I just started using Jack Daniels VDOT for training. I'm in my 30's with about 5 years running experience, basically base building (50 miles a week average) but ZERO speed work. I've been using the Maffetone Method exclusively, so 99% of my miles were aerobic the past 5 years. I have a great aerobic base and ran a 4:59 mile time trial for a VDOT of roughly 60. I'm committing to back to back to 20 week cycles to prep for a 5,000 meters next summer as I want to try and be "fast".
How much of an improvement in VDOT can I reasonably expect each 20 week cycle? I've read Daniels says you can go up 1 VDOT every 4-6 weeks if you have no races to gage improvement off. Is it reasonable to think I can go from a 60 VDOT to a 64 VDOT in a dedicated 40 week period? I'm not young anymore and my base is strong which can both limit upward mobility but I've also done zero speedwork and surely that leaves a little ceiling left. Any thoughts or experiences to help me gage reasonable improvements and whether 4 point improvement in 40 weeks is possible in this scenario? Thank you!