IDK about 7 vs 10 per se, but I’m an advocate of being able to set any start day and number of days for the work/rest cycle. A 7 day week is cultural, not physiological.
Joe Friel touches on this in hid book ‘Fast after Fifty’ although he uses nine days as an alternative. It goes something like this.
Mon VO2
Tues Easy/Recovery
Wed Strength
Thur Sweetspot/Threshold
Fri Easy/Recovery
Sat Strength or Recovery
Sun Endurance (Long ride)
Mon Easy/Recovery
Tuesday Easy/Recovery
Then you’d start again with VO2 on the Wednesday, only problem with this for a lot of people would be fitting the long endurance ride in if it falls on a workday. It is something that is a frustration as trying to cram two interval sessions and endurance rides plus strength training into a ‘normal’ seven day week is a bit much, I’ve often wondered about trying something like this as I think the extra recovery would mean I could work harder on interval and strength days. Might experiment over winter with it.
It just means more endurance and recovery between hard sessions. 2 hard days out of ten with all the other days being endurance, rest or recovery days.
For example, I could never get on well with a Tues/Thurs interval schedule because there isn’t enough recovery time between Tues/Thurs.
Another example is the Cyril Guimard designed training plan in Lemond’s book. It’s a decreasing intensity program:
sprints
threshold
endurance
rest
repeat
If you repeat those blocks, it’s an 8 day “week”. If you need an extra rest day, you just insert it and then it’s a 9 day “week”. A pro with 2-3 months until racing starts can do block after block of that kind of training regardless of the day of the week. This doesn’t work for most weekend warriors with day jobs and schedules.
Another example is Seiler’s 80/20. That is 2 hard sessions out of every 10 sessions. For a cyclist, it’s kind of an odd puzzle since interval day of the week is going to be random and not coincide with work schedules or weekends. Runners do lots of double days (shorter sessions twice a day) so 2 out of ten may work perfectly for them within a week period or it may not.
The only point is that 7 days is an artificial construct just as 10 days would be. One could also meter out the intense days organically based on feel or recovery scores or HRV or whatever metric works for the athlete.