If you want two results from a workout – more muscle and less flab – you need a circuit that forces you to multitask.

With this one, you’re doing a metabolically demanding move with one part of your body while performing a static dumbbell hold for a common problem area (such as your upper back), says Dr Michael Mejia, certified strength and conditioning coach. The result: a kilojoule-torching workout that builds strength where you need it most.

Kneeling overhead step-up

Kneel with your body in a straight line from knees to head, holding two dumbbells just outside your shoulders. With palms facing each other, press the dumbbells overhead until your arms straighten, and hold that position through each rep. Now place your right foot in front of your body and push yourself up into a standing position. Reverse the movement and repeat with your left leg. That’s 1 rep.

Single-arm stability-ball chest press with hip raise

Lie with your head and upper back resting firmly on a stability ball. Hold a dumbbell at shoulder level in your left hand, your palm facing forwards. Bend your knees 90 degrees. Now lift your left foot a few centimetres off the floor and drop your hips until the top of your lower back is touching the ball. This is the starting position. In one movement, press the dumbbell up until your arm is straight, and raise your hips until your body forms a straight line from your knees to your head. Do all your reps, switch sides and repeat.

Stability-ball back extension with T-raise hold

Holding a dumbbell in each hand, lie with your chest on a stability ball and your arms hanging straight down from your shoulders, palms facing each other. Pull your shoulder blades down and together as you raise your arms to form a T. Hold that position. With-out dropping your arms, raise your torso until your body forms a straight line from shoulders to hips. Lower your torso and repeat.