Illustration by Gavin Orpen 

Typically, it is counterproductive to train a muscle again before it has fully recovered from a workout. Muscle recovery entails several stages that are initiated immediately after a workout and continue for several days, depending on how intensely the muscle was trained. The more intense the workout, the more muscle-fiber damage and the longer the muscle takes to fully recover.

The general rule that most bodybuilders follow is to allow a minimum of 48 hours of rest before training the same muscle group again. Many bodybuilders allow seven days of rest for major bodyparts. Bodybuilding is an individual endeavor, though, and what works well for one athlete may not necessarily work well for another. Just as one training method doesn’t fit all, one recovery scheme doesn’t necessarily fit all.


It’s true that the easiest way to ensure adequate recovery for your muscle fibers is to refrain from training them again for a full week. However, that doesn’t mean seven days is your optimal rest period. Not allowing adequate recovery time can be detrimental to your progress in the gym, but resting too long can also curtail your gains as dictated by the physiology of muscle recovery and growth.

Immediately after you train a muscle, genes within the muscle fibers become activated, initiating many processes that lead to muscle growth. Activating muscle genes isn’t like turning a switch on or off. There are levels of activation, ranging from very little to a lot. Most genes stay activated for only a few days after training.

If you wait to train a muscle until it and its genes are completely rested, then you start from zero the next time you work out. However, if you train a muscle before its gene activity returns to resting levels, you can expect greater gains.

Here’s how it works. We’ll assign resting levels of gene activity a value of zero for a given muscle group, and gene activity immediately following a workout will be assigned a value of 100. After one or two full days of rest, the activity might drop to 75; by the fourth or fifth rest day, it might be down to 25; after that, it might return to zero. If you train that muscle group again when its gene activity is at zero, then you’ll possibly only increase its level to 100. However, if you train it after four or five days, when gene activity is still at 25, you might be able to increase gene activity to 125. That translates into a boost in muscle mass and strength.

Then, why not train after just one or two days of rest and get gene activity up to 175? Because you still don’t want to train a muscle before it has fully recovered. Actual muscle growth doesn’t occur until after the recovery phase is complete. To determine the exact point at which your personal muscle recovery is complete, use a recovery test such as that designed by exercise scientists at Western Kentucky University (Bowling Green).


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The researchers wanted to know how many days it took each major muscle group to recover from training. They asked experienced male lifters to perform seven sets to failure using their 10-rep max (10RM) weight for eight exercises: bench press, lateral raise, lat pulldown, triceps pushdown, biceps curl, leg press, leg extension and leg curl. This regimen targeted all major muscle groups. Then the scientists had the subjects return to the lab each day for four days after the workout to test the number of reps they could get for one set of each exercise, using their original 10RM weight. 

Since studies have shown that muscles not fully recovered from a workout are weaker than fully recovered muscles, the scientists knew that if the lifters could not perform at least 10 reps of an exercise, the muscles were still not fully recovered. The day that the lifters could perform 10 reps would signify full muscle recovery, and the day that they could perform more than 10 reps would signify a training effect (i.e., that the muscle had increased in strength).

Upper-body muscles recovered similarly, so the scientists grouped and compared the rep data for the upper and lower bodies.

On the first rest day, after 24 hours of recovery, the lifters were able to complete only about nine reps for the upper-body exercises and only about eight reps for the lower-body exercises. This signified that the recovery process was not complete.

On rest-day two, after 48 hours of recovery, most lifters were able to perform 10 reps, but many were not. This means that for some lifters, muscle recovery is mostly complete after two days of rest, but for many it is not.

On rest-day three, after 72 hours of recovery, the lifters were able to get about 11 reps for the upper-body exercises and about 10 for the lower. This signifies that a training effect was apparent after three days of rest for the upper-body muscles, while the lower-body muscles were fully recovered but not yet showing a training effect. 

On rest-day four, after 96 hours of recovery, the lifters were able to complete about 11 reps for upper- and lower-body exercises — upper- body muscles were maintaining a training effect and lower-body muscles were showing a training effect. 


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The results from the study can be used to make general resting guidelines for bodybuilders. It appears that upper- body muscles — chest, shoulders, back, triceps and biceps — recover a bit faster than legs do. After three days of rest, the upper-body muscles seem to be fully recovered and have undergone a training effect. Although legs have also recovered by the third day of rest, they don’t show a training effect until the fourth day.

This means that the optimal recovery period for upper-body muscles is three to four days. If you wait any longer to train them, you may lose the training effect, as gene activity will continue to decline. For legs, it appears that the optimal recovery period is four to five days (although the scientists did not test the subjects on the fifth rest day, it can be assumed from the upper- body data that legs would maintain some training effect on the fifth day). 

Waiting any longer than this before you train legs again could limit your gains in mass and strength. 

See the “Best Rest Training Split” below for a sample program that optimizes recovery periods for all bodyparts for most trainers. 


  • DAY 1 (Monday) | Quads, Hamstrings, Calves
  • DAY 2 (Tuesday) | Rest
  • DAY 3 (Wednesday) | Chest Shoulders, Triceps, Abs
  • DAY 4 (Thursday) | Back, Biceps, Forearms
  • DAY 5 (Friday) | Quads, Hamstrings, Calves
  • DAY 6 (Saturday) | Chest, Shoulders, Triceps, Abs
  • DAY 7 (Sunday) | Back, Biceps, Forearms
  • DAY 8 (Monday) | Rest
  • DAY 9 (Tuesday) | Chest, Shoulders, Triceps, Abs
  • DAY 10 (Wednesday) | Quads, Hamstrings, Calves
  • DAY 11 (Thursday) | Back, Biceps, Forearms
  • DAY 12 (Friday) | Chest, Shoulders, Triceps, Abs
  • DAY 13 (Saturday) | Rest
  • DAY 14 (Sunday) | Back, Biceps, Forearms

NOTE: Using this two-week training split, you can optimize gains in strength and in muscle mass. It calls for training quads, hamstrings and calves three times; chest, shoulders, triceps and abs four times; back, biceps and forearms four times; and taking three complete days of rest. At the end of the two weeks, simply repeat the program as many times as desired. 


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Use the results of the Western Kentucky University study to hone your training strategies and to maximize your gym progress. Serious bodybuilders will want to use a protocol similar to the Kentucky test to develop their own customized recovery schemes. This will help to ensure optimal recovery and maximal results for all muscle groups. 

With the “FLEX Recovery Test” (below) as a guide, you’ll be able to design a training and recovery scheme for yourself. The Western Kentucky University research project included bench presses and leg presses, but we suggest that you use dumbbell flyes rather than benches and that you don’t perform leg presses. We made these changes to minimize multiple-joint exercises that recruit several muscle groups. We believe that isolation exercises that target one muscle group are a better indicator of recovery for a particular set of muscles.


Follow this test protocol to determine your optimal recovery period for each major muscle group. Use a weight with which you normally are able to achieve 10 reps with good form. On day one, when you perform seven sets of each exercise, rest three minutes between sets. During the entire testing phase, rest about 10 minutes between exercises. After day one, perform only one set of all the exercises daily (again using your 10RM weight) for up to five days. Your optimal recovery period for each muscle group will be the day on which you are able to perform the most reps for each exercise. 

  • BODYPART: Chest | EXERCISE: Dumbbell Flyes
    • DAY 1 SETS/WEIGHT: 7/10RM | DAY 2-5 SETS/WEIGHT: 1/10RM 
  • BODYPART: Shoulders | EXERCISE: Lateral Raises
    • DAY 1 SETS/WEIGHT: 7/10RM | DAY 2-5 SETS/WEIGHT: 1/10RM  
  • BODYPART: Back | EXERCISE: Lat Pulldowns
    • DAY 1 SETS/WEIGHT: 7/10RM | DAY 2-5 SETS/WEIGHT: 1/10RM 
  • BODYPART: Triceps | EXERCISE: Triceps Pushdowns
    • DAY 1 SETS/WEIGHT: 7/10RM | DAY 2-5 SETS/WEIGHT: 1/10RM 
  • BODYPART: Biceps | EXERCISE: Biceps Curls
    • DAY 1 SETS/WEIGHT: 7/10RM | DAY 2-5 SETS/WEIGHT: 1/10RM 
  • BODYPART: Quads | EXERCISE: Leg Extensions
    • DAY 1 SETS/WEIGHT: 7/10RM | DAY 2-5 SETS/WEIGHT: 1/10RM 
  • BODYPART: Hamstrings | EXERCISE: Leg Curls
    • DAY 1 SETS/WEIGHT: 7/10RM | DAY 2-5 SETS/WEIGHT: 1/10RM 

On day one of the recovery test, perform seven sets of each exercise (in the order listed) to failure, using a weight with which you normally achieve 10 reps (your 10RM). The number of reps you perform for the first set of each exercise will be your baseline for recovery for that muscle group — if you perform just nine or as many as 11 reps, that’s the  number to go by. 

On days two, three, four and five, return to the gym and do only one set of each exercise with the your optimal recovery period for that muscle group.

In other words, if you can perform 10 reps of dumbbell flyes on day one and you reach 10 again on day three, then you know that your chest has recovered. Once you know your optimal recovery period for each muscle group, you can design your own training split to optimize muscle recovery and to maximize gains. Then, the rest is up to you. 


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This table depicts the number of reps the trained lifters were able to complete with their 10-rep-max weight on each testing day during the Western Kentucky University experiment. The “reps completed” represent the average number of full reps for all upper-body exercises combined and all lower-body exercises combined. The rep numbers are rounded to express whole numbers. 


  • TEST DAY | Upper Body: 10 | Lower Body: 10
  • REST DAY 1 | Upper Body: 9 | Lower Body: 8
  • REST DAY 2 | Upper Body: 10* | Lower Body: 10*
  • REST DAY 3 | Upper Body: 11 | Lower Body: 10
  • REST DAY 4 | Upper Body: 11 | Lower Body: 11

*Several subjects were unable to complete 10 reps on this day.



K. Hakkinen, “Neuromuscular fatigue and recovery in male and female athletes during heavy resistance exercise,” International Journal of Sports Medicine, 14:53-59, 1993; J.R. McLester et al., “A series of studies — a practical protocol for testing muscular endurance recovery,” Journal of Strength and Conditioning Research, 17(2):259-73, 2003