biomechanics of sprinting. horizontal velocity throughout the race is constantly changing. most...
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Biomechanics
Of
Sprinting
Horizontal Velocity throughout the race is constantly changing.
Most Important part of the race◦ Acceleration
Maximum velocity
Understanding Sprint Performance
Horizontal velocity of an elite sprinter◦ Over 4 meters/sec at ground contact coming out
of blocks
◦ Increases to over 7 meters per second by end of the 2nd touch down
◦ That is over half of the sprinters maximum velocity with in the first 3 steps of the start
Start
From powerful horizontal force to a more vertically directed force.
In part due to raising COG
Mechanics Transition
For the Start the goal is maximum horizontal force and minimizing force in all other directions
Transition phase into maximum velocity
Once maximum velocity is reached the goal is to maintain maximum velocity by producing maximum amounts of vertical force
Basic Mechanics
This means that Horizontal velocity is not the critical mechanical factor in sprint performance
Basic Mechanics
We can understand this change in focus by looking at Newton’s laws
Force= Mass(Change in velocity)/Ground time
@Start
Horizontal force=77.5*(7.0)/.60 = 905 N or 205lbs of horizontal force
Newton’s Laws
*77.5kg=170.8lbs
@ Maximum velocity◦ Horizontal force= 0
@ StartVertical Force= 77.5*(1.0)/.150= 485N or 110lbs
Total Vertical Force=
750N+485N= 1235N or 277lbs
Newton’s Laws
As you transition into maximum velocity the horizontal force output decreases
This is not true of vertical force
Because of gravity, sprinting is a series of alternating ground and air phases
Newton’s Laws
To account for this the change the vertical velocity in the upward direction must increase to about .5 m/s
This is also true in the downward direction so the total vertical velocity increase equals to 1.0 m/s
Newton’s Laws
Vertical force= 77.5*(1.0)/.087= 890N or 199 lbs
Total Vertical Force= 759N+890N= 1,640N or 367lbs
Newton’s Laws
As horizontal velocity increases the segments increase as well.
When segments increase it has a negative impact on the runners ability to produce vertical force
Another limiting factor is the body position
Mechanics
The body positioning of the sprinter at touchdown is actually producing horizontal braking forces
The touchdown point is actually located slightly in front of the COG
The best sprinters minimize this effect
Mechanics
Specific Performance Descriptors◦ Block Distances◦ COG Distance at Set Position◦ Segment Angles at Set Position◦ Segment Angles During Block Clearance◦ COG Distance at Step 1 Touchdown◦ Segment Angles during Step 1◦ COG Distance at Step 2 touchdown◦ Segment Angles during Step 2
Start Mechanics
Horizontal VelocityStride RateStride LengthGround Contact TimeAir TimeTime To Maximum Upper Leg Flexion
Critical Performance Descriptors at Maximum Velocity
The most successful sprinters focus on front side mechanics
Active recovery of the back side mechanics is important
Do not just “spin the wheels”
Front Side/ Back Side Mechanics
Hunter,J., Marshall,R., McNair,P.(2005). Relationships Between Ground Reaction Force Impulse and Kinematics of Sprint-Running Acceleration. Retrieved from: Journal of Applied Biomechanics, 21,31-43
Kovacs,M. Speed Training: Linear Acceleration. Retrived from NSCA
Cavagna, G., Komarek, L., Mazzoleni, S. (1971, May) The Mechanics of Sprint Running. Retrieved from: The Journal of Physiology, 217, 709-721
Mann, R. (2011). The Mechanics of Sprinting an Hurdling.
References
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