By Elizabeth Quinn Updated on July 09, 2021
Medically reviewed by Erin Pereira, PT, DPT
Lactic acid is a common topic among athletes and sports enthusiasts, especially in regards to performance and recovery. Research about lactic acid in recent years explains the effects of lactate on performance, but these effects are different from what was previously believed.
In the past, people have blamed lactic acid for muscle soreness and performance fatigue. However, newer evidence finds that lactic acid actually provides another fuel source for working muscles and may even improve performance.
What Is Lactic Acid?
Lactic acid is a byproduct produced by your body during the process of the metabolic process of glycolysis, or when your body turns glucose into energy. Lactic acid is then broken down into lactate, an action that releases hydrogen ions into the blood.1
Lactic Acid Is the New Muscle Fuel
It is not lactic acid but the increased acidity in your blood that is to blame for the burning sensation you might feel during intense exercise. And the acidity is caused by the release and buildup of hydrogen ions, not lactic acid.
Additionally, research suggests that delayed onset muscle soreness (DOMS) is from microscopic tears and trauma resulting from physical exertion, not lactic acid buildup.2 Lactic acid was always seen as a byproduct of metabolizing glucose for energy and a waste product that caused a burning sensation in the muscles. However, research shows that lactate accumulation may assist in relieving the burn or muscle cramp created during high-intensity physical activity.3
Lactate Threshold Training and Peak Performance
By training at a high intensity (lactate threshold training), the body creates additional proteins that help absorb and convert lactic acid to energy.4 There is an even rate of lactic acid production and blood lactate removal at rest and under low-intensity exercise.
As your intensity of exercise increases, the imbalance causes a buildup in blood lactate levels, which is how the lactate threshold is reached. At this lactate threshold, blood flow decreases, and fast-twitch motor ability increases. This peak level of performance is referred to as lactate threshold training.
Aerobic and Anaerobic Training
Your lactate threshold marks the transition from aerobic training to anaerobic training.5 When referring to your training zone, trainers suggest that you must train in the anaerobic zone to improve endurance and efficiency, which is beyond the lactate threshold.
Team USA running coach Dennis Barker explains that aerobic training doesn't improve performance because, in that state, your body is receiving enough oxygen to meet the demands of the exercise. However, during anaerobic exercise, your body is not getting enough oxygen.
Reaching this threshold helps your body become more efficient by training at or just below the lactate threshold. Thus anaerobic training is essential to improving your athletic performance.
Heart Rate, Lactate Threshold, and Peak Performance
Your lactate threshold is about 80% to 90% of your maximum heart rate. For example, if your maximum heart rate is 205 beats per minute (bpm), then your lactate threshold would be just around 185 bpm, and your aerobic training zone would be between about 125 and 185 bpm.
To maintain your aerobic fitness, you'd work in an aerobic training zone, at which you would be able to talk comfortably. However, to enhance your anaerobic training, you'd have to exercise at or near your lactate threshold. In the end, lactic acid (or the push toward your lactate threshold) is a good thing that could improve your athletic performance if you push yourself toward your peak.