Of course, there are a variety of health-related reasons to do strength exercise. These include increased bone density (Menkes 1993), improved glucose metabolism (Hurley, 1994), faster gastrointestinal transit (Koffler, 1992), better blood lipid levels (Stone 1992), reduced low back pain (Risch 1993), and less arthritic discomfort (Tufts 1994).

Perhaps the most prevalent misunderstanding about strength training, particularly for those who would like to do it, is the time requirement. Many adults simply do not have time to do the multiple-set workouts they have been told are necessary for strength development. Fortunately, time-efficient single-set training can be just as productive as time-consuming multiple-set training when performed properly.

Recommended Strength Training Program
The excellent results attained by the 1,132 research program participants (Westcott 1996) required only 25 minutes of strength exercise, two or three days per week. The recommended strength training protocol, based on the American College of Sports Medicine guidelines (1990), is as follows:

Training Frequency: Two or Three Days Per Week
The standard strength training recommendation of three nonconsecutive days per week is sound, and should be followed whenever possible. However, in a large training study (Westcott 1996), the 416 subjects who did two strength workouts a week achieved almost 90 percent as much strength and muscle gain as the 716 subjects who did three strength workouts a week. For people who have difficulty getting to the gym three times a week, it is good to know that two strength workouts per week produces nearly as much training benefit.

Training Sets: One Set Per Exercise
One study (Westcott 1995a) found one-set and three-set training to be equally effective for increasing upper body strength, and another study (Starkey 1994) found one-set and three-set training to be equally effective for increasing lower body strength. If training time is limited, it is good to know that single-set strength exercise is just as productive as multiple-set workouts.

Training Resistance: 75 Percent of Maximum
The exercise resistance should be high enough to produce a high rate of strength development and low enough to pose a low risk of injury. Empirical evidence clearly indicates that using 75 percent of maximum resistance meets both of these training criteria.

Training Repetitions: 8 to 12 Reps Per Set
Research (Westcott 1993) indicates that most people can complete 8 to 12 controlled repetitions with 75 percent of their maximum resistance. Generally speaking, if you cannot perform at least 8 repetitions the resistance may be too heavy, and if you can complete more than 12 repetitions the resistance may be too light. Working within the 8 to 12 repetition range is recommended for safe and effective muscle development.

Training Progression: 12 by 5 Rule
Every strength training program needs a protocol for progressing to heavier weightloads. While it is important to periodically increase the exercise resistance, it is equally important to do so gradually. A safe and productive progression is known as the 12 by 5 rule. That is, whenever you complete 12 repetitions of an exercise in good form, you increase the resistance by 5 percent or less. The 12 by 5 procedure provides small but frequent training increments to progressively stress the muscular system.