Unusually Low HR during an L5 attempt

[bgoetz]

I am ending my morning training session a bit confused. I completed a 60 mile ride outside on Tuesday, spending most of my time just below FTP. The ride was great and I felt really strong, having no trouble keeping my HR in whatever zone I was targeting. I took yesterday off, as I do every week and then attempted 2x20 L4 intervals on the trainer this morning. I instantly noticed that my HR was unusually low even during my 10 min warm up, in fact I readjusted my HR monitor strap thinking I must have a bad signal, but despite my pace my HR remained low. The time came to complete my first interval and I picked my pace up to my typical L4 pace (~23 mph on my fluid trainer), but my HR would not come out of the low L3 range. I continued the effort, but my HR remained in the L3 range. All aspects of my perceived effort except for the actual physical stress on my legs pointed towards an L3 effort (my breathing, my perspiration, etc.). After the first 20 minutes was up I decided to skip the 2x20 and do a 50 min interval effort maintaining my current L4 pace with a L3 HR. About 30 minutes into the effort my pace began to fall off due to leg fatigue, reflecting the physical effort of an L4 pace. As my pace fell off my HR fell even further. I am really at a loss, my training is based on my HR which until now has been very consistent, it fluctuates some, but never 20+ bpm over the same effort. Is this telling me something (should I take a break, should I push my legs to increase strength to match back up with my HR)? If this trend continues how to I continue forward in my training because everything is based off of HR?

 

[jsirabella]

bg->You pretty much described in a whole the problem of training with HR. It is just not constant enough to build a program around it. It can vary alot given different reasons. This is why power based training is the only way to make sure you are getting the work out you planned. 220 watts will always be 220 watts no matter your HR and how you feel that day.

-js

 

[tonyzackery]

First thing that jumped out at me, and I'd be willing to wager, was that your cadence is probably too low (I'd guess 70-75rpm) when you do your workouts on the trainer. The mention of leg fatigue was the giveaway. With the day off prior, you should not be having leg fatigue issues if your cadence is 85+ rpm, IMO and IME of course.

Another thing is - it is just not reasonable for you to think that you can do two 20min intervals at a true and accurate L5 wattage level. I believe you need to adjust your power levels. Heck, 5mins at a pop is all that I'll EVER attempt.

As JS mentioned above, heartrate can vary considerably and is tough to be trusted - better off using perceived exertion IMO.

 

[bgoetz]

I could definitely understand this, had my pace not been where it typically is during my L4 intervals. Assuming that my fluid trainer did not somehow take a catastrophic ****, my power output should be similar. My heart rate was just low.

Originally Posted by jsirabella .

bg->You pretty much described in a whole the problem of training with HR. It is just not constant enough to build a program around it. It can vary alot given different reasons. This is why power based training is the only way to make sure you are getting the work out you planned. 220 watts will always be 220 watts no matter your HR and how you feel that day.

-js

Tony, thanks for the input. My effort was completed at 85 rpm, I even went down a gear and increased my cadence and without the load my HR dropped. I am going to go give it another crack and see how I end up, maybe it was just a fluke.

 

[daveryanwyoming]

There are a lot of different training systems out there and perhaps the levels you describe map to one I'm not familiar with, but if you're going by Coggan's power levels it breaks down pretty close to this:

- FTP can be just barely be sustained for a full hour and only on a very good day where you're prepared, sufficiently rested and highly motivated. It's NOT your on demand anytime you want one hour power.

- L4 describes work from perhaps 92-94% of FTP to ~105% of FTP so the low end could be sustained longer than an hour and the top end quite a bit less than an hour

- L5 is the area right around VO2 Max and it's a very rare rider that can sustain this intensity for more than 8 minutes and for most of us 5 solid minutes in L5 is really hard work especially if we're doing any kind of repeat intervals.

- L6 is above VO2 Max and drawing primarily from anaerobic metabolism. It's pretty hard to sustain pure L6 work for more than about two to two and a half minutes.

- L7 work is full on Neuromuscular work as in full bore sprints in the five to perhaps 30 second range but for most folks it's more like 5 to 15 seconds for most L7 work.

All systems use a blend of aerobic and anaerobic energy sources, but no one is primarily targeting anaerobic systems for a full ten minute interval, perhaps three minutes for someone with a high AWC that's worked hard at tolerating hard anaerobic efforts but no way that energy system is going to take you through a ten minute effort.

Here's a good description: http://home.trainingpeaks.com/articles/cycling/power-training-levels,-by-andrew-coggan.aspx

-Dave

 

[bgoetz]

Dave/Tony, you guys are right I misread. I really have never used the levels with respect to my training in fact everything I have done is based on the Chris Carmichael levels. However, using those on this forum make it difficult to explain to others where I am training. So I used the Chris Carmichael numbers and tried to correlate it with the Coggan levels. I guess it helps if I read correctly because I placed L4 at below my FTP, when I was referencing L4 I was actually referencing just below FTP, and L5 actually L4. It seems that correlating what I have done from the Carmichael method to the coggan levels is difficult. Sorry for the confusion. I will edit the thread so everything makes sense.

 

[bgoetz]

Back to the issue at hand though, I successfully completed 2x20 minute L4 intervals at my typical HR (162-165), to do so though I had to increase my pace by 1-1.5 mph. So either my fluid trainer is taking a ****, or I have increased strength. I really do need a PM, but I am doing all I can with what I have.

 

[Phil85207]

When was the last time you had a physical? The reason I mention it is I had a similar condition only my HR continued to fall. Or I should say, my HR would not rev up as activity increased. I found that my thyroid had abandoned me as a result the HR was affected. I went from a max sustainable HR of 163 to one of 123 bpm. I actually did the Tour De Safford (104 mile) with a MSHR of 123. For sure it was not a thing of beauty. Good luck and I hope your thyroid is OK. Just saying.