After training off and on (mostly on) for about a year, I recently took a break from the gym and didn't exercise at all aside from gentle walking for close to 3 weeks. When I returned, it seems I lost a fair bit of fitness and strength. I dropped down on bench press reps at the previous weight, pull up reps, and really dropped on running endurance and sustained speed (from 40 min at avg 8min/mi to 16 min at 8:30 and I had to stop!).
It's pretty disheartening, as it feels I have taken nearly six months step backward after just three weeks. (But I admit, I have not tracked things carefully enough to really quantify it.)
So, What (evidence based) "rules" can one rely on to reasonably predict fitness losses after a break of x amount of days? This should take into account things like age, sex, type and intensity of training, break duration, and whatever else is applicable. I want to know because I want to know if this recent loss is in the normal range, as well as how I need to plan ahead in terms of future vacations in which I am away from my gym.