> How To Build Muscle (Explained In 5 Levels). Directed by Jeff Nippard, 2021. YouTube, <https://www.youtube.com/watch?v=lu_BObG6dj8>. # Mechanical tension is the primary factor behind muscle growth ^29dd13 ## Level 1 Lift weights and eat protein. Lifting weights triggers the adaptive response of your muscles, and eating protein gives them the building blocks they need to grow bigger. ## Level 2 Lifting weights requires progressive overload, the gradual increase of stress on the muscles during weight training. For protein, the 1.6-2.2 g/kg range is currently considered optimal. For 75kg of body mass, 120-165g of protein per day is ideal. ## Level 3 Acute training variables: - Effort: you should aim for an RPE of 8-9 (about 2 reps left in the tank) - Volume: number of hard sets per week. There is a sweet spot range. 10-20 sets per body part per week should be ideal. - Intensity: how heavy the weight is. As long as RPE is high enough, intensity does not matter much. You should lift more than your 20% max rep though. - Exercise selection: multi-joint compound movements give more bang for your buck, but single-joint isolated exercises also have their place. - Frequency: minor role in muscle growth. Jeff still recommends hitting a muscle twice a week. ## Level 4 3-factor model of muscle hypertrophy: 1. Mechanical tension: force that stretches a muscle fiber, primary driver of hypertrophy. 2. Muscle damage: physical damage to the muscle. Not significantly correlated with hypertrophy. 3. Metabolic stress: accumulation of metabolites (lactate, hydrogen ions) and muscl hypoxia following weight training, the "pump". Most likely is not driving hypertrophy either. Tension seems to be the key to muscle growth, so we should maximise tension by applying progressive tension increases to the muscle during training. ## Level 5 Training creates active mechanical tension within the muscle (the *stimulus*). This tension is sensed by sensors (possibly costameres, titins or filamines) and the signal is sent to a molecule called mTOR, a regulator of cellular growth in general. mTOR tells the nucleus to produce mRNA, later translated by ribosomes, to synthesise proteins. If this signalling is stronger than that of protein breakdown, myofibrillar hypertrophy ensues. Meanwhile, the amino acids contained in proteins we eat, and especially leucine, also activate mTOR. The other 8 essential amino acids go to the ribosomes to create muscle. Sarcoplasmic hypertrophy (the growth of glycogen, organelles and non-contractile proteins) is not well understood yet.