Introduction to cycling biomechanics

Introduction to
cycling biomechanics
and bikefitting
A 100% free course for passionated cyclists, trainers, coaches, bikefitters
that want to apply a scientific know-how on bike fittings and pedalling style
evaluation to enhance performance and comfort
Made with pride in Italy in 2017

Who we are
Bikeitalia.it (with 1million visit/month) is the most viewed cycling
website in Italy.
We talk about mechanics, biomechanics and bikefitting, training and
nutrition.
We spread our knowledge with courses and seminar. The RD team behind
each event is composed by high skilled technicians in bike biomechanics,
podiatry, human movement science, data analysis, physiotherapy,
nutrition, posturology.
Our goal is to create the new bike professionals generation

Speakers of this course
OMAR GATTI (1985): Cycling technician, specialized in
mechanics, biomechanics and bikefitting
GIULIANO MARTINIANI (1986): physiotherapist, bikefitting
consultant and postural re-education expert
PAOLO GAFFURINI (1981): PhD in Human Movement and
Sport Science, with specific know-how in human motion
capture and data science

Topics
● PART 1: CYCLING BIOMECHANICS
● PART 2: BIKEFITTING RULES
● PART 3: BIKE FIT PROCEDURE
● PART 4: PEDALLING DYNAMICS ANALYSIS

Part 1
CYCLING BIOMECHANICS
Performed by:
Giuliano Martiniani (Physiotherapist)

Cycling and muscles
.
Biomechanics and
professional bikefitting
Cycling is a complete sport, in which all
muscles work together to allow the
athletic movement.
The lower body generates power, the
upper body instead generates stability
and control.
The global work of muscles needs a
balance between the upper and lower
body.

Muscle function
Muscle tissue is composed of fibers that produce contraction.
Contraction exerts force on the bones through the tendons, it allows to support
and move the body.
The work done by a muscle can be static or dynamic.
.
Biomechanics and

Muscle function
Musculoskeletal system produces
movement and mantains posture
thanks to muscle activation.
Muscles work in groups rather than
individually and they will play
different roles depending on their
origin and insertion.
Muscle work can be conscious
(movement) or less conscious
(posture).
Biomechanics and

Posture and movement
Posture is defined as the tridimensional relative disposition of the parts of
the body.
Postural control is influenced by proprioception; the receptors of muscles,
tendons, joint capsules and the skin provide informations that generate a
body position sense.
Biomechanics and

Kinetic chain
Kinetic chain is a combination of
various body segments connected via
joints and moved through muscle
activation.
There are two types of movement:
● Open kinetic chain: the terminal
segment is free to move in space.
● Closed kinetic chain: the terminal
segment meets external
resistance.
.
Biomechanics and

Pedalling movement
Pedalling is a closed kinetic chain
movement, it is characterized by a
large muscle recruitment and
agonist/antagonist co-activation.
The controlled muscle activation
pattern improves joint stability and
generates less shearing force.
Biomechanics and

Contact points and joints
The contact points between body and
bicycle are feet, pelvis and hands.
The movement of ankle, knee and hip
joint allows to produce power, while
spine and upper limb joints provide
stability.
Biomechanics and

Cycling kinematics
Phase 1: (20°-145°) it is a
propulsive phase in which is
developed 65% of the total force,
lower limb extension.
Hip extension
Knee extension
Ankle plantarflexion
Biomechanics and

Hip extensors
Gluteus (one-joint)
Hamstring (two-joint): semitendinosus, semimembranosus, biceps femoris.
Biomechanics and

Knee extensors
Quadricieps:
vastus lateralis
vastus intermedius
vastus medialis
rectus femoris (two-joint).
Biomechanics and

Ankle plantarflexors
Gastrocnemius medialis
(two-joint)
Gastrocnemius lateralis
(two-joint)
Soleus
Biomechanics and

Cycling kinematics
Phase 2: (145°-215°) it is a
transition phase in which is
developed 12 % of the total
force, the body change action
from extension to flexion
through BDC
Biomechanics and

Cycling kinematics
Phase 3: (215°-325°) it is a pulling
phase in which is developed 17%
of the total force, lower limb
flexion.
Hip flexion
Knee flexion
Ankle dorsiflexion
Biomechanics and

Hip flexors
Iliopsoas, rectus femoris, sartorius etc.
Biomechanics and

Knee flexors
Semitendinosus, semimembranosus, biceps femoris, sartorius, gastrocnemius
etc.
Biomechanics and

Ankle dorsiflexors
Tibialis anterior, extensor hallucis longus, extensor digitorum longus etc.
Biomechanics and

Muscles activation
Enroll to our courses to go deep in this argument
Biomechanics and

Cycling kinematics
Phase 4: (325°-20°) it is a
transition phase in which is
developed 6% of the total force,
the body changes action from
flexion to extension through
TDC
Biomechanics and

Three dimensional movement
Biomechanics and
Movement involves all the visualization
plane, infact we can observe the
primary motion on the sagittal plane,
that is more noticeable, but also
secundary motion on the frontal plane
(medial/lateral displacement) and on
the transversal plane (rotations).

Spine and upper limb muscles
Spine, head and upper limb muscles provide stability and the horizontal
position of the eyes.
Biomechanics and

Spine and upper limb muscles
A static contraction of muscles provides joints structural protection:
Lumbo-pelvic stability: abdominals, quadratus lumborum, piriformis
etc.
Shoulder stability: trapezius, rhomboids, pectoralis major, latissimus
dorsi etc.
Neck and head stability: splenius, scalene, deep muscles etc.
Elbow and wrist stability: triceps brachii, radial/ulnar muscles etc.
Biomechanics and

Muscle length and flexibility
Each person is different, some
people are more or less “flexible”
than others.
Muscle length provide flexibility
and influences muscle strength,
physiological muscle length
provides the best performance
through the balance between
agonists and antagonists.
Biomechanics and

Part 2
BIKE FIT RULES
Performed by:
Omar Gatti (Bike fit Specialist)

Contact points
.
Cyclist and bicycle contact points are:
● Feet on pedals;
● Pelvis on saddle;
● Hands on handlebars;
The interaction between these points is
the bikefitting base.
Biomechanics and

Bikefitting procedure
.
During a bike fit, the step by step
procedure is:
● Pedals: fore/aft, lateral movement,
rotation;
● Saddle: high, fore/aft, inclination;
● Handlebar: width, elevation, distance
from saddle;
● Levers: high and position;
Biomechanics and

Anatomical points
.
In professional bikefitting there are some anatomical points to
follow, as they permit to measure joints ROM (range of movement)
● Metatarsal heads - Foot;
● Malleolus - Ankle;
● Femural Condyl - Knee;
● Greater trochanter - Hip;
● Acromion -Shoulder;
● Olecranus - Elbow;
● Styloid Process - Wrist
Biomechanics and

Repere points
Biomechanics and

How to apply markers for video analysis
.
Biomechanics and

Bike fit window / 1
.
Fit window includes a number of position that
are sustainable for the cyclist.
It’s not about measurment but it pay
attention on each joint angle.
The aren’t fixed angle but they change due
to athlete age, flexibility grade, training and
physical state.
Biomechanics and

Bike fit window / 2
.
Biomeccanica e
bike fit professionale

Sustainable position
.
The best position for a
cyclist is which he/she
can sustain without
having problems.
Finding it is a job that
requires a deep
knowledge of the cyclist,
his sport history, his life
and his body.
Biomechanics and

“Sustainable position” application
.
Optimal position Wrong position
Biomechanics and

How to approach professional bikefit
.
● To find the right bike fit
you have to know the
cyclist;
● No position will last
forever;
● Only one adjustment for
each session;
● Each adjustment needs
adaptation;
● The philosophy is always
pedal-saddle-handlebar
● Record each note
● Bikefit is not an healing
procedure;
● It’s very important
understand when to stop;
Biomechanics and

Parte 3
PROFESSIONAL BIKE FIT
Performed by:
Giuliano Martiniani
(Physiotherapist)
Omar Gatti
(Bike Fit Specialist)

Bikefitting gold rule
.
“Adapt bike to cyclist, don’t adapt cyclist to the bike”
Cycling is adaptable and bike is adjustable: always match cyclist needed
and target to the bike setup
Biomechanics and

Bike fit structure
.
A bikefitting procedure is made by:
● Preliminary interview;
● On the saddle evaluation;
● Video analysis;
● Postural and muscle check;
● Bike adjustment;
● Follow up;
Biomechanics and

Preliminary interview
.
Use preliminary interview to understand
cyclist’s problems, targets and needs:
● How old is he?
● How many hours he spent on the bike?
● Which type of stretching he does?
● Any muscular tension?
● Injuries or falls?
● How is he going with the last adjustment
adaptation?
Biomechanics and

.
These test give information
about joint ROM and muscular
length.
In the flexion test we evaluate
back kinetic chain and postural
situation of pelvis and spine.
In muscular tests we can
observe the length of iliopsoas,
hamstring and rectus femori.
Muscle evaluation
Biomechanics and

Postural analysis
Postural evaluation permits to see:
● Misallignment in shoulders;
● Misallignment in pelvis;
● Leg length and differences
● Varism/valgism of knee or foot;
Evaluation permits to understand if the problem is related to the bike or not
Biomechanics and

Foot-pedal interface
.
First of all check the foot position on the
pedal:
● Cleats check;
● Fore / Aft;
● Medial / Lateral;
● Rotation;
Biomechanics and

Cleats: float or not?
.
Float Cleats permit some free rotation to
the foot during a pedal complete turn.
Shimano Yellow 6° Blue 2°
Look/Keo Grey 4,5° Red 9°
Campagnolo Grey 3°
BBB Red and black
3°
Red 4,5°
Xpedo Red 6°
Powertap Red 6°
Speedplay 16°
Biomechanics and

How to choose the right cleats
Biomechanics and

Cleats sign
.
Before to start doing
anything, sign the cleat
position.
In this way is very easy to
come back in case of wrong
adjustment or the cyclist tells
about immediate pain.
Biomechanics and

Cleat fore-aft / 1
. On sagittal plane, pedal
spindle have to stay in
between 1° and 5° metatarsal
head.
This solution permit great
power output and better
pedal efficiency;
Biomechanics and

Cleat fore-aft / 2
.
Sign the position of both
metatarsal head on the shoe
to check the position of the
pedal spindle.
Check the result and make
the adjustment. In case,
record the adjustment on the
report;
Biomechanics and

Cleat position effects
.
Biomeccanica avanzata e
bike fit specialistico
Forward cleat position:
Plantarflexion
Stress point closer to
metatarsophalangeal joints
Backward cleat position:
lower ankle mobility
stretch of the posterior compartment
of the leg

Medial - Lateral /1
.
In the first phase (crank arm
parallel to the ground) the
knee have to allign with the
second finger of the foot.
This move the cyclist to the
natural position and reduce
lateral/medial movement of
the knee;
Biomechanics and

.
Cleat lateral position:
Internal displacement of the foot
Ankle and knee muscles compensation
Cleat medial position:
External displacement of the foot
Ankle and knee muscles compensation
Biomechanics and

Cleats rotation
.
Rotation allows foot and
tibia to move during the
pedal turn.
Each cyclist has his specific
rotation needs.
Check it with observation or
clinical test like femoral or
tibial rotation.
Biomechanics and

Cleats rotation vs Cleat float
.
Don’t make confusion with cleats float and rotation:
● Float is the movement of the cleat into the pedal
without loosing the connection
● Rotation is the orientation of the cleat to allow a
specific foot orientation (podologic name: Fick angle)
Biomechanics and

.
Cleat rotation:
A physiological rotation of the foot
and the knee happens during the
crank cycle.
Is important to allow some degrees
of freedom of the foot.
Biomechanics and

Crank arms length
.
Femur lenght
mm
Frank length
300 162
320 164,8
330 166,6
360 167,4
380 169,1
400 170
420 172,2
440 176
460 177,1
480 177,6
500 180
Cranck length is proportional to the
femur length
Biomechanics and

How to choose crank arms length
.
● Juniores: never go more than 170mm;
● Knee or quadriceps pain: don’t use crack lenght longer than which
indicates in table;
● Winter training: to increase agility, the cyclist can go with a lower cranck
arm;
● Test: it’s important to try every crank arm length during training to
permit cyclist adaptation;
Biomechanics and

Road cycling bike fit window
.
140°-150°
PMS 50°
PMI:110°
80°-90°
150°-165°
Biomechanics and

Saddle high
.
Saddle high is referred to the knee
angle at the BDC:
● The cyclist is on the saddle
● Crank arm is parallel to the seat
tube;
● Verify the knee angle
Bike fit window
140°-150°
Biomechanics and

TDC flexion
.
Always check the maximal knee
flexion to avoid problems or
knee pain.
Literature say the angle cannot
be less than 75° but pro cyclist
can go up to 68°.
Biomechanics and

Saddle height
.
Higher seat height:
Knee and ankle ROM increase
Greater work of hamstring muscles
Less lateral displacement of the knee
Lower seat height:
Greater flexion of the knee
Decrease of performance
Greater stress on the knee

Saddle fore-aft / 1
.
On sagittal plane, moving the saddle to
reduce o increase the saddle-handlebar
distance, affects the knee position to
the pedal spindle.
Knee over pedal spindle is a very
common system to verify the correct
saddle fore-aft;
Biomechanics and

Saddle fore-aft / 2
.
Knee in line with pedal spindle = Neutral
position = Compromise between power output
and force on the knee
Knee advanced from the pedal spindle =
aggressive position = maximise power output
Knee behind the pedal spindle = preservative
position = reduce power output and knee stress
Biomechanics and

Saddle fore-aft / 3
.
Check with Kinovea or with a plumb
line the position of the knee from
the pedal spindle.
Biomechanics and

Saddle fore/aft position
.
Forward saddle position:
Greater work of rectus femoris
Greater patello-femoral stress
Trunk and upper limb compensation
Backward saddle position:
Greater work of hamstring muscles
Less stress of the knee
Trunk and upper limb compensation

Handlebar high
.
Handlebar haigh have to be check
in dynamics.
Check the hip angle on the TDC
and BDC to understand if the
handlebar doesn’t affect spinal
column position and diaphragm
expansion
Don’t install more than 35mm
under the stem
Biomechanics and

TDC handlebar high
.
At knee maximal flexion, hip
and torso angle must be more
than 50°
(go under this angle can
compromise a correct
breathing)
Biomechanics and

BDC handlebar high
.
At the maximum knee
extension, angle between
torso and femur have to be less
than 110°
A bigger angle verticalize too
much the spinal column
Biomechanics and

Respiration factor
.
Always measure the angkle
between torso and femur at the
TDC, with cyclist in the most
aerodinamic position.
This angle has to be more than
42° to permit diaphragm
expansion (experienced
cyclists can go to 38°)
Biomechanics and

Saddle - handlebar distance
.
Saddle handlebar distance
influences the spinal column
curve.
A well fitted cyclist has a back that
design a good column profile.
The angle between homerus and
torso has to stay between 80°-90°
Biomechanics and

Aero position distance
.
This angle will naturally
reduce when cyclist goes
into an aero position
Biomechanics and

S-H distance [correct]
.
Biomechanics and

S-H distance [incorrect]
.
Biomechanics and

Brake levers high in road cycling
.
Brake levers influence the elbow
angle
Bike fit window:
150°-165°
Always check the cyclist neck: when
he puts his hands on brake levers, the
neck muscles must stay relaxed.
Muscles too tight are sign of too much
body weight on front wheel
Biomechanics and

Brake lever position in road cycling
. Frontally, brake levers must stay at
the same high.
Wrist must stay in line with the arm,
to avoid to much compression on
ulnar, medial and radial nerves that
innervate the hand.
Biomechanics and

Aerodynamics
.
Air create friction during the cyclist
movement.
This friction causes turbolence against the
cyclist, reducing his speed and requiring
more effort to sustain the pedalling
speed.
Cyclist aerodynamics is optimal to avoid
too much air friction
Biomechanics and

Air turbolence and friction
.
Air creates a hydrodynamic paradox,
called “Venturi effect”:
Air increases its pressure, despite
reducing its speed.
This situation produces turbolence and
friction.
The most affected parts are wheels and
cyclist neck.
Biomechanics and

Aerodynamics drag
. Cx = ½p * Cp * V2 * S
● p: air density
● V: square yclist speed
● S: frontal surface
● Cd: aerodynamics coefficient
Biomechanics and

Cyclist’s frontal size
.
Reducing the frontal size of the cyclist, dramatically reduces the air turbolence
When pedalling on brake levers, cyclist has a frontal size of 68 cm2. Pedalling
with hands on the drops and with a plane spinal column, frontal size decreases
to 45cm2.
35% of aerodynamic gain.
Biomechanics and

How to work on aerodynamics
.
● L’80% of aerodynamic gain is
reached decreasing the frontal
size, fitting the cyclist in a more
aggressive position.
● Other 20% can be gained
choosing aero components like
frame, wheels and similar.
Biomechanics and

Time trial position
.
Time trial (and triathlion)
position has its own
specification:
● Mor areodynamics
posture;
● Weight shift on front
wheel;
● Saddle higher than
road bike
● Compromise between
sustainable and aero
position;
Biomechanics and

Bike fit guide line
.
More performance needs must match
with some importance issues:
● Position has to be sustainable;
● Less aggressive position is better
than more aggressive but not
sustainable;
● Clip on bars position has to follow UCI
rules;
Biomechanics and

Time trial bike fit window
.
138°-143°
PMS 42°
PMI:102°
80°-90°
90°-100°
Biomechanics and

Saddle position
.
UCI estabilishes that distance
between bottom bracket axis and
saddle most foward point must be
5cm.
Biomechanics and

Saddle tilt
.
To reduce pressure on pelvic pavement
due to more aerodynamic position, saddle
can be tilt forward 1-3°
Biomechanics and

Clip on bar position
.
While cyclist is pedalling
with elbow on clip on bar
supports, the angle
between homerus and
forearm has to be 90°-100°.
A bigge angle avoid aerod
position but a lower angle
shifts dangerously the
cyclist weight on the front
wheel.
Biomechanics and

Road bike vs time trial
.
Biomechanics and

Part 4
DYNAMICS PEDALLING ANALYSIS
Performed by:
Paolo Gaffurini
(Human Movement and Sport Science PhD)

MOVEMENT ANALYSIS TOOLS
Movement analysis to study and measure human movement
● Angles between body segments
● Centre of mass position;
● Force distribution;
● Speed, acceleration and
trajectory;
Biomechanics and

New technique, but old necessity
Muybridge (1830-1904) was an English photographer important for his
pioneering work in photographic studies of motion
Biomechanics and

Biomechanics and

Biomechanics and
MOVEMENT
ANALYSIS
XYZ EMG
ANGULAR
MOVEMENT
FORCE

Study KINEMATIC DATA need measure of BODY MOVEMENT
NON OPTICAL vs OPTICAL
Biomechanics and
New Trend Gold Standard

INERTIAL SENSORS (Non optical Device)
Accelerometer, Gyroscope
Small, portable, cheap and robust = LARGE WIDESPREAD
Biomechanics and

DISPLACEMENT → SPEED → ACCELERATION
Problems about data precision and interpretation
with Inertial Sensor
HIGHEST speed movement,
more accurate MEASURE
SLOW speed movement,
worst precision MEASURE
Biomechanics and
Derivative, SMALL Errors
Integrals, BIG Errors

NO FITTED BIKE FITTED BIKE
Biomechanics and
EXAMPLE OPEN SOURCE AND FREE SOLUTION
ON YOUR SMARTPHONE

VIDEO SYSTEMS (Optical Device)
BIDIMENSIONAL vs TRIDIMENSIONAL
Biomechanics and
Hardware: Commercial
Software: Open Source
Medium Precision related to
good or poor video quality
Only 2D analysis
Hardware: Specific
Software: Closed
Very High Precision
3D analysis
Qualified personnel

2D VIDEO SYSTEMS (Optical Device)
OPEN SOURCE SOFTWARE
Scientific validation and evidence
Biomechanics and

Biomechanics and
HD 60 fps 30/50/100...up to 120 fps
on some models 240 fps
240 fps

CLOSED SOFTWARE
Expensive, Not (so much) portable
Biomechanics and

Biomechanics and
CALIBRATION
XYZ COORDINATES
LAND MARK

QUANTIFICATION OF MUSCLES ACTIVATION
Electromyography (EMG) is a diagnostic procedure to assess the
muscles activation during movement
Surface EMG (sEMG) describes activation of a group of motor unit.
Biomechanics and

Field of interest: medicine, orthopedic, neurology, sport medicine
and biomechanics.
Biomechanics and
sEMG gives:
● information about moment,
durations, and size of activation of a
muscle
● information about muscle
coordination
● information about ability to relax a
certain muscle

Biomechanics and
During voluntary contraction,
number of motor unit activity
and frequency of activation are
regulated by CNS
The order of recruitment,
increase with the increase of
contraction intensity, starting
from smallest to the biggest.
(Henneman's size principle )

Biomechanics and
sEMG is composed by the summation of every MUAPT generated
by every single Motor Unit.

Biomechanics and
Signal acquired by single use electrode, cheap and very adhesive,
placed on muscle belly skin.

Learn to apply EMG to bikefitting
Biomechanics and

DYNAMIC PEDALLING ANALYSIS (by Kinovea)
Kinovea is a video player and a
video editor for all sport expert
and technician
Slow down, study and comment the technique and bike fitting
results of your athletes
It is 100% free and open source
PRO CONS
Biomechanics and

DYNAMIC PEDALLING ANALYSIS (by
Kinovea)
Observe and show
Enrich the video by adding
arrows, descriptions and other
content to key positions.
Compare
Observe two videos side by side
and synchronize them on a
common event.
Biomechanics and

DYNAMIC PEDALLING ANALYSIS (by
Kinovea)
Measure
Measure distances and times
manually or use semi-automated
tracking to follow points and check
live values or trajectories.
Extend
Export your analysis to spreadsheet
formats for scientific study and
further processing.
Biomechanics and

Omar Gatti Bike fit specialist
o.gatti@bikeitalia.it
Giuliano Martiniani Physiotherapist
g.martiniani@bikeitalia.it
Paolo Gaffurini PhD in Physical Exercise and Human
Movement Sciences
p.gaffurini@bikeitalia.it
How to get in touch with the speakers:

Introduction to cycling biomechanics

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