An increase in muscle mass can occur either through producing more muscle fibres, called muscle hyperplasia or by increasing the muscle fibre size, muscle hypertrophy. Although muscle hyperplasia can happen in humans, it is not common. The main method of increasing muscle mass is through muscular hypertrophy.
Let us consider the elements of a muscle fibre and what happens during muscular hypertrophy. A muscle fibre is made up of multiple myofibrils, each containing the contractile proteins actin and myosin. With resistance training, there is damage to the actin and myosin filaments which stimulates a repair and regeneration process within the muscle fibre. This regeneration of new myofibrils, when adequate dietary needs are met, increases the number of myofibrils within the muscle fibre and thus increases the cross sectional area of the muscle fibre, or muscle size.
Muscles need to meet some necessary conditions in order to expand. Firstly, there must be a mechanical stimulation under tension. This is done through resistance training, the process of adding load to a muscle to resist motion. As the mechanical tension increases, muscle mass increases.
Secondly, there must be some muscle damage. An intense resistance workout will cause microtears within the muscle. The body’s inflammatory response kicks in and responds with repair and regeneration of the muscle fibres.
And thirdly, there needs to be metabolic stress. Exercise can cause the build up of acidic metabolites (lactate, inorganic phosphate and hydrogen ions) which promote muscle degradation. Again, when the right conditions are met, the body responds with repair and regeneration and increasing muscle size.
In order to build muscle, there must be an excess of calories, i.e. you are consuming more than you are expending. Of this, adequate protein consumption must be met. A daily protein intake of 1.7g-2g per kg of body weight (or 0.8g-1.2g per lb of body weight) is recommended for muscle hypertrophy. This equates to 116g to 136g (using the kg numbers, with slight variance using the per lb numbers) for someone weighing 68kg or 150lbs.
Carbohydrate intake can vary drastically, but a recommended 3g/kg of body weight is a general recommendation to maximize training performance for muscular hypertrophy.
How to train for Hypertrophy
With all training programs, intensity, repetitions, sets and rest intervals all need to be considered. For muscular hypertrophy, the research supports lifting 67-85% of your 1 Rep max, for 6-12 reps (optimal, although 5-20 have been shown to cause hypertrophy), for 3-6 sets (aiming for 10+ sets per muscle group per week) and anywhere from 30sec to 2min rest between sets. (Eric Curry, https://www.scienceforsport.com/hypertrophy-training/)
If you would like to discuss your training program further, please contact Dr. Marnie D’Andrea at drmarnie@mmdchiropractic.ca or use our online booking system to book your initial visit.