How Does Lactic Acid Affect Your Workout?

Lactic Acid

You will have heard of lactic acid or experienced it without knowing what it is or why it’s happening.

Lactic acid is essentially a by-product of oxygen deficiency. Lactic acid can make a set considerably more intense later in a session. The pain associated with lactic acid is your body’s method of telling you to stop exercising.

There are many incorrect tales going around that this ‘pain’ or intense feeling means that you are getting more out of your workout or that you’re gaining more muscle than you do when you don’t get that burning feeling. This isn’t quite true. Whereas you could be feeling the burn because of a more hardcore workout, lactic acid could also be the reason, in which case you’ve not done what you probably think you have.

For example, when you hold your hand up in the air, it’s lactic acid that eventually makes you lower it, and that hasn’t exactly produced mega mass muscle gains, has it? The build-up of lactic acid can be just shy of debilitating and can feel pain as you squeeze out extra sets, along with other side effects like shakiness, which affects your muscles and joints when lifting.

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So what is it that’s happening when lactic acid builds up?


Glycolysis breaks down glucose and forms pyruvate with the production of two molecules of ATP. The pyruvate end product of glycolysis can be used in either anaerobic respiration if no oxygen is available or in aerobic respiration via the TCA cycle which yields much more usable energy for the cell. Glycolysis results in lactate and hydrogen formation.

So when you exercise, your body converts glycogen into ATP. This energy fuels your muscles when they’re put to work, along with the support of oxygen. As a weightlifter, you will know the importance of nutrition and how protein is your building blocks for muscle growth and glucose is your energy supply that is stored in your body in the form of glycogen as a primary source for your muscles.

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But what happens when they stores run out or are used up?


Your body will then use another source from your anaerobic systems. When they run out, lactic acid arrives and causes the aforementioned burn in your muscles. This is because your body can’t meet the demand for oxygen that is created by repeated intense exercise and pumping weights without rest and nutrition. Because muscle contraction requires oxygen, this action is made all the harder when those supplies run out.

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To keep things simple, you may bear in mind that a build-up of lactic acid is caused by high intensity, heavy lifting and not enough rest.
Following intense exercise, growth hormones increase the use of fat for energy during your recovery. In other words, your body will burn fat to help to help recover when there is a caloric deficit.
When you exercise, your body needs to maintain a steady supply of glucose to the brain. A deficiency in your glucose supply is the reason you might, therefore, feel light-headed at the end of a training session.

Our articles should be used for informational and educational purposes only and are not intended to be taken as medical advice. If you’re concerned, consult a health professional before taking dietary supplements or introducing any major changes to your diet.

Chris Appleton

Chris Appleton

Writer and expert

Chris is an editor and a level 3 qualified Personal Trainer, with a BA honours degree in Sports Coaching and Development, and a level 3 qualification in Sports Nutrition. He has experience providing fitness classes and programs for beginners and advanced levels of clients and sports athletes. Chris is also a qualified football coach, delivering high-level goalkeeping and fitness training at a semi-professional level, with nutritional advice to help maintain optimal performance. His experience in the sports and fitness industry spans 15 years and is continuously looking to improve. In his spare time, Chris likes to dedicate it to his family while training in the gym.

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