Why Do Muscles Ache After Exercise?

Why Do Muscles Ache After Exercise?
A hard workout or a strenuous day on the trail can leave you with achy muscles. There's a name for this pain: delayed onset muscle soreness, or DOMS. It typically sets in about 8 to 12 hours after vigorous exercise and can last for several days.

Lactic Acid

A buildup of lactic acid, which results as muscles burn glucose for energy, causes the short-term muscle "burn" you get during exercise.

Muscle Tears

The days of soreness that follow intense activity are caused by microscopic tears in the muscle fibers and the tissue that connects the muscles. The greater the effort, the greater the tearing, and the greater the ache.


The good news is that this is a natural part of muscle behavior and not an injury. Allowed to rest, the muscles will repair the damage and in the process get bigger and stronger in anticipation of having to repeat the effort.


To build muscle, you have to repeat this process of tearing-and-repairing. Athletes typically do not work the same muscle group two days in a row in order to give the muscles time to repair themselves.


While stretching before exertion is almost universally encouraged to prevent injury, it may offer little or no reduction in DOMS. Similarly, massage and cool-down periods following an intense workout do nothing to shorten recovery time.


Article Written By Robert Leonardi

Robert Leonardi is a freelance writer specializing in eye care and general health-related articles. He is the president and CEO of a chain of eye care centers and has more than 30 years of experience as a licensed optician and administrator in the optical industry.

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