Don’t be put off by the name. Contrary to what it suggests, complexes are incredibly simple – all you need is a barbell and a whole lot of hard work. You’re going to do back-to-back exercises with this piece of kit and that’s it, geddit? Perfect for when you’re strapped for time, or can’t bear another hour spent swapping between sets with a sweaty guy who never wipes down his station.

It works because compound moves with barbells are more effective than time in the preacher curl machine. By working multiple joints at once, you recruit more muscles fibres. “That gives you an increased hormonal effect from exercise, giving you a greater potential to grow and, paradoxically, to lose weight, too,” explains PT Leo Savage, from London’s The Third Space gyms.

That’s because your muscle speeds up your metabolism, which means your body expends more energy doing nothing. Result? You burn body fat in your sleep. Compound exercises are, therefore, your route to body composition change – less fat and more muscle – without the time sink of moving from machine to machine.

These exercises can slash your workout time as well as your waistline when you up the intensity. “Blasting your body with an all-out, 20-minute workout leaves it with no choice but to rapidly increase energy production,” says Savage. “That will carry on for hours after you finish.” Known as EPOC – or excess post-exercise oxygen consumption for those of you looking to score big points at your next pub quiz – this biological process means you bid adieu to that spare tyre long after you’ve hit the showers.

The Simple Muscle Barbell Complex

Now it’s time to put these principles into practice. Use the same weight on the barbell for your entire circuit – changing them wastes time – but don’t try and be Superman. Pile on plates and you won’t be able to finish all the reps of your weakest exercise. Select a weight you can comfortably complete eight reps of military press with, to ensure your muscles don’t burn out too early.

Ready? Complete six reps of each exercise, then move straight on to the next, without resting. Take 30 seconds to catch your breath once you’ve completed them all, then go again, for six rounds in total. Good luck. You might need it.

Military Press

Why: The overhead press works all three heads of the shoulder as well as your triceps, adding strength but also making you look broader.

How To: Barbell at your shoulders, palms facing forward, press the barbell above your head explosively until your arms are fully extended, then lower the weight under control.

Bent Over Row

Why: Target your lats, rhomboids, biceps and rear delts with this exercise. That’s you back, arms and shoulders, for non-bros. You’ll earn a V-shape back, accessorised with T-shirt-filling biceps.

How To: Hold the barbell with an overhand grip, hands slightly wider than shoulder width apart. Legs slightly bent, back perfectly straight, hinge forward at the hip. From here row the weight upwards into the lower part of your chest. Pause. And return under control to the start position.

Romanian Deadlift

Why: A staple exercise when wanting to build power in your posterior chain. Soften at the knees slightly while your hips flex backwards to keep the tension in your hamstrings, strengthening them throughout the rep.

How To: Put the barbell on the ground. Bend your knees slightly to grab it, keeping your shins vertical, and back straight. Without curving your spine, push your hips forwards to lift the bar. From upright, sink your hips back to lower the bar, bending your knees only slightly.

Squat

Why: It’s the ultimate leg day exercise because it targets your glutes, hamstrings and quads – plus your core – for serious strength.

How To: Pick the barbell up and position it across your upper back, with an overhand grip. Slowly sit back into a squat with your head up, back straight and backside out. Once your thighs are parallel with the floor, drive through your heels to push explosively back up.

Lunges

Why: The large range of motion in a lunge recruits maximum muscle fibres in your glutes and hamstrings. As a rule of thumb, the longer the lunge, the more you work your posterior chain; the shorter the lunge the more you recruit the quads.

How To: Keep the barbell across your back as you step forward with your right foot and sink into a lunge. Both legs should be bent, with your back knee as close to the floor as possible. Drive yourself back up and repeat on the other side. Enjoy your breather, then do the whole lot again.