A compound exercise is any exercise the utilizes more then one joint through out the movement. The example we will use today will be the seated row. The seated row is an exercise that is done often but isn't usually done efficiently. Using a cable and pulley system, the individual:
- sits down and holds some form of a handle
- starting with their arms and forearms straight, they pull the handle until their arms are parallel with their torso
Isolating vs Targeting
Despite popular belief there is no way to isolate specific muscles only target them.
Try this example to see this principle in action:
Standing up straight, while keeping your arms and forearms straight, lift your hands so they are shoulder height.
Which muscle group contracted first to bring about this movement?
When I was asked this question I answered the deltoids but I was wrong and maybe you were too.
To discover the correct answer repeat the example, but take one arm and place it behind your back touching the same side as the arm you will be lifting to shoulder height. (If you aren't flexible enough to do this find a friend and have them perform the example while you touch their lower back.)
Did you feel the muscles along the spine contracted? These muscles contract in order to maintain posture while your center of gravity changes as your arms lift up.
With every movement we do, our bodies will utilize different stabilizer muscles. Therefore we can't every isolate muscles. What does this have to do with the seated row? A lot.
Eccentric, Concentric, and Isometric Actions
When our muscles are under tension they can shorten (concentric actions), lengthen (eccentric actions), or stay the same length (isometric actions). Each of these actions can produce different amounts of force. Eccentric being the strongest and concentric, the weakest.
Larger Muscles Produce Larger Amounts of Force
The larger a muscle is the larger number and size of the muscle fibers it contains. This subsequently produces more force. (We will cover more of this in Part 2)
When performing the seated row, most people grab the handle, curl their backs and then pull the handle all the way to their chests. Knowing what we now know, what is wrong this execution of the exercise?
The seated row is designed to target the biceps and the lats but these aren't the only muscles that are involved. When the individual starts with their back curled and then pulls, the muscles along the spine are moving in a concentric action. As mentioned above, concentric actions are the weakest of the 3 muscular actions. Looking back at our stabilizer example, the muscles along the spine contract in order to maintain posture. These muscles are designed to maintain posture not to lift things, during the seated row they are weaker than the biceps and lats. If we don't do something to strengthen this weak link within the exercise the muscles along the back are going to fatigue before the lats and biceps and we won't be able to perform as many repetitions or use as much weight.
An isometric action is stronger than a concentric one, by holding the back straight and only moving the arms we strengthen our weak "link".
When an individual pulls the handle all the way to their chest, they have to move their arms past parallel thus causing a decrease in the length-tension relationship (more on this subject in Part 2) and transferring the force requirements on to the posterior deltoids. The posterior deltoids are much smaller than the biceps and lats and can't produce as much force.
The seated row is designed to target the biceps and lats, there is no reason to bring in a small muscles like the posterior deltoids when they aren't used as stabilizers.
You may be saying "But if I curl my back and pull the handles to my chest I will be working the muscles along the spine, posterior deltoids, lats, and my biceps all at once and that is more time efficient." It might be more time efficient but it isn't more muscle efficient because you would only be working your back muscles and posterior deltoids. Yes, your biceps and lats would be contracting and moving but they would only be challenged as much as your back and posterior deltoids are and that isn't a whole lot for muscles as big as the lats.
There are much more efficient and safer ways to exercise the posterior deltoids and muscles along the spine like practicing correct posture through out the day and bent arm extension.
In Part 2 we will cover muscle physiology and how it affects range of motion.