When considering resistance training, a common question arises regarding the optimal frequency for working out individual muscle groups. The debate often centers on whether it is more beneficial to train a muscle group once or multiple times per week. Understanding how often to stimulate muscles is a key aspect of designing an effective resistance training program.
Understanding Muscle Growth
Muscle growth, or hypertrophy, involves an increase in the size of muscle cells. This process is primarily driven by the balance between muscle protein synthesis (MPS) and muscle protein breakdown. When MPS exceeds muscle protein breakdown, a positive net protein balance is achieved, leading to muscle growth. Resistance training provides the mechanical tension and stress needed to stimulate myofibrils within muscle fibers.
After a workout, muscle protein synthesis typically remains elevated for approximately 28 to 72 hours in adequately fed individuals, initiating the repair and rebuilding process of muscle fibers. For muscle growth, adequate recovery, sufficient protein intake, and a positive energy balance (where more calories are consumed than burned) are necessary.
Training Muscles Once Per Week
Training a muscle group once per week often involves a “body part split” routine. Each training session focuses on one or two specific muscle groups, such as chest or back. This approach typically involves a higher volume of sets and repetitions for that specific muscle group within a single workout session. The rationale behind this method is to provide an intense stimulus, followed by a longer recovery period before the next direct training session for that muscle.
While some individuals may find this frequency effective for maintaining muscle, it is generally considered less optimal for maximizing muscle growth in natural lifters. This extended recovery period means fewer opportunities to stimulate muscle protein synthesis throughout the week, potentially slowing the rate of progress. For larger muscle groups, a once-per-week frequency might involve 60-120 total repetitions, while smaller muscle groups might receive 30-60 total repetitions.
Training Muscles Twice Per Week
Training a muscle group twice per week increases the frequency of muscle protein synthesis stimulation. Since muscle protein synthesis can remain elevated for up to 48 hours post-workout, re-stimulating the muscle allows for more frequent growth signals throughout the week. This approach often utilizes workout splits such as upper/lower body splits or full-body routines, allowing for a muscle group to be trained, recover, and stimulated again within a few days.
A meta-analysis indicated that training muscle groups at least twice per week was superior for muscle hypertrophy compared to once-weekly training, when total volume was similar. This higher frequency can lead to greater overall muscle mass gains, effectively doubling the growth opportunities over a year compared to once-weekly training. This method allows for the total weekly volume to be spread across multiple sessions, which can lead to less fatigue per session and potentially better recovery between workouts.
Choosing the Right Frequency for You
The most suitable training frequency depends on several individual factors, including training experience, recovery capacity, and overall lifestyle. For most individuals aiming to build muscle, current evidence suggests that training each muscle group two to three times per week is generally optimal. This frequency maximizes muscle protein synthesis responses without excessively interfering with recovery.
Beginners often see significant gains with lower frequencies, even two full-body workouts per week, as their muscles are highly responsive to new stimuli. As training experience increases, intermediate and advanced lifters may benefit from higher frequencies to continue progressing.
Recovery capacity is a significant consideration, influenced by factors like sleep quality (aim for 7-9 hours), adequate nutrition, stress levels, and genetics. If you are constantly sore or feel run down, it may be beneficial to reduce volume or frequency. Conversely, if you are making little progress and are not experiencing much soreness, increasing frequency or intensity could be helpful.