Speed Development Part 2: Why Rate of Force Development is Paramount in Sprinting

Before I get started with this blog I want to give a shout out to all the great minds and researchers putting in the work to provide us with this information and help further the field of sports science. I read a lot of research from people like Dr. Michael Stone, Dr. Brad DeWeese, Peter Weyand, and many more. In review from part 1, impulse is force multiplied by the time that force is being applied. We also know that when sprinting a crucial determining factor in ones stride length is the impulse they are applying into the ground during touchdown. Some intelligent guy once told us that every action has an equal and opposite reaction, and in this case that is referred to as a ground reaction force (GRF). The GRF is the force the ground applies on us and it is obviously equal to in magnitude and opposite in direction of the force we applied to the ground.

In order to increase stride length an athlete needs to create a greater impulse. This can be accomplished by increasing either the force or the time in which the force is applied. However, we do not want to increase the time our foot is on the ground, as that would decrease our stride rate. This is why we focus on increasing the force we are applying into the ground.

While sprinting an athlete’s ground contact time (GCT) will range between approximately 0.08 seconds for an elite sprinter, to 0.1 seconds for slower runners. This means that an athlete has less than a tenth of a second to apply the necessary force into the ground when running.

This is where Rate of Force Development (RFD) comes into the picture. RFD can be defined as a change in force divided by time. Due to the short time period allotted to apply force while sprinting, speed is not limited by the maximum forces that can be applied to the ground but rather by the maximum rates at which the limbs can apply the required forces. It has been shown that maximum force production takes approximately 300 milliseconds to produce and as noted in the previous paragraph a sprinter’s GCT is approximately 100 milliseconds. In fact most movements in sport including: jumping, throwing, change of direction, etc., happen very quickly, making RFD a very important performance characteristic.

In part 1 of this series I talked about relative strength, which is without a doubt important, especially when dealing with undeveloped “weak” athletes. As I mentioned, strength is the foundation required to develop speed and power. However, a lot of people relate getting strong with being big and bulky. This doesn’t have to be the case though. When training athlete’s for speed you are training to increase their strength and RFD, which is different than body builders or powerlifters. Body builders do what we call hypertrophy training, which involves extreme amounts of volume in order to increase the size of their muscles. Powerlifters are training for strength, but due to the nature of the sport they have much slower bar speeds as they are lifting very high relative intensities. Also, unless they are cutting to make a weight class, these athletes strive to put on more muscles mass, which isn’t always a good thing for sprinters.

It has been shown that there is a strong correlation between maximum strength and RFD, but the way in which sprinters develop strength is different than a powerlifter or body builder. When training athletes for speed the focus should be on increasing maximum strength and more specifically RFD, without adding unnecessary body mass. Now that we understand RFD, part 3 of my speed development series will be discussing methods to do so. Please leave any questions or comments bellow and thanks for reading!