Your body’s biggest enemy? Time. You can smash double-your-bodyweight deadlifts, but deadlines keep you out of the gym and in your takeaway’s VIP club. Both of which are bad news for your six-pack.

But train right and less work can be a whole lot more effective. “It’s all about intensity,” says Dylan Jones, founder of P4 Body training, and a man who used to whip elite soldiers into shape.

As Jones points out – and a quick scout of your gym proves – half of most sessions are spent sitting down. Cut those rest periods and you spike your heart rate and metabolism. So a brief burst of exercise gives 36 hours of boosted calorie burn.

“If you’re doing this kind of circuit, at the right level of intensity, you don’t need to train for more than 20 minutes,” says Jones. In fact, if you can go longer, then you’re not working hard enough. That means you need to tackle something more taxing than bicep curls. “It’s about moves that offer the biggest bang for your buck.” By targeting the big muscles in your legs and back, you torch more calories, in less time.

But time pressures don’t mean you can cut corners. “If you only put 50 per cent in, you’re only going to get 50 per cent out,” says Jones. “Perfect form makes the exercises harder and more effective.”

A quick warm-up is also vital. “Otherwise you waste your first set as your muscles fire up.” Start with five minutes of dynamic stretching – think lunges, inchworms and lateral bounds – then tackle the circuit.

Remember: the more you sweat, the more fat you burn.

Dylan Jones’ 20-Minute Body Shred

“Your rest periods define how hard the workout is,” says Jones. Start with 30 seconds of exercise, 30 seconds of rest. As you improve, cut your rest and extend your activity – 40 on, 20 off, then 50 on, 10 off.

If you’ve got access to a sandpit, great. “The instability makes your body work harder,” says Jones. If not, grass will prove just as taxing.

Perform one set of each exercise, then rest before moving onto the next. After the V-sits, return to the high knees. Repeat the entire circuit three times.

High Knees

Run on the spot, driving your knees as high as possible. Focus on keeping your core locked and pumping your arms and legs explosively. If it helps, imagine you’re Usain Bolt.

Burpees

From standing, squat down and place your palms on the floor. Kick your feet back into a press-up position, then reverse the movement and jump into the air as high as possible. Drop straight back into a squat and repeat.

Press-Up To T Plank

Start in a press-up position. Lower your chest until it’s just above the floor, then drive back up explosively. In the top position, rotate your body with your right arm extended, so you finish in a T position.

Pause, reverse, then repeat on the left. Focus on keeping your core braced so your hips don’t sag.

Split Lunge Jumps With Overhead Reach

Start in a lunge and drive up through both legs to lift yourself into the air. Swing your arms to drive yourself up and cross your feet over before you land. Sink into another lunge and repeat.

Braced abs will keep you from folding forward. And help carve out that six-pack.

V-Sit Crunches

Lie down with your soles on the floor, fingers at your ears. Lift your shoulders and feet off the ground so your knees come up to your chest. Reverse the movement and repeat without letting your feet touch the floor.

Feel that fire in your abs? You will tomorrow.