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Heart Rate Zones / Power Zones

post #1 of 3
Thread Starter 

Yesterday I did a 2.5 Hour workout on the Kinetic Road Machine. I've set up a training plan using Friel's training bible, and the workout was an E2 (Friel, Zone 2) workout. The book, being a little old-school, uses heartrate, not power for its training zones.

So, I pegged my heart-rate zone (140 - 150 BPM), and did the ride. I ride with a garmin edge, export and save the XML data to my PC, and convert all the speeds to the corresponding power, and make a number of plots of Power(watts), HR, & Cadence vs time, calculating TSS, IF, etc...

In any case, what I quickly noticed, is that, due to cardiac drift (where heart rate gets higher over time, for me, perhaps 5+ or more beats over the course of the ride) - that I needed to _LOWER_ my power output to keep my heart rate in the prescribed zone... For example, to keep my heart rate in the 140/150 zone, I pumped out 230 - 250 watts for the first half-hour, but then had to pedal at only 220-230 watts to keep my heart rate in the same heart zone during the next half-hour...

Now, I could "convert" the Friel Heartrate zones into power zones - and hold that wattage for the prescribed time.

But training with purely a powerband e.g. maintain 230-250 watts - for 2.5 hours - would not take into account cardiac drift and my body getting more tired ... e.g. 240 watts for the first 10 minutes feels easy. 240 watts after 2 hours feels and is much tougher...

That is, a 2.5 hour ride maintaining a tight powerband will certainly be tougher than a 2.5 hour ride maintaining a tight "corresponding" HR band.

I imagine that my over the course of the ride, my body would physiologically move from say 140/150 BPM into another heart-rate zone e.g. from E2 to Friel's E3 -- making the ride a tempo ride at the end, where it was aerobic at the beginning...

So, training with power and holding a tight band for longer steady state rides, would lead to rides which would start easy and become tougher - where as training with HR would allow one to keep the same PE level..

Heart rate is dynamic during the ride, and power - well - a watt is a watt is a watt whether at the beginning or the end of the ride... even though that "easy" watt at the beginning of a ride feels a bit harder at the end...

I know there have been heated discussions on not relying on heart rate (and using power) on this and the topica forum - but I am just trying to determine how I should "zone" my longer (1 - 3.5 hr) steady-state workouts.

Any thoughts on this?

dave linenberg
post #2 of 3

Re: Heart Rate Zones / Power Zones

Most of the adaptations that we seek are metabolic in nature, and thus respond to the actual energy demands within the muscles themselves. If you wanted to produce 2.5 hours of a certain training stimulus then that would mean holding power output steady, even though HR and/or PE tend to rise as fatigue sets in.

The good news is that with power it's pretty easy to predict the level you'll be able to maintain for the whole ride, so pacing becomes easy. If the ride feels easy at the beginning, great.
post #3 of 3

Re: Heart Rate Zones / Power Zones

Friel's zones are fairly narrow and when all said and done, there's a fair bit of crossover between HR zones anyway.

Andy Coggan's HR zones make a lot more sense, there's less of them to worry about and there's a fairly good correlation for the 'upper end' zones (Coggan uses one L4 zone, Friel uses 3 - Z5A, Z5B, Z5C) in that the upper and lower limits are fairly similar.

I use Friel's methodology to set out my training plans but use Andy Coggan's power (and HR) zones for the actual workouts - which also has the benefit of being able to 'guestimate' my power by HR zones when I'm using my race bike which does not have a PM fitted.
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