September 20, 2018

    Forty Yard Sprints and Force Plates: How to Sniper Speed Development

    This weeks guest blog post comes to us from former Sparta coach and current Strength & Conditioning coach of the CAL Bears, Scott Salwasser.

    At the collegiate level we have known about the connection between jump performance and sprint speed for a long time, based off of both research as well as anecdotal hands-on experience. What we have not known is the exact mechanism for this connection, until now. We force plate scanned our football athletes in conjunction with 40 yard dash testing. In the following case study I will explore the results of this testing while connecting specific timed splits to individual force plate scans and explaining how the movement qualities that are statistically proven to be connected to LOADEXPLODE and DRIVE exhibit themselves in our athletes sprint performance. The sample used in this examination will be limited to athletes that ran 4.49 or better, and will include final times ranging from 4.44 to 4.49. There is no question that the skill of sprinting plays a large role in the transfer of general output parameters to the 40 yard dash, but for the purposes of this article, I will be focusing purely on the bio-motor qualities revealed to us by the force plate and the associated sprint qualities displayed by the athletes.

    LOAD, as we know, is the ability to develop muscular tension prior to concentric movement, and is statistically most closely tied to absolute, or maximal strength. Therefore, since maximal strength exerts it’s greatest influence early on in the 40, this variable should have the greatest transfer in stance and start performance, which would be evident by an outstanding 10 yard split. The early part of the 40 also features a greater degree of knee flexion, requiring greater anterior chain force production (another trait of LOAD dominant athletes). However, these variables do not operate in isolation, therefore we would also expect to see a high EXPLODE score in an efficient early accelerator, as this will exhibit their ability to turn the incredible muscular tension created by the LOAD variable into applied force at the onset of concentric movement in the start. Our best 10 yard dash at 1.47 was produced by scan to the right.

    As you can see, this athlete exhibits extremely high LOAD and EXPLODE scores at 76 and 75, respectively which directly resulted in an excellent start. It is also no surprise that this athlete, being LOAD dominant, showed up well in maximal strength indices, performing a 455 pound below parallel back squat (at 185 pounds bodyweight). Squat has been proven as the primary movement to increase the LOAD parameter. Unfortunately, due to the imbalanced scan and lack of Drive, which will be discussed later, this athlete had the poorest 20 to 40, or late acceleration phase, of our sample at 1.94 seconds.

    The next phase of the 40, acceleration, can best be examined by looking at the 10 to 20 yard split, and based on logical progression, we would be looking to see an athlete strong in the EXPLODE parameter excel here. The reasons are several fold. This part of the sprint hinges on the athlete’s ability to apply a large amount of momentum changing force in a small amount of time. This requires a high concentric rate of force development and the ability to reach concentric peak force rapidly, the abilities that we measure with the EXPLODE variable.  Also, the trunk stability qualities that are associated with athletes that test high in EXPLODE are necessary in this phase to maintain an optimal body angle and complete line of extension for optimal force production allowing the athlete to quickly change momentum and pick up speed.  Our best 10 to 20 yard split was produced by the scan to the left.

    As you can see, with a score of 78 in EXPLODE, this athlete has the necessary qualities to accelerate rapidly, and compared to the last athlete, he is more reactive, meaning he exhibits more efficient use of the stretch shortening cycle, and therefore is able to be effective later in the sprint than his previous counterpart, as ground contact times become shorter and reactive strength (EXPLODE/LOAD) is at a premium.  It is also no surprise that, since clean is one of the primary movements designed to improve EXPLODE, this athlete excels in this domain, with an outstanding 315 pound performance at just 180 pounds of bodyweight. The final variable, DRIVE, is the ability to carry accumulated momentum and to finish movements smoothly and efficiently.  This variable maintains, or ideally builds upon, the concentric force developed by the EXPLODE variable, through the very end of the movement’s range of motion.  As legendary sprint coach Charlie Francis so eloquently states: “Sprinting is a sequence of slightly sub-maximal efforts, rather than one separate maximal effort after another.” If one were to purely analyze each individual step in isolation the force producing and reactive strength capabilities of the previous examples might be more impressive. However, due to the cumulative, cyclical nature of sprinting, and higher velocities’ shift to reliance on greater posterior chain force production (another trait of DRIVE dominant athletes), this athlete has the ability to accelerate for longer, providing them an opportunity to chase down the previously discussed teammates. Therefore, in a 40, athletes who excel in DRIVE should be very effective at building speed over time, shown through an outstanding performance in the late acceleration phase, which for athletes of this caliber, would be the 20 to 40 yard split.  The scan to the left resulted in our fastest 20 to 40 yard split at 1.81 seconds

    As you can guess based on the LOAD and EXPLODE scores, this athlete ran a pedestrian 10 yard split, comparatively, for a sub 4.5 forty at 1.57 seconds, however having the highest DRIVE score of the athletes examined so far allowed him to accelerate for longer and almost catch his quicker counterparts over the course of forty yards, closing a .1 second difference to .03.  This athlete also exhibits the anthropometry one would expect in a DRIVE dominant athlete, long and rangy, at 6’3” 190 pounds.

    Obviously, in an ideal situation, the athlete would be outstanding at all of these variables, through a balanced scan that allows them to start fast, accelerate quickly but smoothly and efficiently, yielding a complete race.  Our most balanced split profile was produced by the following athlete.

    This athlete did not win any of the splits but finished with a 4.44 forty on the strength of a balanced scan and complete race profile.  This excellence in each variable is even more impressive given the fact that this was also our heaviest athlete in the case study at 205 pounds.

    Equally as important as performance indices was the fact that over the course of roughly 200 trials as a team, there were no hamstring strains, which is a rarity in the public sector, and would be expected based on our reduction of scan predicated injury risks by 50% (from 60 to 30) over the training period through improved balance (all 3 variables within 15 points and above 45) in our scans.

    While this case study does not seek to present itself as hardcore statistical analysis, it is a good anecdotal example of the force plate in action in “the trenches” of a Division 1 football program.  We can see that it is not exclusively the absolute height of a jump that regulates performance, but rather the shape of the athletes signature, and HOW they jumped rather than how high they jumped.  Ultimately, the goal of the force plate in our program is to identify each athlete’s unique movement signature in order to be proactive in preventing injuries and improving on-field performance.  Our experience during our Winter training block gives ample real world evidence of both.

    Tag(s): Sports

    Other posts you might be interested in:

    View All Posts