Maximizing Your Athletes' Acceleration
by Bill Parisi, Founder, Parisi Speed School
Acceleration is defined in physics as the rate of change of velocity over time, and is an attribute many athletes haven’t fully grasped.
An athlete's ability to accelerate is summed up by their ability to "push". Objects do not speed up, slow down, or change direction unless they are acted upon in some way. Newton’s Second Law sums up this idea when it states that, "The acceleration of an object results from the application of a force. The acceleration (a) of an object with mass (m) produced by a given force (F) may be calculated using the equation F= ma. A larger force produces a greater acceleration; a larger mass results in a slower acceleration given the same force."
Relative Body Strength
Relative body strength plays a major role in acceleration. Relative body strength is a measurement of strength compared to an athlete’s own body weight. The following is an example: If you have two athletes of equal strength, both who can Dead lift 400 lbs, but one athlete weighs 280 lbs and the other weighs 180 lbs, physics and our experience has shown us that the lighter athlete will always be faster. The lighter athlete in this example has better "mass-specific-force". This concept was proven by Harvard Medical School research physiologist Peter Weyand and his team. The actual force generated into the ground by the lighter athlete may not be any greater than the heavier athlete, but in relation to their respective body weights, it most certainly is.
A simple way to test relative body strength is pull-ups. Athletes who can perform 15 or more pull-ups or squat 2.2X their body weight have high levels of relative body strength. This plays a key role in determining acceleration and change-of-direction ability. Relative body-weight strength is not the only component necessary for improved acceleration. Weight training by itself, performed over long periods of time without any speed work, will not maximize an athlete’s full power potential. On the other hand, those who do not weight-train will never reach their speed and quickness potential.
So how do you improve acceleration?
First, get stronger. Next, learn the proper technique. One of the most common mistakes young athletes make is over-striding. If you watch world-class sprinters accelerate, you will see that their first three strides are long, as if they are actually striding out in front of their body. Athletes at this level have very high relative body weight strength ratios that allow them to take longer strides.
These athletes are sort of clawing the ground as their feet strike, then thrusting their feet backward. This action catapults their bodies into the subsequent stride. Most grade school and high school athletes do not possess the high levels of relative body strength and the power needed to take long strides when accelerating. Athletes with low levels of relative body strength can actually slow themselves down with longer strides because long strides taken by weaker athletes act initially as a breaking force when the foot makes contact. It isn't until the body's center of gravity is above the plant leg that the athlete can apply enough force to propel and push himself forward.
Newton's third law states that, "Every action has an equal and opposite reaction." So, if an athlete wishes to accelerate, he needs to apply force in the opposite direction he is heading. The goal of maximizing acceleration is to have your foot make contact with the ground while moving in a backward or opposite direction you are accelerating. For younger athletes this means the foot should land only slightly in front or directly under the hip. The stronger athlete's foot would land more in front of the hip because he has the strength to initially pull and then push the body through. The following is a simple illustration of what I mean. Imagine you're cross-country skiing and driving the poles into the ground. If you were to reach out far in front of your body with the poles, you'd need a tremendous amount of upper-body strength to pull and then push to propel your body forward. If you take shorter stabs into the ground with the poles, only slightly in front or directly under your hips, you would require less strength to move forward. The same biomechanics hold true when accelerating. The only difference is that your legs act as the poles.
This leads us to another concept the athlete needs to be familiar with, joint angles. The shin is the most important angle to consider. The shin acts as the pole for the cross-country skier. The lower leg should hit the ground at a 45-degree angle with the knee in front of the foot, just as the hand would be in front of the ski pole's contact point when driving them into the ground. This angle creates tremendous leverage to apply force into the ground to move forward.