uw cycling symposium v3.ppt - · PDF fileMost Curved Fizik Arione Experimental High Curvature Selle Italia Flite ... Microsoft PowerPoint - uw cycling symposium v3.ppt [Compatibility

3/1/2009
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UW Musculoskeletal UW Musculoskeletal
Biomechanics Biomechanics
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Why Its Hard to Finda Good Saddle
Heidi Ploeg, Ph.D., Assistant Professor
Darryl Thelen, Ph.D., Associate Professor
Departments of Mechanical Engineering and Biomedical Engineering
University of Wisconsin-Madison
Acknowledgements:
Jackson Potter, Julie Sauer, Christine Weisshaar, UW-Madison
Matt Prest, Damon RinardTrek Bicycle Corp.
LabLab
UW Musculoskeletal Biomechanics Research
MusculoskeletalImaging
Motion Analysis
Modeling &Simulation
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Research Questions
During seated cycling:
1. What is the orientation and motion of the pelvis?
2. What is the pressure distribution on the saddle?
Terminology Literature Methods Results SummaryUW Musculoskeletal UW Musculoskeletal
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Terminology Hip and Pelvisposterior
anterior
anterior
posterior
front
back
front
back
Terminology Literature Methods Results Summary
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Terminology Directional Terms
Anterior Posterior
AnteriorToward front of body
PosteriorToward back of body posterior anterior
P
A
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Pelvic Tilt
Bressel and Larson, Med Sci Sports Exerc 2003 20 female cyclists
Standard, cutout & noseless saddles
Anterior pelvic tilt of 16 on the tops
Increases to 29 in the drops
Slightly greater tilt on cutout and noselesssaddles
Only static measures

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Pelvic and Hip Motion
Neptune and Hull, J Biomech 1995
Intra-cortical bone pins
Hip translated forward and down (~10 mm) during down stroke
Hip moved much less than greater trochanter marker
Movement facilitates power transfer from upper to lower body
Only one subject a 45 yr old competitive cycist
LabLabTerminology Literature Methods Results Summary
Pressure Measurement
Lowe et al., Med Sci Sports Exerc 2004 32 males, 1 female (police officers)
70 rpm and 150 W on 4 different saddle designs
Recommended noseless saddles for >2x lower average pressures in perineum
No increase in shoe or handlebar pressure
Upright, recreational-style cycling
Did not vary power, cadence or gender
LabLabTerminology Literature Methods Results Summary
MRI Study
Bressel et al., J Biomech 2006 Males (5)
Custom apparatus loaded perineum with a bicycle saddle
Measured pressure distributions
Urethra and cavernosa artery are compressed
Locations of maximum compression and maximum pressure align
pubic symphysis
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Factors that Can Influence Pelvic Motion and Saddle Pressure
Hand position Power output Bicycle setup Flexibility
malesfemales Pelvic anthropometry
Saddle geometry
Saddle stiffness
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Experiment and ProtocolExperienced cyclists: 12 Males
14 Females
Bike fit to subjects 170 mm cranks
145 mm drop handlebars
Protocol: Powers: 100, 150, 200 W
Hand positions: tops & drops
Cadence: 90 rpm
Measures: 3D full body kinematics
Saddle pressure
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Pelvic Motion Measurement
Pelvic motion tracked using 3 markers placed on posterior anatomical landmarks:
Right and left PSIS Sacral marker

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Dynamic Pressure Measurement90 sensors,100 Hz, 18.75x18.75 mm2
over the whole saddle, Bicycle Pressure mat (Novel, Inc.)
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Flexibility MeasurementsLumbar Flexibility Hamstring Flexibility
Gajdosik et al. Physical Therapy 1992
Tousignant et al., Disability and Rehabilitation 2005
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Anthropometry Measurements
Measured distance between impressions on floral foam
Ischial Tuberosity Width Hip Joint Center
Determined spherical hip joint center of rotation in pelvis
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Results:Anthropometry and Flexibility
Males Females
Hip joint center width (mm)
198.8 (12.5) 192.9 (9.4)
Ischial tuberositywidth (mm)
116.5 (16.0) 134.9 (9.2)*
Hamstring flexibility (deg)
31.7 (11.8) 27.2 (6.5)
Lumbar flexibility (mm)
21.2 (1.0) 20.6 (1.0)
*p

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Pelvic Motion and Dynamic Saddle Pressure During Cycling
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Research Questions
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Hip Translations andPelvic Rotations
Axial rotation
Forward tilt
Lateral roll
Fore-Aft
Vertical
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Hip Vertical Translation
Neptune and Hull 1995
Greater Trochanter
Hip
Hip translates downward during last 75% of the down-stroke
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Hip Fore-Aft Translation
Hip translates forward during last 75% of the down-stroke Similar pattern in males & females and in tops & drops
Neptune and Hull 1995
Greater Trochanter
Hip
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Lateral Pelvic Roll
Roll ~2 toward side of down-stroke
Similar in males and females, tops and drops

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Axial Rotation
~3 inward rotation on side of down-stroke Slightly larger among females at the higher power outputs
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Forward Pelvic Tilt
Pelvic tilt oscillates twice with each pedal stroke
Peak forward tilt at top and bottom dead center
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Average Forward Pelvic Tilt
Females exhibited significantly greater forward tilt in drops
Note location of the ischial tuberosities
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Forward Pelvic Tilt: Males
Less
ForwardTilt
More lumbar flexibilty
Drops
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Research Questions
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Dynamic Saddle Pressure Center of Pressure moved fore and aft
-3 to +3 mm Peaked twice/cycle 0 and 175
kPa

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Posterior Pressure / Body Weight:Effect of Power and Hand Position
Dropped with increasing power
Dropped when hands were moved from the tops to the drops
dropstops

Documents

uw cycling symposium v3.ppt - · PDF fileMost Curved Fizik Arione Experimental High Curvature Selle Italia Flite ... Microsoft PowerPoint - uw cycling symposium v3.ppt [Compatibility