· Power = Force x Distance/Time =Force/Velocity
· Force = Mass x Acceleration +Weight of Mass
· Rate of Force Development= ∆ (force)/∆ (time)
· Maximum Sustained Power =The ability to hold the highest percentage of your absolute power the longest.
Strava bike records, Map my Run, CrossFit Games. All of these roads lead back to the laws of physics. How does a body move through space? They say that you cannot defy the laws of physics, and that’s true. But sometimes, when you watch athletes perform, you can’t help but wonder if it’s always true. The three equations above are of great importance in training your body for improvement on the bike in the Maximum Overload program outlined in my book.
Cycling is a sport that requires thousands of revolutions and the ability to produce maximum sustainable power over long periods of time. This sustainable power is what makes the final climbs of your ride much more enjoyable. By understanding the physics you can better understand how your body works as well.
Let’s start by looking at the first equation. People confuse power with strength on a regular basis. This drives me crazy. Strength is the ability to generate a force. If you were pushing against a wall with your hands you would be creating a force. The force could be measured using a force plate to determine how many units of force you are creating. Force is a measurement of Mass x Acceleration plus the weight of the mass. It is typically measured in Newtons. If you look at the equation for power it takes Force (strength) and incorporates the time it takes to generate the force over a particular distance (velocity).
Think about getting out of a chair. You rise up and generate enough force and velocity to overcome both the weight of your body and gravity to lift you out of the chair. If you continue to increase the speed at which you go from sitting to standing, eventually you would increase the speed to such a point that your body would leave the ground. In each subsequent time out of the chair you are producing more power as you increase the speed (velocity) of rising up. So it is one thing to have the ability to produce enough force (strength) to rise from your chair and overcome the weight of your body and gravity. However, once velocity is increased you will rise higher and higher as you rise from your chair, generating greater and greater amounts of power as the velocity increases.
Ever watch an old person rise from a chair? Usually the hands move to the knees and then with a grunt they rise up. The hands are changing the biomechanics and un-weighting the hips by moving the body forward and incorporating the arms. When force production is low and velocity cannot be achieved, the body will look for biomechanical tricks to execute the movement successfully. In sport this can lead to injury. Stay away from the old person get-up if you can.
Rate of force development equals the change in force and the amount of time it takes to make that change. Rate of force development is what influences your velocity greatly and, subsequently, your power.
If you have ever played the game Slaps, in which one person stands with their hands clasped in front of them and their opponent faces them with their hands to their sides and then tries to slap the other person’s hands, you have a little idea about rate of force development. If you are slow at rate of force production in this game, you are in for some pain. We used to play this game as kids and usually someone ended up walking away with red, sore hands. If you were the hitter, you would stand there and concentrate to try to increase the speed at which your body moved your hands. The faster you were able to fire the muscles and produce a force, the faster your hands would cover the distance and deliver a resounding slap. In boxing they call this beating your opponent to the punch.
Why are these physics equations important to training?
When I am evaluating an athlete, I look at all of the components in these equations to determine where the athlete has the biggest gaps. Many of the short term gains made in strength training are neuromuscular (muscle firing) in nature. In other words we always will see strength gains neuromuscularly in an athlete before we begin to see size gains. If you were to focus on nothing but strength gains, there would be gains in strength but not necessarily in rate of force production. Rate of force production improvement is seen more readily in explosive types of exercises where high levels of power are being produced. (Hakkinen et al., 1985) This type of evaluation is ongoing with the athletes I am training. I am reevaluating areas of fitness that need the most attention. For example, an athlete may come to us with a good base of absolute strength, but be lacking in the velocity side of the equation. In many cases I can identify this lack of velocity just by observing the athlete’s movements. With more highly trained athletes we utilize measurements of power to get specific measurements of our starting point and subsequent progress. The faster an athlete gets to peak force, the faster the rate of force production. With this information we can develop a better training program that will improve the athlete’s ability to generate a force and, subsequently, more power for their specific sport. The D.I.Y. version is measuring distance over time in an exercise requiring power. Start by measuring your time to that mailbox at the top of the hill.
Utilizing the equations above in the evaluation of your fitness can oftentimes lead you to an area of training that could result in a big improvement in your performance in much less time. Understand the physics and you will be able to better utilize the training time you have available.
Truth in fitness,
Jacques DeVore, CSCS and Certified Primal Health Coach