Every workout routine, no mater how good it is, needs to be changed after a certain amount of time when the body gets used to it and you can't milk any more gains from it. This is the main reason behind the idea of training two opposite muscle groups (agonist and antagonist muscles), one right after another in a super set. There are a number of routines that use this principle, of which maybe the most popular one is Charles Poliquin's "German Volume Training" or "GVT".
Just to give you an idea of what agonist and antagonist muscles are, I'll point the biceps and the triceps, where when one of the muscle groups contracts the opposite group relaxes and vice versa.
There are a few reasons of why everyone should try opposite muscle group training at least once:
1. More strength
The main reason for agonist - antagonist training is probably the strength benefit that you get, especially during the second exercise of the super set. Some studies have shown that a muscle group can work harder if it's preceded by the contraction of the opposite (antagonist) muscle group. The antagonist exercise seems to prime the nerves that force the agonist muscle to contract, thus creating a stronger, more powerful contraction.
Let's take the bench press as an example - try doing one or two high repetition sets of barbell rows before you hit your work sets on bench press. You'll be amazed that you feel stronger while doing your bench press after the rows.
2. You will work more muscles at the same time
Whenever you do an exercise there are multiple muscles activated to support the movement. Primarily, the worked muscle group is the one that takes the greatest load. But there are also other muscle groups involved, such as stabilizing muscles and the antagonists to help you control the movement. When you work the opposite muscle group, almost all the same muscles are engaged, but this time the roles are changed as the antagonist muscle group takes most of the load.
Training opposite muscle groups optimizes the number of contracting muscles fibers, which in turn increases the weights being lifted and helps with anabolic hormone production.
3. You will recover faster
Training a muscle group right after you did a set that worked the opposite muscle group will help you recover faster by increasing the blood flow in the worked area and flushing out the lactic acid. Let's say you train your triceps and you do a few sets with a minute of rest between them. During the rest period the blood flow in the triceps decreases, the oxygen flow to the triceps decreases and the disposal of by-products from the muscle is slower. But when you add set of biceps curls right after the triceps set, you are shifting certain amount of blood in the biceps muscles and the triceps keeps contracting to a degree keeping the blood flow higher in that area.
4. You will save time
One additional benefit of this type of training is that you will save time. Doing super sets will give you a lot less time to rest, making your workout shorter and more intense at the same time because you have cut your resting intervals.
Here is how a 3 day split agonist-antagonist workout would look like:
Monday - Chest, Back and Shoulders
Exercise sets reps (ex1) reps(ex2)
1. Bench press / Cable row - 3 8 8
2. Incline BP / Barbell row - 3 8 8
3. Shoulder press / Pull ups - 3 10 10
Wednesday - Legs and Abs
1. Squats / Hanging leg raise - 4 10 10
2. Leg extension / Leg curls - 4 10-12 10-12
3. Calf raises / Sitting Calf Raises - 3 10-15 10-15
Friday - Biceps, Triceps, Abs and Lower back
1. Triceps dips / dumbbell curls - 3 8-10 8-10
2. Triceps extension / barbell curl - 3 8-10 8-10
3. Back extension / crunches - 3 12-15 12-15
Some tips to remember :
- When you choose your exercises, try to choose exercises that look similar but the movement is done in the different direction (ex. bench press and barbell row, shoulder press and pull up etc.)
- Do the two exercises as a super set with minimal rest in between. (a set for biceps followed by a set for triceps with 15-20 seconds of rest)
- Switch the order of the exercises every week.
- Cycle your routines. Do this workout for 7-8 weeks and then return to your regular split