Why I like the broad jump more than the CMJ

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There are a myriad of performance tests out there for talent identification, recovery monitoring, and evaluating the effectiveness of training.  Most people are familiar with the vertical jumps, namely countermovement jump (CMJ), squat jump (SJ) and drop jumps/reactive strength index (RSI). All of which are pretty quick to administer.  In athletes, all three vertical jump scores correlate reasonably well each other as well as with sprint, relative strength, agility, and repeated sprint ability.  However across sports and age-groups, there is no consistent pattern of which jump test correlates best with game performance or scores on other physical fitness tests.  As stated above, the correlations are moderate to good, but not great.  That is why a battery of tests are usually employed, then the data is subjectively interpreted with the help of statistical software or AI. 

Including the broad jump in our test battery at the UNBSJ revealed something interesting.  Compared to all other tests, the broad jump painted a much clearer picture of athletic prowess when normalized to body height. Since then I have used it with youth and adults in many other teams and individual sports with similar results. Why their stature? On its own, absolute distance cleared was interesting but not really meaningful: Like most tests in the battery it helped give us an idea of what areas may benefit from more training emphasis, but that was about it. However, as soon as jump distance was scored relative to the size of the athlete, the quotient became excellent at identifying their overall level of athleticism. It was a bit of serendipitous magic because distance relative to body mass, or leg length ended up becoming rather meaningless. 

What is the broad jump, and how to you measure it? The broad jump is a horizontal jump performed from a standing start. The athlete starts with the toes of their shoes are at the start line. With a full arm swing wind-up, they jump as far forward as possible using a (simultaneous) two-foot take-off and a (simultaneous) two-foot landing. Jump distance is measured from the start line to their rear-most point upon landing —which should be the heels. Measure the distance cleared and divide that by the height of the athlete (i.e. their stature). That number is the athletic key performance indicator (aKPI).

aKPI = Broad jump distance cleared / Stature

Broad jump distance cleared, divided by athlete height correlated very well to other strength, power, speed, and conditioning tests. This aKPI matched the UNBSJ coaching staffs subjective rating of athleticism in current soccer, basketball and volleyball athletes. It correlated highly with player stats and individual awards. It was a good identifier of new talent/team members. And, it was sensitive enough to track players climbing up the depth chart. The sensitivities, predictions, accuracy, and correlations of other tests were less clear.  Ditto when multiple variables were combined in regression equations.  

Why was one test comprised of just two measurements (stature and broad jump) so much better than all the others alone or combined?  Daniel Kahneman wrote that simple models are often better than complex models for explaining complex phenomena 1 , but that does not explain why the broad was better than the vertical jump.

The latter appears more sport-specific to volleyball and basketball, yet was not as good at talent identification in those teams.  Both measure explosive triple extension with a full arm swing.  Both are initiated with a full-body wind-up into a slow SSC.  Why is broad jump/power index a better indicator of athletic performance? I do not know.

From a practical standpoint, the reason why is irrelevant. We found something that was more accurate and more reliable than everything else. As a bonus, it is about the cheapest, fastet, and easiest thing to measure. In the years since, the aKPI has served very well with team and individual athletes in other sports and age groups that I have been involved with. We can get more useful information in a few minutes than in an hour of extensive tests, allowing more time for training or recovery. It is simple. Why it works better than all the other stuff does not matter, but I cannot leave it alone. I am curious individual 2 and have come up with a some plausible explanations.

1) Being able to move explosively in a horizontal direction is key to many sports, even the aforementioned vertically-dominant volleyball.  A broad jump captures the straight ahead version of this, vertical jumps do not.

2) Take off angle.  We know from sprinters that the closer to horizontal they leave the blocks, the faster their 10m time.3, 4  Since body mass and gravity remain constant, the vertical component of the jump force must be sufficient to oppose that and provide flight-time. Trigonometry tells us that if they are more powerful, the same vertical force can be produced at a lower take-off angle, thereby resulting in a longer horizontal jump distance.  From a power production perspective, it does not explain why it is better than a vertical CMJ where more power simply equals more height in a 1:1 ratio.  However, take-off angle is important for understanding each of the points that follow.

3) Landing a broad jump requires deep triple-flexion —thereby adding a dynamic flexibility component.  Static flexibility does not correlate well with performance or injury susceptibility. 5 It remains unknown if dynamic flexibility is any better. Nonetheless the coordination and control to rapidly go from triple extension to triple flexion is itself an athletic task. If an athlete is unable to squat full-depth and rock their weight from heels to toes, they must land before their COM drops too low.  This means their optimal take-off angle must be higher, and/or they must make premature ground contact.  Consequently, their broad jump distance will be less than an equally powerful (and sized) athlete that has full dynamic ROM.  

4) Similarly, the quicker of two equally flexible (and powerful) athletes can employ a lower take-off angle as they require less hang-time to prepare for landing.  That is, less time to transition from maximal extension to maximal flexion.

5) The broad jump does not penalize athletes with heavy arms.  They may even be helpful to increase jump distance.6 (Just like they can be helpful in a number of other sport skills).  Here is little experiment you can do on your own:  Measure your CMJ using a vertec, mat, video, app or whatever tech you like. Then measure your broad jump the old fashioned way: with a tape measure. Holding onto a pair of 2.5kg dumbbells, repeat the tests.  What happened? Your vertical jump decreased, and you felt like you were flying during the broad. Pretty neat isn’t it?

6) It is really hard to cheat at the broad jump. There are many tricks when measuring standing reach that can pad your jump scores using a Vertec, or chalk-on-wall. (Within about 5 minutes of coaching, I help a a player to increase their vertical jump score by 15cm). When using jump mats or smartphone apps, changing your landing posture can also eek out a few cm. Clown shoes will hurt your broad jump score, but excessively short shoes will hinder the athletes ability to push fully through the MTP joints, so it is pretty much self regulating.

In summary, the broad jump is equally dependent upon power, as the vertical jump.  However the broad jump also encompasses quickness, dynamic flexibility, upper body mass and coordination. Testing it is cheap, easy, fast, and non-exhaustive. Dividing the distance cleared by stature gives the key athletic performance indicator allowing for comparison, tracking and monitoring.  This is why I like the broad jump more than any of the vertical jumps. 

—CG