Start with forty minutes in Zone 1. Then move to thirty minutes in Zone 2. By now you should have a sense of whether this is a good day to push harder or if it would be smart to back off and finish the workout in Zone 1, saving the hard work for a day when you feel better. If you do feel good, add on twenty minutes in Zone 3. If still feeling strong, increase the effort for a final five minutes in Zone 4.
