Omron Smartsync heart rate logger to gather this data. Not a bad workout. Average HR of 136 for 40 minutes and, as you can see, totally interval.
1. ambitious start
2. chatting with neighbor
3. admiring my mini igloo
4. detailing mini igloo
5. looking at mini igloo and hoping it snows more
Peter, the csv is in the mail. I opted for a 10 second sampling rate to make the graph prettier.