Before we get into this we need to first understand how muscles actually grow. When a muscle is properly worked, micro-tears and muscle damage occurs. Muscle fibres recover by getting bigger and stronger so that they are less able to tear as easily. This is the process of hypertrophy. Hypertrophy requires 3 things: mechanical tension, metabolic stress and muscle damage.
Mechanical tension refers to how much time under tension your muscles receive during an exercise. Remember that your muscles do not know the size of weights you use, they only know how much tension is being created.
Metabolic stress is when there is a build up of blood and an oxygen deprivation (hypoxia) in the muscle, making it looked ‘pumped’. This is achieved by working at a high rep range (15-20+ reps) to pump blood into the muscle making your cardiovascular system work harder, creating metabolic stress.
Muscle damage is achieved by constantly using progressive overload of weights i.e. increasing the weight in increments as you get stronger. This makes sure that your muscles are still getting damaged causing micro-tears in each session to begin the cycle of tear, repair, grow.
Ok so now you’ve got that - let’s move on to the real part of this topic. Why are compound exercises the best for muscle growth?
They recruit the largest amount of muscle fibres. Unlike isolation exercises, compound exercises recruit more than one muscle group and joint. Isolation exercises, like a bicep curl, usually just involve one muscle (bicep) and one joint (elbow) to do the exercise. Although isolation exercises can be great to incorporate for maximal pump and activation, compound movements are where the real gain are found.
For example with the squat, you are not just isolating the quads, you are using the entirety of your lower body, your core and your upper body for stability, strength and power. This means more muscle fibre recruitment, higher nervous system activation, more muscular damage and thus more stimulus for muscle growth.
Compound exercises create the greatest change in body composition in the shortest time by working a large amount of muscles in the body simultaneously, stimulating the three main mechanisms for hypertrophy mentioned above. Not only this, but these exercises also increase overall strength and size more significantly and effectively than isolation exercises because they promote the production of testosterone and growth hormone. This is because you will be contracting a higher amount of muscles which gets the blood pumping faster and in turn increases testosterone levels.
The key compound movements you need to be doing are as follows:
The best muscle growth workout routine focuses on compound movements with the addition of isolation exercises for muscles that you’d particularly like to strengthen and grow. So a good hypertrophic workout for the legs may look like this:
Leg press 4x6-8
Single leg deadlift 4x10-12
Seated leg curl 4x10-12