How to correctly do warm up sets
When warming up for a specific exercise you need to do a warm up that will prepare you for what you are about to do. I see guys in the gym that are about to go heavy on the bench press using 250 to 300 lbs or more for low reps (1-5) starting to warm up with just the bar (45 lbs) for 10 to 15 reps. That’s not gonna prepare your body for a heavy movement with low reps. That is just gonna be wasted time and energy that you need.
You want to do a weight and rep range appropriate for what you about to do. Say you are going to be doing 5 sets of 270 lbs for 3 reps. You need to do some warm up sets progressively moving towards the weight you are about to do with a reps in the range of what you are about to do. The heavier the weight and the lower the reps the more warm up sets you will probably need.
Different trainers and strength coaches vary some in how many warm ups they do and with how much weight and for how many reps but here is an example of what I would do
For 5 work sets at 270 lbs for 3 reps
Warm up set #1 150 lbs for 4 reps
Warm up set #2 180 lbs for 3 reps
Warm up set #3 210 lbs for 2 reps
Warm up set #4 240 lbs for 1 rep
Warm up sets #5 265 lbs for 1 rep