Why muscle is not picky
When sets are taken close to failure, light and heavy loads build similar amounts of muscle. A 2017 meta-analysis by Schoenfeld and colleagues compared loads above and below 60 percent of one-rep max and found similar growth, while strength improved more with the heavy loads.
What seems to matter is that the last few reps are genuinely hard. A set of 25 that ends with 10 reps still in the tank does very little.
Why strength is picky
Lifting heavy is partly a skill. Your nervous system has to learn to recruit a lot of muscle at once and to hold technique under a load close to your limit. Heavy sets practise exactly that, which is why powerlifters spend so much of their time between 1 and 5 reps.
Choosing in practice
- Big compound lifts such as the squat, deadlift, bench press and overhead press: 3 to 8 reps. Heavy enough to build strength, few enough that technique holds.
- Most other exercises: 8 to 15 reps. Enough load to grow, without the joint strain of very heavy sets.
- Small isolation and machine exercises: 10 to 20 or more. A heavy lateral raise is mostly a way to hurt a shoulder.
- Very high reps, 20 to 30, work too, but they are uncomfortable and it is hard to judge how close to failure you are.
Pick a range, then progress through it
A range such as 8 to 12 gives you a built-in way to progress: add reps until you reach the top of the range on every set, then add weight and drop back to the bottom. This is double progression, and it works at any rep range.
Logging every set is what makes it work. In PushBeyond every exercise keeps its own history, so you can check what you lifted last time and know exactly what to beat.