Simple, But Brutal
Grab a pair of 85 pound dumbbells or kettlebells. This is the weight my former high school football players used, so feel free to adjust for your needs, but 85 is about right for most adults.
The challenge is simple:
Go as far as you can for five minutes.
It works best to go for a walk away from the starting point so the rest of the workout will make more sense.
The rest of the workout is simply this:
Return the weights to the starting point.
Obviously, the difficult part of the challenge is RETURNING the dumbbells to the starting point. What took five minutes "out" can take a long time back to the start. Just hold your posture and discover your traps for the first time.
In a gym setting, do loops around some equipment or go back and forth. (Don't use a treadmill, but if you do, film it so we can laugh at you when you fall.) An unpopular variation of this challenge is to go out for a 15-minute walk, then return, but that might be for lunatics only.