"Do one more. " That is a common refrain heard from many personal trainers. If you are single-mindedly focused on getting more repetitions expect more injuries and less improvement.
Repetitions do not cause the body to change; demanding work of sufficient intensity does. When the body performs intense work that is more than the body is used to handling the body will make a positive change as a form of self-protection - the body becomes stronger. That intense work can come with one additional rep, but that is not necessarily the case. Focusing only on additional reps can actually lower intensity.
I have seen amazing things in the quest for one more repetition.
Some lifters will lock out on each and every repetition of some exercises - bench press, overhead press, dips, you name it. Locking out is when your elbows or knees are totally straight thereby taking the load off the muscles and putting the load primarily on the bones. That is commonly referred to as a rest. Rest and exercise are mutually exclusive. Resting between repetitions lowers the intensity of the exercise and minimizes results.
Lifters will heave the weight with their whole body. When this happens other muscle groups end up doing much of the work that was intended for the targeted muscle group. When you throw your whole back into doing bicep curls your back is establishing the momentum, and your biceps are doing less work - the result is less improvement. Besides, it is dangerous. People hurting their backs doing arm exercises - it happens.
Lifters will bounce the weight of their chest with such force that they bruise their chests or injure their shoulders. The purpose for the bounce is to get the momentum to get that extra rep. Establishing momentum requires rapid acceleration. Rapid acceleration produces great force that can lead to injuries. Besides momentum unloads the targeted muscle and lowers the intensity and lessens results. I have one trainer who used to train in this fashion. By age 23 he had already had both shoulders operated on. The irony is he was trying to improve his health. The result is that he will be compromised the rest of his life. Old injuries will come back to haunt you.
Lifters will lift through just a part of the intended range - a neat trick and often a self deception. “Look I did ten reps with more weight. I improved!". “Big deal, you only lifted half the distance you did when you were lifting the lighter weight. That is not a real improvement in strength. "
Lifters will avoid the position where muscles are fully contracted; this results in lower intensity. On the last repetition of the leg extension try holding the weight still at the endpoint of the repetition where your quad muscles are fully contracted for just one second - one lousy second. Some lift for years and have never (yes never) experienced that intensity. They basically kick the weight up to the point where the quads would be fully contracted, the weight quickly falls from the peak, and the weight is basically caught at a lower point on the eccentric portion of the repetition. You will not experience the intensity associated with a fully contracted muscle when you throw and catch a weight.
Lifting a weight through a sticking point is the most difficult part of a repetition. That is the point in a repetition where your muscles are at a mechanical disadvantage. Instead using momentum to fly through those sticking points, try moving in a smooth deliberate fashion without momentum and also avoid all the pitfalls mentioned above. When you lift in such a manner you will not get nearly as many repetitions because the exercise will be so much more intense. With the higher intensity you will see more improvement and have a safer workout all with less repetitions - imagine that.
John Kelly has been specializing in high-intensity circuit strength training for 28 years. John's websites: Fitness Trainers of New Orleans or Personal Trainers Austin TX