Caffeine doesn't actually work like that. It's not a timed on/off switch. Like most drugs it'll gradually ramp up in effect, stay at max for a while and then taper off again.
So if it's "kicked in" when the 20 min alarm goes off that means the last 5 min of that 20 will have been restless because the caffeine was already working.
Caffeine is the great antagonist of sleep quality anyway. Just drop it for a month, see how that feels. Then see how much it fucks up your sleeping quality as you take even two cups of strong coffee (which is great fun because the caffeine will actually work full power, it's amazing, but your sleep after that night will suffer).
This "coffee power nap" thing is a very nice story, but it's based on nothing. People that have success with it are finding the benefits of having a nap despite their caffeine usage.
You may be right. I read that tip somewhere a few years ago, and it worked the times I tried it. It could have been the placebo effect or just coincidence, and I didn't try napping without it.
So if it's "kicked in" when the 20 min alarm goes off that means the last 5 min of that 20 will have been restless because the caffeine was already working.
Caffeine is the great antagonist of sleep quality anyway. Just drop it for a month, see how that feels. Then see how much it fucks up your sleeping quality as you take even two cups of strong coffee (which is great fun because the caffeine will actually work full power, it's amazing, but your sleep after that night will suffer).
This "coffee power nap" thing is a very nice story, but it's based on nothing. People that have success with it are finding the benefits of having a nap despite their caffeine usage.