Many experts advocate changing routines because a muscle gets accustomed to a particular exercise, leading to a loss of progress. That effect is linked to a neuromuscular adaptation. It relates to a larger theory proposed by Hans Selye, who noted that the body eventually adapts to an implied stress and that those adaptations are usually beneficial. In terms of exercise, when you apply the stress of weight training, the body adapts by increasing muscular size and strength, especially when you give it optimum nutrition and rest. Too much stress, as in overtraining, leads to a lack of adaptation, manifest as loss of muscular size and strength or a lack of continued gains.
The stress theory led to the overload theory of weight training, which holds that the best way to promote muscular growth is by increasing the level of stress on a muscle through gradual progressions in the amount of weight used, limited rest between sets and other methods. A further refinement came with the recognition that constant overload often caused people to become overtrained. As a result, periodic overload systems, or periodization training, became popular.
Periodization usually involves dividing training into cycles, with each cycle featuring different amounts of weight lifted, repetitions, training volume and even rest time between sets. Training cycles last about three months, beginning with relatively light training, leading to a heavy cycle aimed at producing the greatest degree of muscular size and strength. The changing patterns of applied stress keep the neuromuscular system from completely adapting. That, in turn, prevents training staleness and injuries.
Some people, however, suggest that changing training patterns every three months is not often enough. They feel that it’s necessary to ‘confuse’ a muscle by switching training routines as often as every two weeks. A new study takes that concept one step further by comparing a traditional periodization training pattern to one in which subjects varied rep and weight patterns at every workout.1
One group used a traditional, or linear, periodization routine by varying weight and rep patterns every four weeks during the 12-week study. The other group used a more varied, or undulating, pattern by averaging eight reps per exercise in the first session, six reps in the next workout and four reps in the final workout of each week for 12 weeks. Both groups trained three times a week, using the bench press and leg press.
The greatest strength gains occurred in the undulating group, but they occurred only during the first six weeks of the study; after that, progress between the two groups was similar. Despite increased strength gains, the undulating group showed no increases in muscle, an effect thought to occur because of neuromuscular adaptations. In short, constantly varying workout patterns appears to keep rapid neuromuscular adaptations out of kilter, promoting strength increases but not necessarily muscle-size gains.
1 Rhea, M.R., et al. (2002). A comparison of linear and daily undulating periodized programs with equated volume and intensity for strength. J Strength Cond Res. 16:250-255.