An extremely common goal of people that exercise seriously and consistently is to increase their muscle size and strength. There’s a number of factors that help determine how well someone may be able to achieve this, including genetics, intensity of exercise, training status, testosterone levels, and nutritional supplementation. All of these factors play a part in muscular adaptation, but one of the most important variables is the frequency of the stimulus - that is, how often you exercise a muscle group.
Generally, our muscles adapt to the stimulus that is imposed during the workout. The graph below demonstrates the General Adaptation Syndrome and provides a visual of how our muscles adapt to exercise.
After an intense workout, there’s first an alarm phase, which happens one to two hours after the exercise. In this phase, the muscle decreases in performance because of fatigue and the muscular damage caused by a workout. The alarm stage is followed by the resistance phase and the subsequent supercompensation. This supercompensation - an increase in muscular performance from baseline - occurs given adequate rest and nutrition (yet another reason to eat healthy and get enough sleep). The last phase of the cycle is the exhaustion phase, in which performance begins to drop due to a lack of further stimulation. So, the key to building muscle and maintaining this increased muscle mass is to stimulate the muscle group again (via working out) after the supercompensation phase, but before the drop-off of the exhaustion phase. If this is done consistently, the performance of the muscle will increase, resulting in the muscle becoming stronger and larger. If we fail to stimulate a specific muscle group quickly enough, though, after the supercompensation phase, we’ll miss out on the performance improvements.
Above is a graph that shows subsequent stimuli after supercompensation phases. Before the decrease in performance during the exhaustion phase, another stimulus is provided, followed by another supercompensation phase. Keeping this cycle consistent will lead to an increase in performance, strength, and size of a muscle.
So, how often should we exercise a specific muscle group? The research says that we should have around 48-72 hours between stimuli. This time period allows for recovery, but not too much recovery to the point of performance decreasing. A good strategy, and perhaps one of the most attainable for the busy professional, is to do full-body workouts three times per week. During these workouts, a squat pattern, a lower-body hinge pattern (deadlift), a push pattern, and a pull (a row or pulldown) should be done with the proper intensity, rest intervals, and amount of repetitions - and don’t forget to finish off with a core exercise!
Remember, performance (and a continued increase in performance) is the key indicator to looking better, maintaining good health through exercise, and to continued improvement and progress both in and outside of the gym.