Originally Posted by
chasm54
I agreed with everything you said until this. I find tempo rides to be very effective. Of course, given unlimited time, one would spend comparatively little of it in Z3 - long z2 rides mixed with HIIT would be the answer. But few people have unlimited time and a tempo hour once a week or so is pretty useful, imo.
Empirically with few data points I've noticed no difference in the rate of power gain adding tempo rides to a weekly schedule including at least one day of maximum effort 10 minute intervals with 5 minutes rest between.
When I did that my heart rates for power-based Z2/Z3 rides clumped up closer to LTHR suggesting my aerobic threshold was lower. Presumably my maximum power output over longer durations was also a lot lower, although I'd yet to realize I had the patience and motivation to train 14+ hours a week and regularly ride 2+ hours so I could monitor that. When I was down to at most one Z1/Z2 day my weight loss stopped about 40 pounds (37%) over what I weigh now instead of continuing with Z1/Z2 4-6 days a week.
At least one study showed a correlation between time training in polarized zone 2 (Friel Z3/Z4 through FTP, between aerobic and anaerobic thresholds) and worse (longer elapsed time) performance, but improved performance training in polarized zone 1 (Friel Z1/Z2 in average individuals, below the aerobic threshold):
Training-intensity distribution during an ironman season: relationship with competition performance.
It doesn't say whether the training intensity was causal - maybe people do worse because more time in the middle means less at low intensities.
If you're going to do a steady 1-1.5 hour hard effort once a week, make it zone 4. That correlates with hard efforts of that duration feeling easier for me and nets more total training stress, although I suspect the science doesn't support that impression.
Falling into the naive "ride hard to get faster" assumption with plenty of Z3 but minimal Z4/Z5 I arrived at a "not slow" plateau very close to what resulted from just riding Friel Z1/Z2 miles.
Doing a lot of Z3 riding 8-10 hours a week did work well before a week long 418 mile 28,000 vertical foot supported tour.
Tempo is a nice pace for group rides which won't leave you too spent for your hard days, and the appropriate pace for some time trials.
Otherwise it's both too hard to improve your aerobic performance and not hard enough to boost threshold and VO2max.