Muscle hypertrophy, or mass growth, is the result of physical exertion. Muscles are injured and subsequently healed after being subjected to extreme stress, such as in weight training. The muscle will get bigger and stronger as a result of this procedure.
To induce an action potential in a muscle. A stimulus must be delivered at a strength greater than the threshold potential. When the muscle’s activity goes over this threshold potential. The action potential occurs because the muscle can no longer contract normally without being severely weakened or destroyed. This type of injury, however, is the only one that results in “supercompensation”. Or the enhanced regeneration and strength of tissues.  Ultimately, the theory of “increasing overload” states that in order to sustainably promote the growth of the muscles. It must be compelled to do tasks that it is not adapted to.
So yet, research into what causes muscular hypertrophy has not reached a conclusion.  However, three distinct forms of hypertrophic have been recognized:
(1)Hypertrophy of sarcomeric or myofibrillar muscle fibers
Microtrauma is caused to a muscle’s sarcomeres when mechanical tensile pressures. Such as those experienced during intense strength training, are applied to the muscle. The sarcomere is the sole contractile protein structure within a muscle fiber.  After an exercise, your body repairs the damage done. To your muscles by adding new sarcomeres and replacing damaged proteins.
The muscle fiber’s contractile filaments, the myofibrils. Are constantly being replaced as a result of consistent training, with more and more sarcomeres being created. “Myofibrillar hypertrophy” is another name for this condition. Only heavy resistance exercise, like weightlifting, may induce this kind of muscle growth. Whenever the amount of contractile components (sarcomeres) in a muscle cell grows. The resulting muscle becomes stronger.
(2) Sarcoplasmic hypertrophy
This kind of muscle development does not include the synthesis of any new protein structures. But rather an increase in the volume of the muscle fiber’s semi-solid plasma. Muscle bulk is caused mostly by the accumulation of glycogen (a kind of glucose storage) and water. Checkout https://recommendat.com/ to know more about sarcoplasmic hypertrophy. This form of muscle growth does not improve strength to maximal levels but does increase stamina. Since the cells flush out glucose and water after just a few days, this hypertrophy is very temporary.
Sarcoplasmic hypertrophy contributes to bodybuilders’ muscular size. Which answers why they typically lack the strength that belies their impressive physiques. The finest bodybuilders may have more muscular mass, but they are weaker at their prime.
Reason for this is because bodybuilders train differently. Focusing on longer series with therefore lower weights (usually 8-15 repetitions per series). Rather than fewer exercises at maximal strength (see below). By and large, the glycogen reserves in the muscles are depleted by this form of workout. During the restoration process, these will be replenished and expanded somewhat.
(3) Activation of satellite cells: the wild card
Hyperplasia, the process through which new muscle cells and fibers are produced, does not occur in humans. While undeveloped muscle cells cannot be “turned on” or “trained,” it is feasible to do so through exercise. Stem cells in muscles are referred to as “satellite cells” due to their peripheral distribution. A thicker muscle can be achieved by stimulating a greater number of muscle cells.
Muscle increases as a result of increased nutrition and water storage. Due to the activation of muscle fibers hypertrophy & sarcoplasmic hypertrophy. During a standard hypertrophy training of 8 to 15 repetitions to muscle failure. Creatine supplements are used to enhance this procedure. Muscle also becomes stronger as a result of the formation of new contractile protein structures. A healthy diet, high in proteins and calories, is necessary for these transformations to take place.
Muscle development research consistently points to exercising to muscle failure as the most essential element. Because of this, you may work out with lighter weights and yet fatigue your muscles after 20 to 30 repetitions. Recent research indicates that this sort of training leads to the same amount of muscle development. As strength training focused on eight to fifteen repetitions. However, the significance of the strength increase is much diminished when working with lesser weights.
You will stimulate growth stimulus for a longer period of time. And gain more strength if you execute between 8 and 15 reps and till muscle failure (at minimum during the last series).
Do muscle-building pains have to be severe?
Facial pain is not required for muscle development. Soreness is now thought to result from microfissures there in muscle being repaired rather than from lactate overload. However, the Z lines in between the sarcomeres are disrupted due to these cracks. However, the sarcomeres’ contractile parts are what get damaged. When you go after the “development” kind of muscle injury. Consequently, training should produce muscular injury, albeit not necessarily discomfort.
It is inevitable that strength training will result in muscle pain due to the large loads, moderate tempo. And repetitions required to reach muscular failure. Muscle soreness is common among gym-goers. And it is more likely to occur while performing exercises. That involves lowering weights slowly (eccentric contraction) or working in amplitude. Such as the butterfly. However, some people are more prone to bodily pains than others. Because of their own unique physiological makeup.
If minor pains are not likely to inhibit muscular growth. It is best to avoid training while experiencing severe pain. When a person is prone to bodily pains, it’s important to schedule in extra rest and recovery time. For the muscarinic receptors so that the body can supercompensatie. The regularity of the stimulus is suboptimal, therefore sadly, progress will be hindered.  Despite the discomfort, sore muscles are evidence of the training’s intended effect.
In what time frame should I expect to see muscle gain?
You’ve no doubt seen promotions for fitness plans that claim to help you add several pounds of weight in just a few weeks. There are “before” and “after” pictures included to prove the claimed improvement. Regrettably, many initiatives are impossible to implement. As planned, their usefulness is very dubious as a result.
In actuality, it takes a lot longer to bulk up, and even “fast bulking” takes some time. In the first four to six weeks of a bodybuilding program. Beginners shouldn’t expect to see significant gains in muscle growth. To properly use the present muscular mass, their physique must first modify its neural system. While they gain strength, they don’t see the same proportional gains in muscle size.
When can we expect to see progress?
When the body is unable to continue resisting the stresses imposed by weight training. Muscular growth finally occurs. But it will take a little time before you see any changes. It might take anywhere from three to six months before you see results, so be patient.
Only those who adhere to exercise and nutrition religiously. But also those who begin at a very low level, will see rapid muscle growth. So, in the best-case scenario, an under trained young guy will grow around 1 kilogram of muscle every month. Or 12 kilograms per year. A total of 6 kg will be needed in Year 2, followed by 3 kg in Year 3, and so on. 
The bulk of situations will produce rather less dramatic outcomes. Gaining 5 kg of muscle in a year is considered quite successful. For a man between both the ages of 25 & 30 who has just started bodybuilding.  For women, losing just 2–3 kg is considered a remarkable accomplishment.
The bulk of the muscle you may build can be accomplished in two or three years if the right conditions are fulfilled. However, you should plan on spending at least 5–10 years. Exercising hard in order to reach your peak muscular development potential.