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Portable Shadowball packs physics into every punch

A ball with a crust, mantle and core just like the Earth itself might be the future of how boxers and anyone looking to get fit will train.

Shadowball is a free-floating punching bag. No gym required. Cedric Salcedo

Shadowball. It sounds like a futuristic game played on a distant planet (maybe one with two suns?). Fitting, because if Cedric Salcedo's campaign on Kickstarter succeeds, Shadowball might just be the future of exercise.

Shadowball is a boxer's speed bag that doesn't hang from anything -- it's completely untethered. So instead of working on your hand-eye coordination at a gym, you can take the Shadowball outside to any flat wall and punch away. The way the ball is constructed and balanced means that it's more likely to stay in your immediate vicinity than bounce away wildly as would be the case with something like a kick ball or soccer ball.

To find out just how the Shadowball pulls this off, I talked to inventor Salcedo, who says the idea was sparked by his work as a loudspeaker designer studying how sound bounces off walls. He said the challenge was finding the right combination of weight, density and velocity, which he explains here:

Weight. "The ball cannot be too light or too heavy. Too light and it's like punching air, but go too heavy and you'll hurt yourself. Let's remember that the ball is not on a standstill. There is serious kinetic energy involved when you have to hit a moving object coming at you, and then send it in the exact opposite direction. Here we have the equation force equals mass times velocity to deal with."

Density. "The ball cannot be too soft or too hard. Too soft is not good because it does not offer enough resistance and does not represent the normal density of a typical target of a punch -- like a human body. Too hard makes it too difficult to control as it reduces the amount of surface contact between the ball and the fist, not to mention the increased risk of injury. Unlike conventional designs (speed bag and heavy bag), the Shadowball is often hit at unpredictable angles. A harder ball also makes it susceptible to unexpected trajectories due to wall imperfections."

Velocity. "The ball cannot be too slow nor too fast. Too slow and you will not have enough bounce to be at a convenient distance from the wall. Gravity is at play here. The ball is in constant fight against gravity and therefore requires a minimum speed to overcome it. Too fast would just be too difficult to hit."

Salcedo said that balancing these three components was a like a puzzle he had to solve -- a difficult proposition because adjusting one parameter dramatically affects the other two. Eventually, he found what he calls the product's "Goldilocks zone."

"Our patent-pending solution optimizes the three parameters through a ball with multiple layers, very similar to the structure of the Earth -- core, mantle and crust," he said. "The Shadowball is designed with this same layering of materials using a combination of polyurethane foam and polyurethane gel with varying weight and density."

If you tend to zone out over all that physics talk, all you need to do is take a look at the video below to see how awesome the Shadowball is in action. I don't do any kind of boxing-oriented workout, but I still kind of want to get my hands on one to try it out.

If you feel the same, you can snag a Shadowball in microfiber for CAD$95 (about $84) or you can get the leather version for CAD$115 (about $102). Sacedo is seeking to raise a total of CAD$40,000 (about $35,500) and if he does, Shadowballs are expected to start shipping in March 2015.