Hey everybody. I wanted to talk about this next myth because I am so frequently approached in the gym about it. I hope that this clears up some of the confusion.
Myth #4: A new exercise will shock your muscles.
What you should know: Muscles are stupid; they cannot differentiate between two similar exercises.
All a muscle can do is contract or shorten, usually pulling two bones closer together. They do not twist, bend, change shape (other than increase in size) or "tone up". With this in mind, the best exercise for any muscle is one that allows a muscle to contract through a full range of motion in opposition to some form of resistance. A muscle cannot differentiate between a band, a free weight or your own body weight. In a study on muscle recruitment in the quadriceps (the big muscles on the front of your upper leg), there was no difference between squats and leg extensions. The squat caused the quads to contract harder, but this could have been a function on increased load. Stay away from the idea of "shocking a muscle" and try to think big picture. Besides, shocking a muscle is really the "spot reduction myth" in disguise.
So why choose different exercises at all? Although a single muscle does not know the difference between two similar exercises, we can select different exercises that will challenge our body to better coordinate various muscles. Your nervous system and other musculature become more involved when you choose more complex exercises (squats over leg extensions) or train in unstable environments (bands and free weights are more "unstable" than machines). The coordination of various muscles may enhance your performance and allow you to lift heavier weights, do more reps or perform complex exercises that burn more calories.
Most importantly, choose the activities you enjoy. All exercise has its benefits and drawbacks but results can only be realized if you do the exercise often enough and long enough to see results. The best exercise is the one you like and will do with frequency.