The Link Between Pedal Cadence And Heart Rate On The Bike

 

Hi folks,

When you ride a trainer bike there are two main sources of data collection, the dashboard and perceived effort.

When you ride a trainer bike there are two main sources of data collection, the dashboard and perceived effort.

Life is interesting, and even more interesting if you question the obvious. It is becoming ‘obvious’ that the most efficient cadence on the bike is around 90-95, based upon things I have been told by coaches and read on the Internet. But is this true all the time? I doubt it. During long trainer rides you have plenty of time to explore these issues, which passes the time nicely, increases your focus on what you are doing (riding a trainer), and perhaps will lead to something that improves your racing skills.

Comparison of dashboard of the trainer at 140 Watts on Computrainer control, at high (left) and low cadence showing higher heart rate at higher cadence.

Comparison of dashboard of the trainer at 140 Watts on Computrainer control, at high (left) and low cadence showing higher heart rate at higher cadence.

I noticed today, during a 2-hour trainer ride at 140 watts (my zone 2 wattage), that my heart rate was clearly linked to cadence in a highly consistent manner. My approach to this ride was to carry out a repeated sequence, to share load between fast (glycolytic) and slow (oxidative) muscle fibers, with 10 min at 90-95 cadence followed by 5 min at 50 rpm. I noticed the following pattern:

Cadence     Heart Rate     Watts

90-95            114-119           140

49-54            104-110          140

This pattern was consistent for all eight repeats of my ride sequence. I wondered why this is so, and here are my proposed hypotheses (does anyone out there have a proven answer?):

  1. The CompuTrainer is giving a false reading for wattage (I doubt this).
  2. The whole-body physiology of fast twitch (oxidative) versus slow twitch (glycolytic) fibers modifies blood lactate or some other metabolite in such a way as to modify the associated heart rate.
  3. The heart rate (cardiac cadence) is entrained by the pedal cadence as a result of linking signals, such as differences in pulsatile venous return rate or neural connections.
  4. High cadence takes greater mental concentration (for me, anyway), and as the brain uses about 25% of whole-body blood flow, the higher cadence requires greater cerebral flow expending energy for brain function (I’m grasping at straws now).
  5. Heart rate is not a good indicator of effort expended, assuming that it is the same at high or low cadence based on an identical wattage of 140.
  6. Other? – Ideas?

You may wonder about the value of such an observation, which is the whole point of this line of thought. Maybe, if you want to rest your legs (they tire at low cadence) use higher cadence, and if you want to rest your brain, which becomes exhausted by the constant mental effort of pushing forward in a race, use a lower cadence. It’s worth a try anyway.

Interesting!

-k @FitOldDog

Today’s workouts:

WorkoutPLAN Coach: Chris Hauth
 Bike
Duration: 02:00:00
Description:
nothing hard here – just steady Z2 cycling

Important Note: These posts do not provide medical advice. You should always consult your physician before undertaking or significantly modifying an exercise program.

Copyright © 2010 Kevin T. Morgan aka FitOldDog, Old Dogs in Training, LLC.

Comments

  1. Kevin
    Great observation. What you say is true. Lower cadence = lower metabolic output.
    Many studies have shown that a cad or 50-60 is the most efficient. But what those studies dont take into account is muscular endurance and overall riding fluidity nor how the movement of pedaling aids in blood transport.

    I dont agree with most of the work that has been done showing ideal cadences. Most of those studies are flawed.

    So whats your ideal cadence? Its whatever you train for. No one is born to pedal at 90 or even 110 rpm.

    It is a learned skill.

    Most riders can easily train to ride at a cadence of 85-110rpm. Lower rpms will lead to less endurance and more overall muscle and body fatigue.

  2. Also Short bouts of lower cad during your ride does really give a rest. Its a good way to calm your aerobic system for a minute or two.

    • Hi Victor,
      What are your thoughts on my system, which is 30 minute PowerCranks to warmup and engage my hip flexors, followed by repeating sets of 10 min higher cadence, 5 min low cadence, until the end of the trainer ride?
      Thanks for the comments.
      -kevin

      • I would keep the higher cadence sets short. You dont want to be sloppy. I recommend no more than 3 minutes of focused practice. Yes there is science support 2-3 minutes. I think you already know that

        That is of course if the purpose of this workout is to build higher rpm.

        • Hi Victor,
          When working to train my neuromuscular systems to accept a higher cadence I go to 120 -150 rpm, this rate (90-95) is my working cadence on the road. I agree with 2-3 min for high cadence and high load work. I use the 10/5 cycle to mimic hills on rollers.
          -k

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Disclaimer: this publication does not provide medical advice. If you undertake or modify an exercise program, consult your medical advisors before doing so. Undertaking activities pursued by the author does not mean that he endorses your undertaking such activities, which is clearly your decision and responsibility. Be careful and sensible, please.