What does this mean? I see the improvement but can't figure out how you put out 250 - 350 watts for anywhere from 3 -5 minutes and go 5-8 mph? Is this an interval or something?

In response to the OP...yes...I'm improving for three reasons:

• Strengthening my core, primarily with planks
• Improving flexibility with regular stretching
• Riding with a newbie who is 30 years younger and faster than me