To serve in the SAS you must have strength. And to climb Everest you must have agility. But to do both you must be fit.

Quick, coordinated and powerful. Just like the man that's done all three, Bear Grylls.

Read more: Bear Grylls' skills: how to motivate your team

Want to train like him? Try the Bear Grylls Epic Training System, which integrates functional fitness to improve balance, coordination, power, aerobic capacity, muscular strength and endurance.

Complete the following exercises in sequence once for a 10-minute workout, twice for a 20-minute workout and three times for a 30-minute workout. Work for 20 seconds and rest for 10 seconds between exercises.

The Bear Grylls workout

Pull-Ups (overhand grip)

Instructions: This one's nice and simple. Grab a bar (with an overhand grip) and repeatedly pull your body weight above it so your chin reaches over the bar. Done.

Goblet Squat to Double-Hand Military Press

Instructions: Holding a kettlebell (or any weight) in both hands, close to your chest lower yourself into a squat position.

Then during the upward phase press the weight above your head into a press.

Bear Tucks

Instructions: In short, this is a jumping and explosive squat.

Cross Mountain Climbers

Instructions: Start in a normal press-up position. Move your left knee to your right elbow. As you return to your starting position bend your elbows and perform a press-up.

Abdominal Rocks

Instructions: Lie on the floor on your back. Extend your arms above your head and lift your feet off the floor. Keeping the core tight rock forward and back in a 'cradle' like movement.

Kettlebell Russian Twists

Instructions: Sit on the floor with a kettlebell positioned on the right hand side (by your hips). Bend your knees and lift your feet off the floor. Then rotating your torso move the weight to the left side of your body in a twisting motion. Repeat on alternate sides.

Dragon Push-Up

Instructions: A normal push-up but at the bottom of the movement, bring your right knee to your right elbow. Then perform the same on the left.

Tri to Superman Push

Instructions: Start in a normal press-up position. Lower your body to the floor. At the bottom pause. Raise your left leg and right arm. Push up into a "Superman" position. Return to a normal press-up position and repeat on alternate limbs.

Hanging Leg Raises

Instructions: Hold onto a bar. Bring your legs to a 90 degree angle, keeping them as straight as possible. Then hold.

Bicep to Double-Hand Military Press

Instructions: Hold the kettlebell (or weight) in both hands standing up straight. Perform a bicep curl and at the top of the movement press the weight above your head.

Narrow Push-Ups

Instructions: A normal push-up but with the hands closer than shoulder-width apart to target the triceps.

Double-Hand Swings

Instructions: Stand with your feet shoulder-width apart.

Hinge at the hips. Keep your chest upright and hold the kettle bell in front of you with arms extended. Bending your legs slightly pass the kettlebell between your legs. Squeezing the legs and glutes, propel the weight in the air in a thrusting motion. As the kettlebell drops back down drop it between your legs and repeat the motion.

Cross Crunches

Instructions: Lie on your back. Lift the left leg straight and reach your right arm diagonally across to tap the outside of your left ankle. Repeat on the opposite side.

Mountain Climbers

Instructions: Start in a plank position. Engaging the core and keeping the back straight bring your right knee to your chest (at speed). Return to the starting position. Repeat with the left.

Narrow Pull Ups (underhand grip)

Instructions: Again nice and easy. Grab a bar (with an underhand grip) and repeatedly pull your body weight above it so your chin reaches over the bar. Done.

Dorsal Raises

Instructions: Lay on your front, face down. Extend your arms in front of you. Inhale, tense your glutes and muscles of the spine and raise your upper torso off the floor.

There's also some sound sports science behind it.

Military muscle

Bear says, "[During the World Wars] training was no longer about physical wellbeing. It was about survival".

But it was in times of a global conflict that great leaps forward were made. An army physician called Dr. Thomas L. DeLorme pioneered a new rehabilitation technique to help the thousands of injured American servicemen returning home. According to research published in the Journal of Strength and Conditioning, "DeLorme's new protocol consisted of multiple sets of resistance exercises in which patients lifted their ten-repetition maximum. DeLorme refined the system by 1948 to include three progressively heavier sets of ten repetitions, and he referred to the program as Progressive Resistance Exercise." Sound familiar? It should. It forms the basis of most strength-based training regimes used in gyms the world over.

Bear followed a similar training protocol to this for years. But expanding on this "repetition scheme," he developed the more advanced concept of "time under tension" that you see in the BG Epic Training system. But why?

Time to grow

Arguably more important than the repetitions performed is the time your body and muscles are under tension. If you think about it your body doesn't count repetitions or weight, it only counts stress.

Bear says, "What's brilliant is we've had many guys adopt the BG Epic Training System who could bench and lift some impressive weights for an impressive number of repetitions. But as they learnt the principles they learnt to perform things like Turkish Get-Ups with perfect form for minutes on end too."

An idea supported by research published in this Journal of Physiology study that aimed to "determine if the time that muscle is under loaded tension during low intensity resistance exercise affects the synthesis of specific muscle protein fractions." Simply, will more time lifting the weight produce more, better quality muscle?

To test this they took eight men and had each perform three sets of unilateral knee extension exercise at 30 per cent of one-repetition maximum. Some participants completed the exercise slowly, lifting for a total of six seconds. Others performed the same exercise, with the same weight, but completed the action in one second.

The results? After ingesting 20 grams of protein and monitoring how the body absorbed and used it, it was found that the muscles in the group that experienced more time under tension experienced a greater degree of protein synthesis - the repair and regrowth of the muscles. More time under tension equals more muscle.

No gym? No excuse

Another element of the BG Epic Training System is it can be done anywhere. No gym needed. It embraces a method of training known as calisthenics. But in Bear's workout it's all about the right kind of calisthenics. "I don't think I've done a conventional sit-up in years. There's nothing wrong with them as such, I've just not needed to include them in my routine" Bear admits.

But how's this possible? In short, better biomechanical energy.

You can load up a leg press machine and just max out, but that doesn't encourage the joints in the body to work cohesively. In contrast, exercises like the Mountain Climbers, Tri to Superman Push and Cross Mountain Climbers in the workout above use all the muscles in the body and they must work together. This isn't to say you should say farewell to the leg press all together, but to quote research published in the Handbook of Sports Medicine and Science:

Gymnastics, "An increase in skill difficultly corresponds to the demand for higher mechanical energy."

What GQ's Fitness Correspondent says about Bear's Workout

There is no perfect workout plan. This is why the National Strength and Conditioning Journal stated in 1991, "Is there a single, perfect workout? A workout with the best weight training, plyometric, flexibility and endurance exercises? A workout with the precise number of sets and repetitions? A workout that tells the athlete exactly how much weight to use? The answer is "No". There are many." But there are lots of ways to get fitter, stronger and leaner. You shouldn't discriminate against any or strictly favour one. As soon as you do, you close your mind and limit your potential.

But what's great about Bear's is the functionality. It considers the body in its entirety to produce a strong, functional physique.

One that in the broadest sense of the word is just fit.

Everest-climbing, ocean-rowing, fit.

Click here for more about Bear Grylls Epic training, buy your copy of Bear's fitness book *Your Life;

[note]Train* here and sign up to the Bear Grylls Survival Race here[/note]