Yeah…I don’t really know if they do….. I just thought it was one of those fun titles.
To talk about LT (Lactate Threshold) you’ve gotta talk about fried chicken. I love fried chicken. I grew up in East Texas, which is sort of like Alabama or some other place in the Deep South, which means I grew up eating fried chicken at every church function we went to. When it comes to fried chicken there are two camps: dark meat people and white meat people. To chicken people, this is a very serious matter. Personally, I like dark meat and if you’re a distance runner, you should too. White meat on the other hand….not so much. So grab that box of greasy goodness and settle in.
Believe it or not, if you eat chicken you know quite a bit about exercise physiology. Seriously! Think about it. You know that there are really just two colors and they’ve gotta be different colors for a reason. In reality, dark and white meats are an excellent display of the two major types of muscle fibers that exist. And humans, like chickens, also have these two muscle types.
What the heck does this have to do with LT? Slow down, take another bite of that drumstick and read on ‘cause I’m getting there.
The fact that there are two colors of chicken meat is important because each type of meat is used for something different. In nerd speak (which is based on Klingon), white meat is considered Fast Twitch muscle and dark meat is Slow Twitch muscle. The white meat (breast, for example) is used generate a lot of force, like when the bird is taking flight – although I doubt most of the chicken we eat ever got a chance to fly. For the chicken, taking off requires a lot of force (think about trying to slam dunk; you work really hard) and the white meat generates that force. For us, running fast requires a lot of force so we use white meat (Fast Twitch fibers) in this scenario. Conversely, the dark meat (like chicken legs) is used to do things that don’t require a lot of force (like walking around the “Free Range”). We use dark meat (Slow Twitch fibers) predominantly when running slow.
Here is an aside for the true nerd out there (cough, couch….James Dodds…cough, cough) Dark meat is dark for a reason. It contains a lot of myoglobin (huh?). Myoglobin is hemoglobin’s greedy brother. Most (like 2-3) of y’all recall that hemoglobin carries oxygen from the lungs to the muscles in the blood. This myoglobin lives in the muscles itself and steals the oxygen that’s bound to the hemoglobin floating around in the blood….poor hemoglobin….thus transferring oxygen to the muscle. Like hemoglobin, myoglobin also has iron attached to it (you know…the thing college and HS running coaches get all worked up about because of anemia). Welp, iron is red (think rust), thus dark meat is red. Remember, dark meat has myoglobin, myoglobin has iron and iron is red. At this point, you should be asking yourself – in between bites of you chicken wing (you’ve finished the drumstick) – why the breast meat isn’t red. Breast meat is white because it doesn’t have a lot of myoglobin and since we all have a little bit of Sherlock Holmes in us, we’ve deduced that breast meat must not use much oxygen.
Alright everyone, pick up that chicken breast and let’s get back on task. I said that when we run slowly we use mostly dark meat (slow twitch fibers) because slow running doesn’t require a lot of force production. And when we run really, really fast we use mostly white meat (fast twitch fibers) because fast running requires a lot of force. So when we steadily accelerate from slow, easy running (easy-day pace) to fast running (5k pace running), our body transitions from using mostly dark meat to mostly white meat. The majority of the time we are using some combination of dark meat and white meat and, depending on which end of the spectrum your on, the more of one or the other you use. Check out this___*gulp*___graph (sorry, sorry!).
DAMN IT, JEFF! I THOUGHT THIS BLOG WAS ABOUT LACTATE THRESHOLD?!? Relax, relax. It is, I promise. ……Those are just the meat sweats getting to you.
When we accelerate from slow running to FAST running, there is a point when our legs start to feel like they are on fire! They get that heavy, leaden feeling, locking up hurt. Think about running an all out 400; the last 100m of that is hell. You might as well not have knees because you are in all out shuffle mode. That feeling is due to lactic acid (or the consequences of lactic acid). All right, so have you seen a trend here? When we run fast we use white meat; concurrently, when we run fast we generate lactic acid. Thus, dark meat is probably the source of this nasty lactic.
So Jeff, before I fall asleep from the meat coma I noticed that your graph suggests that even when I’m running slower than marathon pace I am using some white meat. I thought you said that white meat generates lactic acid and lactic acid lights my legs on fire? I don’t feel…..yawn…..on fire when I’m running slower than marathon pace….
That’s true! Good point! Even though we are using white meat at some easy paces, thus producing lactic acid, our body can handle it. You know how most doors only open in or out? Well we have special doors on our muscles for lactic acid (aka, transporters in nerd-speak), the lactic-acid door on white meat only opens outward (into the blood) and the lactic-acid door on dark meat only opens inward (from the blood into the muscle cell/fiber). So you can see a direction of flow. Lactic acid is generated in the white meat (Fast Twitch muscle cells), it flows out into the blood and then into the dark meat (Slow Twitch muscle cells). Dark meat can then turn lactic acid into energy. That’s good!
If anyone has ever been to Ginny’s Little Longhorn on Sunday for the Austin icon, chicken shit bingo, you know the place gets crowded. I mean, I’m-feeling-violated-just-standing-here crowded. Imagine that the front door only opens inward and that there is no back door. If this were the case, it would get so crowded inside that the door wouldn’t even open, and even if it could people couldn’t get in because the room can’t handle it. Our body operates the same way. At some point our running speed requires so much white meat that the amount of lactic acid produced can’t go into the dark meat. As a result, it has to hang out in the blood. That’s bad!
Lactic acid is, well….acid. Ever had lemon juice in your eye (e.g., has your drunk friend ever thrown a margarita in your face)? Stings, don’t it? Lactic acid in the blood does the same thing. Once our blood gets all acidic and shit quits working. We can’t lift our legs, we cramp up, our legs are on fire, etc.
So that’s it. That’s LT. Our dark meat can handle the lactic acid from the white meat up to a certain pace but as the pace picks up we use more and more white meat until eventually we produce lactic acid too fast for our body to handle. Thus, as the name implies, it is a threshold. To recap, running fast (~10k-15k race pace) requires a lot of force, a lot of force requires a lot of white meat, a lot of white meat makes a lot of lactic acid and our dark meat can’t use all that lactic acid so the lactic acid is “stuck” in the blood.
So now you see; you can’t talk about LT without talking about fried chicken. In two weeks, I’ll talk about how LT affects your race and how you train your LT.
Jeff Knight coaches Rogue Athletic Club and Team Rogue. He is a nerd and loves using parentheses. If you’d like to train with Jeff (el jefe) click here. Note: lab coats not provided.