That dead spot of time between sets is called a Rest Period
It's a bit of a misnomer
It's also something that the martial arts guys usually really struggle with in their S&C work, but I'll come back to that.
First, why is "rest" a misnomer?
What other words would work?
"Recovery" would work, but that's looking backwards at the last set.
"Preparation" would work as it's looking forward at the upcoming sets.
Here's what I mean:
You just finished a set, we'll say it's the second last set on that exercise.
We're talking an intense exercise here, a deadlift maybe at a high percentage of max load, or maybe kettlebell Snatch at high percentage of max heart rate.
This was the second last set, so your time between now and the next set must be dedicated to maximising the next set.
This means active recovery.
It means long, strong exhales to empty the lungs and reduce the amount of excess CO2 built up over the set.
Maybe use a double inhale followed by a long exhale, the so called physiological sigh.
You may bend over supporting yourself with the hands on the knees, or walk around. Your choice.
You should shake, imagine shaking tension out of the muscles, turning them to jelly or becoming like a "well cooked chicken" (that one is courtesy of a chi gung instructor I knew)
Once the heart rate and breathing are under control, begin visualising the next set.
See yourself succeeding. See yourself correcting any mistakes made in the last set.
Visualisation is a powerful tool but must be realistic, acknowledge your errors, your mistakes and make realistic predictions on how you will improve them. Then when the set comes around, you have a mental picture of what you will do physically.
So you do.
How long should you rest?
This is the trick alright, this is what many struggle with.
For max strength and power you rest longer than you think you you should. For muscle building and mass, a minimum of 1 minute, up to 5 minutes between sets. For fitness/work capacity, play around depending what energy systems / attributes you're trying to emphasise. These rest periods can seem like an age to the martial artists and the over stimulated office jockey who are used to driving forward all the time. But 2 minutes will fly in if you fill it with active breath & HR recovery and visualisation.
You are not resting.
You are preparing.
Now go train.