All You Need To Know About Acceleration: Zero to Sixty With Alex Harrison

The ability to accelerate—to reach top speed from a dead stop—is crucial in almost every sport. Whether you are sprinting on the track, stealing bases, making tackles, or scoring on a breakaway, the power to transition quickly from a standstill to maximum velocity will make you more successful. If a sport involves any sort of running, practicing and training for faster acceleration will improve your performance in that sport—guaranteed!

Physics

To provide a framework for understanding how acceleration happens and how we can exploit that knowledge for improved performance, it is important to consider the physics of accelerating the body. For starters, acceleration happens when force is applied to a mass over some amount of time. The more force there is, the more acceleration (the faster the mass gets going). Second, the more time spent applying force to a mass, the more acceleration there is (the longer the mass continues to accelerate). Third and finally, the less mass there is per given force or duration of application, the more acceleration (the faster the mass will continue to increase in speed). This means that in order to accelerate quickly, you need a high level of force for as much time as  possible while running—working with as low a body weight as possible for that given force.



Force

So, how do we get more force? Train for it, of course! This is exactly what strength training is for. Training for strength in the weight room allows an athlete to put more force into the ground while accelerating, resulting in greater acceleration of their given mass. The importance of this absolutely cannot be understated. If you want to run faster, you must get stronger while gaining minimal weight.  End of story.

An athlete also must put themselves in a good position to produce force against the ground behind them. The direction in which the force is applied is critical because only force directed behind the athlete will result in a forward acceleration of the athlete’s mass. Force directed downward is only desirable to the point that it overcomes the gravity pulling down on the athlete’s mass. Any increase above what is necessary in vertical force application during the acceleration phase is just wasted energy and can actually slow down the process of accelerating! Excessive vertical force production disturbs the second important physics principle mentioned above: time spent applying the force!

Time Applying Force

It is important to maximize time spent applying force to the ground in order to maximize acceleration. Time spent applying force can only be improved by practicing technique. When both feet are off the ground, the athlete cannot be accelerating—so, the goal should be to push off the ground with long forceful strides, and get the next foot back on the ground as soon as physically possible. How exactly to do that will be discussed later.

Mass

It’s harder to accelerate a heavy object than a light one. So, unless a sport requires the athlete to have excess mass for the purpose of competing against other athletes or heavy implements, chances are it’s better for your acceleration ability not to be heavy! Fat mass is not productive when it has to be accelerated in sprinting. 

Technique

Acceleration technique should seek to take advantage of the physics we’ve already discussed. What we’ve learned so far is that the athlete needs to be in a good force-producing position; needs to remain in contact with the ground for a full, long push; and needs return to the ground as soon as possible to begin the next pushing step. Sprinting great, Asafa Powell, exemplifies acceleration technique in the following video:

Forward Lean

All athletes need some degree of forward lean during acceleration. The degree of lean is almost entirely dependent on strength levels relative to body weight. A strong athlete with good technique will have a lean of about 45 degrees or slightly less during the initial two or three  steps.  These are athletes who can full-squat double their body weight or better—i.e., not your normal high-school or even college athlete. Most sprinters should have lean angles of 45-55 degrees, depending on their strength-to-weight and power-to-weight ratio. Younger athletes, or athletes who have not spent years strength training, should realistically have a forward lean of 55-70 degrees. If a young or underdeveloped athlete is asked to lean more than their strength will allow, a coach will notice “piking” or folding over at the hips, and the athlete will feel an unnecessary falling sensation. This is NOT fast! As strength-to-weight ratio improves, then and only then should lean angles decrease.

Limb Action

Arms and legs should have very distinct action during acceleration. Legs should be recovered by swinging forward only at the hip, with the foot staying low to the ground. This is called low heel recovery and is in direct contrast to the more cyclical, high heel recovery action required for upright running. The foot should plantarflex (toes pointed) at toe-off, then return fluidly to a dorsiflexed (cocked, toes up) position just before the next ground contact. This is also different from ideal upright running mechanics, where a much lower degree of “toeing off,” or plantar flexion, occurs at toe-off.

Further, the leg action while on the ground should not be a patient one. The goal of the athlete should be to begin producing force backwards, as hard and fast as possible. Of course, this is done while maintaining technique and not spending excess time in the air between each step (as this creates too much vertical force). The rapid production of force is measured by sport scientists as “Rate of Force Development” or “RFD.” And the only way to have a high RFD it to train for strength and power in the weight room.

The arms should forcefully swing backward and forward, in opposition to the leg action. The arm action in acceleration should be more dramatic than in upright sprinting, with each arm approaching the midline in front of the body during each swing, but not crossing it. Elbows should rapidly open and close as the arms are “hammered” backwards and then returned forward. Full elbow extension is not necessary, but during the first two to three steps, it is acceptable. “Elbows at 90 degrees” is a very common coaching cue that should never be used in teaching acceleration—short arm actions like this encourage shorter ground contacts, which is very BAD for accelerating, but GOOD for upright running. 

An Important Summary

If you want to get better at accelerating, these are the most important characteristics to develop. Done in order, this list is a guaranteed recipe for success. Remember, the best accelerators take full advantage of physics. They possess the ability to produce high forces (strength) and the ability to do it quickly (power). They put their center of mass as far forward as their strength allows, and they maximize time spent applying force to the ground. Here are some key takeaways:

  1. Increase strength.
  2. Increase power.
  3. Develop an appropriate lean angle (not excessive, or too passive).
  4. Forceful backward pushes.
  5. Forceful arm swing with hammer action at the elbow.
  6. Don’t cycle the feet! Use low swings to recover the swing leg.

 


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Alex Harrison, PhD-c, USATF-3, ITC, CSCS, USAW-1, is a guest contributor to the Volt blog. He has personally qualified for USA National level competition in three sports: track and field, weightlifting, and bobsledding. Alex is a Team USA Bobsled athlete, a Preformance Consultant for Renaissance Periodization, and founder of Excelerate Sport. Alex has a master’s degree in kinesiology, and is an East Tennessee State University PhD-c. Learn more about Alex and his path to the 2018 Olympics | @XanderPHarrison