Jan 29, 2015

False Step Acceleration: Friend or Foe?

By Todd Brown, CCS

Using data-driven analysis, the author breaks down the effectiveness of using a “false,” or backward, first step as an acceleration tool. His findings may surprise you.

Watching a college football game last weekend, I saw a tailback begin a play taking what the television analyst described as a “false step” when the ball was snapped. The analyst commented on how counterproductive that step is due to the time he is losing to get to the line of scrimmage and that if the tailback were to eliminate that step and “drop and go,” it would be more beneficial in getting to the hole more quickly.

I have heard this argument for years. Connect the dot wisdom such as this reminds me of one of the greatest logicians in all of fictional literature: Sherlock Holmes. Holmes said, “It is a capital mistake to theorize before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts.” This quote holds true in the case of the tailback and his false step (FS).

At first glance, the FS appears counterproductive. In fact, some training methods attempt to eliminate the backward step to produce a more time-efficient and powerful start. But if this paradoxical movement appears to inhibit performance by impeding acceleration, then why do athletes inherently take a step back to move forward?

The answer is quite simple: In order to propel the body forward from a stationary position, the center of mass must be situated in front of the support area. This can be accomplished by rotating the body forward about the ankles or by displacing the support area behind the center of mass. Either way will provide the necessary outcome, however, does one lead to better performance when compared to the other?

Using a step back has been associated with poorer performance, because the time used to perform the FS could have been used to move forward instead of backward. Alternatives have been used (drop and go [DG]) to minimize or eliminate the step back to improve acceleration. This movement requires the athlete to simultaneously tilt the body forward about the ankles while performing a semi-countermovement of the hips and knees. Once the body lean is steep enough, the knees and hips are extended, producing forward acceleration of the athlete. Which start results in the greatest power development, minimizes start time, and maximizes acceleration?

Research in the last eight years has examined and reexamined the FS and the DG as a means of accelerating. Science has compared these two starts in the following areas: (1) Begin Time (which has been defined as horizontal force greater than 10 N), (2) Impulse Time (defined as finish time when horizontal force dropped below 10 N minus the start time), (3) Horizontal Ground Force, and (4) Velocity/Displacement.

The begin time (was actually slowest in FS. In fact, it was 50 to 100 percent longer compared with DG (0.460 vs. 0.304 milliseconds). Therefore, it appears the anecdotal evidence is supported. On the basis of this information alone, we should begin training our athletes with the goal of eliminating the step back; however, examining impulse may suggest otherwise. In the case of impulse time the FS was only 0.24 seconds, whereas the DG displayed a range of 0.41-0.56 seconds.

So, although it may take slightly longer to begin producing force, the action is completed much more quickly when using an FS. In regard to horizontal ground force (force generated to propel the body forward), starting with an FS produces the greatest mean power of the two starts. The values reported for FS and DG were 8.09, and 0.16 J/kg, respectively. This indicates that the FS is the best way to increase kinetic energy of the center of mass in the horizontal direction (there is a 97-98 percent drop-off when using the DG starting method). It now appears an FS produces not only larger power but also a shorter time (impulse).

Having a quick start and generating large amounts of power are certainly beneficial, but does it translate to moving more quickly? By examining the same time point for each start, the FS was best (1.95 m/sec) compared to the DG (0.42 m/sec). This means by beginning with an FS you will cover more ground in a given period of time than in a DG. This was supported further as the center of mass was displaced 0.25m, and .012 m with FS, and DG, respectively.

Using DG has been suggested to prevent the wasted time of stepping back and provide a much more explosive start. Although force initiation is generated quickly, the time elapsed to complete the task is greater, negatively affecting both velocity and displacement. Furthermore, because a countermovement must be used with this start, the center of mass is displaced downward, which contradicts Newton’s Third Law of Motion indicating there will be a disproportionate vertical return compared with the horizontal movement desired. In other words, the vertical force produced cannot be redirected quickly enough by the rotation about the ankle axes to result in efficient horizontal movement.

Using a FS was originally thought to be wasted motion and decreased the ability to accelerate. Although inherently paradoxical, the research-based information suggests the FS holds the most promise to maximize performance during the first few steps of acceleration. This inherently natural movement demonstrates greater force development with the shortest impulse time. As sports-performance professionals, we need to take heed in what Sherlock Holmes suggests: “It is a capital mistake to theorize before you have evidence. It biases the judgment.”

Todd Brown, CCS, is a sports science consultant working in south/central New Jersey. He has worked with Major League Baseball, the National Football League, and Women’s Professional Soccer. He can be reached at: [email protected]. FEEDBACK:

I think the false start allows for more controlled motion as well as increased power. Do you think the same mechanism applies to basketball players when they do that extra hop just before dunking?