Ground Forces Of Jumping & Running

by James Walker, CCS, STM, Biosig

Ground force or ground impact or ground stress from the foot strike when jumping, running, sprinting may vary greatly depending on the landing height or depth, running speed, and landing surface.  In 2005 I was visiting the Ontario Science Centre in Toronto Canada, which had this facinating interactive sports science center for kids and adults. One of the venues involved a force platform on the ground and a 14-16 inch step. Each participant would step or jump off the step onto the force platform, which would display the force usually between 9-20 G’s or 9-20 times their body weight when landing. Which is pretty significant, a 150 lb person would land with 1,350-3,000 lb of force or stress. So consider this when playing a game of basketball or volleyball where you may jump from 12-24” multiple times during a game. The repeated stress would be in the tens of thousands of lb.

Now research has suggested that jogging produces 3-6 G’s while sprinting may produce 8-11 G’s of force, which translate into 450-900 lb or 1,200-1,650 lb of force per foot each time it lands on the ground for the 150 lb person. So if that same 150 lb person was playing a game of full court basketball 84’ x 50’ and ran up and down the court for 31.4 laps equals a mile at an average of 45 steps per lap or 20,250-40,500 lb of force-stress total. Whereas a world class 100-meter sprinter at the same weight might take 45 steps, which would equal 54,000-74,250 lb of force. Now obviously the basketball playing requires crosscourt and lateral movement as well but you get the point that I’m making. The basket may occur over 8-12 minutes while the 100-meter sprint happens in less than 10 seconds.

Now if you add 16 jumps to the basketball 21,600-48,000 lbs your force totals would resemble something like this: 41,850-88,500 lb of force-stress over the time range. These are accumulative forces-stresses may lead or contribute to a soft tissue injury or a stress fracture over time. The only way to allow the body to perform at either of these levels requires proper preparation and adequate recovery. 

In the next article we will talk about preparation and recovery.

References: UDaily and University of Delaware; and Biomechanical Analysis of Fundamental Human Movement by Arthur Chapman