How fast is it possible to gain muscle? Studies have shown that the answer to this question very much depends on the individual. Two people doing exactly the same exercise regime and following exactly the same diet might add muscle at very different rates. People who use gyms have always known this.

But this does not mean that it is not worth lifting weights if you think you fall into the slow responder category. The take home message is that both fast and slow responders can make excellent progress. Slow responders should not become discouraged when they compare their rate of progress to fast responders. They can still add enough muscle to receive the health benefits of increased muscle mass, and make a tremendous difference to their appearance.

Fast and slow responders

In one recent study, the fastest responders added four times as much muscle as the slowest responders, over a 12 week period. Individuals of comparable age, comparable experience of training, and who followed the same diets, trained on a weight training program for 12 weeks. The lowest responding individuals added just over 1 pound of muscle mass in this time, while the highest responders added 4.5 pounds. The graph helps illustrate just how large the difference is, and this over just 12 weeks of training.

A similar situation applies to strength gains. Over a 6 week study on a strength training program, researchers identified three groups. High responders increased their strength by an average of 29% over 6 weeks, medium responders by an average of 14%, and low responders by an average of just 3%. This is the reason that some individuals quickly become much stronger than others when training with weights.

Now although high responders have a big advantage, it should be noted that even a 1 pound increase in muscle mass every 12 weeks and a 3% increase in strength every 6 weeks will add up to substantial increases over months or years of training. So even the low responders can make good progress.

Genetics and body type are influential

Studies show that some people definitely are better equipped genetically to gain muscle than others. One reason for the difference in response levels was found to be rate of expression of microRNA in muscle tissue which is responsible for muscle growth.

Another was the number of satellite cells around the muscles. A high number of satellite cells correlated with a high muscular response to weight training, and vice versa.

The view that naturally skinny or “ectomorphic” individuals gain muscle less easily than naturally stocky or “endomorphic” individuals appears to be true. Research has shown that over 12 weeks of weight lifting those who fitted the latter body type gained 5 times as much muscle mass as those who fitted the latter.

The flip side of this is that “ectomorphic” types will keep excess body fat off much more easily. So ectomorphs also benefit from their body type, but in a different way. Ectomorphs will find losing body fat to be much easier than endomorphs will.

Ectomorphs have fewer satellite cells than endomorphs. Those who have more satellite muscle cells have more potential to gain muscle, but they also tend to have more fat cells and so have more potential to become overweight. A group of “mesomorphic” individuals also exist, whose characteristics fall between ectomorphs and endomorphs.

Maximise your potential, but know and accept your limits

Factors of diet and recovery make a large difference for anyone trying to become larger or stronger. Studies have shown that an increased protein intake helps with muscle gain. You might have to increase your protein intake a lot in order to fulfil your potential for gaining size and strength, regardless of where you fall on the responders scale.

But it is important to have realistic expectations. Feeling you are failing introduces stress and dissatisfaction into something that should be enjoyable. “Failing” because of natural limits that you can do nothing about is not failure.

You might have to accept a slower rate of size and strength gains than some of those around you in order to feel comfortable with your weight training endeavours.

What is more, with consistent application, even relatively small gains can add up to something substantial over time. Putting on 20 pounds of muscle is a goal that should be achievable for even the slowest responders. Provided you are training properly, the gains will come most quickly to start with, slower in the second year, and slow further still in the third year.

But 25 pounds of muscle is enough to make a tremendous difference to your appearance, and more than enough to result in real health benefits that come from the permanently raised metabolic rate that the lean muscular mass will bring.

Some useful references

Davidsen, P. K., Gallagher, I. J., Hartman, J. W., Tarnopolsky, M. A., Dela, F., Helge, J. W., & Phillips, S. M. (2011). High responders to resistance exercise training demonstrate differential regulation of skeletal muscle microRNA expression. Journal of applied physiology, 110(2), 309-317.

Hubal, M. J., Gordish-Dressman, H. E. A. T. H. E. R., Thompson, P. D., Price, T. B., Hoffman, E. P., Angelopoulos, T. J., … & Clarkson, P. M. (2005). Variability in muscle size and strength gain after unilateral resistance training.Med Sci Sports Exercise, 37(6), 964-72.

Marshall, P. W. M., McEwen, M., & Robbins, D. W. (2011). Strength and neuromuscular adaptation following one, four, and eight sets of high intensity resistance exercise in trained males. European journal of applied physiology,111(12), 3007-3016.

Radaelli, R., Fleck, S. J., Leite, T., Leite, R. D., Pinto, R. S., Fernandes, L., & Simão, R. (2015). Dose-Response of 1, 3, and 5 Sets of Resistance Exercise on Strength, Local Muscular Endurance, and Hypertrophy. The Journal of Strength & Conditioning Research, 29(5), 1349-1358.