As the new year approaches, many of us will be setting exercise goals. For most people, such goals are forgotten in a matter of weeks. I saw this first hand a few years back when I joined a fitness club late one December.

When I showed up on January 2, ready to start the year off right, the place was packed, and I had to wait in line to use exercise machines. When I complained, a trainer said, “It’s like this every January. Wait three weeks and you’ll have your pick of the equipment.”

Sure enough, by the third week the crowd had thinned considerably. By February, there was no one left but a small group of faithfuls.

One reason that exercising goals don’t survive long is because of something called DOMS. That is, Delayed Onset Muscle Soreness. We’ve all experienced it. We are enthusiastic about getting into shape and we overdo it. The next day we don’t exercise because we are so sore we can hardly move.

Why muscles get sore is a question that has been of interest to athletes (weekend and professional) and trainers and coaches for a long time. Back in the early 1920s, a scientist named Otto Meyerhof seemed to have discovered the cause. He was awarded the Nobel Prize for his research. And for eighty or so years, athletic training was based on a misassumption about Meyerhof’s findings.

One of the experiments that Meyerhof performed involved frog legs. He studied and listed the chemicals found in the leg muscles of freshly killed frogs. He put the legs into a solution and gave them electric shocks, causing them to twitch. He continued to shock them until they no longer twitched, then he again studied and listed the chemicals in the muscles.

One of the things he found in the over-worked muscles was a build up of lactic acid. Based on Meyerhof’s research, lactic acid was believed to be a prime factor in muscle fatigue and in DOMS.

Lactic acid builds up slower when there is oxygen in muscles, so aerobic exercise became the rage. Slow running was considered a better training approach than sprinting, because in sprinting, your breath can’t keep up with the demand for oxygen, and lactic acid builds up in the muscles.

Lack of oxygen, it was thought, lead to lactic acid, and lactic acid lead to fatigue. And to sore muscles. Most any running book published in the 1970s, 80s, and 90s will have a chapter about avoiding lactic acid buildup in muscles.

In the last 20 years or so, the idea that lactic acid buildup is a bad thing has been proven false. In fact, muscles use lactic acid as fuel.

So if lactic acid doesn’t cause sore muscles, what does?

Micro tears in muscle fibers. Overworked muscles are slightly damaged and it takes a few days for the body to make repairs. Once it has done so, the body takes measures to prevent repeated damage. That’s why if we continue to exercise regularly, we don’t get sore again.

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