There are two kinds of “cheating” in the strength training and bodybuilding world. On one hand, there is sloppy, desperate, and out of control exercise technique done when it is not necessary. And there are cheat reps which are s controlled and purposeful. The former is obviously bad and dangerous. The latter, however, is more akin to “forced reps.” This can and will be done occasionally in order to force the muscles to work a bit harder in their strongest range of motion than they otherwise would with strict technique.
Cheating in this vein could also be called “tweaking”. Cheating obviously has a negative connotation and this causes many trainees to think that it is never allowed. This is probably for the best as even cheat reps must be done correctly and under control. It is better for trainees to think “cheating is bad” than for trainees to get the wrong message and cheat their way to injury.
Although a small degree of cheating will be used in strength training the practice is more suited to bodybuilding. What many people call “cheating” in strength training movements are actually compensations that are a natural part of lifting maximal loads. These compensations are simply natural deviations from “ideal form” and experienced lifters tend to have an educated sense of acceptable and unacceptable deviations. For instance, a lifter may have his or her lumbar flatten and begin to round during the performance of a very heavy deadlift. But the lower back will not be allowed to flex past a certain range of motion. Past this range of motion, the lifter would abandon the attempt. This is not cheating. Instead, it is the reality of lifting heavy objects. The majority of the lifter’s strength training will not have such severe deviations but pushing the envelope is necessary at certain times.
Using Cheat Reps on Purpose
Usually, however, purposeful cheating is used for single-joint isolation exercises such as biceps curls in order to perform a few more reps than would otherwise be possible or to move a heavier load than usual. Using a cheat movement to actually move a weight that you would not have been able to move at all on something like a barbell curl, is a waste of time and dangerous.
What are Cheat Reps?
Normally the cheating method or cheat reps are a way to eke out a few more reps at the end of sets after you’ve reached positive failure with strict form. This means that a set is performed to exhaustion and then a compensatory movement of the body is used to gather momentum in order to carry the weight implement out of the weaker and into the stronger position. What this means is that if momentum is used to carry the weight through ranges of motion which the target muscles would not otherwise be able to accomplish, then the lifter is no longer cheating “correctly”.
Cheating Barbell Curl
As mentioned, biceps curls is the exercise that most often comes to mind when we think of cheat reps. Look around in any commercial gym and you will observe cheated curls being performed more often than strict ones. But in this case the trainees are not cheating in a controlled manner and are probably unaware they are cheating. However, it is incorrect to say that this is always wrong or unsafe. If used judiciously, some cheating can help to exhaust the muscle or even to add strength.
During a barbell or dumbbell curl, the elbow flexors are weakest (in terms of ability to generate tension) when the elbows are fully extended. They are strongest when the elbow is flexed to approximately 90°, and when I say strongest, I mean in regards to tension generating ability. This means that the maximum amount of weight you can curl with strict form is the weight that can be lifted from the fully extended, or weakest, position. This also means that the muscles do not need to develop their maximum force once the weight has reached the strongest position. This is referred to as the “strength curve.”
To understand this more clearly, simply consider the basic tool used to cheat on any movement, including a biceps curl. That tool is the momentum that is gained by using larger muscle groups to help accelerate the implement. To do this, lifters bend forward slightly and then rock back just at the beginning of a rep. This helps creat momentum. If you use more of this “body English” than is necessary you will accelerate the implement past the “sticking point” and through it, meaning that the momentum has taken the place of actual muscular effort. To use this cheating movement correctly, you instead apply just enough effort to get the implement past the angle at which you cannot move well, and then let the muscles take over at the stronger joint angle. So, again, when a cheating movement uses momentum to take the place of muscular effort of the target muscles, it is incorrect and possible dangerous. But when it is used judiciously, so that the momentum gathered only helps accelerate the weight past the point where you cannot move the weight at all, and then the muscles take over to finish the rep, it can be a valutable tool.
Only Certain Exercise Can be Cheated On Productively
This means that only a few exercises can actually be “cheated” on productively and somewhat safely owing to their strength curve. Basically, for these lifts we are weakest at the bottom and strongest somewhere from the middle onwards. Obvious examples are biceps curls, overhead press, and pullups. In fact, a cheat movement on the strict overhead press has it’s own name, the Push Press, and this can be an effective tool. . So cheating, again, is not always the right word and the appropriateness of it depends on the intentions and context in which it is used. The press is a bit different than the curls and pullups, though, in that the tension generating capacity in former two gets less as the joint angles close
The bench press is difficult to cheat on, but bouncing the barbell off the chest and arching the back are sometimes considered “cheating”. This is a different kind of cheating from above, though, since there is no way to generate much momentum through these tactics. Arching the back helps bring the lower part of the pectorals into the movement and can give a slight advantage. The back should be arched in the bench press to start with: it is only when the glutes start to leave the bench that the “cheat” has begun and it is darned hard to get all your PR’s with your glutes glued firmly to the bench. Although it is not a good idea to do this all the time, we all sometimes resort to it on very heavy max lifts as a natural compensation to create an advantage. Notice in the image of the bench press a few paragraphs above that the bar is locked out and the glutes are just beginning to drift off the bench. No big deal.