When an individual exercises, the muscles require energy in
order to contract. Usually large amounts of ATP is created through oxidative phosphorylation
when there is enough oxygen to use the electron transport chain. However in
times of high intensity exercise, such as sprinting or long distance running, not
enough oxygen is delivered to the muscles in order to use the electron
transport chain. Glucose is still broken down to pyruvate from glycolysis when
there is no oxygen available, as the function of glycolysis creates a net gain
of 2 ATP. During times of high exercise, pyruvate is broken down to lactate
which then leads to more glucose breakdown. This creates energy at a high rate that
can be used for the short burst in exercise. Normally, the body cannot sustain
the usage of lactate as the breakdown of lactate to lactic acid creates many
free hydrogen ions to be in the muscles. This leads to acidosis of the muscles
and is generally what is felt when your body starts to burn during heavy
exercise. It is the body’s mechanism telling you to stop overworking your
muscles so hard.
Knowing this, the story of Dean Karnazes is incredible. Measuring
an individual’s lactate threshold is measuring the body’s ability to clear
lactate in the body and convert it back into energy. The size of one’s
mitochondria effect how efficient the body’s ability to clear lactate is,
therefore genetics play a large role in your lactate threshold. Dean Karnazes
does not have lactate threshold. Among the feats that he has completed with
this rare condition is running 3 days straight (350 miles) without sleep, 50
marathons in 50 states in 50 consecutive days, and completion of the “The Relay”
(a 199 mile run performed by teams) by himself 11 different times. What is also
incredible about Dean Karnazes, is the fact that his body doesn’t produce high
levels of creatine phosphokinase. CPK is an enzyme that is found in the
bloodstream if there is muscle damage, such as after a marathon, which creates
the muscle soreness. In a normal person, after a marathon their CPK levels will
rise from 163u/l to 2400 u/l. During his 50 marathons in 50 days, his enzyme
level peaked at 450u/l and then slowly declined as his body adapted to the
marathons over the 50 days.
https://www.runnersworld.com/runners-stories/dean-karnazes-runs-50-marathons-in-50-days
https://www.theguardian.com/lifeandstyle/the-running-blog/2013/aug/30/dean-karnazes-man-run-forever
These are great articles, Davis! I think Dean Karnazes is superman. To not have a lactate threshold is mind boggling to me. There are so many top tier athletes that will train all their life and will still never attain a fitness level like Dean's. This makes me wonder if this rare blessing has improved his body in any other aspects? Seeing as how he has has competed in such grueling competitions without any struggle, I wonder about the level of changes in his arteries, how strong his bone density is, and even how efficient is his heart? Could there possibly be any downside to this? While his metabolism is superhuman, the continuous strain put on his muscles and bone may not show until later on. I guess we'll just have to see!
ReplyDeleteFurthermore, I would love to know more about the genetic component and why it appears to be so rare. You had mentioned that the size of one's mitochondria affects how efficiently the lactate is cleared. So I am assuming that Dean has gigantic mitochrondia. This brings to mind the reflection paper that we had to write on 3-parent embryos and the ethical implications of mitochondrial replacements. Currently, the procedure is being debated about its uses in curing mitochondrial diseases. If a technology like 3-parent embryos were to advance, could we potentially start replacing mitochondria in order to create a world of potential super humans? There are obvious ethical implications but could this be a potential solutions towards minimizing the obesity epidemic in the US? This procedure has a long way to go before or if it will ever reach this stage but this was just a thought!
Before I had the chance to read your comment Wes, I was planning on writing a lot of the same thoughts and questions! I did a little research into lactate threshold (sometimes used interchangeably with "anaerobic threshold") and here's what I found:
ReplyDeleteKey mechanisms for regulating lactate threshold are believed to be:
1) the rate of lactate removal
2) the recruitment of slow-twitch vs fast-twitch motor fibers
3) balance between glycolysis and mitochondrial respiration
4) ischemia/hypoxia
Mitochondria, as Davis mentioned, are used to break down pyruvate for further synthesis of energy. When more pyruvate are produced than are able to enter the mitochondria, they will then be converted to lactate. Those with larger or more mitochondria will therefore have a greater ability to undergo mitochondrial respiration. Additionally, some research indicates the recruitment of slow-twitch muscles enhance mitochondrial respiration, and fast-twitch fibers cause an energy metabolism shift into low mitochondrial respiration and higher levels of glycolysis.
Apparently lactate threshold training programs are not uncommon for endurance athletes and those in other sports. These programs generally focus on "high volume, maximal steady-state, and interval workouts" (Kravitz & Dalleck, 2005). These programs also focus on increasing VO2 max and heart rate deflection point, which are reportedly related to lactate threshold as well. Because lactate threshold can determine endurance ability, it is interesting in reading how we might make changes on a cellular level through specific training to help on a larger scale.
https://www.unm.edu/~lkravitz/Article%20folder/lactatethreshold.html
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3438148/
As a runner myself, I find this post highly intriguing!
ReplyDeleteThis idea of lactate training threshold is fascinating. The ability to maintain an athlete's pace which is higher than their competitors at their lactate threshold gives the athlete the upper hand in being able to be faster. Training at an athlete's lactate threshold also extends the longevity which the athlete is able to rely upon their aerobic system (Hyman).
Wesley, you make a great point about the genetic component which makes this condition so rare, and you bring up a good point about replacing mitochondria in people to create a race of super humans. This idea of replacing the mitochondria in people addresses the question I had with lactate threshold training, "Can lactate threshold training lead to a new form of blood doping such as mitochondria or pyruvate doping?" While I do not believe that we are at that point yet, just looking forward, I would be interested to see if something comes of this in that respect.
Hyman, L., CTS Pro Coach. (n.d.). The Performance Benefits of Lactate Threshold Testing and Training. Retrieved from https://trainright.com/the-performance-benefits-of-lactate-threshold-testing-and-training/