Transcript Biomechanics of a Freestyle Stroke - CCVI

By: Samantha Stratford
April 15th, 2013
Overview
 Focus point of analysis
 Interesting facts
 The 5 phases of movement
 What levers are used?
 3 Free body diagrams
 7 (5) principles of biomechanics
 Newton’s laws
 Max velocity and acceleration
Interesting Facts
 Freestyle was the first stroke to be introduced in
1896,when swimming was first brought into the
Olympics
 Water is 73 times as dense as air and 55 times as
viscous
 Water’s buoyancy make swimming the ideal exercise
for physical therapy and rehabilitation or for anyone
seeking a low-impact exercise.
Focus Point of
The Analysis:
The focus point of
my analysis is the
hand entry into
the catch phase,
then pull phase,
finally the push/
finish phase and
the recovery into
the next cycle.
Description of movement: Set-up
 Set-up : Streamline and kickout
 Muscles used:
 Used to stabilize the body during the kickout: Rectus abdominus,
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transversus abdonimus, Internal obliques, external obliques
Used for hip abduction and extension during the kickout: Gluteus
maximus, gluteus minimus, gluteus medius
Used for knee extension during dolphin kick: Vastus lateralis,
Vastus intermedius, Vastus medialis, rectus femoris, Sartorius
Used for knee flexion during dolphin kick: Semimembranosous,
semitendanosus, bicep femoris
Joints used: Hip joint (ball and socket), knee joint (hinge joint),
ankle joint (synovial hinge joint)
Description of movement:
Backswing
 Backswing: Catch phase
 Muscles used:
 Used to stabilize the body during the stroke: Rectus abdominus,
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transversus abdominus, internal obliques, external obliques
Used for arm flexion to initiate catch: Brachialis, bicep brachii,
flexors, extensors
Used for lateral arm rotation during the catch: Subscapularis,
supraspinatus, infraspinatus, teres minor
Used for arm adduction in the middle of the catch: pectoralis
minor, pectoralis major, latissimus dorsi, trapezius
Joints used: Shoulder joint (ball and socket), Wrist joint (condyloid)
Planes and axis: sagittal plane, antereoposterior axis, longitudinal
axis
Description of movement: Force
Movement
 Force Movement: Underwater Pull/ pull phase
 Muscles used:
 Used to stabilize the body: Rectus abdominus, transversus
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abdominus, internal obliques, external obliques
Used for arm adduction during the start of the pull: Latissimus
dorsi, trapezius, pectoralis major, pectoralis minor
Used for arm flexion and extension: Brachialis, bicep brachii, tricep
brachii, flexors, extensors
Used for lateral rotation and retraction: rhomboids, subscapularis,
supraspinatus, infraspinatus, teres minor
Joints used: shoulder joint (ball and socket), elbow joint (hinge),
wrist (condyloid)
Planes and axis: saggital plane, antereopostierior axis, longitudinal
axis
Description of movement: Critical
Instant
 Critical Instant: Finish Phase
 Muscles Used:
 Used to stabilize the body during the finish: rectus abdominus,
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transversus abdominus, internal obliques, external obliques
Used for arm flexion and extension: brachialis, bicep brachii, tricep
brachii, extensors, flexors
Used for arm adduction: latissimus dorsi, trapezius, pectoralis
major, pectoralis minor
Used for lateral rotation and retraction: rhomboids, subscapularis,
supraspinatus, infraspinatus, teres minor
Joints used: Shoulder joint (ball and socket), elbow joint (hinge),
wrist joint (condyloid)
Planes and axis: Saggital plane, antereoposterior axis, longitudinal
axis
Description of movement: Follow
Through
 Follow through: Recovery
 Muscles Used:
 Used to stabilize the body: rectus abdominus, transverus
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abdominus, internal obliques, external obliques
Used for lateral rotation and retraction: subscapularis,
supraspinatus, infraspinatus, teres minor, rhomboids
Used for arm abduction: deltoid(3), teres major
Used for arm adduction: pectoralis minor, pectoralis major,
latissimus dorsi
Joints used: shoulder joint (ball and socket), elbow joint (hinge),
wrist joint (condyloid)
Planes and axis: transverse plane, saggital plane, antereoposterior
axis, longitudinal axis
What Levers are Used??
 First Class Lever:
 This happens when the arms are at opposite ends of the body. One
arm is starting the catch and the other is finishing the stroke.
Third Class Lever:
• This happens when the bicep bends and extends to initiate the
catch phase of the stroke.
Free Body Diagrams
*all phases’ center of mass is the
whole body because of the waters
velocity which keeps the body in a
floating position .
•While swimming a person moves in
the frontal and sagittal plane.
•The swimmer is also on the
antereoposterior axis
Principle 2: Maximum Force
 Production of maximum force requires the use of all possible
joint movements that contribute to the tasks movements.
 Maximum average propulsion force=average resistance
 Propulsion comes from the vector sum of lift and drag forces
 To propel forward we use multiple joints to contribute for the
maximum propulsion speed possible.
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We use our shoulder joint (ball and socket) which provides maximum range
possible so we can reach and get the maximum pull possible.
We use our elbow joint (hinge) to initiate the pull phase of the stroke
We use our ankle joint (condyloid) to propel ourselves forward with the kick
motion of our ankle joint.
We use or hip joint (ball and socket) which is a multiaxial joint which allows
maximum range to help with the kick timing of the stroke and roll.
Principle 3: Maximum Force
 The production of maximum velocity requires the use of joints and
muscles in order from largest to smallest.
 During a freestyle stroke a swimmer uses their biggest muscles to
start the pull and the further you get down the stroke you use the
smaller muscles groups.
 During the start of the stroke the swimmer initiates the pull with
the biggest muscles to apply maximum force. They use the deltoid ,
latissimus dorsi and rotator cuff.
 The next phase of the stroke the swimmer uses the bicep brachii
and brachialis
 The next phase you start to use your tricep brachii , bicep brachii
and latissimus dorsi
 During the finish phase of the stroke you use you trip brachii and
you felxor and extensors to finish the stroke and start the recovery
Principle 4: Linear Motion
 The greater the applied impulse, the greater the
increase in velocity.
 The rate of change of the position of an object
increases when the swimmer applies more pressure on
the catch and push phases of the stroke
The circled hand in this
picture is the start of the
push phase in the freestyle
stroke.
Principle 5: Linear Motion
 Movement occurs in the direction opposite than the
applied force.
 Once the swimmer initiates the pull by rolling their
hips and utilizing the stabilizers of their torso they
push the water backwards which results in forward
motion. Once the one arm finishes the push phase and
starts to recover the opposite arm begins to accelerate
again.
Principle 6: Angular Motion
 Produced by the application of a force acting at some distance
from an axis by choice. This produces change in angular motion.
 By initiating the roll with the hips the swimmer is using torque.
The swimmers hips initiate the catch phase of the stroke because
by rolling your hips you are twisting your body the opposite way
of where your body would lie while completely relaxed.
 Statistics show significant increase in torque production in
swimmers for most motions tested. These shifts in the torque
ratios in swimmers' shoulders resulted from sport-specific
repetitive activity that emphasizes adduction and internal
rotation.
 Hip rotation occurs slightly before the shoulder rotation to place
the trunk muscles in a stretch.
Principle 6 Cont’d
 As the arm pulls back on the water, the hips rotate to
the opposite side to help pull the arm back.
 As trunk rotation stops, some of the angular
momentum of the trunk is transferred to the recovery
arm to assist in optimizing recovery body position.
Newton’s
st
1
Law
 Inertia: an object will remain in constant state unless
otherwise acted on. An object will move or continue to not
move unless something else “makes” it.
 This is true with a freestyle stroke because unless the
recovery phase of the stroke is acted upon the swimmer
will not move or accelerate any further.
 Mass is the measure of inertia, therefore decreased mass in
the water means faster acceleration rate speed ability.
Newton’s
nd
2
Law
 Acceleration: An object will continue at a constant
speed in a linear direction unless acted upon by an
outside force.
 The greater the applied force of the stroke the greater
the resulting acceleration rate.
 A person will remain in a linear direction at a constant
speed while swimming unless acted upon. In this case
the person would be acted upon by coming to a wall
and having to start a flip turn to turn around.
Maximum Acceleration
 The maximum acceleration rate in during the 21st
frame at 5.067 seconds while the swimmer is ending
the finish phase.
 The person in my video is doing the stroke correctly
because the finish phase is the strongest and most
powerful phase of the whole stroke, therefore the
maximum acceleration speed occurs in the proper
place.
Velocity VS Time Graph
Questions??