Basic Principles of Bike Fitting: The Role of the Physical Therapist Matthew S. Briggs, PT, DPT, SCS, ATC

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Basic Principles of Bike Fitting:

The Role of the Physical Therapist

Matthew S. Briggs, PT, DPT, SCS, ATC

School of Health & Rehabilitation Sciences, The Ohio State University; OSU Sports Medicine

OSU Sports Medicine

Objectives



By the end of this presentation you should be

able to:



Describe important, basic bike anatomy



Describe common overuse injuries associated with

cycling



Understand basic principles of bike fitting to avoid

and/or treat cycling injuries & help your patients/clients ride safer

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Terms to Know



Saddle

(vs seat)



Reach

:



tip of saddle to center of handlebar



Bottom Bracket



Fore, Aft:



bottom bracket to saddle



Drop

:



saddle to handlebars



The Drops

:



One position for a

very long time!

 Cervical Extension  Lumbar Flexion



Injury

 Type of cycling  Duration  Intensity  Mechanics  History

Cycling Injuries



Sport of Repetition -

Overuse



80-90 rpm, 6 hour century ride



32,400 strokes PER LEG



Any minor misfit causes MAJOR problems

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Risk Factors:

Overuse Injury



Males



Miles/Week



Low # of Gears



Less Experience



Females



More training time/year vs. races



Less time stretching



2x risk for

neck/shoulder

(Wilber 1995)



Other considerations:



Poor lumbopelvic/ thoracic muscular endurance

Neck Injuries



Cervical spine pain



Headaches



Radiculopathy



Positioning / posture



Thoracic musculature weakness



Prolonged extension



Deep cervical muscle weakness



Helmet / glasses fit

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Knee Injuries



Anterior Knee Pain



Iliotibial Band Syndrome

 Poor tracking



Proximal stability weakness / lack of control



Overuse / training errors



Bike Fit

Saddle position

Shoe-pedal interplay

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Low Back Injuries



Lumbar pain



Increased Pelvic/lumbar extension



Iliopsoas inflexibility



Bike fit

Hand Injuries

Ulnar nerve

Median nerve

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Groin / Pelvis Injuries



Pudendal nerve palsy



Between sacrotuberous & sacrospinous ligaments, at

ischial tuberosity (stretched during pedaling)

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Weight Distribution

Cycling Biomechanics



(and efficiency) Alter with changes to:



Saddle Height



Saddle fore/aft position



Crank Arm Length



Foot Position



Cadence (revolutions / minute)

Examination: Interview: Cycling History

 Injury history  Events?:



recreational



criterium



century



tours



triathlons

 Shoe / Cleat / Pedal

 Orthotics

 Days / Week cycling

 Weekly Mileage

 Longest recent ride

 Typical speed

 Typical Cadence

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Examination: Interview: Cycling History



Type of bike



Type of use



Recreational



Triathlons



Tours



Cyclocross



Track



Mountain



Injury History



Time on Bike

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Physical Examination



Functional tests

:



e.g. SFMA, FMS, unilateral testing



Movement patterns



Mobility vs. stability



Leg length

“

Make the bike fit the body…

…don’t make the body fit the

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Bike Fit Basics:

Necessary Tools



Bike



Trainer



Riser blocks

(towels?)



Goniomete

r



Level

(phone app?)



Plumb line

(tape measure?)



Basic allen wrenches

28

Patient/client need to bring anything they would wear on the bike!

Bike Fit Basics:

Session



At least 1-2 hours long



.5-1 hour evaluation & history



1 hour dynamic bike fit on trainer



Our bodies change so an annual fit

should be part of training

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Bike Fit Basics:

Lateral View

 Saddle Fore/Aft

 Cervical Posture (check with cycling glasses/helmet on)

 Spine Posture (neutral spine)



Be sure the bike is level: set level across axels

 Shoulder Angle  Elbow Angle  Wrist Angle  Hip Angle  Knee Ext @ DBC ~30°  Ankling Angle

Bike Fit Basics:

Saddle Size

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Bike Fit Basics:

Saddle Position



Most important variable to get right



Includes height, setback, tilt, and width



Too low

= anterior knee pain



Too high

= pain behind knee



over stretching the hamstrings



Saddle sores & crotch irritation-rocking pelvis



Find balance maximizes patellar fulcrum, while

Bike Fit Basics:

Saddle Height



Put bike on trainer & pedal for five minutes



This helps you loosen up & find position



Quick & Dirty Check:



Unclip shoes & place heels on the pedals



Pedal slowly & watch knee at bottom of stroke

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Bike Fit Basics:

Saddle Set Back



Setback (fore/aft)-you in relation to the bottom

bracket



Determined by femur length



Knee center of rotation (COR) directly over pedal



Long legs should move seat back



Short legs should move seat forward



Correct position: COR over pedal & ischial tubes on

Why is Set-Back Important?



Put the power of your leg into the pedal at the

point in the crank circle when it does the most

good



To get maximum power the knee should be over

the pedal axel

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Bike Fit Basics:

Optimizing Set-Back

 Measure Saddle Fore/Aft:



plumb from knee to front of crank arm

 Seat too Forward:



increased patelofemoral load

 Seat too Aft:



patella becomes an ineffective fulcrum

Bike Fit Basics:

Saddle Tilt



Tilt- should “almost” always be level



If not something else is most likely wrong with the fit

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Bike Fit Basics:

Knee angle



Dead Bottom Center (DBC)



Knee Ext @ DBC

~30°



Changes with load and RPMs



Knee angle vary between

20-40°

Bike Fit Basics:

Torso Angle

 Most riders are 30-50°

 Euro racers 30-35° on brake hoods

 Old & Young riders 35-45°

 Fitness Enthusiasts 50°

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Bike Fit Basics:

Elbow/Wrist Position



Handshaking

position (wrist in neutral)



Adjust hoods to achieve this position

Should be level with top bar

Or adjust so the end of the bar points to the center of the seatstay

Bike Fit Basics:

Shoe/Cleats



Last aspect to consider



Unless they are new



Can eliminate hip, knee, and foot pain



Ball of foot over pedal axel

Symptom Likely Cause Try…

Scooting forward on seat Stem may be too long so you pull yourself forward as _{you ride; saddle nose may be tipped down too much} Install a shorter stem; level saddle Scooting back on seat

Stem may be too short so you feel cramped and push yourself back; saddle nose may be tipped back; saddle may be too far forward on the rails

Install a longer stem; level the seat and center it on the rails; move your seat back

Lower back hurts

Stem too low or too long; must strain back to reach bars; or seat may be too high, causing rocking when pedaling

Try raising the stem/handlebars; still hurts? try shorter stem; check and adjust seat height

Neck hurts Stem too low; must crane neck to see Raise the stem/bars

Hands hurt Stem too low; too much weight on hands; saddle may

be pointed down

Raise the stem/bars; level saddle

Front of knee hurts Seat too low and/or too far forward, straining knees Raise seat; may need to move seat further

back as well

Back of knee hurts Seat too high, over-extending leg Lower seat

Numb bum

Too much weight on the seat; may need to slide back a little on the seat. Try to sit such that you feel the weight on your sit bones rather than the front or center of your crotch

Lower handlebar position; check seat height as it may be too high; May need to try another brand of shorts and or seat; lose weight

Achilles tendon hurts

Pedaling too much on your toes; cleats too far forward on your shoes; feet may not be forward enough over the pedal

Keep the balls of your feet over the pedals when you’re pedaling; move cleats back.

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Final Thoughts

 Focus on injury prevention, movement dysfunction, & performance.

 Detailed medical history.

 Physical examination = mobility, stability, strength, etc.

 Biomechanical & biometric measurements.



Many different fit systems

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Thank you!



Matt Briggs PT, DPT, SCS, ATC