Lactate

Lactate (often incorrectly called lactic acid), is a chemical produced by the body during certain physiological processes, including exercise. It plays a crucial role in energy metabolism, particularly when the demand for energy exceeds the oxygen supply available to the muscles. Understanding lactate and its relationship to running can provide insights into athletic performance and training.

Common wisdom states that Lactate is a bad by-product of high intensity exercise and ‘flushing from your muscles’ is good. This is a myth!

During intense exercise, such as running, the body relies on the breakdown of glucose (a simple sugar) in the presence of oxygen to produce energy. When there is an insufficient supply of oxygen to meet the energy demands of the muscles, the body additionally turns to anaerobic metabolism. In this process, glucose is partially broken down without the use of oxygen, resulting in the formation of lactate.

Contrary to popular belief, lactate is not harmful and does not cause muscle burn. The burning sensation is actually caused by the build-up of hydrogen ions in the muscles. These hydrogen ions make the muscles acidic, which causes the pain and discomfort. Lactate acts as a buffer, mopping up free hydrogen ions, mitigating their build-up, becoming Lactic Acid in the process.

As required, lactate can be converted back into glucose to be further used as a source of energy. This primarily occurs in the liver, through a process called the Cori (lactic acid) cycle.

During exercise inactive muscle and non-muscle cells also produce and release lactate into the bloodstream. Interestingly, their production of lactate extends beyond the point at which your previously exercising muscles have stopped producing it. Your previously exercising muscles switch to consuming this lactate to aid in repair.

There are a number of published articles around this topic, but probably the most appropriate starting point is understanding the ‘Lactate Shuttle’, for example ‘The tortuous path of lactate shuttle discovery‘ by George A Brooks.

Regular training can improve the body’s ability to utilise and transport lactate. Endurance training, in particular, can enhance the capacity of the aerobic energy system, reducing the reliance on anaerobic metabolism and the subsequent production of lactate. This adaptation helps delay the onset of lactate accumulation and fatigue during running, allowing athletes to sustain higher intensities for longer durations.

Lactate threshold is a term often used in endurance sports, including running. It refers to the exercise intensity at which lactate production exceeds lactate clearance, resulting in a rapid increase in blood lactate levels. Training at or near the lactate threshold can improve an athlete’s ability to sustain high-intensity efforts and delay the accumulation of lactate, leading to enhanced endurance performance.