The general rule of thumb for increasing running volume is no more than adding 10% per week, but in my experience, especially with fit people, that’s quite conservative. One thing that is really helpful with using AeT is that it tends to make running be more of a run/walk if you’re not as efficient with the movement. Because of your background, I bet you could safely start with 30-45 min. of running (at or under AeT) and see how that feels. To add more volume you could do an uphill walk either outside or on the treadmill. One of the biggest differences in terms of movement from skiing is the quicker tempo, so try to keep a high leg turnover, to lessen the stress on your muscles and tendons. “They” say 180 steps per minute (3 per second is an easy way to check in on it anytime during your run) is the most efficient in terms of lower chance of injury. For building up week to week, I would start with a few times a week of 30-45 min. and if that goes well, increasing the frequency to 4-5 days, and then start increasing the duration of the runs. There is much more impact that skiing so that will likely be your limiting factor. If you’re really stiff after a run that’s relatively normal as you get started, but it should resolve by the next day. I would wait to do any higher intensity until you can do several weeks of easy running, and then start with hill sprints or strides which serve as a specific strength workout, help with running economy and are low injury risk.
Steve Magness has a great website called Science of Running, with some articles on running form. I wrote an article here on downhill running technique, but it applies to all running: https://uphillathlete.com/downhill-running-technique/
Have fun! You never know, you might love it and become a runner…
