Some folks have asked for an example of what my coach calls a "Turbo"  cycling workout. Here is a pretty hard one. Note that the meat of the workout is the 3x10min intervals at a hard effort and anerobic.
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Warm-up: 15-20 min easy to moderate speed

3x (20 sec fast / 40 sec easy, 40 sec fast / 20 sec easy, 1 min fast / 1 min easy)

Main set: 3x 10min as: 2x (1 min >100 RPM sitting up/ 4min at 80-90rpm in aero position) 3 min easy after each 10 min interval- all at Hr #3 low to mid,
10 min as: alternating 1 min standing in big gear at <70rpm, 1 min seated in big gear at <70rpm,
2x 10 sec fast spinning jumps/ 1:50 easy  after each. To perform shift into an easy gear and get your rpm up to a normal 85-95, then for 15 sec  as fast as you can without falling off the bike, then 1:45 easy back at a regular cadence, Stay seated and keep the upper body quite, trying not to bounce.

2x 10 sec Big gear jumps/ 1:50 easy spin after each. Very similar to fast cycling jumps, but start in a very big gear at a very slow cadence of <50rpm. For 10 sec stay seated and power very hard to get up to speed while keeping the upper body quiet and working only from the hips down, then shift into an easy gear and go for 1:50

Cool-down: 10-15 min easy to moderate pace.
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Here are the basics of how the HR bands work in this plan:
HR 1 = easy (below 132 for me)
HR 2 = moderate all the way up to high end aerobic (133-149 on bike for me)
HR 3 = low end of anerobic to hard anerobic (150-170 on bike for me)
HR 4 = all out melt down zone (170 up to my max of 192)