Biomechanics Of Sprinting

 Horizontal Velocity throughout the race is constantly changing.  Most Important part of the race ◦ Acceleration Maximum velocity

 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 2 nd touch down ◦ That is over half of the sprinters maximum velocity with in the first 3 steps of the start

 From powerful horizontal force to a more vertically directed force.  In part due to raising COG

 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

 This means that Horizontal velocity is not the critical mechanical factor in sprint performance

 We can understand this change in focus by looking at Newton’s laws  Force= Mass(Change in velocity)/Ground time  Horizontal force=77.5*(7.0)/.60 = 905 N or 205lbs of horizontal force *77.5kg=170.8lbs

Maximum velocity ◦ Horizontal force= Start Vertical Force= 77.5*(1.0)/.150= 485N or 110lbs Total Vertical Force= 750N+485N= 1235N or 277lbs

 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

 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

 Vertical force= 77.5*(1.0)/.087= 890N or 199 lbs  Total Vertical Force= 759N+890N= 1,640N or 367lbs

 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

 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

 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

 Horizontal Velocity Stride Rate Stride Length Ground Contact Time Air Time Time To Maximum Upper Leg Flexion

 The most successful sprinters focus on front side mechanics  Active recovery of the back side mechanics is important  Do not just “spin the wheels”

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, Mann, R. (2011). The Mechanics of Sprinting an Hurdling.