Honestly, quite quickly. Within 48 hours after exercising there is muscle growth from a variety of activities - not just weightlifting.
Knowing this is useful for building muscle, but also for boosting endurance too.
When you regularly perform resistance exercises such as body weight exercises, yoga, calisthenics or weightlifting, you gradually increase the amount of muscle tissue on your body and produce visible changes in your muscle size. These changes come from the breakdown / ripping of muscle fibers and the formation of new muscle fibers in-between the damaged tissue. How quickly you see results varies depends on how much your ripped, your metabolism, your diet / protein / nutrient intake, age, testosterone levels and other factors.
Generally speaking the changes take place within 48 hours after exercising - which is a relatively short period of time.
Rest periods in-between exercise periods are very important. Most of the muscles growth happens within the first 24 hours after exercising - and most of that growth happens while you are sleeping and your body is rejuvenating.
Understanding Muscle Growth Basics
When you lift weights or perform other types of resistance exercise, you trigger the formation of new muscle tissue by temporarily damaging your existing muscles. This process begins when resistance exercise causes minute injuries in your muscle fibers. It is therefore important to not over exercise and injure yourself. Too much weightlifting can cause more harm than good, because if you rip too many muscles at once it will take a lot longer for those muscles to heal properly - even with proper diet, a high metabolism, etc.
To heal these injuries, your body activates nearby cells called satellite cells. Once activated, some of your satellite cells bind to the damaged portions of your existing muscle tissue. Other satellite cells bind to one another and form new strands of muscle fiber.
How Fast Does It Grow
Resistance exercises trigger muscle-building changes in your muscle tissue within two to four hours after your exercise session, and the process typically lasts for as long as 24 to 48 hours. It often lasts as long as two sleep cycles. However, each resistance training session triggers new minor muscle increases, and you must keep working on two or three non-consecutive days a week to produce noticeable results. If you exercise the same muscles every day you may simply rip the already damaged tissue, thus setting you back 24 hours in terms of your body's "internal repair schedule".
Depending on your metabolism and workout routine, it can take anywhere from several weeks to several months for you to see significant changes in the size of your affected muscles. Especially if you trying to target one part of your body - such as the biceps - and you are overdoing that muscle group when you would be better off with an all over approach. Overdoing one muscle group will only slow down repair time, whereas an all over approach will build multiple muscle groups simultaneously. So if you are looking to build muscles faster start by using a variety of exercises.
Repetitions and Weight Amounts
Most people get sufficient muscle growth when they perform a single set that contains 8 to 12 repetitions of a given resistance exercise. It isn't really necessary to do 20, 30, 50, or 100 reps unless you are also training for endurance.
To gain the benefits of a lower number of repetitions (10), you must use enough weight or resisting force to cause temporary muscle fatigue. You lift the heaviest weight you can 10 times and when you can perform more than 15 repetitions at a given weight, you will typically want to slightly increase the weight you use to keep fatiguing your muscles and triggering the process that leads to new muscle growth. The idea is so that every time you lift weights you are challenging yourself - and ripping new muscle tissue.
To gain the benefits of a higher number of repetitions (20 or more), you want to use a lower amount of weight that you can more comfortably lift that many times. This lower number, but increased number will send different signals to the muscles being ripped, and the existing muscles, to build muscles which are higher quality and in the future will be able to withstand more ripping / pain. (Note: Women often do very well in this category as estrogen boosts muscle quality, whereas the opposite is more difficult because women are less likely to rip muscles due to the higher quality of their muscle tissue - and because their lower testosterone levels decreases how quickly they build muscle mass. This doesn't mean that women cannot be strong however, it simply means they have to work twice as hard in order to build muscle mass, and likewise men need to work their endurance harder if that is what they are looking to build.)
Regardless of whether you are training for size or endurance, you will be slightly stronger within 48 hours or less. The problem however is that slight increase is so small it is barely noticeable, which is why it is necessary to workout 3 or 4 times per week in order to see visually noticeable results.
Eating lots of nutrients and protein are very important to building muscles. It is not all protein. You also need vegetables, which includes lots of minerals and vitamins that your body needs to quickly build muscle tissue. You also need an adequate supply of carbs so your body feels energized. A variety of natural supplements exist (eg. Creatine) which boost the speed at which you grow new muscle tissue.
Conclusions
People new to resistance training typically see relatively rapid increases in muscle size due to building muscles that haven't really been challenged before, as can people who "used to exercise very often" and are getting back into things due to muscle memory.
As your body becomes accustomed to the effects of your new activity, your rate of muscle growth will taper off. While you can try to jump-start your muscle growth by increasing the number of sets you perform for a given exercise, you will usually see only modest size increases - muscle gain is a matter of patience.
Being impatient means you might simultaneously raise your risks for a workout-related injury. To enhance the effects of your workout routine and safely maximize your potential muscle size, I recommend using a combination of body weight exercises (which are safer to do), yoga, free weights and weight machines.
If you need more help consult your friendly neighbourhood personal trainer in Downtown Toronto.
