There are so many exercises people do to "isolate their muscles" for that "perfect definition". Well, I hate to be the one to call you "mooks" (I actually love it!), but the truth is that there is no way to shape your muscles.
There is no such thing as "perfect definition"!
Understanding Your Muscles
When you exercise - say by doing a bicep curl - your entire muscle contracts. The mitochondria and myofibrils along the entire muscle are tapped for energy, and they are broken down equally. When your body repairs the muscle fibers, it adds more of these fibers to store more energy in the future. That is what causes your muscles to grow.
However, notice that I said "the entire muscle contracts". That means that the fibers all along the length of the muscle are worked, and thus broken down and repaired evenly. There is no way to "isolate" a certain portion of your muscle to give it that beautiful rounded look that we all want.
There are two factors that determine your muscle's strength and shape:
- Leverage -- The further away from the joint the tendon connects to the bone, the more strength the muscle will have - and the larger the "swell" of the muscle will be.
- Motor Units -- White twitch fibers are built for power, and they are larger. Red slow twitch muscle fibers are built for endurance, and they are slimmer. Everyone has their own unique balance of red fast, red slow, and white fast twitch muscle fibers - and that will not change.
No matter how much you lift, you will never be able to escape these two genetic factors - which control muscle size and definition.
Isolation and Perfect Definition Are Myths
You know how there are certain exercises that are "isolating" the muscle - for example Isolated Curls or Preacher curls? You feel the pain at the front part of the muscle where it connects to your elbow joint, and you think that you're really building that portion of the muscle.
Pain is actually misleading, and it just means that you're straining that part of the muscle. The entire bicep is being worked as you do that Preacher Curl, but the strain is placed on the tendon connecting the bicep to the elbow. There are no exercises that will target muscles, so getting that "perfect definition" is impossible.
Interestingly enough, none of the muscles in your body can contract alone - they all need synergistic secondary muscles to work. There's really no need to isolate your muscles, so isolation exercises are kind of a waste of time.
The only "isolating" exercises you should do are:
- Cable pushdowns (triceps)
- Preacher curls (biceps)
Pretty much every other exercise that you do will hit multiple muscles at the same time, and that will do two things:
- Use more energy (meaning more fat burned)
- Strengthen multiple muscles (meaning less time spent focusing on those muscles)
Focus on compound movements - which involve as many muscles as possible - for the best results in your strength training!