Based on current research studies, there are 3 ways of triggering muscle growth; mechanical tension, metabolic stress and muscle damage.
Mechanical Tension
Our muscles experience tension in two ways, actively by contraction, or passively through stretching. When you lift weights your muscles are placed under both active and passive tension. In order to create enough tension to force your muscles to adapt and grow. You must select exercises that allow you to move through a decent range of motion, spend enough time under tension, and lift moderate weight to heavy weight until you are close to or reach failure (think 1-12 reps).
Examples:
- Deadlift 80% of your 1 rep max for 4 sets of 4 reps
- Pull Ups until failure rest 15 seconds and do 2 more
- Bench Press your 12 rep max with a 3 second pause for 3 sets of 6 reps
Metabolic Stress
Metabolic stress is caused a combination of the muscle burn and pump that most gym goers are very familiar with. The burn is caused by lactate build up while the pump is caused by blood being trapped in your muscles which results in your cells swelling. In the gym the main difference between the two is that it generally takes multiple sets to get a good pump while for a good burn one long set of high reps will do the trick. You can create metabolic stress by doing high repetition sets quickly with short rests in between, using supersets, dropsets or burnouts and many other techniques.
Examples:
- Single Leg Glute Bridge for 4 sets of 25 reps
- Lateral Band Walk for 3 sets of 30 seconds
- Hip Thrust your 10 rep max 10 times, drop 20% of the weight and go for 10 reps repeat for 2-3 more sets
Muscle Damage
Muscle damage is the most overrated and least important of the three mechanisms. Most people believe that being constantly sore is a requirement for growth not only is this not true but it can work against your progress. Being too sore can prevent you from being able to handle as much volume. it has also been shown to inhibit muscle activation. Muscle damage is generally caused by doing a new exercise, increasing the range of motion of an exercise or deliberately slowing the tempo down on each rep of an exercise. Delayed Onset Muscle Soreness (DOMS) is a strong indicator of muscle damage.
Examples:
- Deficit Reverse Lunge
- Perform a new exercise
- Eccentric Weighted Chin Ups
In closing, these three mechanisms work hand in hand. Although it is impossible to single one out, you can emphasize each one by choosing certain exercises, or manipulating the weight and tempo you’re using. Big compound movements that allow you to use heavy loads are great for creating mechanical tension. Exercises that require constant tension or high tension from your muscles in a contracted position are the best for metabolic stress. Movements that stretch your muscles under load are best used with the goal of muscle damage in mind.