Trying to get fit again
First post, apoligies for asking obvious questions and missing out details i have no doubt.
Im 19 years old, student. Young football referee trying to get fit. Used to swim competitively for over 10 years but have had 2 years off so have lost all fitness. basically need a routine to get myself mega fit to cover all areas of pitch when refereeing. A typical game involves lots of sprints but enough stamina to last whole 90 minutes.
Happy to train 5 times a week ( have been weight lifting for a year training 5 days a week so used to it).
Looking for advice on possible routines/ interval training or continous runs to follow. prefer to run outside but have access to gym also. Also have a top of the range heart rate monitor if that helps.