Have you ever noticed how you excel on some workout days and lag behind on others? Perhaps you've got great glamor muscles (chest, shoulders and arms), but your back is weaker than it should be. Or maybe your upper body is tough as nails, but your legs just can't handle it?

Everyone has weak spots on their bodies, muscles or muscle groups that just can't keep up with the rest of their body. It's time to turn those weaknesses into strengths by training those muscles hard!

Double Down

If you've got weak areas, it's time to train them twice as hard as the rest of your body. Let's say you've got knee problems, so your quads and hamstrings aren't keeping up with the rest of you. Well, for the next two months, train all of the other muscles in your body just one day, and give your legs an extra day.

It's going to hurt bad, and you're going to feel the burn because your legs just aren't used to all the attention. But, by the time those two months are done, your legs will be caught up to the rest of your body.

Add Intensity

If you train your muscles to the max every day, it may be hard to think about adding even more intensity. Well, the important thing is to up the intensity of the workout targeting your weak areas, not necessarily your whole body. Keep your regular workout consistent, and focus on really shredding those weaker muscles.

It's tough to know when to increase weight, but sometimes you've just got to do it and work through the pain. Adding a few pounds to your workout is the only way to know if you can push harder, and you may find that you can. Speed up, lift heavier and spend less time resting in order to see maximum gains.

Don't Let Lack of Progress Get You Down

If you're focusing on those weak spots, chances are you're not seeing as much progress with that body part as you did with many others. Don't let that get you down, but just keep pushing.

Sure, right now you're really motivated to work that weaker body part, but what happens when your enthusiasm wanes in a few weeks? Instead of giving up, keep pushing and targeting those weak spots.

Change the Routine

Too many people fall into a set pattern of exercises and never change it up. While the concept of "muscle confusion" is great for preventing boredom, it won't really do much to help you shred muscle. The purpose of changing your routine is to encourage you to keep working hard.

That being said, changing the way you do certain exercises can be the key to improving your fitness. For example, if you've been doing barbell bench presses for years, why not try dumbbell presses, flys or cable presses? They work the same muscle but in a different way, and that change could be all you need to start seeing progress in areas you've been lacking.

Don't Forget the Secondary Muscles

Everyone focuses on the back, the chest, the arms, the legs and the shoulders, but what about the secondary muscles--the stabilizers? If you give these muscles their proper workout, you'll help your entire body grow much more effectively.

The lack of strength may not be in those big muscles, but in the secondary muscles that don't receive enough attention. Give those secondary muscles their due, and you'll find yourself much stronger and better able to do the tougher exercises.