I had open heart surgery this past May to address a leaky aortic valve. After following post surgery sternal precautions (6 weeks of no lifting and restricted movements), I’m wondering when it would be sensible to introduce intensity (zone 3+) back into my training. My cardiologist says I can pretty much transition back to my pre-surgery activities after 6 weeks as long as I slowly ramp up into it (but I find that guidance pretty broad). Pre-surgery I trained 400+ hours/year, comprising of xc skiing, trail running and biking. To date (now 9 weeks post surgery), I have eased back into running, keeping everything largely in zone 1. I know this is a long shot but has anyone else had heart surgery and gone through the process of getting back to their pre-surgery levels of training and share their experience? Thanks.