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