Thursday:  As expected, no time to train.  I took the redeye home from San Jose.  I was not able to get any reasonable sleep on the plane.  Highly unpleasant.

Friday:  I arrived in Boston at 6am.  Then drove home.  Almost immediately, I turned around and drove my wife to the airport.  She is off to visit my daughter in St. Louis.  I was home again by around 11 am.  My eyelids were drooping severely but I managed to stay awake to attend a work conference call at noon.  After that, I took a 3 hour nap.  My intent was to get up around 4, head out to Lake Quinsigamond and do a long and easy technique session.  But, when I was packing my things, I got a text from a friend of mine telling me that there was a wakeboarding competition going on and the whole lake was a really treacherous place to be.  Time to go with Plan B.

Plan B

• 4 x 20′
• 1:30 rest
• Power target: 10W x stroke rate
• HR cap: around 150
• Lactate target: 2.0

It was massively hot and humid.  Around 95F and 70% RH.  Rowing at 190 watts felt pretty easy for the first 10 minutes.  Then the room warmed up, I started sweating, and it started to feel like a lot of work.  By the end of the first 20 minutes, my HR was still OK, only around 144, but my RPE was really high.  I was breathing hard, and my first lactate reading was 3.3mmol/l.  Way too high.

So, my intent was to dial it back to 170W from 190W and just take it easy.  After the rest, and a big drink of water, I started again.  It felt like really hard work, and I seriously considered just bagging the whole thing.  I even coasted to a stop about 2 minutes into it, but I thought better of it and decided that I should at least finish this 20′ piece.  I felt a lot more comfortable at 170W, but it was still a pretty sweaty affair.  After this one, I tested out a 2.8mmol/l.  Still too high.  But my RPE was right on.  My breathing was easy, and my ending HR was again around 145.

Well, I had come this far.  I had another drink, and decided to just paddle through one more 20′ piece.  This one I started off thinking I’d target 150W, but ended up pushing that up to 160.  Still very slow.  After this, my lactates were 2.6mmol/l.  RPE right on target, but HR had climbed up to be close to 150 by the end.

The session seems to add some weight to a few thoughts that I have been pondering.

1. My aerobic fitness is not so good right now.  I need more low intensity minutes working on my ability to metabolize fat.  My high lactate numbers show that I am crossing over to CHO respiration at pretty low levels.
2. The effect of heat and humidity on endurance training is pretty profound.  I think it could as much as 10 or 20 watts impact in terms of what power you can hold and maintain a <2.0mmol/l lactate.
3. I haven’t seen any research to back this up, but I feel like there is some hysteresis in the crossover between fat and CHO metabolism.  Something like this.  I feel like I have to go way down in power to “shut off” CHO metabolism once it has been started.  I think this is another reason why some folks have found lower ultimate lactate readings if they start with a few minutes at a very low warmup power before they slowly increase to their target.

I think this is fascinating because it brings a physiological angle into a age old debate around how to do HR capped training.  The question that I have seen asked over and over again is this…If you are training to a specific HR cap, is it better to start faster than what you think you can hold for the whole piece, and then start to bleed off pace once you are in the training HR zone and approaching the cap, or is it better to hold a constant training power and adjust that power so that you are around the cap at the very end of the workout?

I have seen recommendations about this from very credible people that are entirely opposite of each other.  One conclusion that one might draw from that is doesn’t matter much in terms of training effect.  But, on an individual basis, if you are trying to specifically train fat burning endurance, it probably makes a lot more sense to slowly build power, or hold it constant  versus bleeding off pace.  Anyway, its food for thought.