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# Topend Sports Newsletter: 28 July 2015

## Vertical Jump Testing & Physics

The vertical jump is one of the most widely used fitness tests, and rightly so as it is an excellent test of an athlete's leg power. There are quite a few different devices for measuring vertical jump, from the basic technique of using a wall to jump up against to expensive force plates. I prefer the direct measurement of jump height minus standing reach height, but many people use a technique that requires a more complex calculation to determine jump height, usually based on hang time.

Basic physics is used to calculate jump height based on time in the air. Timing mats and force plates can be used to measure 'hang time', but you can also use video. My colleague at www.whatsmyvertical.com has created a nifty tool to assess the height a video-recorded jump.

It is possible to measure vertical jump height using video because jump height is a function of the time between take-off and landing (hang time). Using video of known frame rate, one can determine the hang time by subtracting the timestamp of the take-off from the timestamp of the landing. Playing around with basic physics equations you end up with this equation that can be used to calculate the jump height:

jump height = 4.9 * (1/2 hang time)^2

Each method of measuring vertical jump has its limitations, and it all comes down to what equipment you have available. Even the basic jumping against a wall method can be cheated by athletes who don't extend fully their standing reach height. With the methods using hang time, the scores can be manipulated by not landing back on flat feet or with the legs extended.

### Think you can't dunk? Think again...

 Pro baller Adam Folker and the world's most badass dunker Justin Darlington have just revealed the exact process they use to systematically transform ordinary guys like you and me into dunking BEASTS with the precision of a Swiss watchâ€¦ It's kinda hard to believe this is possible but they've been doing it for years and are finally pulling back the curtain on the system they've been secretly developing. Check out what all the insane hype is all about. See more. PS: There's a downright brain-melting video of Justin's crazy dunks on that page so check it out.

### Poll: Which equipment do you use to measure vertical jump?

There are quite a few ways of measuring leg power using a vertical jump test, different techniques as well as different equipment. In this poll I'm asking what equipment you use to measure vertical jumping ability. See the poll here.

### Video: Box Jump World Record

See the (grainy) footage of the Guinness World Record for the highest standing jump onto a platform - 152 cm (5 ft) by Justin Bethel (USA) of the Arizona Cardinals. Bethel's vertical jump at the 2012 NFL combine was 39.5 inches (100cm), only 5th best behind that year's leader Kashif Moore who jumped 43.5 inches (110.5cm).

Rob's Blog