Old habits are hard to break. But if you keep doing these 5 old school exercises you will be breaking more than old habits.

1. Leg extensions - Unfortunately this exercise seems to be the extent of most guys leg training. Probably because sitting down and pumping out reps of quad extensions are a lot easier than squatting down with hundreds of pounds on your back. Despite the "burn" you may feel from your upper thighs when performing this exercise, it is not a very efficient leg exercise as it only isolates the muscles above the knee. The only time this exercise has much benefit is in a rehab setting where these muscles directly surrounding the knee need to be developed for stability and strength. Otherwise opt for any variation of the free-range squat.

2. Behind the neck pulldowns - This is another exercise that I still see people doing in the gym. I cringe every time I see someone take a wide grip on the angled ends of the pulldown bar and starting pulling it down behind their neck. The angled ends of the bar are an outdated design and are not where you should be gripping the bar. This puts your shoulders and rotator cuffs in a very vulnerable position. Putting most of the stress on the shoulders and limiting range of motion away from the back muscles this exercise should be crossed off your list. Work on being able to do bodyweight chin-ups instead or at least pulldowns to the front.

3. Behind the neck shoulder press - Similar to the behind the neck pulldown, the behind the neck barbell shoulder press places your shoulder in a delicate position. It is basically the same movement but by adding additional weight to the bar and pushing up in the vertical plan you are putting your rotator cuffs at an even greater risk of injury. With the extra weight you can pile on the bar with this exercise, trying to even unrack the bar will soon send your shoulders screaming in pain. Switch to the safer option; the front barbell shoulder press.

4. Concentration Curls - Probably the most popular bicep exercise for beginners wanting to "get the pump" and get Arnold-like biceps. It's too bad a lot of experienced trainers still waste their time on this exercise. No matter how many reps of concentration curls you do, you won't get that bicep peak like the Terminator, as muscle SHAPE is genetically determined. Muscle SIZE on the other hand can be increased through basic movements that allow a heavy weight while use many muscles instead of isolating one smaller muscle. Standing barbell or dumbbells curls are a better choice for bicep development, but better again are close grip chin-ups, which put a lot of stress on the upper arms while working many other muscles.

5. Crunches - If would be nice if all you had to do to get that ripped six pack would be to lie on the floor and pump out hundreds of reps of back breaking crunches. Despite what the infomercials want you to believe, this is NOT true! You wouldn't build your biceps by doing 100 reps with no weight, so why would you think you would develop your abdominals by doing 100 crunches or more? Your abdominals primary purpose is to actually stabilize your spine and to keep your torso from twisting in half under times of physical stress, not lift your neck off the floor.

Overall, the best exercises for your abs are exercises that allow your body to use your core the way it was meant to be used: for stability and support. Bodyweight planks, and compound exercises like squats and overhead presses will work your abs better than any crunch will ever do. Combined with a clean diet you might just see those abs looking back at you in the mirror.

OK quiz time. Do you see a trend with these 5 exercises?

They all involve sitting down, (which we are all experts at already) and they work only a small section of muscle, allowing you to pump out endless reps without much effort.

For you busy guys who want to get the most out of your workouts, stop wasting your valuable time on these old school exercises that break your body down instead of building it up.

Author's Bio: 

Get your FREE report "The Truth On Fat Loss, How To Finally Lose That Beer Belly" from Sean Barker at dadfitness.com.

Sean is a Certified Personal Trainer and a proud and busy Dad. Sean has been involved in the health and fitness industry for over 15 years and have appeared in High Performance Muscle Magazine, been on health and fitness radio shows and was selected as a sponsored athlete by one of the top supplement nutrition companies in the world. His popular Dad Fitness fat loss workouts have helped Dads around the world lose fat, gain muscle, and get lean in less than 3 hours per week. For more information on the Dad Fitness workouts that will help you burn fat without spending hours in the gym, visit dadfitness.com.