Thursday, December 16, 2010

Why should you care about Physics?

Power = Force x Distance/Time =Force/Velocity, Force = Mass x Acceleration +Weight of Mass,  Rate of Force Development= ∆ (force)/∆ (time)

They say that you cannot defy the laws of physics.  That is true, however sometimes when you watch athletes in sport you wonder if that is always true.  The three equations above are of great importance in training athletes and must be addressed in the training and evaluation of athletes and the development of training strategies.  

I have mentioned in the past that different sports require the body to produce power at a multiple of an X factor.  In other words how much volume and how much intensity of power does a particular sport require?   These differences in the type of power place different metabolic energy needs on the body.   The X factor is determined by the requirements of the specific sport.  For example a shot putter has an X factor that is very small.  There are only a handful of throws at maximum power necessary to compete in a track meet.  A boxer has an X factor that requires power to be produce in much greater volume.  The boxer has to produce power in punches hundreds of times in a match.  Understanding this X factor and how the body produces power is where the understanding of how physics comes into play.  
Let’s start by looking at the first equation.  People confuse power with strength on a regular basis.   Strength is the ability to generate a force.  If you were pushing against a wall with your hands you are 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. Once again, strength  is the ability of an athlete to generate a force. 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 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 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.   
Rate of force development equals the change in force and the amount of time to make that change.   What influences your velocity greatly, and subsequently your power is the rate in which your muscles produce the force.  If the rate of force development is increased then you will be producing force at a faster rate and velocity will increase if all else is equal.  If you have ever played the game when one person is standing with their hands clasped in front of them, and the other person is facing them with hands to the sides and then you try to slap the person’s hands you have a little idea about force development.  Ouch, if you are slow at force production in this game.  We used to play this as kids and someone was walking away with red hands. If you were the hitter you would stand there and concentrate to try to increase the speed at which your body moves your hands.  The faster you were able to fire the muscles and produce a force the faster your hands would cover the distance delivering a resounding slap.  In boxing they call this beating your opponent to the punch.    
Why are these physics equations important to training?  When evaluating an athlete at Titan we look at all of the parts in these equations to see where the athlete has the biggest gaps.  Much of the short term gains in strength training are neuromuscular in nature.  In other words we see strength gains in an athlete before we 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 increases are seen more readily in explosive types of exercises where high levels of power are being produced.  (Hakkinen et al., 1985) A strength coach needs to determine the best course of training needed for a specific sport, and tie that to the athlete’s current strengths and weaknesses.  This type of evaluation is ongoing with the athletes training at Titan to determine areas of fitness that need the most attention.   For example, an athlete may come to us with a good base of absolute strength, but is lacking in the velocity side of the equation.  In many cases you can eyeball this lack of velocity.  With more highly trained athletes we utilize our Isokinetic equipment to measure the time to peak force and get specific measurements of our starting point and subsequent progress.  This piece of equipment can measure time to peak force and give us a window into the rate of force development. The faster an athlete gets to peak force the faster the rate of force production.   With this information we can develop a training program that will improve the athlete’s ability to generate a force and subsequently more power for their specific sport.  
In previous posts I have discussed tipping points in training.  These are gains in fitness that have a huge impact on an athlete’s performance and are visible after a short amount of training.  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 on the field. 
Understand the physics and you will be able to better utilize the training time you have available. 

Train smart, have fun, and you will prevail!

Jacques DeVore, CSCS

1 comment:

Anonymous said...

Il semble que vous soyez un expert dans ce domaine, vos remarques sont tres interessantes, merci.

- Daniel