Exercise Analysis - The Pre-exhaust Principle
Last month, I received an e-mail from a reader who questioned my contention that straight-legged heel raises should be done prior to a similar bent-legged movement. His question made me realize that a thorough explanation of the pre-exhaust principle was in order. An understanding of this is essential if you choose to incorporate this type of protocol into your program, but it’s also important when you’re determining the correct order to train muscle groups when you work multiple ones during the same workout session.
If you’re lifting weights for health purposes or to improve appearance, it’s important to remember the critical stimulus that will facilitate positive changes in these directions. It is not the quantity of weight you lift or the amount of times you successfully complete sets or repetitions with that weight. Instead, it is the degree of effort that is associated with your performance. In other words, if it isn’t hard, it isn’t working, no matter how impressive the actual performance you’re demonstrating might be. Weight is but a tool we use to make lifting hard and that’s why pre-exhaust training works so well. It makes it hard to lift a weight that would normally be much easier.
Pre-exhaust training makes light weight feel heavy, but it’s important to realize that not all manipulations that bring about a similar effect will be useful for taxing a target muscle. And that’s why the pre-exhaust principle can also be applied incorrectly. Consider training designed to build the two predominant muscles housed in the rear section of the lower leg (calves). Each of these (gastrocnemius and soleus) function to angle the foot down, as would happen if you were to stand up on your toes. The difference is that the gastrocnemius also crosses the knee, so when the knee is bent, it is shortened and its relative contribution to motion at the ankle is reduced. The soleus bears the brunt of the effort under these circumstances.
Both calf muscles contribute to heel raises when your knees are straight. Therefore, it is only logical to do this type of exercise first in your calf training session. On the other hand, if you performed bent-legged heel raises first, you would effectively weaken the soleus and it would be less capable during the straight-legged maneuver. That means it would give out first, thereby precluding you from working the gastrocnemius at the degree of effort required to elicit a training effect.
Pre-exhausting the soleus prior to straight-legged heel raises will render it the weak link on the exercise that incorporates both muscles. A similar problem occurs if you choose to train your elbow flexors with curls prior to performing compound movements for back (pulldowns, chin-ups or rows, for example). Making the biceps less capable prior to using them in conjunction with your back muscles will render them the weak link once you get around to working back. And that means you’ll be unable to stimulate your back by forcing it to operate at the appropriate degree of effort.
If you train the muscles of your back with movements that require elbow flexion prior to training your arms, you can be certain that both your back and elbow flexors will receive considerable stimulation from those efforts. Upon completion, you can then use movements that isolate your elbow flexors (curls) and still be able to drive them at the appropriate degree of effort. The only difference is you won’t have to use as much resistance in order to do so.
Just like compound movements for back involve your elbow flexors, presses that stress either your chest or shoulder muscles require significant involvement from the muscle that extends your arm at the elbow (triceps). Consequently, isolation movements for triceps (cable pushdowns or dumbbell kickbacks, for example) should only be done after all of your presses have been completed. But there are isolation movements you can perform prior to presses that won’t compromise their efficacy. The difference is these would have to involve the major muscle you are trying to target with the press. For example, flyes work your chest muscles the same way presses do; they require you to draw your arm horizontally toward your body’s midline against opposition. However, they do so without associated motion at the elbow. Therefore, if you perform flyes prior to chest presses, you will pre-exhaust your chest so that subsequent pressing performance will be compromised. But that matters not because it simply means you’ll have to work against less weight to achieve the same result – fatigue in the specific muscle you’re trying to target.
Pre-exhausting chest presses with flyes is useful if you are interested in achieving the desired result without having to use as much weight. This might come into play if you are training around an injury or forced to use facilities that are not fully equipped. It is also beneficial if your triceps are the weak link during your presses. Under these circumstances, it will be impossible to train your chest effectively with presses because your triceps will always give out first. Weakening your chest with a single-joint chest movement beforehand solves this problem.
This article was originally published in New Living Magazine, which can be accessed on-line at www.newliving.com.
