Building a chiseled, resilient body requires more than lifting heavy weights—there's good nutrition, proper rest and recovery, and taking super-supplements at the right time to help boost muscle growth and strip body fat. But on the physical side, one of the most underrated methods for building a true warrior body—and perhaps one of the most effective—is short-burst work at maximum intensity.

If you need a label, you can call it intervals, HIIT, complexes, or circuit training. Martin Rooney, trainer to some of the top combat athletes in the country, simply calls it hard work.

Known for getting his athletes into top physical and mental shape in record time, Rooney is a master of torture and results. His most recent favorite method, something he's dubbed "100 Reps in 100 Seconds," is exactly as hard as it sounds and will help you build a more rugged body (if you don't wuss out).

This Isn't Hard Work For Hard Work's Sake

Caveman

This method translates into actual physical results.

"I came up with the idea when I started working with Colton Brown, one of the top judo players in the country," says Rooney. "When he first walked in to my gym earlier this summer he weighed 182 pounds. Now he's a monster at 198."

Rooney attributes at least part of Brown's muscle gain and superb conditioning to this new protocol.

"I believe if you can take a light weight—sometimes even your bodyweight—and pour all of your energy into five exercises for a total of 100 seconds that you'll hit more motor units than you would even touch with a regular weight-training session," he says. And according to Rooney, it's a great way to rapidly drop body fat and increase mental toughness.

"When my guys are on the mat they can't give up," says Rooney. "This method increases their work capacity, strengthens their connective tissue, and gets them leaner and tougher quicker than most methods I've tried."

Now there's nothing magical about the timeframe or even the reps. Rooney is the first to point out that "100 Reps in 100 Seconds" is more of a challenge that is to be done once per week instead of a stand-alone program. It should be part of a regular weight-training program.

But if you want to challenge your body in a new way—and reap the muscle gain and fat loss that goes with it—you'll want to try one of Rooney's five challenges below the next time you hit the gym.

Challenge #1 - Full Body Barbell

Grab your stopwatch and set it for one minute and forty seconds (100 seconds). With this method you're going to load a barbell with a relatively light weight—Rooney suggests starting with 95 pounds—and perform the following exercises one after another as fast as you can with good form.

Bar Push-up * x 20 reps
Stiff-Leg Deadlift x 20 reps
Military Press x 20 reps
Back Squat x 20 reps
Bent-Over Row x 20 reps

* To do the Bar Push-up, simply put your hands on the bar and get into a normal push-up position. Bring your chest down to the bar and explosively push back up.

Isn't 95 Pounds a Bit...Wussy?

It may seem light at first, but you won't be thinking that for long. "Try holding that sucker for 100 seconds and you'll see how heavy it can get," says Rooney. That said, Rooney suggests choosing a weight you think you can get all the reps with. If you use 95 pounds the first time you do it and beat 100 seconds, try bumping it up to 100 pounds or more the next week.

How Long Do I Rest?

Rooney suggest resting three to five minutes before moving into another Challenge. "Ideally you'll have another guy with you timing you," says Rooney. "So after he goes, you'll go right after and that'll be his rest period. Once you finish, he'll be getting ready to start his next challenge."

Challenge #2 –The Gun Show, aka The Bodybuilder Killer

This pure upper body challenge will fill out your shirtsleeves and leave you gasping for air. But be warned: by then you're only halfway done.

10 Chin-ups
10 Dips
10 Biceps Curls
10 Overhead Presses
10 High Pulls

Repeat one more time without rest in order to make 100 reps.

How Much Weight Should I Use?

Rooney suggests starting with a barbell that you can curl for 12-15 reps and using that for your curls, overhead presses, and high pulls. Oh, and don't bother adding any weight to the chin-ups and dips. Trust us.

Challenge #3 - The Lower Body Torcher

Although Rooney and his MMA athletes hang two twenty-pound chains around their necks before doing this tough lower body challenge, he suggests you start off with just bodyweight (unless you have some chains lying around). You can also wear a weighted vest.

25 Squats
25 Good Mornings
26 Alternating Side Lunges (total)
24 Alternating Front Lunges (total)

If you didn't make the 100 seconds the first time, Rooney is sympathetic. Not many people do. "This is the toughest Challenge to conquer in a minute and 40 seconds," he says.

Challenge #4 –The Gut Check

Got a pull-up bar hanging in your doorframe or a tree with a low branch nearby? Then get out of your chair and try this bodyweight challenge right now (then come back and report your time).

22 Push-ups
21 Ankle-grab Sit-ups*
21 Sit-outs * *
21 Bodyweight Squats
15 Chin-ups

Why the odd number of reps?

Since Rooney hasn't seen many athletes get over 15 continuous chins, he won't ask you to do 20. To make the 100 seconds, you'll have to get through those chins without letting go of the bar once.

* To perform the Ankle-grab Sit-up

Ankle Grab Sit Ups

Begin by lying on your back with your hands stretched overhead. In one motion bring your arms and legs together while sitting up and grabbing your ankles. Reverse the movement before repeating.

* * To perform the Sit-Out

Sit-outs

Begin in a pushup position with your feet wide. Shoot the left foot under your body and out to your right side while lifting the right hand so that your body is supported on the left hand and right foot as shown. Then bring the left foot back to the original position before shooting the right foot under the body and out to the left side while lifting the left hand as shown. Keep repeating. Your hips should be turning side to side as you are reach each foot out.

Challenge #5 – The Two-Hitter Quitter

A quick warning from Rooney: "This is not as easy it looks. "My first try I did it in 101 seconds, but some of my guys completed it in over 150 seconds," he says. "Prepare to be humbled."

10 Pushups
10 Ankle-grab Sit-ups

Switch back and forth between both exercises as fast as possible and complete for five sets one after another. Throwing up is optional.

Important: The Crucial Warm-Up

Although these challenges seem like something you can just waltz into the gym and perform, you have to prepare your body. "You'll get gassed even faster if your adrenaline is pumping and your body isn't warmed up," says Rooney.

Before you do any of the challenges, quickly go through this warm-up written by Rooney.

A1) 10 Jumping Jacks
A2) 10 Seal Jumps (Similar to a Jumping Jack but bring your arms in front of you and "clap".)
3 sets with no rest in between
B) 50 Pogo Jumps (Act like you have a jump rope and quickly bounce on the balls of your feet.) 3 sets with 20 seconds of rest in between
C1) 10 Bodyweight Squats
C2) 10 Push-ups
C3) 10 Ankle-grab Sit-ups

3 sets with 30 seconds of rest between each circuit.

After finishing the warm-up, rest 3 minutes. You should now feel loose and ready to move into the first challenge. (If you feel worn-out, you're about to be in big freakin' trouble.)

"Oftentimes guys can't even get through my extended warm-up when they first come through my gym," says Rooney. "But after a few sessions it's a breeze."

A Few Final Tips From Rooney

• On the challenges that use barbells, make sure to select a weight where you don't compromise quality for intensity. Then again, don't use a bar that's too light either. "You'll have to do these a few times to get a feel for it," says Rooney.

• Start with one challenge per week and gradually build up to doing two or three challenges in one day. "Do it right and it'll be the longest 200 or 300 seconds of your life," says Rooney. "Two sets will kill most people."

• Make it a competition. "Grab a group of guys and a stopwatch then hit the gym," says Rooney. "Trust me, if you're by yourself the urge to stop halfway through will be intense. With a couple of training partners watching and ridiculing you, you'll make sure to finish."

• Attack every single rep as fast as you can with good form. "Don't slow down or hold back. You're going into the gym to better yourself, so make sure not to cheat or give up. You'll only be letting yourself down."

• If you don't make it in under 100 seconds, don't start crying. Just beat your time the next week.