A few years ago, a friend of mine took me walking. He believed that walking would improve my health. I walked a few hundred meters, and my legs started to burn. After a while, I could not take it anymore. It was obviously my body telling me that I was unfit. However, I remember wondering why my legs burned. The science behind this is fascinating.
As you perform any strenuous exercise, you breathe faster. The increase in oxygen is to help your body generate energy. When there is insufficient oxygen, your muscles work anaerobically to produce energy. It does this by sourcing glucose (sugar) from your muscles. Glucose is broken down into a substance called pyruvate. When your body is producing pyruvate in an oxygen deprived environment, is converts into lactate. The lactate produced allows you to continue training your body for another two to three minutes.A bye product of lactate is increased acidity of the muscles along with a disruption of other metabolites. The increased acidity is what causes the burning sensation. The strange thing is that this is your defence mechanism kicking in. What if you forgot to stop working out?
There are several myths associated with lactate. For example that athletes produce less lactic acid that regular people. In reality, the are more efficient at using lactate as energy. Also, that lactate is not beneficial to training. However, the production of lactate stimulates the production of mitochondria. An increase in mitochondria helps improve performance. Finally, that lactate is responsible for delayed onset muscle soreness. That wonderful feeling you get after working out for an hour where your entire body feels like it will break down; today! The pain is due to damage to your muscles as your break the muscle fibre. It will heal, and you will get two for every one that you break. Sounds like a good deal to me.