It used to be believed that lactic acid was a waste by-product of metabolism. It also used to be believed to be the cause of muscle fatigue. New research has contradicted that long-held belief. According to this article:
Lactate threshold is the point at which lactate is produced faster than the body can use it for energy. Now, if you've ever see the "Chocolate Factory" episode of I Love Lucy, you're probably already laughing. If you've seen it, and you're scratching your head....or if you've been deprived, like my son (who had never seen it until today), here it is:
Your muscles only contract when your central nervous system (CNS) tells them to. Your CNS does this by sending an electrical signal to your muscle cells. Your muscles contract when the electrical charge causes potassium inside your muscle cells to exchange places with sodium outside your muscle cells. During intense exercise, potassium ions have a hard time finding their way back inside the cells and they start to build up outside your muscle cells. This build up reduces both the electrical charge and the ability of your muscles to contract. In other words you begin to suffer from muscle fatigue.
This is where lactic acid comes to the rescue (emphasis added). Both studies showed that accumulating lactic acid is used to diminish the effects of the accumulating potassium ions, help them back inside your muscle cells and restore the function of the CNS signaling system.
((Be sure to pause the music player before hitting "play" on the video.))
((That's as funny today as it was probably 35 years ago when I first saw it!!))
So, let me say it again.... Lactate threshold is the point at which lactate is produced faster than the body can use it. Therefore, lactate threshold training (basically) increases the body's ability to utilize lactate. (It would be like training Lucy and Ethel how to wrap those chocolates faster!!--The chocolate is the lactate, it needs to be in the candy box, it's coming through faster than Lucy and Ethel can handle it......)
According to this article, true lactate threshold training is done at speeds faster than 10K pace. (Not short interval sprints, but extended runs.) Running at paces faster than 10K is necessary to increase the lactate threshold, however, training at that intensity for extended periods on a consistent basis is not advisable, which is where tempo runs come in. True tempo training is performed at paces between 15-45 seconds slower than 10K pace. Tempo training is at the lower end of lactate threshold training, but is not going to be fast enough to improve lactate threshold.
The best way to improve your lactate threshold is by training at paces that flood your body with lactic acid long enough to train the body how to deal effectively with it. Ethel and Lucy would never learn to wrap those chocolates faster if the conveyor belt never moved faster than that original speed, or just sped up in short spurts!!
Soon, I'm going to write a post on Hershey's kiss-wrapping training....he he he. (I hope you never look at your LT/tempo runs the same way again!) Now, go wrap some chocolate!!
Thanks for stopping in, come again soon.