I just reviewed the plan. It looks like stress points are the same as TSS. The summary says 441 per week average. The first 3 weeks are 7 days per week and week 4 is 6 days. Week 4 is 382, week 3 is 452, week 2 is 477, and week 1 is 441.
Here is a summary of my thoughts:
The plan does not take into account training history. 450 TSS is quite a bit. It may be way too much for some and certainly is too much if you are a new rider and new to real training. On the other hand some riders who have long term hard training even decades a 450 TSS week may be relatively easy. Those riders may have 600-800 TSS training weeks.
On the bike 7 days a week for the 1st 3 weeks and the first 5 days of week 4 means that you start with 26 days on the bike. That sounds demanding to me.
Having a day completely off the bike has me feeling so much better. Remember that hard work only makes you fitter after you recover from that hard work.
My preference is 2 to 3 hard workouts a week and then fill in with Z2 as I feel able. I would consider the 2 to 3 hard workouts to be hard if they are threshold work or harder. That really means something like 60-90 minute workouts with 30-60 minutes in whatever zones are being trained. This also means a day off altogether if not 2. Life usually is the limiter and I am off the bike more days than that sometimes. Sweet Spot can be done more often to a point. Z2 almost as much as you want. I try to avoid tempo work.
Just a preference I suppose… I like concentrating on a particular system. Say focusing on VO2 max and doing a block focused on that. The Zwift plan seems to train all sorts of systems and is not a focused block that I can tell. No idea if that is good or bad.
I would drop the intensity on the recovery week. Maybe 1 hard workout with intensity but I just go all Z2for that week. Then take a rest day and re-test FTP.
Age is not considered. As we age we do not recover as quickly. Maybe 20 days in a row is ok for a well seasoned 28 yr old but not for a 48 yr old and certainly not a 68 yr old (there are some seriously fast 40+ yr old make no mistake). Adjust the workload, rest days, and recovery rides based on recovery rates and as age plays into this.
Bottom line is that yes, I could see this plan becoming overwhelming. Take additional rest days as needed or make a hard intense workout a simple Z2 ride. You can bury yourself if you overdo it and just keep pushing. It should be difficult but fatigue builds and accumulates. There needs to be a balance.
Pay attention to your body, are you continually failing workouts? Are you sleeping enough? Are you eating well and taking in good recovery after workouts? Do you feel sleepy/tired all the time? Trouble sleeping and/or falling asleep? Trouble getting heart rate up during workout? Waking heart rate up above normal, especially 10+ bpm more than normal? Are you losing motivation to ride/train? Does it feel dreadful to climb on the bike knowing you are about to bury yourself in a workout? Are there other stresses in your life… work, family, health, etc. All questions you should look at when training in high and intense volumes.
I knew I was too fatigued when I could not perform a threshold workout that called for 4X10 minutes at Th. Dont get me wrong 40 minutes at FTP is very difficult but theoretically you should be able to go approx 60 minutes straight at FTP. I barely made it through the first 10 minutes and called it quits about 5 minutes into the second interval. I took a week where I did nothing but Z2 and had two days off the bike… I am just back from that and I feel strong. Beat my previous 20 minute power last night in a Zwift race. That would not have happened had I not recognized the need to step back and take it easy for a while to allow recovery and absorption of the training stress.
Long answer but I hope it helps. Keep in mind that any online training plan is not like having a personal coach. The plan should fit a good percent of the population but not everyone in every situation at every age. Take care.