Friday, March 9, 2012

How much fat are you REALLY burning?

Sometimes it's fun to geek out over data, but you have to have some data over which to geek out. So, today I did a test to try to nail down how much fat I burn during exercise vs. how much sugar. It's interesting information, and proves that endurance performance is all about efficiency.

Amy the trainer put me on a treadmill with a mask capturing my exhalations, measuring oxygen and CO2. Warmed up a couple of minutes at 3.5, 4.0, 4.5 mph. Finally got to 5.0 mph, then steadily increased the incline. The goal was to reach anaerobic threshold, then only stay there long enough to get three more measurements (less than a minute). Then cool down.

My heart rate (HR) was 60 while I was standing on the treadmill waiting to start. It took a 10% incline at 5.0 mph to reach threshold, and HR peaked at 141 then settled at 138. The HR dropped 15 beats in the first minute of cooldown, then another 9 in the second minute, which means I'm recovering quickly. So it looks like I need to spend more time training in lower zones w/some intervals thrown in, and try to raise VO2 (my peak HR/fat burning threshold) as much as I can. There is a genetic limit to how much this can change, but I can certainly try to become more efficient. Don't need to worry about the ticker; it's working just fine, and better than most.


The graph shows that my body burns fat at a fairly steady level with only a small decline until I hit peak. This is good. Goal is to raise that steady level to more than the current 40-50% of calories to 50-60%. Then I could probably go even longer with less perceived difficulty.


Bike workouts are definitely helping. Last night was half hour warmup followed by 8 intervals of 3 minutes in zone 5 (harder than "comfortably hard") with 3 minutes rest in between. Felt it but it didn't suck. Would have been incredibly painful a month ago, but last night I actually had something left in the tank when we were done.

I was surprised at the low heart rate today. I knew it would be lower to start, but didn't expect it to stay so low while exerting myself. Used to be up around 163 when I was running hard. And 65-70 if I was walking around. It's nice to see positive results from training. Tomorrow: a 15K trail run!

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