Lactic Acid Build Up in Sport & Exercise Explained

Ever felt your muscles burn or your legs become lead weights during a race?  The main culprit is lactic acid, and in today’s article we’re going to be looking at…

Why does lactic acid build up in muscles? 

Lactic acid builds up in our muscles as a result of repeated or suistaned contractions as a result of exercise or sport.

What causes lactic acid? / How is lactic acid produced?

To understand lactic acid build up, we need to look at some basic exercise physiology.  Lactic acid is produced as a by-product of an energy generation process called anaerobic glycolysis.

During glycolysis, glycogen is broken down to provide energy, a process that results in a substance called pyruvate being leftover.  Now normally, in the presence of oxygen (aerobic glycolysis) this pyruvate would be further broken down and turned into more energy. 

However, without the presence of oxygen (anaerobic glycolysis) this pyruvate cannot be broken down in the same way, and is instead broken down into lactate and hydrogen ions (H+).  This is what we call ‘lactic acid.’

Why does lactic acid cause soreness?

Lactic acid, as it’s name would suggest, is acidic.  The H+ ions lower the pH of the muscles they accumulate in, resulting in what is commonly known as the ‘burn.’

When do we see lactic acid build up in sport?

Lactic acid builds up in sport when the intensity or duration of certain types of exercise move beyond the level at which other energy systems can manage them.  This typically occurs in one of two ways.

1) Long duration exercise starts to become too intense

Let’s say you’re running a half marathon, and you typically run an average 7 minute mile.  This time, however, you’re challenging a friend, and want to beat them to the finish line, so for the last couple of miles you push your pace up to just over 5 minutes per mile.

Well, at a 7 minute mile pace your body was comfortably using it’s aerobic systems, but now at a 5 minute mile pace those systems are having to provide so much more energy that there’s not enough oxygen to keep up.  Your body is therefore forced to increase the activity of anaerobic glycolysis in order to meet these new demands.  The price you pay for this extra speed is the buildup of lactic acid.

2) High intensity exercise starts to last too long

Let’s say you’re a tennis player and your rallies normally last less than 10 seconds.  This time, however, you’re facing an absolute demon of an opponent, and you’re forced to play rallies that last almost 30 seconds.

With the shorter rallies your creatine phosphate system was able to supply most of your required energy.  However, this system starts to max out at around 10 seconds, so with the longer rallies your body is forced to increase activation of anaerobic glycolysis.  

Lactic acid removal / prevention

How does the body remove lactic acid?

Your body is constantly removing excess lactate in your blood through a process called the Cori Cycle, which eventually converts it back into energy.  Additionally, your blood contains a selection of ‘buffers’ to help restore your normal pH levels.

But what if you produce lactic acid faster than your body can remove it?

Great question…

Now, your body isn’t stupid, it isn’t just going to sit there and allow your muscles to become big pools of acid, because this could lead to damage.  So the first thing your body does is significantly reduce function to the muscle.

Most of us have probably experienced this if we’ve ever trained to failure with high enough repetitions in the gym.  You might be able to do 10 reps that are okay, the next 10 are tough, the next 5 are painful, the next 3 are excruciating, and then finally you simply physically cannot perform another rep no matter how hard you try.

Most of us rarely train to this point, mainly because it is EXTREMELY uncomfortable.

How to get rid of lactic acid quickly

The quickest way to get rid of lactic acid is to stop your activity, allowing your body’s removal systems time to catch up.

There are no magic tricks or shortcuts I’m afraid.

Can you prevent lactic acid build up?

You can absolutely prevent lactic acid build up, and the way to do so is by training within the acceptable parameters of other energy systems.  For example…

If you are doing longer duration exercise, keep the intensity lower (i.e. no more than 6 or 7 out of 10 difficulty).

If you are doing high intensity exercise, keep the duration lower (i.e. less than 10s) with good rests between sets.

What training is effective to prevent lactic acid build up?

The good news is that you can quickly and effectively train in ways that prevent lactic acid build up, improve lactic acid buffering, and extend the amount of time you can perform at higher intensities.

The bad news is that this type of training is very uncomfortable.  

Put simply, the best way for your body to adapt to and prevent lactic acid build up is to have repeated exposures to lactic acid build up on a regular basis.  That means you are going to have to do hard, intense training sessions that make your muscles burn to the point of being significantly painful.

Lactic Acid Buffering Workouts

Here are two example workouts to improve your body’s ability to buffer lactic acid.

Running Workout

This is an example running workout for an 800m runner.

  • 5 Minute easy warm up run
  • 400m at a pace slightly faster than 800m race pace.
  • Walking recovery for 2-3 minutes.
  • Repeat x 5.
  • 5 Minute walk

Gym Workout

This is a great all round gym-based option to compliment most sports.

  • Dumbbell or Barbell Squat 10-15 reps
  • Straight into Walking Lunges 20-30 reps
  • Rest for 90s, repeat x3
  • Regular Press-Ups until failure
  • Straight into knee-press ups until failure
  • Rest for 90s, repeat x3.

What other factors affect lactic acid build up?

Baseline aerobic fitness

Your baseline aerobic fitness also impacts your lactic acid build up.  Essentially the better your low intensity cardio ability, the more your body will be able to tolerate before it has to switch to the lactic acid producing anaerobic system.


Certain medications, for example Metformin, which is used in the treatment of diabetes, can increase lactic acid formation.

Hydration Levels

Studies have shown that even mild levels of dehydration can negatively impact your body’s ability to clear lactic acid.

Next Steps

  1. If you enjoyed this article, we also have content on similar topics such as muscular endurance and aerobic glycolysis.
  1. If you have any questions, feedback or suggestions for future content, feel free to let us know down below.

Further Reading


If you quote information from this page in your work, then the reference for this page is:

  • Parry, A (2021). Lactic acid build up in sport & exercise explained. Available from: [Accessed dd/mm/yyyy].

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Alex Parry
British Weightlifting Tutor & Educator at Character Strength & Conditioning | Website | + posts

Alex is the Owner and Head Coach of Character Strength & Conditioning, and specialises in strength & power development for athletes.

He currently works as a Tutor & Educator for British Weightlifting, and has previously delivered S&C support to gymnastics and swimming talent pathways.