The training method that made this 48-year-old one of the fittest men on earth

In fact, if you were to hold a competition where men of any age had to lift and then run a long distance, I’d put money on Paul to win. The guy set a Delaware powerlifting record when he deadlifted 485 pounds at a bodyweight of just 164 pounds. He also completed three IRONMAN competitions in Kona—that’s a 2.4 mile swim followed by a 112 mile bike ride and a 26.2 mile run—and his best time is eleven hours, which is ungodly fast for someone over 40.

There’s more: Paul was also recently the top-placing American in the Crash B Indoor Rowing World Championships, finishing a 2,000-meter row in 6:45.

Paul is a living example of a fitness principle that I’ve always preached at Gym Jones and in my new Men’s Health book : Don’t specialize. Train to be good at any physical task life throws at you.

There are many people today who choose only one fitness skill to train at the expense of all others. Marathoners fall into the trap of only running. Lifters choose to only lift. Bodybuilders decide to only build muscle mass. This is called “specialization.”

But a person who trains—and excels—in both endurance and strength is someone who has truly useable fitness. What’s the point of being able to deadlift a compact car if you become winded walking up a flight of stairs? Who cares if you can run a fast marathon if you don’t have the strength to pick up your kid and carry her when she becomes too tired to walk on a family vacation?

There are two reasons people neglect to train other fitness skills. First, they don’t realize that exercising in other ways will actually make them better at their primary sport (more on that soon). Second, they believe in the idea of “specialization,” something you may have heard trainers talk about.

“Specialization” in fitness is the idea that all fitness skills have a cost, and to improve in one skill, such as running, you must become worse in another, such as strength. Proponents of specialization point to marathoners and powerlifters as primary examples of why you should specialize.

Running marathons and powerlifting require completely opposite skills. The former requires a robust cardiovascular system and well trained slow-twitch muscle fibers, which are muscle fibers built to power lower intensity, long duration activities like running, walking, or cycling. Think of slow-twitch fibers as the Toyota Prius of muscle fibers—they can go a long distance on just a little bit of fuel.

Powerlifting, on the other hand, requires you to use and build your fast-twitch muscle fibers. These fibers are designed to drive short, powerful efforts, such as lifting something heavy a couple times, or sprinting a short distance, like 100 meters. They have little endurance, require a lot of fuel, but move big weights and propel you from point A to point B very quickly. That’s why I like to think of them as the drag racers—hugely powerful for just a handful of seconds but inefficient over the long haul.

Proponents of specialization argue that when a marathoner starts to lift heavy, he decreases his efficiency. That’s because strength training adds size to all of his muscle fibers, making him stronger, yes, but also hurting his ultimate goal of running 26.2 miles as fast as possible. It’s like throwing a bunch of heavy luggage on top of your Prius. You now have to carry that extra weight, and the miles per gallon drops. You can either slow down to maintain efficiency, or run out of gas before you reach the finish line.

The equivalent argument for powerlifters is that when a powerlifter starts to do cardiovascular exercise, he replaces some of his powerful fast-twitch fibers for the slow-twitch variety. Our powerlifter may now have more endurance, but it’s at the expense of his strength. It’s like downgrading the engine of your drag racer in order to drive it further and save on gas mileage. That puts him at a disadvantage when he’s trying to generate as much power as possible for a big lift.

Here’s the problem: Specialization only holds true at the highest levels of elite sports. This means, yes, that a marathon runner with a 5-minute-mile pace probably shouldn’t try to gain too much strength or else his speed and endurance will drop, and a powerlifter who can deadlift over 1,000 pounds likely shouldn’t go out for long runs, or he’ll lose some strength.

When I teach fitness seminars, there are inevitably those who think they should specialize because they’d like to be just as good as the best in the world.

I’m sorry, but for the average person, that’s not realistic. It takes years of round-the-clock training to reach that level. You essentially have to become a full-time athlete and do nothing else.

There’s also an obvious catch to specialization: It makes you worse at everything else. With world-class skill in one area comes a deficiency in other areas, not to mention the potential for a host of sport-induced imbalances and health issues.

Don’t get me wrong, I think specialization is great for a person who is winning championships, competing as a professional, or earning a living from his or her sport. But how many people do you know who are in that boat? How many people do you know that can run a sub 2:15 marathon, or deadlift over 1,000 pounds? The average person is not even close to the highest, elite level of their favorite activity.

So what should you do? Most people should train like Timmons: Lift at least a couple days a week, do long endurance sessions once or twice a week, and do hard interval efforts once or twice a week. You can find my go-to program for building elite, all-encompassing fitness in my Men’s Health book —which also features 100+ workouts—out now. I’ve used the program with everyone from CrossFit Champions and NFL pros to Special Forces soldiers and some of the most ripped men on the planet.