Higher HR with Increased Leg Speed

Training
1

Hi all

I have been working on my leg speed recently. Yesterday whilst out on the road I noticed that my HR is higher as I am spinning a higher cadence. My overall cadence from my rides has increased by 15rpm and my legs to the latter end of a 100km+ ride do feel better.

My question is, will I see my HR drop as my body gets used to the higher spinning?

2

In my experience, yes. You will notice a drop as your muscles become more efficient working at those leg speeds. But, heart rate is pretty personal, and it will depend on the wattage you’re putting out. My heart rate is higher for 200w @ 110rpm than 200w @ 80rpm for example, but it’s not as high for the same given watts and rpm as last year.

Pretty anecdotal, and with very little scientific knowledge to back it up, but that’s my experience. Some of it will likely be down to FTP increases and general fitness gains.

3

Increasing your cadence shifts a degree of the stress away from muscular strength towards your cardiovascular system, so you should see a higher heart rate with an increase in cadence for any given power.

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4

Well just to clarify there’s two things you’re getting into:

  • At your current state of fitness for the power your pushing a high cadence works the CV system more and HR will elevate.

  • And then there’s decoupling. The more aerobically fit you are you will (all things equal) see less HR decoupling over XXX duration of riding.

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5

I believe there are a couple of reasons for higher HR at higher cadence.

  1. Higher cadence recruits more slow twitch fibers (vs fast twitch) which tend to burn more fat. And burning fat is less oxygen efficient than burning glycogen. Hence more oxygen needed and higher HR for a given power.

  2. Spinning your legs itself takes energy. So the faster you spin, the more oxygen is needed to keep your legs moving.

I don’t know how either of these change as you get fitter. I suspect they generally stay similar.

But a few things that do change as you get fitter is volume of blood in your body, heart stroke volume and ability of your muscles to extract and use the oxygen from your blood. So your HR will go down for a given power output as you get fitter. But I think you’ll still see higher HR for a given power at higher cadence.

6

Thanks for the replies, much appreciated.

My legs the next day felt a lot better and I didnt feel as smashed in the evening. That’s a bonus for sure!

7

I rode Antelope yesterday (5x10 Sweetspot) and I wanted to focus on leg speed. I watched a POV Crit on youtube with a real time RPM display and tried to keep up with it (roughly 100-110 rpm). It helped immensely. Heart rate averaged only 3 beats higher than the last time I did Antelope, but increased my average cadence from 83 to 91. Legs definitely felt better with the cadence increase.

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Dave Brailsford (Team Sky - Director Team Manager) uses low cadence high torque for it’s training benefit. Just to throw in a curve ball. (He does this because that’s what his physiologists to the riders recommend - its on his Strava a/c).