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.
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?):
- The CompuTrainer is giving a false reading for wattage (I doubt this).
- 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.
- 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.
- 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).
- 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.
- 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.
|WorkoutPLAN Coach: Chris Hauth|
nothing hard here – just steady Z2 cycling