How Does Cadence Impact Power Output? | GCN Tech Clinic

Welcome to the first GCN Tech Clinic of 2023 and we’re starting the year as we mean to go on - with a combination of bike tech knowledge and awkward humour! This week we answer your questions on whether some watts feel easier than others, where is the best place for heavier cyclists to ride in a group on a climb, how long it takes to make a GCN video & more!

00:00 Intro
00:26 Same watts at different cadences?
03:42 Oval chainrings vs aero handlebars upgrade?
05:24 Patch inside tubeless for difficult punctures?
06:28 Heavier riders at the back of group up climbs?
08:56 How long does it take to make a GCN video?
10:26 How does one acquire a pudding trolley?
11:13 ‘Pudding Trolley Paton’ t-shirts?

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[gcntech]

Let us know your tech queries below using #AskGCNTech! 💬👇

[jefferycampbell]

An oldie but goodie rule of thumb on cadence on hard efforts: If your legs are hurting, use an easier gear. If your lungs are hurting, use a harder gear. If both hurt equally you in the correct gear.

[jeffreylines]

Love the cadence/power discussion! I have always found 75-85 comfortable and only push my cadence up when the conditions call for it

[matt_acton-varian]

I would have to agree that a behind the scenes video would not be in the spirit of the channel. However, the editing and production team are the unsung heroes of the entire GCN family of channels, and should be given the credit they deserve. A year or two ago GMBN did an office fun day video where the presenters and some of the backroom staff did a slalom race in a field. A Road equivalent with a number of the BTS crew would be awesome.

[stephen_]

I'm a road biker, pedaling with speed,
Taking on the hills and the winding trails with ease.

My bike is my trusty steed,
I ride it with passion and all of my heart's zealous need.

I hit the road before the dawn breaks,
The wind in my face, my body aches.

But I push on, my determination strong,
For the love of the ride, I can't go wrong.

I'm a road biker, fierce and free,
Riding is my life, it's where I feel alive, you see.

I'll keep on pedaling, rain or shine,
For the thrill of the ride, I'll always be mine.

[kurre_kallkvist]

I'll apply for the pudding trolley club; just planted myself on the couch thinking about what to get for desert... After surviving Ollies group ride on Zwift, I think I've earned it!

[leisterj]

For cadence, one of the things lightweights leave out is for heavyweight riders where guts or flexibility impact the ability to spin freely. Lower cadence can be more efficient. Personally, I'm at about 75 on my roubaix road and 68 on my shiv tri bike. But higher cadence is better for group rides with small speed adjustments in the pace line.

[andewbritton]

I think a pudding trolley T-shirt sounds like a great prize for something like Question of the week in the tech show like the GCN water bottle over in the main CGN show

[gustavorincon]

The thing people get wrong about power is this: watts are watts, but watts are not feelings, efforts at a given power will feel different every time, and that's because power is an objective effort measure, all other variables are used to explain/understand it (heart rate/gas exchange/lactate/perceived effort/muscle recruitment)

[JayLato]

I recommend a Heavy Rider series from shoes/cleats to spoke count, rotor size, internal rim width, tire size, tire pressure, hooked or hookless rims (heavier riders may want hooked for higher pressures)

[Philip_Hatchet]

On the first point, a watt is a measurement of power per second. So it is measured over time. You can therefore very easily understand that with a higher cadence, you have more pedalstrokes in the same timespan compared to a lower cadence. The amount of power you will have to input for each paddlestroke is therefore also lower on a higher cadence.
This lower power per paddlestroke eventhough the actuall watts are the same makes a higher cadence feel lighter compared to a lower cadence. And it is also why a lower cadence will have more impact on the muscles, the actuall pressure delivered by the legs has to be higher for a same wattage with a lower cadence.

[DoNuT_]

It's funny that I did a Zwift workout covering the power/cadence topic exactly when the video came out. Slightly under FTP with comfortable 90 rpm for 4 mins and then 10% over at 60 rpm for just one minute. My heart rate actually dropped a bit even though I was doing +30 watts but my legs could not have done it another minute (in the saddle, at least). I'm pretty sure the over-FTP effort would have been a lot easier a comfortable cadence - but that was the point of workout, simulating a steep climb when you're out of gears and can't pedal any faster and you need the muscle/torque to keep on moving.

[roberttell]

I would proudly be a card carrying member of the Paton Pudding Trolley Club. Club motto: Slow but Sweet.

[popeyebouldercreek]

Another point on cadence: the faster the cadence at a given power, the less energy required per pedal stroke. A watt is one joule of energy per second, so that’s 14, 400 joules per minute. Divided by 60 pedal strokes, that’s 240 joules/stroke. Divided by 90 pedal strokes, that’s 160 joules per stroke. Taken to its logical extreme, pedaling at an infinite cadence would need zero joules per stroke…. Ooo, I think I just invented warp drive!

[billkallas]

As Alex said, in climbing a "little ring" hill in a group, a not so "feather light" rider should start near the front, if possible. On the other hand, I've found that if the group is going up a longer "Big ring" hill at 20mph (32kph), a larger rider should use his power to start in the middle of the group and work his way closer to the front of the group, whenever gaps form, always leaving two are three riders in front of him to draft off of.

[G-rig]

Easy to find the right balance if you've been cycling for a while. I like keeping the cadence between 80-100. A lot of people don't have the correct gearing, especially for hills. The vegan cyclist explained the oval chainrings benefits in simple terms, would be a good setup with a big 1X.

[johnstrac]

Agree with big lads at the front when the climb starts, "slide rule climbing" I call it.

[rondvivre]

Power is applied force and the rate at which that force is applied.
To maintain the same power at, say, double the cadence, applied force will be halved.

[jonmcgoey]

I suspect the explanation to cadence, wattage and sustaining both is better described with reference to muscle fibre types (rather than keeping the conversation somewhat vague via aerobic and anaerobic terms.
From what I've gathered, your high force type II fibres (i.e., anaerobic) fatigue faster than your low force all day fibres (type I). So the idea that each person has his/her own best cadence gets explained in terms of individual muscle fibre percentages. (and ys, there's the muddiness of subtype type IIb and type IIa and IIx being interconvertible via training). Additionally, the cells of low force fibres have the ability to sponge up and catabolize lactate produced and leaked out from adjacent high force muscles, which effectively means low force aerobic workouts will have a knock-on effect of increasing sustainability of high force fibres.
I'm a big fan of physics (i.e., newtonian theory) and chemistry (e.g., thermodynamic theory) and Ollie represents these well, but when it comes to physiological processes. let's not avoid cell theory.

[Ed.R]

The most efficient cadence is an interesting topic and most people seem to get it wrong. Cadence should vary depending on power output. Power = torque x rpm and our legs and body function together most efficiently within a narrow torque range. So if torque remains fairly constant rpm should vary with power.
The mistake most people make is to copy the pros thinking 80 - 100 rpm is best. This is true if you are putting out 300 - 400W. However at a more normal 200W for example 70 - 80 rpm will be more efficient. Dropping the power even lower to say 150W then 65 - 70 rpm is good.
The optimum is about finding that sweat spot right between grinding and spinning. If you want absolute optimum it's a surprisingly accurate cadence you need to maintain for a given power output. Something hard to achieve with gears and this is where CVT comes in. Not so efficient in itself but can really optimise the body and muscle efficiently. Which is the most efficient overall is a very good question.