Most of us who run have felt that burning sensation in our legs during the end of a heavy tempo session, or a few repeats from finishing a session of 400’s. You’re urging your legs to keep going despite the very obvious slow down in pace. The session finishes and you walk off the track. The talk about the session as you gather for your cool down is how tough but good the session was. Your mind is screaming, “well it wasn’t good for me”. You chip in your two cents worth about how difficult the last few reps were. “I was fine, then all of a sudden my legs began to burn and I couldn’t keep the pace up”. Club mates nod in knowing agreement. “That’s the lactic acid in your legs” It slows you down when you go above your lactic threshold. You’ll probably be a bit sore tomorrow”.
This conversation is very common among athletes across the world. Its basis comes from and early 19th century chemist, named Jacob Berzelius. He measured lactic, in animal tissue. He found high levels of lactate in a hunted animal and thus concluded that as the animal tired its lactic and the acidity in the muscle increased.
We know that lactate plays a role in muscle fatigue as a result of increased acidity in the muscle, which affects the signalling to convert lactate to energy.
How Lactate Works
Exercise at a moderate or easy intensity allows us to get our energy aerobically (with oxygen). As the intensity increases the body requires a quicker energy production. It does this by producing energy anaerobically (without oxygen). This occurs when glucose (sugars/carbohydrates) are broken down into a substance called pyruvate. When working anaerobically, pyruvate is converted into lactate which allows for energy production. After around 1-3 minutes lactate levels rise. This leads to an increase in the acidity of the muscle cell, which slows down muscle contraction. Thus, we slow down and begin to derive most of our energy requirements aerobically again.
The muscle soreness is sometimes referred to as DOMS (delayed onset muscle soreness). This occurs as tiny tears occur within the muscle after bouts of intense exercise. It is usually felt within the first 24 hours but may only peak at 48-72 hours.
Ways to reduce the effect of DOMS
- Go for an easy run or bike session to ease the muscles
- Foam rolling has shown to have a positive effect on DOMS
- Ice baths – ancedotal