-tube
• BB27cm (10.6) subtract extra height from
  seat-tube length
  
• Small riders subtract 27.5cm from inseam (if
  less than that, results in less than 1 2.5cm
  stand-over clearance)
  
• Large riders subtract 32cm from inseam

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Zinns Frame Size Selection cont.-Break out the
tape measure and calculator

• TT lengthtorso length (sort-of) center of seat
  tube to center of head tube
  
• Important can ride frame smaller to get
  correct TT length for riders with short torso and
  arms, just as long as bars can be raised

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Zinns Frame Size Selection cont.-Break out the
tape measure and calculator

• Subtract inseam from inseam torso measurement
• Add arm length to answer
• Multiply arm torso measurement by .47-.485
• Casual/recreational .47
• Aggressive/racer .485
• Stem length
• Arm torso by .9-.11 (dependant on riding style)

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Zinns Frame Size Selection cont.-Break out the
tape measure and calculator

• Crank arm length
• Handlebar width
• How measured center to center or outside to
  outside?
  
• Width of shoulders
• Want efficient, non-restricted breathing
• Arms in line with shoulders

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Lemonds Frame Size Selection (Pruitt, 2001)

• Use measurement discussed later (between thighs
  to floor) by .65
  
• Ex. 87cm X .65 56.5cm
• Frame size 56-57cm from center to top
• virtual seat-tube height for slopped
  seat-tubes
  
• Exceptions
• High handlebar use .7 as multiplier
• Long arms/torso
• As seat-tube lengthens, so does TT

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Dynamic vs. Static Fitting

• Static most utilized-easier and cheaper
• Dynamic-done while riding with use of reflective
  markers and video analysis via 3D computer

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Saddle Positioning-key variable and most important

• Height
• Too Low too much knee bend at top of pedal
  stroke leading to anterior knee pain
  
• Shear forces greater on post. Patella
• Too High post. Knee pain from reaching for
  pedals
  
• Excessively stretched hamstrings
• Power affected patella no longer good fulcrum
• Fore/Aft
• Tilt

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Saddle Height

• Can be icing on the cake with proper frame size
  selection
  
• Michael Despires used EMG measurements of leg
  musculature and found as saddle height increased,
  the activation of muscle fibers was initiated
  earlier in the pedal stroke thus being active
  for longer (Burke, 2002)

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Saddle Height

• Simplest formula-stationary trainer in cycling
  shoes
  
• 5 warm up to loosen muscles and get into
  personal riding position
  
• Unclip from pedal, place heels on pedals and
  pedal slowly
  
• Knee at full ext. at bottom of stroke (6 oclock
  position)
  
• Heels almost lose pedal contact

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Saddle Height cont.

• Lemond Method
• Bare footed in cycling shorts against wall with
  feet 6 apart
  
• Text book, broom stick, or old vinyl record
  between legs so flush with wall and level with
  floor
  
• Raise object into section between legs until
  contact equal to what saddle pressure would be
  during easy pedaling
  
• Measure distance from the object to the ground in
  cms
  
• BB axel to top of saddle.883 x measurement
• Ex. 87cm x .88376.8cm

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Saddle Height cont.

• Lemond cont.
• Remember only ball-park estimation
• Orthotics/insoles lengthen legs
• Thick clothes
• Mountain bikes exception is length of crank
  arms
  
• Longer crank arms causes saddle to be lowered
  equal in difference in length from road bike to
  ATB
  
• Ex. 170mm road cranks lower ATB saddle by 5mm

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Saddle Height cont.

• Zinns method (Zinn, 2000)
• Multiply inseam measurement from before by 1.09
• Measurement is length from center of pedal
  spindle in 6 oclock position to where ischial
  tuberosities (aka sit bones) contact saddle

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Saddle Height cont.

• John Howard Method (Burke, 2002)
• 30 degree () knee bend angle in saddle
• Goniometer-femur and tibia, vertex midpoint of
  femur
  
• Andy Pruitt Method (Pruitt, 2000) similar to
  John Howard
  
• Use of goniometergreater trochanter, lateral
  condyle, and lateral malleolus (25-30)
  
• Known to get efficient saddle heightpowerful and
  nominal strain on the knee
  
• Decreases anterior knee stress by decreasing
  patella compression

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Andy Pruitts Method
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Saddle Setback

• Andy Pruitt (2000) prevents injury and properly
  transfers power to pedals at most beneficial
  crank position
  
• Correct when knees center of rotation is
  directly over pedal axel (ball of foot) of
  horizontal forward crank arm (Pruitt, 2000)
  
• MA
• Andy Pruitts Method Femur length dependent, use
  of plumb line (string with washer or nut)
  

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Saddle Setback cont.

• Andy Pruitts Method cont.
• With bicycle on indoor trainer, spin 5
• Horizontal crank arms-right foot forward with
  heel parallel to floor
  
• Drop plumb line from front legs patella
• Should be at end of crank arm
• Adjust
• Repeat for left leg

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Saddle Setback cont.

• Andy Pruitts Method cont.
• Concerns
• Saddle height changed with fore/aft position
  possible
  
• If measure from tibial tuberosity (bump below
  patella) plumb line should intersect pedal axel
  for correct position

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Saddle Setback cont.

• Zinn (2000)
• Plumb-line from tuberosity of knee in line with
  spindle most proficient
  
• 2cm behind spindle encourages powerful, seated
  climbing
  

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Saddle Tilt

• Keep set level- No questions!
• Carpenters level
• Yardstick compared to windowsill
• Concerns
• Up forces on hands and arms causing numbness and
  fatigue
  
• Down
• compressed blood vessels, soft tissues, and
  nerves
  
• Reduced control because my weight on front wheel
  (center of pressure/center of gravity) offset as
  well
  

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Saddle Tilt

• Exceptions
• Persons with swayback (excessive lumbar lordosis
  and thoracic kyphosis Hamill and Knutzen, 2003)
  or pelvic tilt may require adjustments weight
  distributed on sit bones not soft tissues
• Time Trials

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Handlebars-personal preference

• ReachTT and stem length
• Determines the relative angle of torso to ground
• Established by riding type, goals, and bodys
  limitations (Pruitt, 2000)
  
• Dependent on following variables
• Experience
• Flexibility
• Hamstrings
• Lower back
• Shoulders
• Age
• Arm and torso lengths

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Handlebars cont.

• Height (Zinn, 2000)
• Two measurements
• 1) Vertical height from ground to top of saddle
• 2)Vertical height from ground to top of
  handlebars
  
• Aggressive/tall riders bars no greater than 10cm
  higher than saddle
  
• Recreational/smaller riders want less drop from
  saddle to handlebars
  
• Beginners less drop initially, but can alter
  after adaptations to riding occur
  
• Higher barsincreased weight on saddle/aero drag
• Stem can be flipped

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Leg Discrepancies

• USA Cycling Club Coach Manual (2004)
• Can lead to eventual injuries
• Hip tends to tilt to accommodate for length
  difference lower back pain
  
• Recommendation of using insoles in shorter leg

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Problems

• Knee injuries
• Too low saddle
• Bend too much at top of pedal stroke causing
  patella tendon distresses
  
• Seen with saddles too far forward as well
• Too high saddle stress on posterior tendons and
  ligaments

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Works Cited

• Burke, Edmund R., PhD. Serious Cycling. 2nd ed.
  Champaign, IL Human Kinetics, 2002
  
• Hamill, Joseph and Kathleen M. Knutzen.
  Biomechanical Basis of Human Movement. 2nd ed.
  Philadelphia, PA Lippincott Willams and Wilkins,
  2003.
• Pruitt, Andrew. L., Ed.D. Andy Pruitts Medical
  Guide for Cyclists. Chapel Hill, NC RBR, 2000.
  
• Zinn, Lenard. Zinn and the Art of Road Bicycle
  Maintenance. Boulder, CO VeloPress, 2000.
  
• 2004 USA Cycling Club Coach Manual. USA Cycling
  Coaching Staff. Colorado Springs, CO. 2004.