When you're trying to make the most of limited exercise time, the last thing you want to do is waste effort on exercises that don't pay off. There are two types of exercises we should avoid — those that can easily lead to injury, and those that don't produce results. Here are some exercises that are potentially unsafe exercises:

Lat pull-down behind the head

This exercise is done sitting on a machine with a weighted, cabled bar overhead. You reach for the bar, then pull it down behind your head and neck.

So many things can go wrong with this exercise. Alignment is number one: Only people with very mobile shoulder joints can keep their spines straight enough to do this exercise properly. Most people's shoulders aren't that flexible. So the move can lead to shoulder impingement or worse, a tear in the rotator cuff.

Not only that, but the tendency is to hit the back of the neck with the bar, which could injure the cervical vertebrae.

A safer alternative: On the pull-down machine, lean back a few degrees and bring the bar down in front of your body to the breastbone, pulling shoulder blades down and together. Contract your abdominals to stabilize the body, and avoid using momentum to swing the bar up and down.

Military press behind the head

In this exercise, you lift weights or barbell starting from behind the head at shoulder level, and press up and down behind the head.

It can cause the same problems the behind-the-head lat pull does and should be avoided. It's also wiser to choose an exercise that targets several muscle groups at once, rather than putting all the strain on the shoulders.

A safer alternative: When doing the military press, keep the weights or bar in front of your head. Press up and down from the nose or chin level, going no lower than the collarbone. Always sit straight against a back support, and keep the natural curve in your spine, with upper back and glutes glued to the chair,

Upright row

Pulling weights, a barbell, or a weighted cabled bar up under your chin is a big no-no. When people pull their hands (carrying the weight) up to their chin, they are going to compress the nerves in the shoulder area, impinging the shoulder.

A safer alternative: Instead, do a front or lateral shoulder raise, lifting weights out to the front or side of the body. Even better, try the bent-over row: Bending forward at the hips, hold weights down beneath your shoulders, then lift toward sides of your body. This exercise is much safer, and targets all the muscles of the upper back as well as the biceps.

Lying leg press with knees bent too deeply

Lying on your back with your feet on a weighted plate, you push the plate up and bring it down, with the aim of working the quadriceps, hamstrings, and glutes. The problem with this exercise comes when you bend your legs too far.

This can be very dangerous if you come down too deep. That's mainly because form falls apart. Your spine cannot maintain proper alignment when your legs come back too far, so the pelvis tilts and the lower back begins to take over. And the weight used is usually heavy enough to injure the back, causing strain to muscles or damage to disks. In addition, bending your knees too deeply can injure or damage your knees. If you want to do this exercise, a good rule of thumb: Keep your butt from rotating off the back of the machine, and don't bend past 90 degrees at the knee and hip.

Using bad form on cardio machines

Walk into any gym and you'll see some people sweating through their treadmill, elliptical, or stair-climber workouts with their bodies hunched over and a death grip on the handrails.

People will put a really huge incline (or high resistance) on the machine and then grab on, this is totally contraindicated. If you can't run or walk with your hands off, you shouldn't do it. Exercising in a hunched-over position can keep you from breathing deeply, and that the improper alignment of your spine can make the workout more jarring to your shoulders and elbows.

Use a natural gait. And don't hold the handrails because it breaks the natural biomechanics of the body.

Always lifting with a weight belt

Bodybuilders have long used these belts to provide low back and abdominal support when lifting heavy weights. But now they seem to be standard equipment even for many occasional weightlifters.

Too many people wear weight belts too often. They should only be used when you're getting 85 percent to 90 percent of your one-repetition maximum. Most people are not working at that level. Unless you have a back injury or another medical reason to use the belt, the level at which the average person works doesn't require a weight belt. And it can do more harm than good. When the belt is on, you're not allowing your normal core muscles to get strengthened.

Ronald Abvajee is founder of My Personal Trainer Wellness, South Africa's first 'virtual gym'.

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