Have you ever been struggling through a workout feeling sluggish and out of breath, and then suddenly get reinvigorated? You may have experienced a “second wind.” A second wind is a phenomenon where you quickly gain energy and/or strength during a run or workout immediately following a stage when you feel out of breath, fatigued, or unable to continue.

So, what causes this “second wind” phenomenon and why are you suddenly reinvigorated?

What is the “Second Wind” Phenomena?

Some theories suggest that the second wind is a result of the body counteracting the balance of the body’s oxygen consumption requirements and the build-up and removal of lactic acid within the working muscles. Exercise may become easier after the first 10 to 20 minutes because you start to use aerobic metabolism to supply energy to your muscles. When you first start an exercise session, your body uses mostly carbohydrates as fuel, and it burns them anaerobically, without oxygen. It takes time for the body to start using fat as fuel, which it uses in an aerobic manner (with oxygen). When your body burns carbohydrates in the absence of oxygen lactic acid builds up, and you feel sluggish and fatigued.

As you continue to exercise at a moderate-intensity, your body increasingly turns to fat stores and aerobic metabolism to fuel your workout. With aerobic metabolism, lactic acid build-up isn’t a problem, and you aren’t fatigued. Exercise starts to feel good at this point.

Once you’re trained and have reached a certain level of fitness, your body is able to use aerobic metabolism sooner, and you’ll get your second wind more quickly. As long as you keep running or working out at no greater than a moderate intensity, you’ll stay in the aerobic zone, and exercise will feel relatively comfortable. If you increase the intensity, anaerobic fuel use will again take over, lactic acid levels will rise and you’ll start breathing harder and become fatigued.

The Role of Endorphins

Other researchers claim the phenomena relates to the release of endorphins during running or exercise. Endorphins are “feel good” brain chemicals produced by the body and nervous system in response to pain or stress. Endorphin release could explain the pleasurable feeling runners get after they’ve run for a while, also known as “the runner’s high.” Generally, endorphins are released later in a run, not in the first 10 to 20 minutes when most people experience their second wind. Still, it’s possible that small amounts of endorphins may be released early on and could still play a role in the second wind. Others believe the phenomena may be psychological.

Wait For It!

The time it takes to get a second wind varies with each individual and his fitness level. Typically, fitter, more highly trained individuals get their second wind sooner than those who engage in less regular and less rigorous workouts. While there’s no scientific answer to the second-wind phenomenon, researchers speculate that it is related to the changeover during the first 10 to 20 minutes of exercise when your body starts to use aerobic energy production. Whether or not endorphins also play a role still isn’t clear. But either way, if you’re struggling to get through a workout or run, wait for your second wind to kick in and reenergize your workout.

Prepare Better and Recover Faster >> Enhanced Medical Nutrition

Authored by Zach Meeker, Research Assistant for Midwest Orthopaedics at Rush University Medical Center


Exercise Physiology. Theory and Application to Fitness and Performance. Seventh edition. 2009.

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