Amy, good evening I hope you are well and having a great night. With regard to your question, consider the following. Every muscle in your body has a "partner" (called the antagonist) which is capable of opposing its contractile forces. For example, when you perform a biceps curl, the biceps muscle would be termed the "agonist" and the triceps would be the "antagonist." (the easy way to remember these terms is to think that the agonist is the one that is in agony because it's performing the work). As you curl the weight, the motor cortex of your brain signals the triceps to relax in order to allow the biceps to contract. This phenomenon is called Sherrington's Law of Reciprocal Inhibition. Here's how we can take advantage of this phenomenon in a very practical way:
You first perform a set of barbell curls, and then rest perhaps 1-2 minutes. For set two, you perform a set of lying dumbbell triceps extensions. As you do so, the biceps muscles are "inhibited." The triceps contraction actually forces the biceps to de-activate, which simply means they will recover faster as a result of having performed the set of triceps extensions. You then rest, go back to the curls and back and forth until all sets for both exercises are completed.
There are three additional benefits to the use of antagonistic pairings:
If you perform (for example) 5 sets of biceps curls one after the other using two minutes of rest between each set, you obviously get two minutes of rest between each set. However, if you perform a set of curls, then rest two minutes, then perform a set of triceps extensions, rest two minutes, etc., you now achieve more than four minutes of rest between two sets of the same exercise, even though the total workout duration remains the same.
Training muscles in antagonistic pairs ensures equal (or at least similar) strength development around both sides of the joint. This is very important for overall size and strength gains, because if the strength ratio between agonist and antagonist is significantly disparate, the brain will reduce your strength levels in an effort to protect your joints.
We hope this helps. Take care and have a great night.
