The Awesome Power of a Fully Inflated Earth Ball

Yesterday was Field Day for my daughter’s school. Grades K through 8 converged on a local park and rotated through a series of field games. Each team was made up of about 12 to 15 students from all the grades. They had team names and colors and many of them came in coordinated costumes.

The day was beautiful: blue skies, light breeze, and a broad expanse of grass and clover that was tall enough to cushion a fall but not so tall as to get everybody worried about ticks and chiggers and poison ivy. The kids were in high spirits. The teachers and parent volunteers were relaxed (well, as relaxed as can be expected with 200 or more kids in a field full of games).

With 15 minutes to go before the buses arrived, I was trying to work out in my head the rules for a game that would utilize two giant “Earth” balls AND would not result in debilitating injury.

Earth BallFor those who don’t know, an “Earth” ball is just a giant, inflatable ball (also called a cage ball). I grew up calling them Earth balls because they are huge (anywhere from 48 to 72 inches tall) and because the ones I played with as a youngster were scale replicas of good ol’ planet Earth. I spent many years as a camp counselor and many more working for camps and adventure programs. I’ve led countless field games that use giant cage balls of every color and yet I always call them “Earth” balls.

This is the second year I have volunteered at Field Day. Last year, I noticed that they had a giant pink “Earth” ball for a game called Sumo Wrestler. I immediately volunteered to be the adult supervisor. In part I volunteered for this activity because “earth” balls invite all kinds of fun, physical play: jumping, hitting, pushing, kicking, etc… But the bigger reason I volunteered was because all of those activities inevitably result in injuries—injuries that always take us adults by surprise.

It was my hope to fend off at least a few of the worst ones, because nothing ruins a field day more than a dislocated shoulder or a case of whiplash.

The game of Sumo Wrestler is one of those games that are instantly attractive to kids and most adults. The idea is that the giant ball is in the center of a circle that is split in half. Two contestants start on opposite sides of the ball and try to push it past the opposite side of the circle. Kids get really excited about challenging their friends. Even kids who don’t usually go in for physical conflict will line up to take a turn in the ring. I attribute this to the fact that they focus on the ball more than the conflict. Adults also see it as a safe way for kids to wrestle. The ball is big and soft and filled with air—how could a big ball of air hurt, right?

newton's second lawWell, all that air and the membrane that surrounds it are excellent conduits for Newton’s laws of motion. Especially the second law. In short, if there is even a small difference in the mass of the kids who are pushing against the ball, the smaller one will almost always be catapulted away with often surprising force. It gets worse if one or both of the kids manages to get even a little running start before they hit the ball. After all, force equals mass times acceleration. And if the kids are not pushing on opposite sides of the ball, if they are both even a little to one side of center, the ball shoots off and the two kids collide with whatever part of their body was foremost at the time—generally the noggin.

Although I abandoned Sumo Wrestler early in the day, my attempts to come up with an energetic replacement that would involve fewer than two kids leaving my station in tears left much to be desired.

So this year, with a little trial and error, I came up with a game that I called Sumo Volleyball (please feel free to make suggestions in the comment section—PLEASE). Teams get to push not just one but two giant balls. Here’s the set-up and rules:

  • Set out cones to form 2 parallel lines (about twice the width of your ball apart and maybe 30 feet long).
  • Teams face each other across the space between the lines. Teams play on their knees at all times.
  • An adult stands at each open end of the lines to keep the ball in play.
  • GOAL: push one of the balls over the opposing team so that it lands on the ground behind them. As soon as one ball hits the ground behind a team, stop play and start over.
  • RULE #1: all players must stay on their knees at all times. No standing up. No squatting. If someone gets off their knees, stop play and give a point to the other side.
  • RULE #2: Knees may not cross the line of cones. You can reach across the line but you can’t “walk” across the line. If someone crosses the line, stop play and give a point to the other side.
  • OPTION: every 2 points have the teams switch sides (gives them a chance to stand up, rearrange, and not have a disadvantage because of wind)

Earth Ball GameOnce the kids got over the disappointment that they wouldn’t be knocking each other out in a semi-sumo match, they had a blast. With 2 balls almost everyone is included and you can still get a very satisfying hit on the ball although it is harder to generate as much force compared to when you are standing up. You can still be knocked over, but when you are on your knees your center of gravity is much lower. The greatest risk actually comes from getting knocked over by one of your own team mates. The ball can still shake up a smaller child, especially if it catches the child on the head, but I saw that happen only twice and both times the kids came back after sitting out for a round.

What I loved seeing was that there were many times when the kids just loved hitting the ball back and forth. I think if I had made the lines farther apart they would have been just as happy to spend 20 minutes or so battering these giant balls back and forth with no score at all.

Field Day play at its best. Silly, active, and fun.

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