Ask the Expert – Erin Holt – October


Q: Is a buildup of lactic acid why my muscles ache long after working out?

A: “I’m so sore from all the lactic acid from our last workout,” is a comment I hear all the time from clients. Lactic acid is commonly blamed for muscle soreness in the days following a workout or any unpleasant response during exercise, and there are many negative myths surrounding it. My goal here is to assure you that lactic acid is not damaging and to clear up some of the misconceptions surrounding what really causes muscle soreness.

Lactic acid—constantly being produced by the body—serves as a source of energy and is a natural component of metabolism. The muscle “burn” you may feel during exercise happens when lactic acid accumulates faster than your body can remove it. Many of you may have experienced this sensation during training or in your sport. The uncomfortable burning sensation is actually a natural protective mechanism and ensures that you do not injure yourself. As you slow down, your body’s energy requirements decrease and lactic acid is converted to a fuel your body can use. All of the excess accumulated lactic acid is gone within approximately 60 minutes after high-intensity exercise.
Lactic acid is not responsible for muscle soreness because it is removed directly after exercise. Muscle soreness is due to micro-tears to the muscle fibers, which result in swelling and pain. This phenomenon is called delayed-onset muscle soreness (DOMS), and is most evident 24-48 hours after exercise. The following steps will ease delayed-onset muscle soreness:


  • Allow for proper warm-up
  • Gradually increase the level of exercise
  • Follow a periodized strength-training program
  • Allow for proper cool-down

As your body adapts to an increase in exercise you will notice you can perform the same amount with very little or no muscle soreness. Consistently participating in high-intensity exercise will result in improvements in your body’s ability to manage lactic acid production. And following an appropriately designed training program will result in your body producing less lactic acid so you will be able to exercise at longer at high-intensity.

A Certified Strength and Conditioning Specialist and TPI fitness professional, Erin Desharnais also holds a B.S. in Exercise Science from the University of New Hampshire.

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