Muscle Hypertrophy is the increase in the size of muscle cells. Hypertrophy for a bodybuilder or general gym goer is the prime goal in the majority of cases, so must be understood properly if you are to achieve it. There are different types of hypertrophy, different ways of achieving it and they will all have different effects on the body.
The 2 forms of muscle hypertrophy are myofibrillar hypertrophy and sarcoplasmic hypertrophy. Myofibrillar hypertrophy is the increase in number of the contractile proteins actin and myosin. These proteins join onto the myofibrils (the chains in a muscle cell) and increase the size of the muscle as well as improving the strength of the contraction. Myofibrillar hypertrophy increases strength as well as size. Sarcoplasmic hypertrophy is the increase in volume of sarcoplasmic fluid in the muscle cell. This increase in fluid greatly increases the size of the muscle but doesn’t affect strength. The effect on strength that these 2 forms of hypertrophy have shows why a 90kg power lifter can lift more weight than a 120kg bodybuilder.
When training with weights you will see both types of hypertrophy occur. It is very unlikely you will achieve one form of hypertrophy without the other but you can change your training to focus more on one form than the other.
Training for myofibrillar hypertrophy involves low reps and heavy weight. Usually training will be in the sub-5 rep range and loads above 85% one rep maximum. Heavy compound lifts will be used for the most part in training with isolation exercises used as just assistance exercises to help with the main lifts. Due to the fact that your size will not increase much but your strength will improve greatly, your strength to bodyweight ratio will increase massively.
Training for predominantly sarcoplasmic hypertrophy involves higher rep ranges than myofibrillar hypertrophy. Usually the reps range between 8-12 and the load is between 65% - 80% one rep max. The target muscle is what is important so more isolation exercises are performed on top of the basic compound exercises. Muscle size will increase a lot but strength will not be affected by the increased volume of sarcoplasmic fluid. Luckily with any weight training myofibrillar hypertrophy occurs so even at these rep ranges you will still improve strength; just not to the same degree as with low rep training.
Many studies have been done on hypertrophy and the training to affect it. There has been one training principle that has been shown to greatly affect hypertrophy. Obviously diet plays a huge role in hypertrophy but we will leave that for now and look at the simple principle of progressive overload training. POT is a simple system that dictates that you must aim to make constant improvements in either weights used or reps performed every workout. Some people may bench 100kg for 8 reps, and then go for 110kg for 5 reps, and then 120kg for 2 reps. This is not the method for POT. With POT you must pick a starting weight and perform a pre-arranged number of sets and reps. When you can achieve this pre-arrangement you increase the weight by a small amount. So for example if you plan to bench press 100kg for 3 sets of 5 reps and you only achieve 2 sets of 5 reps and 1 set of 3 reps, then you will stick at 100kg for your next training session. If next time you achieve 3 sets of 5 reps then you will increase the weight to 105kg for next time. Stick at this weight until you have completed it. This principle when performed on all exercises will give the greatest gains in strength when using low reps and size when using higher reps.
There are other methods to achieving hypertrophy that can be used alongside POT (not instead of) such as drop sets, rest pause training, FST-7’s and so on. These are used to shock the muscles every once in a while and go past the point of failure. They are not to be used on every exercise.
So these are some basic principles of hypertrophy in regards to weight training. With a little understanding of how you grow you will be able to plan your routines more effectively in order to achieve your goal.