The following is very simple yet brutal. It will target your anaerobic endurance, core and grip strength like nothing else. See how many rounds you can get through in one piece, before your 45minutes are up.
For this workout, you will need a running track or football field, and a 45lb weight (Kettlebell / Dumbbell / Jerry can).
WORKOUT 45min AMRAP - (As many rounds as possible)
400m Single Arm Farmers carry (200m each hand)
** Rest only where needed but the goal is to get as many rounds in as possible so pace yourself.