We train hard at Gym Jones, the gym where I’m the general manager. Some people say we’re the world’s most hard core, hard working gym.

The fitter me and my crew become, the more we need extra work to keep improving. This rule applies to anyone who has ever hit a plateau in their exercise program.

Our fix: A handful of carefully selected “finishers.”

We do two types of finishers. The first kind correct imbalances, fix exercise technique, or injury proof your body. The second type—and this is where it gets fun—are a final ass-kicker of the day, an opportunity to absolutely drop the hammer and suffer in the name of improvement. There are 10 finishers in my new Men’s Health book Maximus Body, along with 100 full-length workouts.

But here’s my go-to finisher: The 500-meter row. It’s beautifully simple. In it, you just row 500 meters as fast as you can. I’ve seen it radically improve the fitness of everyone I work with, ranging from beginners to special forces soldiers and CrossFit Games champions.

The distance is long enough that your lungs need to be efficient so you don’t gas out. But it’s also short enough that your muscles have to be powerful to rocket you through the meters as fast as possible. This helps fill your fitness gaps, and creates a balanced athlete who is good at most tasks.

The other reason I love the 500-meter row: It’s a psychological test. To finish as fast as possible, you have to block out your brain screaming at you to slow down or quit. Learn to do that consistently, and magic happens where you become truly fit. (If you’re interested in how you can hack your psychology to improve your fitness, Maximus Body from Men’s Health features an entire section devoted to just that.)

Add this finisher to the end of any workout. The key: Go your absolute hardest and try to improve your time each session. A good goal is to finish in less than 1:30.

Directions: Set a rower’s computer to count down 500 meters. Set the “damper”—the toggle on the rower’s fan—to a higher number, such as eight, nine, or 10. In general, for short, hard efforts, you want that number to be higher, whereas for longer rows you want it to be lower. Begin, rowing as fast as you possibly can. Go for 500 meters, and try to finish in 90 seconds.