When beginning or recalibrating a resistance training program, there are a ton of unknowns. How many sets and reps should you do? What about rest periods? The variables are nearly endless. One of the most important factors to consider is how often you train a muscle group or movement pattern. Known as training frequency, this variable can have a significant impact on your results. Here’s how to navigate it.
Training Frequency
Training frequency, which describes how often you train a muscle group or movement pattern, is almost always framed as X days per week. (As in, “I train legs twice per week.”) Why the calendar week was chosen as the timeframe, I frankly have no idea. But when it comes to training frequency research, we almost always look at weekly frequency.
Now, when you delve into said research, you’ll generally find that training each muscle group two days per week is probably best for muscle growth. However, good science is done rather strictly, and when you look at training frequency as a research variable, you have to limit other variables. This means that if you set up a study with three different groups of subjects, each group has to perform the same exercises, reps, sets, and overall volume (and use the same rest periods) whether they train once, twice, or three times per week.
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When you isolate just frequency as the variable, you don’t always see remarkable results. However, in the real world, people generally use training frequency to change the overall weekly volume they train a muscle group with. If you currently train arms once a week, adding a second day per week would effectively double your training volume, leading to more gains!
So, Why Not Train A Muscle Group Every Day?
Of course, more isn’t always more. The main reason we can’t (well, shouldn’t…) train a muscle every day comes down to one major outcome of exercise: muscle damage.
When you lift weights, the tiny little proteins in your muscles become damaged. This could be due to a variety of factors, but mechanical and chemical stressors are probably to blame. Though this muscle damage occurs immediately, it doesn’t hurt. What hurts is the inflammation that arrives on the scene to repair and rebuild, stimulating pain receptors in the process—particularly when it peaks between 24 and 48 hours after you tear up those muscles (at least on a microscopic level).
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These little injuries, plus the pain caused by inflammation, have a unique effect in that they send signals to your brain to reduce output to that given muscle. So, if your biceps are sore from your workout a couple of days ago, your central nervous system cannot activate them as well. This means that the muscles aren’t in a position to perform very well—and that they face risk of further injury should you try to push them again too soon.
This is why you need ample time for muscle recovery between workouts. If you crush legs on Monday and try again Tuesday, your sore peg legs won’t let your brain push them to their limit. You’ll have a crummy workout and potentially get hurt. Bottom line: Always wait for that soreness to dissipate before destroying your muscles again.
Training Frequencies for Different Muscle Groups
Though general advice suggests training each muscle twice per week for maximum gains, every muscle group has a few inherent qualities that influence how quickly it recovers from training. While hitting each muscle group twice per week is probably fine, you might just be able to get away with a higher frequency for certain muscles.
One of the main factors that dictates how much damage a muscle experiences from training is its predominant muscle fiber type. Generally, we have two muscle fiber types: Type I and Type II. Type I fibers are called slow-twitch fibers, and they predominantly rely on aerobic respiration. This means they’re super efficient and great for endurance. Type II fibers, on the other hand, are fast-twitch fibers. These mostly rely on anaerobic respiration, which means they fatigue quickly but produce a ton of force and power.
Interestingly, those Type II muscle fibers are more prone to muscle damage than the Type I fibers (for a few reasons we don’t need to get into here). What you need to know is that a muscle with more Type I fibers can probably be trained more often since it will experience less muscle damage and soreness. Lightbulb moment!
With this understanding, you can craft a training plan that really maximizes the potential of different muscle groups. Here’s a look at which muscles are primarily slow- or fast-twitch—and how often you can probably get away with training them.
- Fast-Twitch (train twice per week): Definitely the pectorals, triceps, and biceps; probably the deltoids and latissimus (no conclusive data on these yet).
- Slow-Twitch (train three to four times per week): Glutes, quadriceps, calves, trapezius, and abs. (Note that the quadriceps are about 50-50 on fiber type percentages, but since they do not activate very easily, they don’t experience much muscle damage.)
- Somewhere in the Middle (train two or three days per week): Hamstrings
The Bottom Line
Altering how often you train a muscle group can be a powerful stimulus for new gains, especially if it allows you to increase your overall weekly training volume. Predominantly slow-twitch muscles will likely respond better to this since they recover more quickly between workouts. Muscles with more fast-twitch fibers need more time to recover and thus probably wouldn’t garner much benefit from more frequent training. Knowledge is power—and power leads to gains!
Known as ‘The Muscle Ph.D.,’ Dr. Jacob Wilson has a knack for transforming challenging, complex concepts into understandable lessons that can support your body composition and health goals. A skeletal muscle physiologist and sports nutrition expert, Wilson is a leader in muscle sports nutrition. As the CEO of The Applied Science & Performance Institute, he researches supplementation, nutrition, and their impact on muscle size, strength, and power.