By Max Mulitz
Except in very rare cases (possibly defensive backs and receivers) the actual height of a players’ vertical jump is not directly relevant to their ability to play football. The broad jump is even less immediately applicable. That said, both the broad and vertical jump are important metrics for predicting football success because they measure leg power.
Bill Walsh also points this concept out in his book, Finding The Winning Edge where he states, “Although the vertical jump is a reliable indicator of explosive leg power, this test has a few limitations as an evaluative tool. For example, vertical jump scores are affected by body weight. All factors considered, a 260-pound offensive lineman, who would be considered light by NFL standards for his position, would normally be able to jump higher than his 300 pound teammate. Even if both players were in comparable physical condition, the 300 pounder has to do more work than the 260 pound player because he has to move more weight over the same distance.”
Pat Kirwan demonstrates the importance of Jumping Metrics with his Explosion Index from his book Take Your Eye Off the Ball where he shows Vertical Jump + Broad Jump + Bench Press Reps is a meaningful predictor of which pass rushing prospects will be successful. While the Bench Press has largely been shown to be uncorrelated with success, I like that Kirwan uses both Broad and Vertical Jump because, as Zach Whitman points out in the FAQ for his site using more than one test reduces bias that can result from measurement error/a player having an randomly particularly good or bad day at one of the tests, so by combining two leg body power tests you are likely to get a more accurate estimate of a players true leg power than by using either test individually. Based on the above studies, we can expect metrics such as Pat Kirwans, which are already useful for predicting successful NFL players, to become even more powerful if we use weight adjusted jumping and instead of simple jump height, because weight adjusted jumping is a more accurate measure of leg power than jump height alone.