Okay this is going to be kind of vague, but perhaps someone here can help me out

I don't have a power meter but I have an HRM and a cyclometer that measures cadence.

I did a 3:20:00 ride yesterday and I noticed something strange that I've noticed before. During the last 40 minutes I had a "brisk" (~160bpm/80%) interval planned at 80-90rpm. When it came time for the interval I started pedaling harder and shifted up to keep the cadence at 80-90rpm. About 20 minutes into it I noticed I wasn't breathing as hard as I do at the beginning of the day, but heart rate was still up there, RPE was constant and about where I thought it should be, speed and cadence were staying level. I pumped it up a little bit, thinking that something must be wrong. Speed went up, cadence went up too (didn't shift), heart rate went up to about 170bpm/85% and I started to feel the burn, just barely. Breathing moved slightly, but not nearly what I thought it should be based on an interval earlier in the ride. It felt like great news!

My question is whether aerobic conditioning can improve slightly from the beginning to the end of a 3hr ride. I recall thinking that if I was performing this well at this level of breathing, perhaps if I forced a higher rate of breathing I could go even harder. (Now that I think about it though, lactate doesn't depend on how oxygenated the blood is. Or does it?)

The other side, of course, is that heart rate and RPE were high because I was hitting fatigue and limits, and breathing has nothing to do with it. But since speed and cadence were coupled with RPE and HR, I thought not. I was heavily carbed-up though, and bonking was a long way off. I guess there's no way to know without a power meter, right?

Thoughts?

I'm not an expert, but IMHO you should.

Breathing definitely makes cycling easier.

Did you account for temperature, wind, and grade?

Use a time signature for your breathing during long rides, or any ride except for sprinting or radical climbs. I use 5/4 time, inhale for 3 pedal strokes, exhale for 2. Adapt you internal music for this beat and the miles go by nicely.

No. Your body will tell you when to breathe

This is kinda way off on a tangent but I noticed on a treacherous hill climb once that my breathing fell into a rythm where I would do a long, forceful exhale, and the inhale kinda took care of itself. Since then I've tried to make it a conscious effort to exhale completely at intensity to expel the CO2. I don't really have a point.

Yep. Your HR was likely higher because you were dehydrated relative to the beginning of the ride. That's one of the reasons HR is often a misleading indicator of power/effort.

+1

This will never work for cycling unless you are always pedaling with a constant effort. Your O2 consumption (and hence breathing rate) varies with power output not cadence.

When I run, usually on pretty flat courses, I have a breathing pattern that's in time with my cadence. On the bike, I'll often catch myself breathing in sync with my pedal stroke...usually when I realize I'm not breathing nearly fast enough and hurting my performance. Many times I've told myself "just breath!".

Yesterday was hot and humid in Austin, so you probably were much more dehydrated than you realized, especially after 3 hours. Also, until you get warmed up, your breathing and heart rate won't necessarily work together well as reliable indicators of your effort. To get out of my neighborhood, I have to go over about 10 small hills and my breathing will skyrocket before my heart rate catches up and I'm warmed up. But again, make sure you're well hydrated and if you start getting an elevated heart rate on a hot ride, you should rehydrate immediately, even if you don't feel thirsty.

+2

Thus if you're doing intervals by HR, you need to adjust the HR you're trying to maintain on the intervals toward the end especially with a hot, long workout.

If your last intervals feel too easy, they probably are,and you need to up your effort, even if it puts you above the targeted HR zone.

In that instance RPE, correlated with experience, can give you an idea of how much higher your HR should be on the final intervals.

Agree that HR is misleading, I don't even wear the strap anymore. Without a PM, Cadence is only useful if it's the same route, drag conditions and gearing. Thing about cycling is our bodies want to do it efficiently. If that means our brains can trick us into thinking an RPE of 6 is really an 8 then it will.

All breathing patterns tells us is how we're doing at that moment based on atmospheric conditions, effort, fitness, hydration, comfort, mental state, etc. Comparing that to speed, cadence, time or anything else is kinda pointless.

Which is why a PM helps because Cadence (angular velocity) is part of the power formula. Knowing two numbers (applied power and angular velocity) helps when adjusting the third (torque) and now everything makes sense. If you put out 240 watts at the beginning and at the end of a long ride and you're breathing easier then that would be a phenomenon. I'm guessing that's not going to happen. GL

It very well could be that your were breathing deeper and more efficiently during the interval. That would give you more O2 per breath.

Wasn't there a Tropical storm in that part of TX ?

I experience a similar phenomena when I'm on the treadmill at the gym. I've always thought it was a combination of warming up + the body producing endorphins (feeling less pain so not breathing as hard?). Also my mental state is more relaxed (watching the gym TV or listening to music, etc.) which helps with the breathing.

+3 on dehydration. I dehydrated badly on my last century (a brutal 100 degree day) and my heart rate was in the upper zones with power outputs down in the low 100W range. It wouldn't go below 155 or so just standing up.