BASIC TRACK & FIELD BIOMECHANICS

Cameron T. Gary

• USA Track & Field - Level II Coach • Jumps • Sprints, Hurdles & Relays

• USA Weightlifting • Level 1 Performance Coach

DEFINITION OF BIOMECHANICS

⦿Bio = Body (living) ⦿Mechanics = The study of the mechanical

principles of living organisms, particularly their movement and structure

PLANES OF THE BODY⦿Frontal: Front side,

Back Side ⦿Sagittal: Left side, Right

Side ⦿Transverse/Horizontal:

Upper, Lower

THE NATURE OF ENERGY⦿You can hear energy as sound ⦿You can see energy as light ⦿You can feel energy as wind

FORMS OF ENERGY⦿Heat ⦿Chemical ⦿Electromagnetic ⦿Nuclear ⦿Mechanical (our primary focus) ◼When work is done to an object, it acquires

energy. ◼This is mechanical energy.

MASS⦿The amount of matter accumulated in an object ◼ Mass never changes, regardless of location

⦿Center of Mass (COM) ◼ The point where the object is perfectly balanced ◼Where the object’s center of acceleration is also located

WHEN YOUR COM IS OUTSIDE YOUR BASE OF SUPPORT...

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WEIGHT• The amount of gravitational pull on an object

• Gravity pulls at a constant rate of 9.81 mps² – Weight changes relative to one’s location – Moon is 1/7 the mass of the earth, so your weight would

be 1/7 that on earth...but your mass would be unchanged

FORCE

⦿Strength of a force is defined by the rate at which it can speed up one kilogram of mass

⦿“You can see movement, but you cannot see force.” ◼ Dr. Gideon Ariel

KINEMATIC PARAMETERS• Description of the appearance of

movement, particularly as it pertains to the position of the human body

• Basic Kinematic Parameters

– Displacement/Velocity/Acceleration

– Momentum/Speed

DISPLACEMENT, VELOCITY & ACCELERATION

⦿Displacement ◼The change in the position of an object ◼ Shortest distance between the starting and

ending point ⦿Velocity ◼Displacement of an object in a particular

direction ⦿Acceleration ◼The rate of change in displacement of an object ◼For our purposes, there is a unit of time with

respect to a particular direction

MOMENTUM & SPEED⦿Momentum ◼ Is the product of mass and

velocity ◼Has direction and

magnitude ◼Transfer of Momentum ○ When the momentum of a

system is imparted to a part of the system

○ This requires stopping a part of the system ! Throwing an implement

MOMENTUM & SPEED (CONT.)

⦿Elastic vs. Inelastic Collisions

⦿Speed ◼ The magnitude of velocity ◼ How fast something moves,

regardless of direction ◼Generally a measurement of

length, divided by time (Kps, Mph, etc.)

◼ Speed is not the same as acceleration

◼ Speed is relative to the object’s position

NEWTON’S 1ST LAW⦿ Inertia ◼ Objects in motion/at rest tend to stay in motion/at rest, unless

acted upon by a net force ⦿ Example ◼ The mass of the car/occupant is moving at 60 mph ◼ The net force is the immovable concrete block ◼ Unless something restrains the occupant, the momentum will

transfer to him and he will continue to move after the car is abruptly stopped

NEWTON’S 2ND LAW⦿F = Ma ◼ F = Force, M = Mass, a =

Acceleration ⦿Net force causes an object

to accelerate ◼ The magnitude of

acceleration is directly proportional to the force on the object, ○ Larger forces are capable of

creating more acceleration ◼ and inversely proportional to

the mass of the object ○ It takes less force to accelerate a

smaller object than a larger one

NEWTON’S 3RD LAW⦿In every action,

there is an equal and opposite reaction. ◼ If an object A exerts

a force on another object B, then object B will exert a force on object A ○ Equal in magnitude ○ Opposite in direction ◼Newton’s Cradle

ACTION/REACTION $100 BET...

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ANGULAR INTERPRETATIONS OF NEWTON’S LAWS

⦿ All of the above apply in a Rotating System

⦿ Rotating inertia is called Angular Inertia

⦿ Rotation-producing force is called a Torque ◼ Torque = Twist

⦿ A torque force always produces rotation about an axis

ANGULAR VS. CURVILINEAR VELOCITY

⦿Objects rotating about an axis have the same angular velocity

⦿However, objects further from the axis have a higher curvilinear velocity ◼Can you find the axis? ◼Where is the highest

curvilinear velocity?

SUMMATIONS OF FORCE⦿Proximal: Closer to the center of the body ◼Proximal joints tend to be more heavily muscled ◼Proximal muscles/joints tend to produce more

force ◼Proximal muscles/joints tend to be slower moving

⦿Distal: Away from the center of the body ◼Distal joints tend to be less heavily muscled ◼Distal muscles/joints tend to produce less force ◼Distal muscles/joints tend to be faster moving

FIRING ORDERS⦿This is the sequence of

joint usage ⦿Generally Proximal to

Distal ⦿Not consecutive ◼Tends to overlap

⦿Slower/Stronger muscles/joints tend to move first ◼VOLUNTARY movements

- Reflex reactions are the exception

HINGED MOMENT⦿ Combination of Linear and

Angular Momentum ◼ Requires a change of direction

from linear to angular ◼ Stoppage of momentum at one

end of the system ◼ This becomes the axis ◼ Resultant energy is transferred

toward the distal end ⦿ The energy does not go away

– is increased at “free” end ⦿ Running/Jumping is a series

of controlled “trips”

HINGED MOMENT IN ACTION...

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ACKNOWLEDGMENTS…⦿I would like to express my gratitude to Coach Jim Kiefer of Vista Murrieta High School for allowing me to borrow (quite liberally) from his “Essentials of Biomechanics” presentation. ⦿And Thank YOU all very much for your kind attention to this presentation. I hope you enjoyed it!

CAMERON T. GARYUSATF CERTIFIED - LEVEL 2 COACH JUMPS SPRINTS, HURDLES & RELAYS USA WEIGHTLIFTING – LEVEL 1 COACH

www.ctgdevelopment.net 619-895-4699

jumpmaster@ctgdevelopment.net