Author Topic: Heart rate relationship with power and thus speed  (Read 639 times)

Heart rate relationship with power and thus speed
« on: 17 September, 2021, 10:57:55 am »
I’ve just completed LEJOG with my son. Self support over 12 days. We rode minor roads, cycle paths and towpaths. Normal RHR 50BPM, max approximately 175 BPM. I’m 60. As the ride progressed our average moving speed 12.5 mph remained roughly the same but my average HR came down from 125 to 100. I dummies that as I couldn’t recover from previous days effort, my legs were leaden and unable to find usual power and therefore my heart didn’t need to do much other than keep me chugging along. Perhaps I bonked repeatedly and so nature protects us. I’m no Doctor

T42

  • Old fool in a hurry
Re: Heart rate relationship with power and thus speed
« Reply #1 on: 17 September, 2021, 01:23:43 pm »
Over a 4-day Audax that would happen to my HR too. The max would descend as well - 158 at start, 132 at end.  I always used to be in great form on day 3, between 600 & 900 km in, then dead-ass mutton on the last day.

I mentioned it once to my cardiologist (happy the man who cannot say "my cardiologist"): he shrugged and said "adaptation, then fatigue".

But they never got to Carcassonne.

hellymedic

  • Just do it!
Re: Heart rate relationship with power and thus speed
« Reply #2 on: 17 September, 2021, 03:38:25 pm »
That's about right.

Nutrition and metabolism are a factor. I wore a HRM when I tried riding to work whilst fasting: I found it difficult to raise my HR and impossible to exceed about 12mph on the flat.

Getting some sugar on board changed all of this...

ElyDave

  • Royal and Ancient Polar Bear Society member 263583
Re: Heart rate relationship with power and thus speed
« Reply #3 on: 23 September, 2021, 08:28:47 am »
I think adaptation to a lower carb diet helps with that as well, but I have seen similar effects when I had a week off earlier this year and got out for 50km+ most days, later in the week my HR just stayed lower but speed not badly affected.
“Procrastination is the thief of time, collar him.” –Charles Dickens

fboab

  • It's a fecking serious business, riding a bike
Re: Heart rate relationship with power and thus speed
« Reply #4 on: 23 September, 2021, 08:33:22 am »
I remember talking to both Teethgrinder and the Things about this.

Getting your HR above Z2 on day 2 and beyond is nigh on impossible.
TSS is not Total Sex Score, Chris!

FifeingEejit

  • Not Small
Re: Heart rate relationship with power and thus speed
« Reply #5 on: 23 September, 2021, 01:12:47 pm »
Over a 4-day Audax that would happen to my HR too. The max would descend as well - 158 at start, 132 at end.

Similar for me after about 8 hrs I'll have gone from being able to max at 180, run in the 150s/160s to sitting comfortable at ~130
I determined this even before doing Audax (although I suppose I did a couple of multi-day sportives and 200/300 for fun), and realized that if you want to go long and fast, you needed to build speed in Z2, which I did by going as hard as I could for the odd hour and got it past 25kmh, now I just about manage 20kmh because i'm not getting a chance to train speed in the way i was

T42

  • Old fool in a hurry
Re: Heart rate relationship with power and thus speed
« Reply #6 on: 23 September, 2021, 02:41:08 pm »
Heh.  I've never bothered with this zone malarkey so I just typed heart zones into Google and got, i.a. a number of handy links entitled:

- What are the 5 heart rate zones?
- What are the 4 heart rate zones?
- What are the 7 heart rate zones?

So Z2 could mean several shades of light.
But they never got to Carcassonne.

ElyDave

  • Royal and Ancient Polar Bear Society member 263583
Re: Heart rate relationship with power and thus speed
« Reply #7 on: 23 September, 2021, 05:45:32 pm »
Over a 4-day Audax that would happen to my HR too. The max would descend as well - 158 at start, 132 at end.

Similar for me after about 8 hrs I'll have gone from being able to max at 180, run in the 150s/160s to sitting comfortable at ~130
I determined this even before doing Audax (although I suppose I did a couple of multi-day sportives and 200/300 for fun), and realized that if you want to go long and fast, you needed to build speed in Z2, which I did by going as hard as I could for the odd hour and got it past 25kmh, now I just about manage 20kmh because i'm not getting a chance to train speed in the way i was

Very true, I've been doing regular TT efforts on the same course over the summer for the last few years, and as well as that element improving, I've been seeing improvements at the 60-80km distance as well, being able to sit at 28-30km moving average regularly this year with HR in the sub-150 region.
“Procrastination is the thief of time, collar him.” –Charles Dickens

Re: Heart rate relationship with power and thus speed
« Reply #8 on: 24 September, 2021, 09:32:36 am »
Zone 2 in the 5 and 7 zone models is basically the same place - endurance. Trainer Road uses a 7 zone power model and says it's 55% to 75% of FTP, you can talk but it's still a bit taxing. Zone 2 is basically where "base" miles were traditionally done, and probably where most audaxers live (Zone 1 is "recovery").
Polar uses 5 HR zones, and zone 2 is 60-70% of HRMax, which is probably about the same effort.

Re: Heart rate relationship with power and thus speed
« Reply #9 on: 25 September, 2021, 09:57:38 pm »
Cornwall and Devon are pretty hilly starts then it gets easier. Don’t dismiss working harder on the hills to start to maintain that average speed. Then settling into an easier effort on easier terrain as your LEJOG progressed.

Average doesn’t tell entire picture either. If it’s a case of not being able to hit higher HR later on. That’s one thing.  If you just managed effort levels more evenly later on. That’s another.  You can have the same average HR and entire different effort profiles throughout the ride.

Also higher blood volumes and haemoglobin will reduce HR vs. effort as the days go on. You see that happen in acclimatisation to high altitudes. Sure it happens with repeated high volumes of daily exercise as well.