Progressive overload is the number one principle one should follow when trying to increase strength and trigger muscle growth.
Progression can be achieved in many forms but the most popular method of progression is adding more weight to the bar with each consecutive workout session. A question arises: when should you add more weight and how much?
When to add weight?
The answer to this question will depend more or less on your goal. If your main goal is muscular hypertrophy and you’re working within a range of 8-12 reps you will want to increase the weight once you’re able to do all of your working sets at 12 reps (the top of the range) and beyond for 2 consecutive training sessions while keeping strict form. You will need to adjust this rule for heavy compound movements like deadlifts and squats, though.
When performing these movements, you should be thinking in terms of doing a set of singles, doubles or triples. For example, instead of doing 2-3 sets of 12 reps, you should be doing 12 sets of 2-3 reps. You should be resting for a short period of time and do a complete reset in form after each repetition to avoid rushing through the motions, losing form and in the end, risking serious injury.
It is generally recommended that you should start with a weight slightly below your target reps for several workouts. This means, instead of increasing the weight and trying to stay within the 8-12 rep range, you should go for 6 reps for a workout or two. Then, you can move to the normal bodybuilding range.
If your main goal is muscle strength and you’re working within the 1-6 range, you can shoot for the top of the range for at least 3 consecutive workouts before increasing the weight. Much of your strength gains will be because of neuro-muscular adaptations and the central nervous system will need a little more time to properly recover.
How much weight should You add?
Generally, you can go for 5% increase on upper-body movements and 10% on lower-body movements, provided that you maintain strict form during exercise execution.