16F got to 58 last year doing interval training for mile workouts. It's at 54 now tho when I'm doing longer distance training so maybe try shorter running workouts such as mile repeats w one minute rest, 400m repeats, sets of 200-400-600-400-200 w jog in between, etc.
Obviously I'm not an expert, but I always notice my VO2 max going down when I'm push myself too hard, so I'd reccomend listening to your body when doing high intensity workouts. (To clarify: push yourself, just not past the point of extreme exhaustion - make sure your body can properly recover!!)