Training & Nutrition - Lactic acid in heart muscle.

Yesterday I again went against my newest rule of not taking a road that I have not driven first. We have a lot of hills here in NE Tennessee and I decided to take a shortcut on Siam Road from 19E to the dams on Wilbur and Watauga lakes. It has a good angle and after 50 miles was probably more than I should have bitten off, but eh, I like challenges.

As I neared the top I knew I was well into my anaerobic areas. We all get there sometimes. I looked at my heart monitor (2 small persistent dogs chased and distracted me for 300 feet or so) and saw that it is reading 200. It ended up showing a max of 205. I pulled over and took a good breather and watched it come down through the 190's to 180's etc... until it stabilized and I was able to continue. Two miles down the road I ended up getting a low tire and had to change tubes so I had a bit more recovery time.

I know that I pushed my heart beyond what I should have as I felt drained but didn't have any discomfort from it. It just got me thinking of how lactic acid is handled by heart muscle. We know how our muscles feel sore the day after a long ride. Anyone else ever push themselves this hard?

Heart muscle is unlike other muscle. Your heart has to beat continuously for 70-100 years if you're lucky and healthy.

Heart muscle (like other muscle) use lactic acid (lactate) as fuel. It doesn't accumulate and cause pain and fatigue like in other muscles.

Now... someone will dispute me....

Now... someone will dispute me....

But it won't be me. The heart gets first crack at all of the nutrients and oxygen that are in the blood, so, especially in someone who is good cardiovascular shape, the oxygen that is required to use lactate as an energy source is readily available. Not to mention the fact that part of cardiovascular fitness is an increase in the vascular density of the cardiac muscle (more blood vessels per unit of tissue).

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I believe the heart really does not generate lactic acid to any extent. The heart has very large amounts of mitochondria in it. It has much more mitochondria than skeletal muscle does. The mitochondria are the organelles responsible for aerobic metabolism. The heart never gets out of its aerobic zone. Also the heart gets first crack at oxygen in the blood.

On bike rides, I have seen people push so hard that they blacked out. That must be a lack of oxygen to the brain. None of them seemed to suffer any ill effects from the experience beyond the inevitable crash. If people were capable of killing themselves by red lining themselves, we would have deaths every week end on every fast club ride in the country.

Oh, I have noticed that when I push really hard, my peripheral vision starts to go. It is sort of like looking down a card board tube. I back off in those situation. No one is paying me to ride fast on my bicycle so it does not make sense to injure myself or others in an all out effort.

Very insightful comments. Thanks.

I believe the heart really does not generate lactic acid to any extent. The heart has very large amounts of mitochondria in it. It has much more mitochondria than skeletal muscle does. The mitochondria are the organelles responsible for aerobic metabolism. The heart never gets out of its aerobic zone. Also the heart gets first crack at oxygen in the blood.

On bike rides, I have seen people push so hard that they blacked out. That must be a lack of oxygen to the brain. None of them seemed to suffer any ill effects from the experience beyond the inevitable crash. If people were capable of killing themselves by red lining themselves, we would have deaths every week end on every fast club ride in the country.

Oh, I have noticed that when I push really hard, my peripheral vision starts to go. It is sort of like looking down a card board tube. I back off in those situation. No one is paying me to ride fast on my bicycle so it does not make sense to injure myself or others in an all out effort.

I sort of get the same thing. Last time I did an interval, I actually got a bit dizzy. My speech always slurs, and I can't think as straight.

I pushed so hard the other day I saw grandpa at the top of a hill and he has been dead since 1975.

If you can't touch your dead grandfather and aren't having a political conversation with him, you didn't go hard enough.

the heart doesn't use glucose as a main energy source, so it doesn't go into lactate metabolism. it uses fatty acids instead.

I once had a doctor tell me that one can kill themselves by building up too much lactic acid in the heart. I dunno. I've tried lots of times and I'm still here. OTOH, my club has lost two members that I know of to heart attacks at the tops of hills. We assume it was a pre-existing condition, but there you are.

I pushed so hard the other day I saw grandpa at the top of a hill and he has been dead since 1975.

At least he is still riding!