What is Lactic Acid?

By Singapore 2010 Youth Olympic Games

Many fitness-conscious people have been lead to believe that lactic acid is a vile waste product that should be avoided at all costs. However, the complete opposite is true. Lactic acid is a very valuable fuel source for athletes that undertake intense exercise.

Lactic acid is simply a glucose molecule split in two via anaerobic energy metabolism.

Energy that can be used by muscles
Just the same as slicing an apple in two, these pieces of glucose still contain a lot of energy that can be used by muscles. Lactic acid is a smaller molecule than glucose, (a tri-carbon molecule as opposed to the 6 carbon glucose ring). Therefore, it can enter other energy-producing pathways such as the Krebs cycle (aerobic metabolism) via conversion to pyruvate. However, it can also travel back to the liver to be converted back to glucose within the liver, a process that requires energy.

However, the draw-back in splitting the glucose molecule to form lactic acid is the production of hydrogen ions. Excessive lactic acid production causes too many of these ions to accumulate in muscle.

Lactic acid doesn’t hang around for long
This triggers a potential drop in pH; a process that retards the chemical processes that enable muscle contraction. However, lactic acid doesn’t hang around for long, it is utilized or transported very quickly one it is produced. Therefore, it contributes very little to muscle soreness that is experienced after training.

In fact, recent work has clarified that consistent training reduces blood levels of lactic acid, even while muscle cells continue to produce the same amount. Training increases the number of lactic acid transporters molecules in mitochondria, to speed uptake of lactic acid from the cytoplasm into the mitochondria for burning; this is often called the “lactic acid shuttle”.

Keep lean and optimize performance
Intense cardio exercise generates big lactic acid loads. Muscle adapts by building up mitochondrial enzymes that clear lactic acid quickly to metabolize this into a usable form of energy. It’s one reason why a year-round approach to cardio exercise is so important; keeps lean and optimize performance.

Hashimoto T, Brooks GA. Mitochondrial lactate oxidation complex and an adaptive role for lactate production. Med Sci Sports Exerc. 2008 Mar;40(3):486-94.

Dr Paul Cribb is an award-winning sports scientist, author, personal trainer and the creator of mp-body.com – the first ever science-based, research-proven, nationally accredited body transformation program. Learn more here.