Does Lactic Acid Really Cause Muscle Soreness? Science Says No

The Myth of Lactic Acid and Muscle Pain

If you’ve ever finished an intense workout with burning muscles, you may have heard someone say, “That’s lactic acid buildup!” For decades, this myth has been widely believed — but modern research has debunked it. Lactic acid is not the cause of post-exercise soreness.

Instead, the soreness you feel a day or two after a tough workout is due to a process called Delayed Onset Muscle Soreness (DOMS), which is linked to microscopic damage in your muscle fibers, not lactic acid.

What Actually Causes Muscle Soreness?

When you engage in intense or unfamiliar exercise — especially eccentric movements (like lowering a weight or running downhill) — tiny microtears occur in your muscle fibers. This triggers the body’s natural repair process, leading to inflammation and sensitivity in the area.

This phenomenon, known as DOMS, usually appears 12–48 hours after exercise and can last for 2–3 days. Far from being harmful, this muscle damage is part of how your body rebuilds stronger, more resilient fibers.

What Does Lactic Acid Really Do?

Lactic acid (more accurately, lactate) is simply a byproduct created when your muscles burn glucose for energy in low-oxygen conditions, such as during high-intensity exercise. It does not “stay” in your muscles for days — your body clears it within 30 to 60 minutes after you stop exercising.

In fact, lactate may actually help your muscles perform better during short bursts of activity, serving as a temporary energy source.

How to Reduce Muscle Soreness

While you can’t completely avoid DOMS, there are ways to minimize discomfort and support faster recovery:

1. Warm Up and Cool Down: Light dynamic stretches and warm-up exercises prepare your muscles for work.
2. Active Recovery: Gentle movement (walking, cycling, yoga) increases blood flow and aids healing.
3. Hydration and Nutrition: Drinking plenty of water and eating protein-rich meals help repair muscle fibers.
4. Gradual Progression: Increase workout intensity or duration slowly to give your muscles time to adapt.
5. Massage or Foam Rolling: Both techniques reduce muscle tension and improve circulation.

Do you believe cold plunges help with muscle recovery? Learn more in our blog here.

When Muscle Soreness is a Concern

DOMS is normal, but sharp, sudden, or severe pain is not. If soreness lasts more than a few days, or if you notice swelling, weakness, or reduced range of motion, it may be time to consult a sports medicine specialist or physical therapist.

BASS Medical Group’s sports medicine team can help diagnose and treat overuse injuries or lingering pain, ensuring you recover safely and avoid setbacks.

Key Takeaway

Lactic acid does not cause muscle soreness — microtears and the repair process do. Understanding this difference can help you recover smarter, train more effectively, and prevent unnecessary worry about “acid buildup.”

Frequently Asked Questions (FAQs)

Does lactic acid cause muscle soreness?

No. Lactic acid is cleared from your muscles within an hour after exercise. Post-workout soreness (DOMS) is caused by microscopic muscle fiber damage and inflammation.

How can I prevent muscle soreness after a workout?

Focus on proper warm-ups, progressive training, hydration, and recovery techniques like stretching and light activity to support muscle healing.