choddo

This is true but my easiest gear is 36:28 so I definitely get away with an unrealistically high cadence on the steepest climbs with my trainer difficulty set where it is.

rsbob 

This is what I read on the ZWIFT Insider page,

“Trainer Difficulty is set to 50% by default, which is why Zwift says it “treats the gradient as half of the true grade.” So when you hit a 10% climb in Zwift, your trainer is only giving you the resistance of a 5% climb.Bump your Trainer Difficulty up to 100% and you’ll feel the full gradient. Set it to 0% and you won’t feel gradient changes at all!”

Then it goes on to say, “Changing Trainer Difficulty does not change the power needed to get up the hill. You still have to put out the same watts to move the same distance as before… you’ll just be doing it in a different gear.”

Setting it to Max and climbing the Radio Tower yesterday at 14% forced me to stand to do the majority of the climb, where before the change, I could spin up seated with out nearly the exertion as my heart rate would indicate. On Max my heart at the top was 188. It just seemed more difficult. Psychological? Out of shape? It felt like I was climbing using the big ring.

choddo

All comes down to what cadence is optimal for you, and for most people they are most efficient at about 85-95. Having to deliver much more torque at 60-70 to get the same power is more difficult and physiologically demanding for most.

So I would say that reducing the TD is “playing the system” when it comes to racing but it’s an option open to everyone so I don’t consider it cheating.

And as far as simulating the workload for real climbs, if your gearing is similar, you’re probably getting more training benefit at 100%

terrymorse 

This is true of all the "real" climbs in Zwift, but there's one adjustment you can do to climb portal climbs, and it makes a big difference. It's called "Elevation Scaling", and it literally adjusts the height of the climb. You can set the elevation scaling to 50%, 75%, 100%, or 125%.

PeteHski

This is correct. Your avatar speed on the virtual gradient for a given power is unaffected. So you could set trainer difficulty to 0% and still climb at the same virtual speed for a given power. But it would be like training for a hill climb on a flat road ie not very realistic since your crank inertia would be much higher for the same power. Spinning 250W on the flat doesn’t feel like grinding 250W on a 10% slope. On the flat you would have far more momentum and almost certainly a higher cadence.

The Radio Tower climb is a good example of this. At 100% slope resistance it is a proper low cadence grind fest, while at 50% difficulty it is a fairly comfortable seated climb.

It only makes sense to reduce the Trainer Difficulty if your road bike has lower gearing than your trainer bike. So you can compensate for the difference in the ratio. Or if your trainer cannot provide smooth resistance on steep gradients. The latter often applies to budget and mid-range trainers, especially for riders above average weight.

PeteHski

The difference with the portal climbs is that the scaling changes the virtual slope gradient. So at a scaling of 50% the virtual slope gradient is halved and your avatar will move faster for a given power. But the Trainer Difficulty setting is still applied on top of this. So if you also have TD set to 50% then your trainer resistance will be set to 25% of the slope, while your avatar will move according to power at 50% of the original slope.

choddo

The weird thing is, I find it easier/more natural to push at 300W on a hill than on the flat. Having the resistance to work against seems to help.

PeteHski

It's certainly more natural to push higher power on the climbs, but being "easier" is probably an illusion. When riding IRL I find that pushing 300W on the flats can be challenging due to the relatively high road speed (especially with a tailwind), unless it's a dead straight road with no obstacles. Either way, it is a very different feeling in a big gear with loads of momentum. Riding on the flat in a strong headwind feels much more like climbing because of the similar resistance and lower momentum.

Sierra_rider

I understand this perception completely...despite doing FTP testing on a regular basis(on the trainer,) my best 20 minute power of the year is always set on a real life grinder of a climb. Put me on a straight, flat road, and I'm not sure that I could actually replicate that same power.

I think it's partly perception/a mental game, but I wonder if there is actually some science to it. I almost think hip angles might come into play...I actually put out better/more consistent power with a tight hip angle/aggressive position, but riding in that aggressive of a position puts a lot of pressure on my arms when on the flats. Meanwhile on a climb, I can replicate that same agro position, with my forearms nearly parallel with the ground. The difference is that the angle of the grade puts my weight back into the saddle.

I don't know how much merit there is to my thoughts on that...something like aero bars would probably solve the issue, but you'll never see those on any of my road bikes.

asgelle

This is false. Studies show people are most efficient around 60 rpm.

choddo

Have a link? That’s really interesting

asgelle

Just because this is the one that showed up first in a search for cycling, efficiency, rpm. There are plenty more.
https://link.springer.com/article/10.1007/s004210050634

spelger

i spent about 20-30 minutes spinning at 65 RPM. it was not really fun. don't normally do that, i think i'll be feeling it tomorrow.

terrymorse 

That’s metabolic efficiency (lowest oxygen consumption).

If you define "efficiency" as how much power you can produce in a given time, the optimal cadence is definitely higher than 60. More like 85 or higher.

choddo

I found this one after posting that last night. Really well designed study. https://link.springer.com/content/pd...011-1914-3.pdf

Wow. I’d like to see them have extended that to -20 below preferred cadence though to see if the almost linear relationship holds. (Edit: they make the same point in their discussion although weirdly they also say the preferred cadence range was limited to 86-106. Yet they have a data point at about 66 in their chart. And I’ve never met anyone who prefers riding at 106. I wonder if the fact they did the preferred cadence setting test with big 50W jumps made people inclined to a high cadence to reduce the torque jumps)

This was also metabolic efficiency. Why is time to exhaustion different terrymorse - I’d have thought the two would be related? This study says there was no significant anaerobic component to the work rate.

choddo

edit: just completely changed this post due to having a coffee

I don’t undersand the last comments, that agrees with my assumption that people prefer higher cadences, in that abstract (which is all I can get to).
“However, in contrast to GE, DE (Delta Efficiency) increased as a linear function of pedalling rate. The rate at which pulmonary ventilation increased was accentuated for the highest pedalling rate, even after accounting for differences in exercise intensity and V˙O2. Pedalling rate per se did not have any influence on heart rate which, in turn, increased linearly with V˙O2. These results may help us to understand why competitive cyclists often pedal at cadences of 90–105 rpm to sustain a high power output during prolonged exercise.”

A maybe related commment / proposal in a 2009 paper from a researcher in the UK who went on to make gin from elephant dung in South Africa, that tries to encompass energy use, muscular stress and perceived effort; “We propose that the point at which the energetic vs. power and the muscular stress vs. power curves intercept is defined by the cadence at which the perceived effort is minimized (i.e. the preferred cadence). However, cadence fluctuations occur under field conditions that are unrelated to physiological factors and, therefore, the ability to identify an “optimal” cadence is limited to the laboratory environment and specific field conditions.”


and now this post is too long.

Jughed

My trainer (zwift) wigs out when set at max on the Radio Tower. I'm about 181#'s right now - the trainer simply can't handle the weight/grade combo at the watts I'm putting out. I try not to go into the red during my longer workouts, last time up the tower I still had the Alp to look forward to... Sub threshold power levels - the trainer just can't deal with it. Set at 85% or so, same power, same speed, the added cadence allows the trainer to function properly.

The grades on the radio tower mimic the grades of a climb I hit up in Philadelphia - the Manayunk Wall. 13-17% all the way up. With my 1:1 gear ratio - my power output/cadence and heart rate are similar to each other in both situations.

PeteHski

But it's not the most efficient cadence for generating sustained power. Hour record attempts are typically done at a cadence of around 100 rpm and certainly not 60 rpm. If they attempted to ride at maximum efficiency in terms of oxygen consumption then their leg muscles would soon fatigue from the increased torque at the lower crank speed.

Our preferred cadence is not influenced by efficiency alone, otherwise the pros would all be cruising along at 60 rpm rather than the usual 85-90 rpm.

eduskator

I lowered my cadence this winter on Zwift to see how different it would be / feel and I am impressed to far. Staying at around 70RPM instead of 80RPM, my legs and heart prefers it.

I ride in mid zone 2 mainly.

eduskator

Link of the study(ies) to support this claim please? And what's the definition of ''efficient'' in your statement?

asgelle

12 hours after I post a link you come out with this? Please try to keep up.

asgelle

Yes indeed. If you redefine words they can mean whatever you want them to. If we define efficiency to mean time to exhaustion, maybe we should redefine time to exhaustion as lowest energy consumed for work produced. That way we maintain two descriptors for two distinct concepts.

RChung

Hmmm. Both Graeme Obree and Vittoria Bussi set world hour records at much lower cadence. F1 race cars run at much higher rpm than my Prius, but my Prius is much more efficient. And in several studies cited, power is held constant and cadence is varied while measuring efficiency.

People throw around the word "efficiency" without really understanding what it means, or how it's measured. The pros (and hour record holders, and F1 cars) are optimizing on things other than efficiency.

MoAlpha

Like delta-efficiency? I didn't look carefully, but I think the cited study stated that it went up with cadence over the normal operating range.

terrymorse 

Also, about that claim that 60 is the most efficient cadence. That number is not etched in stone. The most energy efficient cadence appears to be training dependent:

Elite cyclists did time trials at various cadences [1], and their most energy efficient cadence was 80, not 60.

This study also found that finishing times were similar for 80 cadence, freely chosen cadence (mean 90), and 100 cadence.

The takeaway: As long as your preferred cadence is between 80 and 100, you're good. It's probably pretty close to optimal.

1: Foss & Hallén, Cadence and performance in elite cyclists, European Journal of Applied Physiology, 210 October 2004