How to Evaluate Your Acceleration in Sprinting

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When evaluating anything there are usually key indicators as to whether that performance or action is successful. With sprinting or acceleration, this is much of the same: There are key indicators that tell a coach whether it was a successful action or if there are adjustments that could make the action more efficient. I spend a great deal of my coaching hours observing live speed and agility reps or breaking down videos of movements. Typically, within a few seconds of beginning the video I have a good idea of what I will see throughout the video. This is not due to some sixth sense, it is because the initial movements in any direction lay the foundation for the movements throughout the remainder of the sequence.

Movement within the human body, like nature, has a tendency to tip you off when something is going to occur. In nature, we know that when the humidity rises and the pressure in the atmosphere builds then the likelihood of rain increases. Similarly, in movement, when one limb creates a propulsive action there has to be a weight shift or opposing movement by another limb to create balance within the system. As I go to take a step with my right foot from a standing position there will be a simultaneous forward arm swing with my left arm. This action maintains balance and equalizes rotation within the body.

So, what does all of this mean as it pertains to coaching?

This means that as I watch you take your initial steps in any direction, I can, with a fairly high level of certainty, assume what the following steps will look like.

Let’s look at a few examples…

Lack of Extension

In this image you can see the lack of extension through the rear leg. The green line shows the proper position of the rear leg at the fully extended position. The red line represents the current fully extended position.

One of the first performance indicators that I will look for will be the extension during the initial step. Any lack of extension will cause multiple issues throughout the duration of the run. First of all, it will dramatically slow the time of the run while also limiting the ability to achieve maximum velocity quickly. As the limb is extending, the action itself is becoming faster and more power. If the action is stopped in order to initiate another movement then you are starting all over again in the force generation process. The final degrees of extension are the most powerful piece of the movement.

Additionally, by cutting the extension short, you are also decreasing the amount of time that you are in that particular stride. While you are extending through that particular leg the opposing leg is preparing for the next step. By shortening the time spent in one stride the opposing leg has less time to prepare and inevitably begin its decent. This early decent diminishes the leg’s ability to apply force into the ground.

Finally, this will also limit the length of the stride for each step. There are two reasons that this occurs. The first is due to the fact that the rear leg is not at length which means that we are striking the ground in the next step a few inches shorter than we potentially could. In one stride this isn’t a big deal. However, if it occurs in a 100 meter sprint where, roughly, 50 steps are taken, then that 2 inches per stride can mean sacrificing 8 feet due to improper stride. The second reason this shortens the length of the stride is referenced above. Since the timing of the stride is shorter the recovery leg has less time to get back to position which causes it to make contact with the ground before it potentially needs to.

As you can see, even a slight breakdown in technique, when extrapolated out over a distance can severely impact that athlete’s ability to separate themselves from the competition.

Lateral Steps

Another inefficiency that I see very often, which many don’t see as an issue, is the use of lateral steps when accelerating. I see this in basketball and football players as well as the horizontal jumpers in track and field (i.e. long jump and triple jump).

In this image you can see the foot driving outside of the hip. The green line denotes the proper leg position under the hips.

This error can be identified, often, before the run begins. When athletes set up and their feet are outside the width of their hips the first step has to be a lateral step. Physics tells us so. If the foot is outside the hip and the force that is being created moves along the length and direction of the leg then the force will be to the side of the center of gravity causing it to move away from that leg. When this force is created, the body then has to create balance and bring the body back to center so it creates an opposing lateral force on the opposite side of the body.

As the athlete accelerates the opposing forces will cause the athlete to bounce from side to side until the athlete moves into an upright position and the forces begin to become more vertical.

Luckily, this is a very easy characteristic to correct by simply setting the athlete up in a narrower stance and bringing attention to the inappropriate acceleration trait. Often times, athletes are unaware of what they are doing. Simply shedding light on this can clean up many of the faults.

However, there are times when the lateral steps are not due to the starting position and instead they are due to the functional movement of the athlete.   

This image represents rotation at the hip. This particular position illustrates internal rotation at the hip. The knee falls inside the hip which drives the foot outside of the knee. The red line represents the current position. The green represents the ideal limb position.

Hip Rotation During Hip Flexion

This improper functional movement can be caused and emphasized by a lack of flexibility and/ or mobility within the soft tissue or a specific joint. In these actions the body will create movement through the path of least resistance. One of the most common issues that we address with our baseball, basketball, softball and tennis athletes is rotation at the hips causing the ankle to deviate from the desired position under the knee. When this occurs it will create a shearing force at the ankle as the foot makes contact with the ground.

This improper pattern is easiest recognized by using a vantage point directly in front of the athletes. You will notice as the athlete drives one knee up in front of the body the ankle will begin under the knee but slowly travel inside or outside of the knee. Based on the path of travel the coach can begin to deduce what is causing the undesirable movement.

Just like the first two examples, this deviation from the desired movement will cause a loss of power output, diminished stride length and additional fatigue to the system as it struggles to fight its anatomical limitations in the process of reaching maximum velocity.

The issue of rotations at the hip typically requires time and focused attention on tissue quality (stretching) and proprioceptive awareness (cuing).

As you can begin to see from these examples, even the slightest deviation from the desired position can cause a loss of power, force, and overall speed, as well as, increase the risk of injury. Like many movement skills and qualities this requires the evaluation and assessment of a coach to better understand the best path forward.