Set
A group of consecutive reps performed without resting.
A set is a group of repetitions performed consecutively without rest. It is the basic unit of resistance training prescription, which is why programmes are written as sets and reps and why weekly hard sets per muscle has become the standard way of counting training dose.
What makes a set count is how close it comes to failure. Motor units are recruited in order of size, so the largest and most trainable ones join in only during the final difficult reps. A set stopped well short costs time and fatigue and contributes little, which is where the phrase junk volume comes from.
Hard sets are therefore the useful currency, not sets in general. Most productive work sits within one to three reps of failure, close enough to recruit everything without the disproportionate fatigue that training to absolute failure adds.
How many is a dose response question with a plateau. A meta-regression found each additional weekly set associated with roughly 0.37% more muscle growth, which is how most people arrive at somewhere between 10 and 20 hard sets per muscle per week before recovery becomes the limit.
Rest between sets matters more than the old advice suggested. Longer rests, two to three minutes on compound lifts, preserve performance on subsequent sets and produce better outcomes than short rests that leave you underperforming for the rest of the session.
Sets can be structured in variations, supersets, drop sets, rest-pause, which mostly buy time efficiency or extra stimulus per minute rather than a fundamentally different result.
In practice, count hard sets per muscle per week rather than exercises or sessions, and let our training volume calculator do the tally including indirect work.