Have you ever gone jogging and felt a burning sensation in your leg muscles? Or been doing bicep curls and experienced intense burning and fatigue in the arm? These sensations come from a buildup of compounds in the muscles—what some people call lactic acid. But is this byproduct really the villain so many people think it is?

What is Lactic Acid?

The truth is, your body can’t produce lactic acid — it's found in fermented foods. What is actually produced during a workout is lactate, which is one hydrogen atom shy of lactic acid.

Lactate comes from the carbs you consumed before you started exercising and is created when your body begins to burn these carbs for energy.

jogging woman has pain in her thigh from fitness


How Does Lactate Develop in the Body?

Lactate (also known incorrectly as lactic acid) is a by-product of intense exercise. If the body isn’t getting the oxygen it needs to do aerobic exercise efficiently, a metabolized version of glucose, which comes from carbs, is turned into lactate.

Lactate lets the body keep making energy, but it also builds up beyond what the body can use.

man at gym feeling pain in tricep during workout


Does Lactate or Lactic Acid Cause AOMS?

AOMS stands for acute-onset muscle soreness, that burning ache you sometimes feel in your muscles when you’ve worked really hard. But it’s not caused by lactate directly. Yes, lactate is building up in the muscles, but it’s the hydrogen released during a different chemical process that combines with the lactate.

Remember how lactate is one hydrogen atom shy of lactic acid? When these by-products get together, the tissue becomes too acidic, resulting in this burning feeling.

woman in gym experiencing lactic acid buildup in arm muscle


Should You Push Through the Pain?

It’s important to understand the difference between discomfort—or soreness— and pain when doing any kind of physical activity. You can work through some soreness, often caused by microtears in the tissue that are necessary for building muscle; repairing these tears teaches the body that it will need to make these muscles stronger, so they don’t tear next time.

You shouldn’t work through pain, though. Often, pain is your body’s way of letting you know you’ve pushed a muscle, tendon, or ligament past its available range of motion, max strength, or flexibility, and if you go any further, you’re going to injure yourself.

man feeling pain while lifting barbell weights


Other Workout-Related Pain: DOMS

Delayed-onset muscle soreness or DOMS is normal. It develops after you’ve started a new exercise or restarted something you haven’t done in a while.

DOMS is the cause of the ache we often feel up to 48 hours later. The more you do that new exercise, the shorter this period of DOMS will last.

woman waking up in bed with back soreness


Does Lactate or Lactic Acid Cause DOMS?

DOMS is not caused by hydrogen or lactate or lactic acid buildup, though many people think it is. Hydrogen combined with lactate causes the burning sensation you feel, but as soon as the body has enough oxygen again, it can filter out lactate and other byproducts fairly quickly.

Essentially, lactate acts as a warning system telling us to back off so it can get enough oxygen again.

woman walking after a workout


Should You Workout When You’re Still Sore?

Working through DOMS is an individual decision. Consider doing an upper body workout if your lower body is sore from running, or do strength instead of cardio that day—or vice versa.

Ultimately, listen to your body, not the pressures of phrases like "no rest days". Most of us can tell whether we’re just achy because we had a good, challenging workout, or if we’re actually in pain and need to take it easy for a few days.

woman doing incline pushups on the couch


Can You Help Get Rid of Lactate?

Just like the liver is capable of detoxing itself without juice cleanses, the body is very good at removing lactate from the system once the extreme intensity of the exercise is over. But a cool down after your workout is still vital.

Remember the hydrogen that caused the acidity and muscle burn? Your cool down will increase circulation and decrease this acidity. Ten minutes of low-intensity exercise like walking or using a stationary bike will help return your body to balance after your workout.

personal trainer helping an older man on an elliptical machine


Can You Prevent Lactate Buildup?

The amount of lactate that can build up in your body is directly related to the intensity of your exercise. Doing intense exercise sometimes is good for you—assuming you’re a fit, healthy person whose doctor hasn't warned you against it—but if you wanted to avoid lactate buildup for some reason, you could avoid intense exercise.

Moderate exercise is great for physical and mental health, too.

women rolling out her yoga mat


When It’s More Than Lactate

Anyone participating in a fitness regimen should be able to tell the difference between soreness and pain.

If you are jogging and your ankle or knee joint begins to ache, you should back off. You may need better shoes or to work up to this intensity more gradually.Tendinitis can develop during exercise and the pain can be hard to tell apart from joint-specific pain. The tendon is irritated and inflamed, so it’s still best to stop or ease back on the exercises causing the pain.

Shooting pain along the bone could be a stress fracture, and cartilage can also become irritated. Listen to your body. Stop if an exercise is actually hurting you, and consider seeing a medical practitioner to find out what to do next.

man having a physical therapy treatment


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