Monday, December 3, 2012

Effective Strength Training: Understanding the Intensity-Duration Relationship - By Dave Durell

Originally posted on on June 1, 1999

The optimal number of sets of resistance exercise required to produce maximum increase in strength remains a very controversial topic. In order for any strength training program to be considered effective, obviously that program would have to produce an increase in strength. If two different systems both produced an equal increase in strength, then other criteria must be utilized to determine which is truly the most effective. These additional criteria would be the amount of time invested to achieve the desired result, as well as the amount of effort expended. Thus, the most effective system of strength training (or anything else) would be the one which produced the greatest possible results with the lease possible amount of effort in the shortest possible time. The purpose of this article is to compare single set training to multiple set training to determine which training protocol comes closest to being the previously mentioned most effective system.

Multiple set training is defined as performing more than one set of a certain resistance exercise, typically 2 to 5 sets. Usually a 1 to 2 minute rest period is taken between sets. Traditionally, multiple set systems have been considered a requirement to stimulate maximum strength gains (1). While multiple set training has produced unquestionably good results in a multitude of trainees over the years, this system contains one inherent flaw: it attempts to defy the principles of logic, reason, and human physiology by disregarding the incontrovertible relationship between intensity and duration.

Intensity is defined as the percentage of possible momentary effort being exerted (2). Duration is the amount of time over which such efforts are conducted. To paraphrase, intensity is how hard it is, while duration is how long it takes. There is universal agreement that intensity is the single specific stimulus required to generate increased muscular strength. The critical, yet often ignored, factor involved in strength training programs is that intensity and duration are inversely proportional. This means that as the intensity of effort increases, the amount of time that such an effort can be sustained will proportionately decrease. These are incontrovertible facts not subject to debate which can be readily observed in everyday life. It is literally impossible for a human being to sustain 100% intensity for prolonged periods of time.

Consider, for example, the activity of running, something almost all of us have had experience with since we were children. Picture yourself sprinting at top speed for a distance for 50 yards. Now imagine yourself running a distance of one mile. Can you run the mile at the same all-out pace you used in sprinting the 50 yards? Of course not. Why? Because intensity and duration are inversely proportional. Since you drastically increased the duration of your run, the intensity had to decrease, whether you wanted it to or not.

Once the facts regarding the intensity-duration relationship are clearly established, it becomes possible to manipulate these variables to produce the desired training result. Since intensity is the factor responsible for stimulating strength gains, and duration is inversely proportional to intensity, an ideal strength training program would combine the highest possible intensity with the lowest possible duration. One set per exercise, performed until no further volitional movement is possible, satisfies these requirements.

Have any studies been performed comparing multiple set to single set training? One study performed at the university of Florida (3) consisted of 25 subjects performing 1 set of lumbar extension exercise 1 day/week for 10 weeks. Strength increases ranged from 42% to 102%. A second study performed at the University of Florida (4) utilized a total of 110 subjects who performed either 1 or 2 sets of lumbar extension exercise 1 day/week for 12 weeks. The results showed significant and similar improvements for both groups as compared with controls. The researchers concluded that performing more that one set was unnecessary for increasing strength in the muscles of the lumbar spinal area.

Another interesting study was performed by Golds Gym of Bristol, CT and ESPN cable television network (5). This study compared the effects of a 3-set, 2-set, and 1-set upper extremity resistance training program on 61 subjects. Results showed an average overall strength increase of 16.42% in the 3 set group, 23.54% in the 2-set group, and 26.95% in the 1-set group.

How do these results compare with other similar studies? A review by Fleck and Kramer (1) showed that the average increase in strength for most studies using isometric or isotonic testing and training of a variety of different muscle groups was between 20% and 30%. Thus from a theoretical as well as practical standpoint, it appears that single-set training systems produce comparable or superior strength gains in less time and with less total effort than typical multiple-set training systems.

How can this information be utilized by the individual wishing to make his own training program as effective as possible? The following guidelines are offered:

1. Make each repetition as intense as possible by maintaining strict form. This includes controlling the repetition speed, taking care to move the weight by muscular force alone without momentum. No quick starts, bouncing or heaving. Lift the weight smoothly, pause at the end position, and lower slowly under full control.

2. Make each set as intense as possible by continuing that set until no further volitional movement is possible, that is, to muscular failure. Continue performing strict repetitions until you are stopped in your tracks during the repetition despite your greatest effort. Remember, if you complete a repetition, no matter how hard it was, you must attempt another one! Make sure, however, you have the proper safety measures in place first, i.e. racks to catch the weight in a safe position and a competent spotter.

3. Make each workout as intense as possible by performing only one set per exercise in the fashion described above. Remember, intensity and duration are inversely proportional; if you do extra sets , the intensity of your workout will decrease, reducing its effectiveness. In addition, keep your workouts as brief as possible by limiting the total number of exercises performed to one, or at the most two, per muscle group.

I hope this article has provided a clearer understanding of the intensity-duration relationship as it applies to effective strength training. Such an understanding, properly applied, is the cornerstone of an effective strength training program.

1. Fleck, SJ; and Kramer, WJ: Designing Resistance Training Programs. Human Kinetic Books; Champaign, IL 1987.
2. Mentzer, Mike: Heavy Duty. Self Published, 1992.
3. Pollock, ML; Leggett, SH; Graves, JE, et al: "Effect of Resistance Training on Lumbar Extension Strength". Am J Sports Med 1989; 17: 624-629.
4. Hochschuler, SH; Guyer, RD; and Cotler, HB (ed): Rehabilitation of the Spine. Mosby-Year Books, Inc., 1993.
5. Sansone, J; and Fitts, B: ESPN/Golds Gym Fitness Study. Unpublished Study, 1993.

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