NEWS FLASH - YOU DON'T HAVE TO DO 3 OR 4 SETS
The most common set rep scheme has to be 3 or 4 sets of 8 to 12 reps.
There's nothing inherently wrong with that, but it's not the most effective way to train for athletes.
Louie Simmons (founder of Westside Barbell) is all about "first reps."
First reps are the number of reps you take on a given exercise after a period of rest. The more first reps you can get into a session, the higher the neural stimulus, the greater the signal for strength development.
Let's use 3x10 vs 10x3 for an example.
Both of these set/rep schemes have the same amount of volume = 30 reps.
3x10 has 3 first reps (because there is 3 sets).
10x3 has 10 first reps (because there is 10 sets).
In doing 10x3, you get 7 extra reps where there's less fatigue because you're coming into them straight after a rest period. This way you are able to lift more weight (higher intensity), produce more force and generate more power.
Which means you are able to stress the nervous system more. Which means you’ll get stronger.
You’ll probably get less sore too... that’s why soreness is a poor indicator of progress (particularly for strength).
Moral of the story - not all reps are created equal.
On 3x10 your 5th, 6th, 7th, 8th, 9th and 10th rep are no where near the quality of the first reps on a 10x3. So don't be afraid to mix up your set and rep schemes. You can even do things like 15x2 or 30x1.
If you're someone that's constantly doing 3 or 4 sets of 8 to 12 reps, try flipping that equation around and watch your strength numbers shoot through the roof.