Youth Football Training: Speed Over Strength

Football is America's most favorite sport and the NFL cashes in on millions of revenue every year. The Super Bowl is an event watched by nearly every person in the country and it is atleast second to the World Cup in football (or called soccer in the US) in popularity.

Many of today's youth play football in competitive events such as in high school and special tournaments. However, the way a child develops is drastically different during puberty. There will be a significant variation in size and consequently, many youth will feel hestitant about playing football because of the fear of going toe to toe against larger players.

However, the laws of physics always come into play and high school and college coaches are becoming more aware of forces that are not dependent on factors of mass. Many kids are turned off by football because the stereotypical view is that one must be physically strong in all forms - but it is not so clear cut. Strength is only a small factor that comes into play. The greatest determinants of football are kinetic energy and velocity.

What is kinetic energy?

It is a much simpler concept that the word makes it sound. It is the energy an object possesses while in motion. In everyday terms, picture a 200 pound linebacker charging straight toward you. He's going to be carrying a lot of kinetic energy.

To easily understand the concept, equate kinetic energy with damage, pain, or impact. It is not the same thing as force.

Force = Mass x Acceleration

It is a vector quantity with both magnitude and direction.

Kinetic energy on the other hand is a scalar quantity that is commonly measured in joules.

Kinetic Energy = ½ Mass x (Velocity)^2

Remember that force is a push pull phenomenon. Isaac Newton discovered the law of action and reaction. A 200 pound linebacker that hits another player is going to receive the force of his tackle back at him (equal and opposite reaction). However, his recoil will be different according to the player he tackles. If his victim is a much smaller player, there would be little recoil for the linebacker.

Now let's apply how kinetic energy works in favor of smaller players over larger players.

There are two things to consider when calculating who is going to tackle who, or more specifically, who will damage the other player more. It is difficult for small running backs to hit a linebacker head on and still keep moving.

All football players know that it is easier to tackle a large slow player than a small fast moving player.

Scenario

Player A is 80 kg (176 lbs) and is charging toward Player B at a velocity of 6 meters per second.

Player B is 60 kg (132 lbs) and is charging toward Player A at a velocity of 8 meters per second.

Player A's Force = 80 kg x 6 m/s = 480 N (Newtons)

Player B's Force = 60 kg x 8 m/s = 480 N

The head on collision will be brutal and the forces are similar. But it is most likely that the lighter Player B will be knocked down hard due to his relatively low mass. Even if he exerts the same force on the heavy linebacker, it only means there is no net force. Think of the famous bullet and rifle analogy.

Rifles fire bullets at incredible speeds - 600 to 5000 feet per second.

But did you know that bullets exert the same force back on the rifle as the rifle exerts on the bullet?

Since the rifle is so large in mass compared to the bullet, the resulting recoil is much less. Think of the bullet recoiling in its own way and it will make much more sense. The same thing happens when you're cruising down a lonely highway in your car and an insect goes splat on your windshield.

The insect exerted the same force on your windshield as your car did on the insect. However, the damage it causes is a completely different story. Compare the sizes of the insect and the car and you'll understand why the insect explodes and the car's velocity is virtually unchanged.

Now back to football. Why is the fast small player feared by the larger players?

Kinetic energy is where it all begins.

Player A's Kinetic Energy = ½(80 kg) x (6 m/s)^2 = 1440 Joules

Player B's Kinetic Energy = ½(60 kg) x (8 m/s)^2 = 1920 Joules

The small running back will inflict much more pain to the larger linebacker. More specifically, he has 33% more kinetic energy contained as he is in motion. Large football players try to avoid charging runners because it can cause serious injury if angular hits are taken. Running backs can take advantage of this and use their smaller build for optimum performance in a game.

Mass is only one factor and it is directly proportional to kinetic energy. However, velocity is squared. This is why speed is significantly more important to train in than strength. Football is a game of speed and power.

Small players should not be hesitant in trying out for football. Less mass means more acceleration, and that means more agility. An experienced running back is quick on his toes and will be able to avoid head on collisions and instead take on angular movements. Vectors come into play here and can make all the difference in the smaller player taking advantage of relative momentum and impulses.

Coaches in America use physics as a tool in determining how players can overcome physical disadvantages and use smart tactics to win football games. Maybe the perspectives of society will change in that bigger is not always better.

Perhaps we will start referring "bigger" to a "bigger brain" in the distant future.

How Can Coaches Improve Their Players' Speed?

Speed can be a number of different things but the two most important concepts to deal with is change of momentum (impulse) and acceleration. If a player does not follow through and maintain an accelerating rate of speed, he easily be taken down.

Fitness training and health are important, as well as conditioning. While endurance training is important, the running back primarily needs burst speed, or anaerobic exercise to specialize in sprinting. Plyometric Training is the term used for exercises that stress explosive power. Explosive power is the core principle behind almost every sport - including basketball (jumping), sprinting (acceleration), boxing (high intensity movements over shurt durations).

The youth of today can learn a lot from simple physics and with proper guidance from coaches, they can prioritize training in speed over strength to play the best they can on the football field.

References:

Newton, Isaac (1999). The Principia Mathematical Principles of Natural Philosophy. Berkeley: University of California Press. ISBN 0-520-08817-4. This is a recent translation into English by I. Bernard Cohen and Anne Whitman, with help from Julia Budenz.