Sets, reps and failure: a lifting primer

A set does its job when it ends close to failure, which is the point where you couldn't complete another rep with good form. Stopping a rep or two short of that point gives up very little.²

One 2024 analysis estimated how many repetitions people had left at the end of their sets across many trials.³ Muscle growth improved as sets ended closer to failure, while strength gains looked about the same across a wide range of effort.

Counting reps in reserve is the simplest way to judge this. A 2016 study tested a scale where 10 means no repetitions left and 9 means one left.⁴ The researchers concluded it was a practical way to regulate each day's effort.

Judging it takes practice. In that study, beginners rated a true one-rep maximum as easier than experienced lifters did.⁴ That suggests new lifters often stop further from failure than they realize.

Bottom line

Finish most sets with a rep or two left. Effort near the end of the set is what drives growth.

Once a set is difficult enough, the number of repetitions matters far less than most people think. Sets of 6 and sets of 30 grow muscle about equally, and heavier sets build more strength.¹

In the 2017 review, muscle growth was similar whether people lifted light weights or heavy ones, as long as each set ended at failure.¹ Gains in one-rep max strength were clearly larger with heavy weights.

A 2021 review of 28 studies with 747 adults sorted sets into three categories.⁵ Light meant more than 15 repetitions, moderate meant 9 to 15, and heavy meant 8 or fewer. Muscle growth didn't differ between the three, but strength improved more with heavy and moderate loads than with light ones.

Light sets have a practical cost. You need many more reps to get close to failure, so each set takes longer to finish.

Bottom line

Pick a rep range you can push hard in. Lift heavier when strength is the goal.

Taking a set all the way to failure isn't necessary. Stopping just short of it builds about as much muscle and strength.

A 2022 review of 15 studies found no clear difference between training to failure and stopping short, for either strength or muscle size.² All the studies were in young adults, so the result is untested in older people.

Another review, from 2023, found a trivial edge for failure in muscle growth when any definition of failure counted.⁶ When failure meant the point where the muscle simply couldn't lift the weight, the edge disappeared.

The 2022 review did find a small benefit of failure for muscle size in people who were already trained.² If you've lifted for years, an occasional last set to failure on a safe exercise is a reasonable choice.

Bottom line

Failure is a tool, not a requirement. Stop a rep or two short on most sets.

Additional hard sets per muscle each week build more muscle, and about 10 weekly sets is a common target.⁷

A 2017 review of 15 studies found that each extra weekly set added about 0.37 percent more muscle growth.⁷ Groups doing 10 or more sets per muscle a week tended to grow the most.

An older 2010 review compared single sets with multiple sets per exercise.⁸ Multiple sets produced an effect on muscle growth about 40 percent larger. The gain from two or three sets to four or more was smaller and less certain.

The 2017 review's highest group was 10 or more sets, so it can't tell you how far past 10 the gains keep coming.⁷ Add sets only as fast as you can recover from them.

Bottom line

Build up to about 10 hard sets per muscle per week before you think about more.

Longer rest between sets lets you lift more in the next set, and over weeks that adds up to more strength and more muscle.

In a 2016 study, 21 experienced young lifters followed an identical plan for 8 weeks, with three sessions a week.⁹ The only difference was either one minute or three minutes of rest between sets. The three-minute group gained more strength in the squat and bench press and grew more muscle in the front of the thigh.

It was a short study in 21 young men with lifting experience, so treat it as one good data point rather than a rule.⁹

Bottom line

Rest about three minutes on big lifts. Short rest saves time, but in that study it cost strength and muscle.

1. 01

   End most sets with a rep or two left in reserve.

2. 02

   Light and heavy sets build muscle about equally when they're hard enough, and heavy sets build more strength.

3. 03

   Going all the way to failure adds little, except perhaps for experienced lifters.

4. 04

   More weekly sets build more muscle, and about 10 per muscle is a common target.

5. 05

   Rest about three minutes between hard sets on big lifts.