This idea popped into my head right as I was falling asleep, so we will see how good it appears when I am actually awake.
The game is a running/agility competition. Imagine 2 parallel half-meter wide rectangular areas that are about 10 meters long. At either end of each of these rectangles are large quarter-meter diameter red buttons on the ground. The basic goal of the game is for each player to pick a rectangle, and run back and forth pushing the buttons on their corresponding rectangle more times than the other player. If you have ever played basketball and gone to training sessions, you will recognize the run back and forth and touch the lines on the court exercise is the same as my exertion game.
This gameplay is simple, and doesn't really grab any part of the human psyche other than the "hard fun" beat the other player part. To fix this, there will be a little obstacle course in the middle of the rectangle. An IR array will be set up that the player must navigate to get to the other end of the rectangle. This array will be very simple, but will need to take some time (4-5 seconds) to get though. The punishment for breaking one of the IR beams (either running though the array or or making a mistake in the obstacle course) will be to receive an electric shock from a little electrode pair mounted on the player's arm. If the player really wanted to complete a loop quickly, they could run through the array, intentionally getting shocked in order to press the button faster. The shocks would get more and more powerful as the player ran through more times. The player would only get a minor shock for accidentally breaking the beam while contorting themselves in order to get through the array.
This arrangement adds more interest to the game on two levels. It allows players to feel a bit of schadenfreude when they see the other player getting shocked, but it also lends a sense of immediacy and adds adrenaline when the player really wants to run to the touch the button, but must carefully navigate the beams first in order to not get a painful shock.
If the gameplay works out, a social/team element can be added on top of this, taking advantage of the fun of watching other people getting shocked.
After seeing this video I realized that electrical shocks have many gameplay possibilities: