What is a pyramid set?

In one line

A pyramid set is a way of doing sets where the weight goes up (or down) from set to set, while the number of reps changes the other way.

What is a pyramid set?
Changing the weight one step each set
On workout plans you may see the word 'pyramid' next to a different weight and rep count for each set. It is the same exercise, but the weight changes from set to set. This post explains what a pyramid set is, how it is done, and how it differs from normal sets.
In short
Weight goes up, reps go down, set by set
A pyramid set means changing the weight each set, while the number of reps changes the other way. Most often you start light with many reps, then raise the weight and cut the reps each set, ending heavy with few reps.
First, reps and sets
Normal sets use the same weight every set
Lifting a weight up and lowering it once is one 'rep'. A group of reps done in a row without resting is one 'set'. Normal sets use the same weight for every set. A pyramid set changes exactly this weight from set to set.
How it is done
Example: 12 reps, then 10, then 8
For example, the first set is 12 reps with a weight you can just barely lift 12 times. The next set uses a heavier weight for 10 reps, and the last set goes heavier again for 8 reps. This is a pyramid pattern that studies have used.
The reverse pyramid
The heaviest set comes first
There is also a 'reverse pyramid' that flips the order. The first set uses the heaviest weight for few reps, and each set after that lowers the weight and adds reps. The idea is to make the muscles work hardest early in the workout.
Why do it?
From light to heavy, step by step
A rising pyramid uses the light sets to get the body ready before moving to the heavy sets. In one workout you work with a range of weights, from light to heavy. Researchers see its main use as a way to organize a workout.
How it differs from a drop set
A pyramid rests between sets
A drop set also changes the weight, but you go until you cannot do another rep, then lower the weight and keep going with no rest. In a pyramid set you rest after each set like normal sets, and change the weight for the next set. One pyramid study rested 1 to 2 minutes between sets.
Common myth
Do pyramid sets build more muscle than normal sets?
No. In studies that matched the total amount of training and used around 8 to 12 reps per set, pyramid sets and normal same-weight sets showed no difference in muscle growth or in strength gains. Researchers see the pyramid not as a more effective method but as one of many ways to organize a workout.
Summary
Change the weight each set, reps go the other way
A pyramid set raises or lowers the weight each set, while the number of reps changes the other way. In studies that matched the amount of training, it did not build more muscle than normal sets; it is one way to organize a workout. Related terms: drop set, training volume, progressive overload.