Monday, August 23, 2010

Measuring Michael Jordan's 1987 Slam Dunk Contest Vertical Leap

Comparing the vertical leap of past winners of the slam dunk contest would give us great insight into who really has the best dunk. So time for a Video Analysis of Sports Vertical Leap Dunk Off.

Last week we discussed how we could use broadcast footage of the slam dunk contests to measure the vertical leap of each player during the dunk. We looked at Vince Carter's 2000 Slam Dunk Contest win and estimated that his vertical leap was about 37.6 inches. see Measuring Vertical Leap at a NBA Slam Dunk Contest

The above story was picked up by Patrick at, who said "I would love to see how other dunks measure up".

The original plan for last weeks article was to use video of Michael Jordan's dunk from the free throw line in his 1987 Slam Dunk contest win. However Carter's dunk from 2000 gave us a better example. To measure the vertical leap from broadcast footage of the slam dunk contest we needed one view and image from the video that contained 4 elements. 1. A full view of the player, 2. a view of the underside of the backboard, 3. the basketball rim and 4. the floor below the backboard. All 4 of these features need to be in the image. want to see how other dunks measure up so I went back to YouTube to try and find better footage of Jordan in 1987.

Although the dunk from the free throw line is iconic, it may not be the dunk in which Jordan obtained his maximum vertical leap, because for this dunk he needed to cover the distance from the free throw line to the basket and therefore height was less important. During the same slam dunk contest though, Jordan completes a sideways dunk which scores him a perfect score of 50.

This dunk required Jordan to get higher to complete, so lets use this one to compare his vertical leap to Vince Carter's 37.6 inch leap in 2000.

Here is the video. Jordan's sideways dunk can be seen at about 1:59 for his highest point and the dunk from the free throw line can be seen later on.

Assuming his highest point is at 1:59 in the video, we take a snap shot and then use our known measurements. This time we do not need to use the width of the backboard because we have a side on view that allows us to measure the distance from the rim to the ground:
  1. Height of the rim is 120 inches above the ground.
  2. Michael Jordan is listed at 6 foot 6 inches or 78 inches.
  3. Hip height of a standard man is approximately 53% of his total height. Therefore Jordan's hip height is about 41.3 inches.
These measures are ideal for making a comparison between Carter's vertical leap and Jordan's. The fact that they are of the same height, 6 foot 6 inches, allows us to ignore any height advantage. As an example Nate Robinson needs to have a higher vertical leap than Dwight Howard to make a dunk, for the simple reason that he is much shorter. In our comparison both players are the same height and therefore they both require the same vertical leap to make the dunk. In a slam dunk contest it is not only about making the dunk and this is why we are interested in comparing their vertical leaps during the dunk.

Lets look at the image at 1:59 and the measures we can make.

Because it is difficult to make out the backboard we chose to use the height of the rim above the floor for our scale measure. We know this height is 10 feet or 120 inches. We draw the blue line down from the rim to the floor and give it the scale we desire 120 inches.

Now we can measure how high Jordan's hips are above the ground. This measure at 83.88 inches (yellow line). Subtract Jordan's standing hip height of 41.3 inches from this measure of his hip height at the top of the dunk and we get an amazing 42.6 inches or 6 inches (half a foot) higher than Carter's hip height in the 2000 slam dunk contest.

Of course the different angles of the cameras and footage and the differences in how the vertical leap measurements were made (not using the backboard for scaling in this image but using it for Vince Carter's dunk) means that inaccuracies will still exist. However a quick look through the literature and some past studies of Jordan at his best suggest that he could regularly jump 42 inches during a one handed dunk.

We will therefore assume our measure of Jordan's 1987 dunk to be a good estimate and based on the 2000 video footage of Carter's dunk we will assume that our measure of 37.6 inches is a good estimate of vertical leap for his dunk.

There is no doubt then that Jordan wins this video analysis of sports dunk off. Anyone think they have footage of a dunk with a vertical leap that can top Jordan's?


Nels said...

I'd like to see this one: - D-Rose on Dragic. Hard to get a good image, but might be possible in the first 5 seconds.

Patrick said...

Great stuff, thanks for taking a look at one of the iconic dunks in NBA history. It really puts Jordan's freakish athletic ability into perspective as well - the fact that he jumped 6 inches higher than Vince Carter; a player who at one time was considered Jordan's equal in terms of his dunking ability.

Dudley Tabakin said...

Thanks Nels. That video is not too bad, but Dragic is blocking D-Rose a little in the video at an important part of the video. Slam Dunk contests are great for analyzing this type vertical leap because the player is on his own and filmed from numerous different angles.

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