How does skiing compare to running?

For the last 5 days, I've been on a ski trip to Vail. I haven't run since Saturday (though I intend to rectify that situation today), but I have done a lot of skiing. So how does skiing compare to running? Unlike running, you get an assist on the uphill portions. However, the downhill portions are very active, and I'm often winded at the end of a ski run. But it does make me wonder: How much of a workout do you get in a day of skiing?

To find out, I wore my Garmin GPS trainer for an entire day of skiing. The lifts open at 8:30 a.m. and close at 4, so that's a potential 7.5 hour workout. But naturally you need to take a break for hot chocolate, and another break for lunch. How much actual ski time remains?

According to Garmin, I spent a total of about 5 hours and 21 minutes skiing. There were, however a couple of mistakes — I left it running for a bit during one break, and I forgot to turn it off once when I restarted. So let's call that a wash and say there were about 5 hours and 20 minutes in my workout. But some of that "workout" was actually resting time. How much? At first glance, it's difficult to tell. This graph gives my pace (in MPH) for the whole workout:

How do you make sense of that? Since I didn't stop the Garmin when I was riding the lifts, how do I know when I was skiing and when I was resting? Fortunately, the lifts travel at a pretty consistent pace— right around 10 mph. So the flat parts of the graph at the 10 mph mark are probably resting time. Note that there are also a couple of flat parts at around 5 mph — those correspond to a couple rides on an old-skool, fixed chair lift. But a much better way to tell how much time was spent actually moving is to look at the elevation chart:

Now things become much clearer! I took exactly 18 runs that day. And how much time did that take? Garmin says my average moving speed was 11.2 mph. The total moving time was 4.5 hours or 270 minutes -- the rest of the time was probably spent waiting in lift lines or taking quick breathers on the slopes. I traveled a total distance of 51.6 miles, half of which was spent riding lifts moving 10 mph (except for those two 5 mph rides, which we can probably ignore for these purposes). At that rate, since each mile takes 6 minutes at 10 mph, 25.8 uphill miles were covered in 154.8 minutes. That leaves 115.2 minutes of active, downhill skiing. My average pace per mile was about 4.5 minutes, or roughly 13 miles per hour. That seems rather slow, but remember, that includes picking through mogul fields, skiing slowly in traffic or on gentle slopes, and so on. My top speed was more like 30 mph.

So over four days of skiing, I got about 8 hours' worth of workout. In the 28 days of February, I ran a total of 235.72 miles, in about 35 hours. So in a typical four-day period, the number of hours spent running was about 4.85. Even though I got a free ride uphill when skiing, I actually spent more time actively exercising than I do while training for a marathon.

Which workout was tougher? I'm not sure. One thing I can say is that I was thoroughly worn out after each day of skiing. Normally at home I get about 7 hours of sleep, but at the ski resort I slept 9 hours every night. So while I took four days "off" of running, I did get a very good workout when I was gone.

Update: On second thought, I made one assumption that probably isn't right: That the distance traveled uphill was the same as distance traveled downhill. The lifts go straight up the hill, so I probably traveled fewer uphill miles than downhill miles. But that means I spent even more time actively exercising. So the point remains: A day of skiing is in fact a pretty good workout.

Details of the day's ski workout are below.