So, @chad, @Nate_Pearson, @Jonathan in doing a workout like Baird +6 I can do the intervals at the prescribed wattage at +100rpm or I can do the prescribed wattage at ~90rpm in the next harder gear. What is the difference exactly? I have a feeling that you are going to say that one is more aerobic and the other is more anaerobic… but if ultimately the goal is to get stronger and push a bigger gear then wouldn’t it be preferred to do the workout in the harder gear, at ~90rpm?
Actually the difference between 90 and 100rpm can be quite significant depending on the trainer, the gearing and on the individual even when using erg mode. The heavier the fly wheel and the bigger the gear for example, the easier it is to keep the inertia of the flywheel at a higher cadence. .
@webbsb Aside from those mechanical issues above and how cadence affects things, it is not that one is necessarily aerobic vs anaerobic but the recruitment of fibre type can be different and the higher cadence CAN prevent burning the quads out but not necessarily. All dependent on some personal variables, but in most instances this would be the case. VO2 work done in different cadences can be a useful tool however. Both low and high cadence can come into play depending on the terrain and how it is approached by the rider so it can be useful to also replicate this on the trainer while doing those workouts depending on the goal.
I did my first TR VO2 workout a couple days ago – Huffaker – and @chad’s in-ride dialogue told me that higher cadence works the cardio more and lower cadence works the muscles more thus the instructions to keep revs@ 100+. (It was a real treat letting 'er rip @110rpm!)
Perhaps in much longer intervals this effect would be much more pronounced, but when the VO2 interval is only 3 min max, the difference may not be that dramatic.
Interested in this thread and to see what people come back with.
I been riding on road at 89rpm for years (for training rides) and after 2 weeks on TR my cadence has shifted up to near 100. Happy to keep it up there for this round of base-build then switch it down in new year when start CX training (as rarely pedalling hard at high cadence).
From a performance perspective, trainer inertia aside, altering cadence can shift the muscle fiber type recruitment a bit. But mostly, I’m concerned with 1) riders holding power close to target power in order to really challenge their aerobic capacity, both at the muscle and more centrally, at the heart & lungs, and 2) making things transferable to the way they’ll ride or race outdoors, especially as they move through the Base/Build/Specialty cycle.
As far as point 1, slow twitch fibers are capable of producing relatively low amounts of force but fatigue very slowly while fast- and “mid”-twitch fibers are the opposite–more force as you work your way up through the fiber type continuum but greater sensitivity to fatigue. So if you turn the pedals slowly, with higher force, you’re recruiting more fatiguable fibers and also fibers that rely more on anaerobic metabolism and hence produce lactate as well as muscle acidification. The lactate is a good thing, as long as you have an aerobic system robust enough to process the excess before the hydrogen that accompanies it acidifies the muscle and stalls contraction. But even then you’re shifting your energy usage to more costly anaerobic turnover (more glycogen for less ATP) while remaining more aerobic–a quicker spin with lower-force contractions–yields far more ATP per glucose molecule cleaved from your muscles’ stored glycogen.
This is a more detailed than usual explanation of the “oxygen cost” of ATP (frequently referred to as “aerobic efficiency”, not to be confused with mechanical efficiency which is also a concern when you pedal poorly at high or low cadences) and how it differs between aerobic and anaerobic energy production. And on top of this, the more intense contractions take a greater toll on the muscle tissue (and not just the obvious pedaling muscles) which can see you fatiguing earlier for reasons beyond energy depletion.
All of this is to say, you make better use of your energy stores (and intake) and keep fatigue at bay when you spin a lighter gear more quickly than grinding a bigger gear. But sometimes grinding is a necessity, and training as such, often or occasionally, depending on your cycling discipline and time of season, is advised and built into each plan and governed over the course of each BBS cycle.
Worked/struggled my way through Tray Mountain today as I’m finishing week 3 of Traditional Base lll mid volume. Long intervals are my weakness and it definitely was on display in this workout. Reading the explanation of slow twitch versus fast/mid twitch fibers, I’m not understanding why my default when exhausted is to find comfort in 65-75 rpms when I normally prefer mid to upper 90 rmp.
Is it because my slow twitch fibers were just exhausted so I relied on fast/mid twitch?
If I’m exhausted how can I hold a SS interval at such a low cadence?
I basically did the entire last 20 min SS interval bouncing above/below 70 rpms for an average of 71. I tried to lift my cadence and I just had nothing.