Title: Proper Bicycle Fit
1Proper Bicycle Fit
2Make 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
3Frame 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
4Zinns 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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8Zinns 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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10Zinns 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
11Zinns 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
12Zinns 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)
13Zinns 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
14Lemonds 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
15Dynamic vs. Static Fitting
- Static most utilized-easier and cheaper
- Dynamic-done while riding with use of reflective
markers and video analysis via 3D computer
16Saddle 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
17Saddle 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)
18Saddle 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
19 20Saddle 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
21Saddle 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
22Saddle 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
23Saddle 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
24Andy Pruitts Method
25Saddle 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)
26Saddle 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
27Saddle 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
28Saddle Setback cont.
- Zinn (2000)
- Plumb-line from tuberosity of knee in line with
spindle most proficient
- 2cm behind spindle encourages powerful, seated
climbing
29Saddle 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
30Saddle 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
31Handlebars-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
32Handlebars 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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34Leg 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
35Problems
- 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
36Works 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.