M Newman

When is big; big enough?

Sprinters are renowned for their exceptional physiques, muscle size , density and definition.  In fact the event requires power and explosive strength.  It is a well known fact that a high muscle mass is required to be successful at the highest levels of the sport.  Though this maybe the case; how much muscle is needed or to be more precise, when is big; big enough?  Well… the answer lies in the realms of science.  We could use muscle physiology, or revisit Isaac Newton’s laws of motion to fully understand the pros and cons of increased body weight as a result of an increase in muscle mass; after a purposeful and productive strength training programme.

Let’s us look at Newton’s laws of motion to understand how the application of force requires greater muscle mass; and why the need to overcome interfering forces from the earth may limit the functional mass required to be successful in Track and Field and many other sports that require running or sprinting. So here goes.

NEWTON’S FIRST LAW

This law states that; objects will stay in place or continue to move with constant velocity unless interfered with.

Well athletes are not astronauts in space, they have to deal with gravity, air resistance, and friction.  As a result; they will need to “escape” gravity by applying force to the earth. So we need to be strong to overcome gravity to run sprint, jump, throw.  To do that we need to get stronger!

NEWTON’S LAW OF INERTIA

Now Newton’s Law of Inertia  takes into account the mass of an object.  In our context, that would be an athlete’s mass, whether muscle, fat or organs.  This law states that all objects with mass have inertia.

The higher the inertia the more difficult it is to move an object; the larger the mass, the greater the inertia of  an object.

Put simply; the heavier you are the harder it is to get moving.  So regardless of how muscular you are, if your mass increases then the harder it will be to get going, so you may increase your power levels by getting larger muscle mass but now you have to deal with greater inertia.

NEWTON’S SECOND LAW

This law states that if we want to increase our velocity or speed we need to accelerate.  Acceleration of a body is proportional to the force applied to move that object and negatively proportional to the mass of the object.

Have you noticed a pattern with the laws so far?  Well let me help you,  MASS once again has popped up in the second law of motion.  This law simply states that to increase your velocity you need force,the greater your force the greater your acceleration.  The bigger your mass the smaller your acceleration.  So if you are lighter, then you should be able to accelerate faster AND you will need less force to achieve that because you have less inertia to overcome because of your smaller mass.  Ok, so where does the forces that we apply go?  Well, we shall deal with that next.

NEWTON’S THIRD LAW

This law states that for every magnitude of force applied to the ground, we will get an equal and opposite force applied back to us by the Earth!  These forces are known as reactive or ground reaction forces.

Simply put, the stronger you are; the more forces will be applied back by the Earth.  So if you can apply great force, then the Earth will assist you by applying equal but opposite forces back to you to help you.

As you can see, Newton had it on lock. We can’t escape science.  Any coach or athlete who decides to go against these basic rules will suffer.  Yes force is a must in power and speed events like the 100m sprint, but if a coach and athlete forget these three basic rules, or oppose them in anyway, ie lacking strength or having too much muscle mass, then they will not achieve athletic fame and riches! The keyword is optimal.

Practical application

You can’t be strong enough as a sprinter or power athlete, the stronger the better.  Strength is synonymous with power.  Ideally, a sprinter would want to see a small change in body weight and a large increase in strength.

Remember, a small mass is easier to accelerate.  A small mas has less inertia and also requires less force to accelerate.  In that case, a small mass that has a very large force applied will have greater acceleration.  Other factors

will dictate the ideal mass of an athlete such as impulse and momentum.  These two important aspects of sprinting will be covered in the future.

Summary.

• An object will move at constant velocity unless interfered with. Athletes have to deal with gravity, air resistance, and friction, they interfere with performance. Force is needed to overcome the interference.
• Greater mass equals greater inertia or more force needed to move.
• The heavier you are, the harder it is to accelerate.  The stronger you are the greater the acceleration.
• The greater the amount of total force applied to the ground, the greater the ground reaction forces applied back to help you.