Two equally important factors facilitate the strength building process. The first is progressive resistance exercise to stress the muscles and stimulate physiological adaptation. The second is sufficient recovery time to permit tissue repair, building, and protein overcompensation, leading to larger and stronger muscles.
Our muscles actually become weaker during a standard set of high-intensity strength exercise. That is, performing eight to 12 controlled repetitions to the point of muscle fatigue, with both positive and negative muscle contractions, produces some microtrauma to the working tissues. It is believed that a degree of microtrauma is necessary for muscle development.
Apparently, however, there is a direct relationship between the amount of microtrauma and the amount of recovery time needed for tissue repair and building. It is also likely that too much microtrauma leads to tissue injury and a lengthy rebuilding process.
Consider the following hypothetical example of a muscle stimulus-response. Suppose that, as illustrated in Figure 1, your biceps strength is 100 pounds at the beginning of Monday’s workout.
Immediately after your exercise session, your fatigued biceps can produce only 94 pounds of strength. The next day, your biceps strength has recovered to 99 pounds, the third day it has climbed to 103 pounds, the fourth day it has dropped to 102 pounds, and the fifth day it has almost returned to its original level of 100 pounds.
In this example, you would experience the best training effect by training your biceps again on Wednesday, two days after your original workout. That is, you should perform your next workout at the high point of your strength building process. Training your biceps again after one day, on Tuesday, would probably be counterproductive, because the muscles have not returned to their previous strength level. Delaying your workout until Thursday should be effective, but the rate of strength development may be a little slower. Waiting until Friday to exercise the biceps again will not interfere with your muscle-building process, but the rate of strength development may be further reduced.
Due to physiological differences, such as the percentage of slow-twitch and fast-twitch muscle fibers, some individuals may attain their peak training response sooner or later than other individuals. Also, advanced trainees typically require more recovery and tissue-building time between successive exercise sessions because their workouts are more demanding. Our research studies with previously untrained participants show excellent results with both two-day and three-day training, but favor the every-other-day exercise protocol.
In the Lab
We conducted two specific studies comparing the muscular effects of two versus three exercise sessions per week during a two-month training period. The first study involved 33 college-age subjects and examined strength gains using the bench press exercise. As shown in Table 1, the trainees who performed two workouts per week increased their bench press strength by 17 percent, and the trainees who performed three workouts per week increased their bench press strength by 24 percent. Although both training groups made significant improvements, the rate of strength-development for the two-workouts-a-week program was about 70 percent of that of the three-workouts-a-week program.
The second study included 48 middle-aged, mostly male subjects and examined lean (muscle) weight gains using a 12-station Nautilus circuit. As presented in Table 1, the trainees who performed two workouts a week increased their lean weight by 3.0 pounds, and the trainees who performed three workouts a week increased their lean weight by 3.9 pounds. Although both training groups made significant improvements, the rate of muscle development for the two-workouts-a-week program was almost 80 percent that of the three-workouts-a-week program.
We recently analyzed body composition data on more than 1,100 men and women who completed our eight-week Keeping Fit program during the past five years. The 716 subjects who strength trained three days per week gained 2.5 pounds of lean weight and lost 4.6 pounds of fat weight. The 416 subjects who strength trained two days per week gained 2.2 pounds of lean weight and lost 4.0 pounds of fat weight. On a comparative basis, the twice-a-week trainees added about 85 percent as much lean weight and lost about 85 percent as much fat weight as the three-times-a-week trainees. As illustrated in Figure 2, two strength sessions a week is almost as productive as three strength sessions a week with respect to body composition changes.
Research (Westcott 1995) indicates that there is a direct relationship between the exercise effort and the recovery period required for optimum muscle development. That is, a harder exercise session produces more muscle microtrauma and requires more recovery time for the tissue-building processes to be completed. It is also clear that more advanced strength trainees need longer recovery and building periods than less advanced strength trainees, due to their greater exercise effort.
Our studies, conducted with previously untrained individuals, suggest that two or three strength workouts per week represent effective training protocols for increasing muscle strength and muscle mass. The rate of improvement for the two-a-day-a-week trainees was about 70 to 85 percent that of the three-day-a-week trainees, with less difference among middle-aged participants than among college students. These findings are consistent with those from the University of Florida (Braith et al. 1989). These researchers reported that two workouts a week produced about 75 percent as much strength development as three workouts a week.
In my opinion, beginning strength exercisers should be encouraged to perform three training sessions per week. However, those individuals who are unable to schedule three training days should be informed that two exercise sessions per week product excellent results. Although the rate of improvement may be slightly slower, the eventual training outcome should be similar. For persons who choose twice-a-week training, it is recommended that they space the exercise sessions as equally as possible, such as with a Monday-and -Thursday workout schedule.
Whether you exercise two or three days per week, you should achieve high levels of muscular fitness by applying the Nautilus strength-training principles. Perform one set of eight to 12 repetitions for each major muscle group. Train with a slow movement speed through a full movement range to the point of muscle fatigue. Whenever you can complete 12 repetitions with proper form, increase the exercise resistance by about 5 percent and continue your progress.
Table 1: Effects of two versus three exercise sessions per week on muscle strength and muscle mass.
|Two Month Training Program||2 Days Per Week||3 Days Per Week|
|Muscle Strength (N=33)||+17.0%||+24.0%|
|Muscle Mass (N=48)||+3.0 lbs.||+3.9 lbs.|
Braith, R. W., Graves, J. E., Pollock, M. L., et al. (1989). Comparison of two versus three days per week of variable resistance training during 10 and 18 week programs. International Journal of Sports Medicine, 10: 450-454.
Westcott, W. L. (1995). Strength Fitness: Physiological Principles and Training Techniques, Fourth Edition. Dubuque, Iowa: Wm. C. Brown and Benchmark.
Westcott, W. L. and Guy, J. A physical evolution. IDEA Today, 14 (9): 58-65.