sub_pop says:This has a decent explanation
(trouble posting a link to apple.com)
Quoted from threadID=619828:
Here is what I know so far.
1. kmSplit is the automatic kilometer distance at which the kit records the time (duration).
2. Duration is the number of milliseconds it took to run the recorded distance.
3. mileSplit is the same thing but in miles.
4. onDemandVP is the duration and distance at which you press the center button to hear your stats.
5. powerSong is the duration and distance you played your power song.
6. extendedData dataType="distance" intervalType="time" intervalUnit="s" intervalValue="10" is the distance in kilometers you ran at every 10 seconds. This is actually the data that the Nike+ site uses to plot your pace. Nike+ plots the difference between, I think, every 6 points (60 seconds). If they ploted every point the graph would look to jagged. This plot will just show you the change in pace, you will need to know your pace at look at the pace from your duration. This is why I think the Nike+ site does not show the actual graph pace and distance increments. Notice it just shows faster with an arrow and distance with an arrow on the axis of the graph.
I hope this takes away some of the mistery of the xml. I actually import the xml file into MS Excel to keep track of my workouts as a backup.
Fred