Approximately 80% of resistance training should be below failure, with 20% at higher intensity to maximize benefits without causing damage.

Training to failure can lead to greater muscle growth but also increases fatigue significantly, so it's important to balance intensity and recovery. Going from some number of reps in reserve all the way to failure in a single mesocycle is a good practice for many, but not required; you can go two or three reps in reserve as long as you do enough sets to achieve close to ideal hypertrophy outcomes.

To improve strength, you should perform anywhere from two to 20 sets per week, with five sets being sufficient to maintain muscle mass.

Hypertrophy can be stimulated through a broad repetition range of 6 to 30 repetitions, with a recommendation of 10 sets per muscle group per week, emphasizing high volume and going to failure or beyond to stimulate growth.

Training should be intense enough to exceed your minimum effective volume, which means you should feel a pump and some soreness after workouts.

The total amount of working sets is by far the biggest determinant of how much muscle you're going to grow per session. You can do anywhere from one set to as many as 12 to 15 sets for a muscle group in a session, but if you exceed your maximum recoverable volume, you risk reaching junk volume where your nervous system is too fatigued to recruit muscle fibers effectively.

You can build muscle strength and hypertrophy with weights ranging from 30% to 80% of your maximum, not just heavy weights.

To get stronger, focus on progressively increasing the loads you move; for hypertrophy, aim for localized, intense muscle contractions, and moving weights in the 30% to 80% range of your one repetition maximum is the most beneficial for muscle hypertrophy and strength.

Most people should aim for 5 to 15 sets of resistance exercise per week per muscle group to offset declines in muscle strength.