As clinicians working with patients, we are prescribing therapeutic exercises on a daily basis in order to improve our patients’ strength levels. In essence, this is one of the most basic goals we, as physical therapists are trying to achieve with our patients. This article will focus on how to effectively apply PREs to improve strength in the rehabilitation setting.
How much thought have you given to the best ways of improving strength? Where did the standard “3 sets of 10 reps” come from anyway? How do we adapt these methods to the injured population? Hopefully these questions will be answered by the end of this article.
The term PREs stands for “Progressive Resistive Exercises”. I mention this fact, not because I believe the reader doesn’t know what the acronym stands for, but rather to emphasize the simple importance of the first word- PROGRESSIVE. In order to improve the quality of strength, the stimulus must be progressive over time in order to force a physiological adaption. To continue seeing gains and improvements from an exercise program, the intensity of the exercise must gradually become increasingly more challenging. Historically the first recorded anecdotal evidence of PREs comes from Greek Mythology, in the legend of Milo of Croton. Milo was a famed wrestler and in order to increase his strength, he acquired a new born calf and carried it around day after day, week after week, month after month. As the calf grew, so did Milo’s strength, until he was capable of carrying a full grown bull over his shoulders. Obviously, this is a fable and there are limitations to our ability to increase strength, but the Greeks recognized the concept of progressive resistance training and the body’s ability to adapt to increasing demands. For those of you who are CSCS, you may recognize this as an example of “linear periodization”.
The principles of progressive resistance exercise (PRE) for increasing force production in muscles have remained virtually unchanged since they were described by DeLorme and Watkins almost 60 years ago. DeLorme, et al. first detailed the Progressive Resistance Exercise (PRE) method to rehabilitate quadriceps strength after injury, and it became the basis for contemporary resistance training prescription.(1) The DeLorme method required his patients to perform 3 progressively heavier sets of 10 reps in a given exercise. The first two sets were considered progressively heavier “warm up sets” with the third and final set, the “work set”. The third set was the heaviest and performed to momentary muscular failure. This is exactly where “3 sets of 10 reps” came from.
These principles have been detailed more recently in the guidelines of the American College of Sports Medicine (ACSM)(2), where it is recommended that loads corresponding to an 8 to 12 repetition maximum (RM) be lifted for a total volume of 3 sets. Recommended frequency for training is 2 or 3 days each week. ACSM guidelines were basically the same as the DeLorme Method, but they added a “range” of repetitions from 8-12 reps instead of a hard fast target of 10 reps. Now, obviously 10 is the average of this range, but it does give us an option to manipulate the variables of Intensity & Volume over time in the most basic of manners.
Many clinicians may rightly argue that the intensity level of performing an exercise to repetition maximum is too high for the injured population or patients recovering from surgery. Granted ACSM guidelines are recommended for healthy individuals, but Thomas DeLorme performed his study on orthopedic patients recovering from femoral fractures and various other injuries. This is where clinical judgment and the understanding of the healing continuum come into play in the determination of the proper application of stress or load. Research conducted by Dr. Kraemer found loads approximately 45-50% RM capable of eliciting strength gains in untrained individuals and those recovering from injury.(3) As the individual adapts to these loads in an order to improve strength levels, heavier loads are necessary.
Over the years we develop individual treatment-styles and hopefully apply evidence-based practice to our own clinical practice. Here are some practical recommendations for the clinic that we have successfully developed over the years to improve strength without injuring our patients:
Provide a repetition range (i.e. 10-15 reps) that is specific to the goal at hand.
Determine the appropriate level of resistance that allows the patient to perform 3 sets in good form within the 10-15 reps range.
On successive treatment sessions keep the level of resistance the same until the patient can demonstrate the ability to perform 3 sets of 15 reps in perfect form.
Next session, increase the resistance level and reduce the number of reps to the low end of the range, in this case 3 sets of 10 reps.
Repeat this process of increasing volume (reps) over time, followed by an increase in intensity (load) and reduction in volume (reps).
This is the basics of modern day linear periodization adapted to the clinical setting.
Helpful hints on ways to communicate to your patients in the clinic.
Initially it may be difficult to find the correct load in a given exercise. I have found it helpful to provide a subjective rating scale to my patients, by ranking the level of resistance as light, moderate or heavy. I tell them they want to use a weight or resistance band that feels “moderate” and allows them to complete 10-15 reps. By definition, if the patient cannot perform 10 reps, then the resistance is too heavy, and likewise if the patient is able to perform more than 15 reps, then the resistance is too light. A perfect example of this, which you may encounter in the clinic, is the patient who performs 30 reps in a row and thinks this is the same thing as performing 3 sets of 10 reps. It is most certainly NOT the same thing. The patient in fact performed 1 set of 30 reps with a light resistance, which may improve muscular endurance, but will do very little in the ways of improving meaningful strength.
I hope we’ve addressed the three questions posed in the beginning of this article, as we certainly just gave significant thought to the ways of increasing strength. We certainly know by now the origin of “3 sets of 10 reps” that we have all prescribed over the years. And hopefully we have outlined a safe way to adapt the concept of effective strength training to the injured population.
DeLorme TL, et al. Restoration of Heavy Resistance Exercise. J Bone Joint Surg. 27:645, 1945.
American College of Sports Medicine. Progression models in resistance training for healthy adults. Med Sci Sports Exerc. 2002;34:364 –380.
KRAEMER, W. J., and N. A. RATAMESS. Fundamentals of Resistance Training: Progression and Exercise Prescription. Med. Sci. Sports Exerc., Vol. 36, No. 4, pp. 674-688, 2004.