Triathlon at Retirement

Without previous experience in winter triathlon, I signed up for US National Championship in duathlon (run + ski) and triathlon (run + bike + ski). With all my participation in regular triathlon and cross-country skiing, how hard can it be? Answer: very hard. Maybe it was the altitude (>9000 feet), maybe all the fresh snow, but it was exhausting. I was worried about the altitude, and I also needed to get back into skiing, so I arrived in Breckenridge a week before the competitions.  I got an extra workout right away the first morning when I had to clear my car of snow and shovel my way out to the road. I did not want to push my limits the first day and skiing felt fine, but really, that slow? Mile splits of 12-14 minutes! I checked the Strava segments, and I was quite high on them, for my age group number 1 or 2. I realized high altitude has a big impact. After a few days, I rented a fat bike and tried the biking. It had snowed in the night and even though the track had been prepare