Traditional exercises that are commonly used in workout plans do not hit all parts of your muscles. Changing the motion of the exercise will help you to work muscles more than these exercises usually do. Using variations of workouts will have you feeling much sorer because your muscles will not be used to these movements. It is also a great way spice up your workout, which will motivate you to push harder. Variations play a huge role in avoiding plateauing because the changing of your workout will force your body to adapt to these new stresses that you have brought about on your muscles.
Decline skull crushers
How to do it: Can be done with a bar or dumbbells. Using the decline bench lift the weight up so that it is above your chest. Keeping your elbows straight (not letting them flare out) lower the bar to your forehead by bending your elbows. Extend your arms so that you finish in with the bar above your chest again. Doing a skull crusher on the decline bench as opposed to the flat bench you are taking stress off of your elbow joints and putting it more so on your triceps. The decline also allows you to get a greater range of motion with a better stretch in the triceps. This means that the triceps are being worked more than they would be in the traditional flat bench skull crusher exercise. I prefer to do this exercise with dumbbells as you are working both arms evenly easier. I find that with a bar it is easier to end up pushing more with one arm than the other.
Reverse grip bench press
How to do it: Have a spotter. Lie flat on bench press and grasp the bar using an under-hand grip. Lower the bar to your chest and lift it back up to the starting position.
The traditional bench press works the middle part of your pecs the most. It also works your deltoids triceps brachii and a little bit of your biceps as they are used to stabilize the bar. In the reverse bench press all of those muscles are worked but instead of the middle of your pecs being predominantly worked it is the upper part of your pecs. It is estimated that this exercise utilizes your upper pecs 30% more than traditional bench press does. If you want to work your upper pecs even more try doing this exercise on the incline press.
Bent Over Tricep Extension on the Seated Cable Row Machine
How to do it: Use a single handle as this exercise is performed one arm at a time. Put a knee on the bench. With the arm that is on the same side as the knee that is on the bench grab the handle using a neutral grip. Bend over about 45 degrees making sure your back is straight. Bring the handle towards you so that the handle is at your torso. Position your arm so that it is parallel to the floor and your forearm is pointing towards the floor so that it makes a 90-degree angle. Keep your arm still extend the weight behind you by bending your elbow. You should feel your tricep doing most of the lifting here.
Dumbbell tricep extensions only provide resistance on the tricep for a short amount of the rep. By using the seated cable row machine your are adding more resistance to the entire rep thus working your triceps more.
Curls using the seated cable rowing machine
How to do it: Use a straight bar or an easy curl bar on the seated cable rowing machine. Grab bar and lay down flat on the bench. Curl bar just as you would in a normal barbell curl.
An unorthodox looking exercise that is actually more difficult than it looks. By laying down flat and doing a curl there is an even amount of resistance throughout the rep. This challenges the bicep more as there are no easier parts of the rep. Also by lying down you are able to focus more on your posture and will not let you use momentum to bring the bar up, a mistake that I see too many people doing too often.
Reverse Preacher Curls
How to do it: Using the preacher curl bench or the machine. Sit on bench putting front of arms on the bench and grasp the bar with an overhand grip. Raise bar until arms are vertical. Lower the bar until arms are fully extended. Try not to let your elbows flare out, as this will take the pressure away from your forearms.
I find that many arm workouts neglect working forearms. Stronger forearms will help you to strengthen your grip and will work your biceps, brachialis, and your shoulders a little bit. By doing a reverse preacher curl you are able to more intensely work your forearms just like in a regular preacher curl where your bicep is more intensely worked. This is because almost the whole lifting motion is generated from that concentrated area instead of the effort being more spread out. I prefer to do concentration curls using free weights because I find that it is more comfortable than the machine.
It is not to say that doing these traditional exercises is bad. These exercises are very good for building muscles, however they do not work every part of your muscles evenly. By adding these variations into your workouts you will be able to work these muscles harder and achieve more gains. As I have always said it is better to train smarter than to train harder!