I’m a TrainerRoad guy. I cribbed this from my post in the What the heck is Zwift thread, with some edits. I’ve screen shotted a lot of TR workouts in the did you ride today thread. If you like, pm me with your email address and I can get you a free month.
TrainerRoad consists of structured plans that start with laying a base, building on it, and then fine tuning your fitness to arrive in peak condition for a goal event. Base is anywhere from 12 to 16 weeks, build is 8 weeks, followed by specialty which is 8 weeks. As such the entire course is 28-32 weeks. There are low, mid, and high volume plans that range from 3 rides at 3.5 hours per week to 5-6 rides at about 9 hours per week. I do low volume as I still ride outside 1-2 days per week during the course of completing the three phases. During Covid I’ve reduced outdoor riding significantly and stopped all group rides, so I’m now doing 4-5 rides a week, which is mid volume. I’m in between plans at the moment because you can’t really ride structure 52 weeks a year. Ideally if you want to be in top shape for a goal event you just count backward 28-32 weeks before the event and begin the program at that time
The premise is that fitness gains occur as a result of workouts focusing on a percentage of your functional threshold power, or FTP, basically your "hour power" or what your best effort in a one hour time trial would be. Your FTP is tested not by riding all out for an hour but by either an hour long workout in which you do 2 efforts at 8 minutes or one effort at 20 minutes, or by a "ramp test" where power rises 6% percent every minute and you ride until failure. Your FTP is extrapolated from your watts on those efforts and that number guides the remaining workouts in the plan. Endurance rides are maybe 50-70% FTP, and those percentages rise through tempo, sub-threshold, threshold, super-threshold, VO2 max, and anaerobic efforts, with the harder workouts left to the build and specialty phases. Plan workouts range from 60 minutes to two hours for the most part. There is no workout shorter than an hour nor longer than 90 minutes in the low volume plan, until the last week of specialty when you taper and the rides are 30-45 minutes. Mid and high volume plans have long rides of 2 hours.
FTP is re-tested at the end of base, build, and specialty to track your improvements. There is a recovery week every 4th week in the plans to guard against over doing it. At my age, 63, I’m beyond being able to continually get faster. I’m at 3.4 w/kg, and the goal is just to maintain that for as long as I can against the inevitable decline. High intensity interval training is really the only way to try to lessen the effects of the gradual drop in heart rate and stroke volume that comes with age.
When I completed the three phases last year I did all my riding outside. I would do an occasional TR workout on rainy days or if I was time crunched and couldn't get outside. That meant that my rides from late May through mid-November were all outside. Structured training probably isn't everyone's cup of tea. I really like it. I get to make the most of the limited time I have to ride, about 325-350 hours per year.