Working your middle doesn't have to mean lying around on the floor. Here are six elevated exercises for a slimmer, stronger midsection.

Sometimes the hardest thing about stomach crunches is finding a spot to do them.

The gym is crowded, the floor is filthy and Bruno the bouncer keeps dropping 25-kilo dumbbells near your head.

Also, crunches can be pretty boring. So we asked former Mr Universe Lee Labrada to suggest a few off-the-floor alternatives that use a chin-up bar and other things you'll find at any gym.

Unlike standard floor movements, most of these exercises get you to raise your legs instead of your head and shoulders.

Labrada's top tip: remember that it's the job of the stomach muscles to pivot the pelvis towards and away from the rib cage. The legs merely provide resistance.

To get the most from each repetition, concentrate on rolling your pelvis towards your rib cage before lifting your legs.

This helps the abdominal muscles contract and prevents you swinging your legs, which is cheating.

"Be sure to stay in control of each exercise throughout the entire range of motion, bringing your legs down as slowly as you can," adds Labrada.

The lowering part is the most productive, because it stresses the abs more than the lifting phase, thereby firming and toning them.

That said, try one set of each exercise for as many repetitions as possible. And save the exercise mat for the rest you'll need afterwards.

Hanging Side-Twist Raises
Hang from a bar with your hands spaced a little more than shoulder-width apart. Your legs should hang straight down.

Curl your trunk upwards, raise your knees and slowly roll your hips to the left. Hold for a moment.

Slowly lower your legs and repeat, this time raising your knees and rolling your hips to the right. Slowly lower your legs. Repeat.

Side Bends
Stand with your back straight and your feet shoulder-width apart.

Hold a dumbbell in your left hand and place your right hand on your hip. Your left arm should hang straight down at your side.

Now slowly bend to the left, so that the weight drops towards your knee. Return to the starting position. Perform 20 repetitions before switching the weight to your right hand and repeating.

Once you're able to do this comfortably for two or three sets, add 2.5 kilograms to the weight.

Angled Bicycles
Lie on an incline sit-up board with your head resting at the higher end.

Reach back with both hands and grab the top of the footrest for stability. Raise both legs until your feet are about 10 centimetres off the floor, keeping your knees unlocked.

In a slow, controlled motion, move your legs as if you were pedalling a bicycle.

Be sure to keep your head and back flat on the bench throughout the exercise. This will help prevent stress on the lower back muscles. Cycle in the air as long as you can.

One-Arm Pull-Down Crunches
On your knees, face a high-pulley machine. (You should be about a metre away.)

Grab the handle above you with your right hand and pull it down until it's level with the right side of your head, with your palms facing in. Your left hand can rest along the left side of your head.

Turn your body slightly to the left until your knees point to the left side of the machine.

Keeping the handle close to your head, bend straight down, slowly curling your rib cage towards your pelvis. (Bring your head down about 45cm to 60cm from the floor.)

Slowly rise to the starting position. Do 10 to 12 repetitions, then switch to work the left side.

Hanging Knee Raises
Grip a bar with your hands spaced a little more than shoulder-width apart. Your legs should hang straight down.

Curl your trunk upwards, then slowly raise your knees towards your chest as high as you can.

Try not to arch your back - it should remain rounded during the lift. Now slowly lower your knees until your legs are extended. Repeat.

(Note: if you can't raise your knees all the way, lift them as high as possible. Also, go slowly so that your body doesn't start to swing.)

Angled Leg Tucks
Lie on an incline sit-up board with your head at the higher end. Reach back with both hands and grab the top of the bench for stability.

Keep your head and back flat on the bench and draw your feet towards your backside. This is the starting position.

Now slowly roll your trunk up and tuck your knees into your chest. Roll up like a ball. (Note: as you become stronger, increase the bench's incline to make the exercise more challenging.)

Slowly lower your legs to the starting position. Repeat.