Improve endurance and aerobic fitness, familiarize yourself with your HR zones.
For best results you need to know your zones.
mPaceline has these plans under "CDE Training". Printables are coming soon too.
Duration: 4 weeks
Repeat weekly for 4 weeks. Each day pick a class of duration that best matches your time available. There are two instructors to choose from -- Christine D'Ercole and Jennifer Jacobs.
If you've never taken an FTP test and were using perceived effort for your HR zones, it is a good idea to take one at the end of this plan and properly calculate your zones.