Taste receptors inside a muscle

[Sasha Pachev]

Are there any receptors inside a muscle that are similar in function to taste receptors? I noticed when running at faster paces that my quads feel as if they had a tongue, and I were tasting lemon juice with it.

That appears to be a major limiting factor of performance for me. I can only handle that much lemon juice for that long.

[Paul (RivertonPaul)]

Too bad you can't just mix in something sweet.

[Sasha Pachev]

You actually can. Load the muscle with glycogen. Interestingly enough, the sour feeling happens at a slower pace and at a lower heart rate when glycogen is likely low, and it takes a faster pace when you would expect it to be high. Which is why I am wondering if there is a sensor in the muscle that is like a taste sensor.

[Paul (RivertonPaul)]

Another example of the wonders of the human body.

[adam]

I don't really understand your question.

Within the neuromuscular system there are pain receptors, pressure receptors, receptors that sense changes in muscle length and speed of change of length, and more.

Increases in duration or intensity of exercise manipulates the energy systems used to power the exercise. While glycolytic and oxidative systems are at use continually throughout the exercise, their are shifts in porportion. Drops in glycogen are sensed through the muscle and liver, and signals the release of stored glycogen or recreation of glycogen through gluconeogenisis (using amino acids, lactate, or non-gylocgen substrates to produce glycogen) if the duration is high enough. The sour feeling may be you feeling these changes. It may also be a shift in the blood pH, which would lead to an acidic (possibly lemon like?) changes. Why you would "taste" lemon in your muscle is beyond me...

[Sasha Pachev]

Perhaps nobody who studies those receptors has run enough and has pushed himself enough to notice the similarity between the taste of lemon and the feeling you get when you cannot run any faster. Or perhaps those who have were distracted by other forms of pain.

The sense clearly comes from the muscle group that is working the hardest (the quad), and its intensity increases with the pace and the duration of effort. If you try to push too hard through it, you feel like you are going to throw up. In fact, sometimes after a very hard effort I do a dry vomit.

Lower glycogen levels bring this on at a slower pace (experienced the lemon at mile 15 in the marathon while running only 5:55). So does the lack of sleep (big lemon on the third leg of Del Sol last year at 5:44 going down 1% grade at near sea level) . What is interesting is that it can be experienced at a variety of heart rates and their corresponding paces. I never feel limiting me  below 153, but depending on the day it can be anywhere above that (my max is 174).  So one day I can get the lemon running 5:45 pace at the HR of 153, while on a better day the lemon does not come until I start running 5:20 with the HR of 164.

I suppose one way to test the connection is to check for the brain activity when tasting a lemon, and when trying to run at your limit to see if there are any similarities.

[adam]

Or maybe I haven't tasted lemons often enough to spot the difference.

maybe the lemon is an associated taste like you say. maybe for others it is chocolate. or even certain smells. i've heard of people noticing certain smells at odd points of their runs that weren't associated with anything around them.

[Jon Allen]

I noticed certain putrid smells at odd points of my runs when I am running with some of the guys... though I can say that the smells WERE associated with something around me...

[Fredrick Teichert]

Perhaps your muscles are trying to send a signal. Are they crying for something associated with the taste of lemons or trying to get rid of it? This is an intriguing observation. As I learn to listen to my body more, I'll ponder your experience. By the way, you all tell me to "listen to my body" more as I train. There's a difference between the voices in my body, the voices in my head and now, the voices in Sasha's quads. This is starting to get interesting.

[James Winzenz]

I noticed certain putrid smells at odd points of my runs when I am running with some of the guys... though I can say that the smells WERE associated with something around me...

Were those putrid smells coming from you or from the other guys?  I seem to recall a picture on either Paul's or Logan's blog when they helped you break 2:40 at (was it Ogden?) which elicited a great deal of laughter, especially the captions . . .

[Jon Allen]

Often the putrid smells are coming from me, though I will always deny it.  But that particular incident was at TOU marathon and they were coming from Logan... he just about killed me.

[Nathan Bundy]

I smell corn ships after I run sometimes... What does that mean?

[James Winzenz]

I don't know, but my 8 yr old son often states he can smell chicken nuggets as we are running 

[Sasha Pachev]

Guys - I think you've missed the point. I am able to identify a specific location of the sensation, and that location is somewhere in the middle of the quads. I am not feeling anything on the tongue or in the nose. Those would be pure imagination. This one is a real physical sensation correlated to a specific physical condition. It can be reliably reproduced. It cannot be ignored for long. I am not imagining it anymore than somebody would image the pricking of the needles while sitting on a porcupine.

[Dallen]

In all seriousness, you body has all sorts of receptors to tell it what is going on. I am not exactly sure what you are trying to describe, but I assume what you are feeling is something similar to the sensation of lactic acid buildup that we have all felt. Maybe you are sensing low oxygen, muscular fatigue, recruitment of rarely used fibers, or some other exotic sensation. Your brain is just interpreting it as a smell in you legs. Doesn't seem all that strange to me, but I have no idea what it actually means.