There needs to be a reason for your muscles to get bigger otherwise they just won’t grow. A quite obvious reason for your muscles to grow is for them to get stronger. But for muscles to get stronger, they need to be subjected to physical levels of stress. The muscles adjust to new levels of stress by getting stronger. Once your muscles start to get stronger, they will eventually adapt to these new strength levels by getting bigger.

The higher the intensity levels, the more stress you place on your muscles. So, as you gradually add more intensity to your workout program, you add more stress to your muscles and they will continue to grow.

Muscle doesn’t start growing after doing just a few sets of bench presses at the gym. This is a gradual process that takes time and commitment. Once your muscles start to get stronger, you should start seeing some growth in about 2 weeks to a month after the initial strength increase. This is of course not exact and everyone is different, so for some it can be more and some less, and can depend on various factors.

These 5 factors can affect how long it takes to build muscle:

1. Years of Training
   How long have you been training/working out. You will gain more muscle faster if you’re a beginner compared to someone who’s been working out for years.
2. Hormonal Profile
   How much testosterone as well as other muscle building hormones in the body varies. Men also naturally build muscle more efficiently than women because they have larger reserves of testosterone with a greater capability of producing growth hormone. The female body responds just as quickly to exercise, but not with the same intensity as the male body. So women generally build muscle about 2-3 times slower in comparison to men.
3. Muscle Memory
   If a person weighing 170lb then you decided to train for a marathon, you may lose a solid 20lb of muscle. So how long will it take you to gain back those 20lb of muscle back? Answer: Not long at all. Maybe only a 1-2 months, because your body has a mechanism for restoring the previous homeostasis, which is often referred to as “muscle memory”.
4. Supplements
   Besides the harmful performance enhancing substances that can help you build muscle much faster, there are other less dangerous supplements like creatine that can help with muscle growth.
5. Genetics
   There is a concept of a genetic bell curve. To summarize, some men (and women) are naturally inclined to build a lot of muscle because of factors such as hormonal balance, or the thickness of their frames whereas others have trouble building much muscle no matter how hard they try. Most people of course by definition (roughly 68%) are genetically average.