One of the most popular questions I receive is: “How often should I train each body part?” I wish there was one simple answer to this question, but there is not.

You must take into account many variables such as: training intensity, volume of training, genetics, nutrition status, rest, barometric pressure, and your astrological sign.

Ok, so I made the last two up, but you get the idea.

Although there are an infinite amount of considerations to take into account when it comes to training frequency, they all boil down to one common denominator: you should train a muscle again when it has fully recuperated from it’s previous workout.

I’ll bet you could tell someone how to go about getting a suntan. Your recommendations would go something like this: “Lie out in the sun for about 15 minutes around midday. If you’re not pink the next day then go ahead and lie out again for about 20 - 25 minutes. If that burns you slightly then wait until the pink color turns brown, then you can lie out again for about 30 minutes.”

In essence, the sun damages the skin. The body responds to this stress or damage by bringing melanin closer to the surface, making the skin appear darker. Once this adaptation has taken place, you can go ahead and tan again, this time for a little longer because the body is better equipped to handle the stress. Resistance training is the same way.

The goal of resistance training is to place a stress on the muscles to which they are not accustomed. This will cause small (microscopic) tears in the muscle called microtrauma. The body will respond by laying down more actin and myosin filaments. In other words, your muscles will become slightly bigger and stronger. As a very desired side effect, these muscles will become firmer and more “toned” looking.

The body adapts to the stress of resistance training so that next time you ask it to do the same task, your muscles will be better equipped to handle that stress. Sounds good, right?

What if you train a muscle again before the microtrauma has completely healed? Here’s where a common problem arises. You will cause more microtears within a muscle that has not yet healed from the previous bout of exercise. This is one of the primary factors involved in a syndrome we call overtraining. Overtraining leads to muscles that are weaker, smaller, and more susceptible to injury.

What if you wait too long before you train a muscle again? Once a muscle has fully recovered it will slowly begin to atrophy (shrink) and get weaker. Keep in mind that it takes at least a few days after full recovery for this to occur.

The frequency of training obviously depends on how much damage you did to the muscle the last time you trained it. If you did two easy sets of ten reps, then you could likely train the muscle again the next day. If you performed 20 sets of 15 repetitions and all sets were to muscular failure, it’s going to be a while before you need to train that muscle again.

By the way, 20 sets of 15 repetitions for one muscle would, for most people, be comparable to getting burned in the sun and peeling - you never really get tanned that way. It’s overwhelming to the body.

Combining my experience in the gym with my formal education, I have devised some training guidelines for training frequency. If after you train a muscle it is excruciatingly sore, you have done too much damage to the muscle. Think sunburn. The tissue that forms as a result of this will have a more haphazard arrangement and be less functional that normal tissue.

If you train a muscle and it is a little sore for about 24 - 48 hours, you probably did a good amount of muscle damage. I typically recommend being free of any muscle soreness for a full day before training that muscle again. As an example: you train legs on Monday and they’re a little sore on Tuesday but not on Wednesday, train them again on Thursday.

What if you don’t get sore at all? For some people certain muscles are very resistant to getting sore. As a general rule, try to induce a little soreness in the muscle by increasing either the intensity of your training. However, just because you don’t get sore doesn’t mean you didn’t induce any microtrauma to the muscle. That is definitely not the case.

I encourage you to take your new understanding of microtrauma and training frequency and take a hard look at your training program. Are you training often enough? Are you training too often? Don’t blindly follow what others are doing. Find what frequency allows you to make continued progress. Good Luck!

Dr.Clay Hyght