How Much Rest Between Workouts for Muscle Growth?

If you've done any amount of research on strength training and muscle growth, you probably already know that muscle grows during your recovery period, not during the actual training. Therefore, adequate rest between workouts is crucial for mass gain. At least 48 hours is a good goal, but how many rest days you need between workouts depends on individual factors.

There are three fundamentals of muscle growth:

• Resistance training causes micro-tears to muscle fibers.
  
• After training, the body repairs the torn muscle fibers by synthesizing new muscle protein.
  
• Each time this breakdown/repair process occurs, the muscles adapt by growing bigger and stronger.
  

After that, understanding muscle growth gets a little more complicated.

First of all, the load and tension has to be great enough to exceed the amount of stress your muscles have already adapted to. To do this, you have to lift increasingly heavier loads. This causes recurring damage that leads to inflammation in the muscle fibers. Your body's response to this inflammation is what increases muscle size.

Muscle protein synthesis (MPS) is a period of heightened muscle growth after your workout. It varies in length and depends on several factors including the intensity of your workout and your level of conditioning. Generally, the tougher the workout, the longer the MPS period. Additionally, experienced lifters typically have a shorter MPS window than novices because their bodies have adapted to the stress.

MPS lasts at least 24 hours to 48 hours for most people. However, the untrained can experience it for even longer. In addition, very intense workouts can extend MPS. Lastly, an experienced lifter who changes up her routine may experience increased MPS while her muscles adapt.

But just because your body is making more muscle protein, doesn't mean you're necessarily gaining mass, at least in the beginning. A 2016 study in the Journal of Physiology found that although novice lifters synthesized more muscle protein in the beginning of a training program, they did not gain mass.

This is because the rate of muscle breakdown was greater as the lifters adapted to the stress, and the rate of MPS was only enough to repair the damage, but not to add mass. When measured at the third week of the program, muscle breakdown had reduced, and MPS was enough to produce muscle growth.

Other factors also affect MPS, including protein intake after a workout and total protein intake, sleep, stress levels, overall diet, gender, age and the length of time between workouts.

​Read more:​ The Best Way to Gain Lean Muscle Mass

Muscles grow when protein synthesis exceeds protein breakdown. Training breaks down muscle so your body can rebuild it; not allowing enough rest days between workouts can cause muscle breakdown to exceed MPS and you can actually lose muscle mass. You don't want to do that. So you must be sure to get enough rest.

Not only can lifting too often lead to plateaus in muscle gain — or even muscle loss — it can affect your performance in the weight room, which will also reduce your gains. Overtraining can also negatively affect your overall health and well-being.

Some signs of overtraining that you should look out for include:

• Feeling like your workout has gotten harder when nothing has changed
  
• Excessive fatigue
  
• Muscle weakness
  
• Moodiness, agitation or depression
  
• Insomnia
  
• Lack of appetite
  
• Chronic or recurring injuries
  

If you experience these symptoms and they last for more than a few days, it's a signal that you are not allowing enough recovery time between workouts. Overtraining syndrome can take a while to resolve and it may require consultation with a medical professional. Keep in mind that overtraining is also influenced by all the factors that influence MPS.

By now you understand that more is not always better when it comes to building muscle mass. But how much is enough? There are many schools of thought on this, ranging from one high-volume workout per muscle group per week, to three total-body workouts per week, or more.

The truth is there isn't just one right way to work out for muscle growth. It's a matter of trial and error for each individual, because of all the factors that are at play in mass gain.

Working out each muscle group once a week at a high volume is probably not the best plan. If you do six sets of bench press, chances are your chest muscles are depleted by the last couple sets. You may even have to lower the weight you're using.

If you split that workout over two days (non-consecutive), you would be able to fit in more sets, and likely be able to lift a heavier weight without fatiguing so quickly. Theoretically, working each muscle group three days a week would allow you to increase that volume even more.

The best answer, according to a 2016 review of research in Sports Medicine, is training each muscle group two days per week. The authors found that training two times per week led to greater muscle gains than training once a week. However, they did not find enough evidence to determine whether training three times per week had any added benefit.

Therefore, you can allow three to four rest days between workouts for each muscle group.

Only you can decide what training volume and frequency works best for you, or how much recovery time you need. Pay attention to how you feel during your workouts. If you feel fresh, rather than fatigued, you are likely allowing enough recovery time.

If your performance is suffering, you're not gaining strength or mass, or you have other symptoms of overtraining, you need to dial it back and take more recovery. Also be sure to keep up with your healthy diet, get adequate sleep and work to reduce your stress levels.

​Read more:​ The 6 Rules of Gaining Muscle Mass