If you work out, especially if you run, you’ve probably experienced a phenomenon called the “second wind.” When you first start exercising, you feel sluggish, slow and out-of-breath. Then suddenly you develop new vigor and energy and are able to pick up the pace. It feels good when you’re doing a tough workout at the second wind re-invigorates you. What causes this well-known phenomenon in people who run or work out?
What Causes a Second Wind?
Have you noticed when you first start exercising it feels like a real chore, and you just want to head back to the comfort of your easy chair? But if you keep going, your movements become more fluid and your energy level rises. Exercise starts to feel much more comfortable, even pleasurable in some cases. One of the reasons exercise becomes easier after the first 10 to 20 minutes is 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 time it takes to get the second wind varies with each individual and how fit they are. More fit and highly trained individuals will get their second wind sooner than people who have just started to work out.
The Second Wind Phenomenon and Endorphins
Some experts speculate that endorphin release partially explains the second wind. Endorphins are “feel good” chemicals produced by the brain and nervous system in response to pain or stress. Endorphin release is thought to explain the pleasurable feeling runners get after they’ve run for a while. This is 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.
The Bottom Line?
The second wind phenomenon seems to be 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.
References:
ACE Fitness. “What is a Second Wind?”
Exercise Physiology. Theory and Application to Fitness and Performance. Seventh edition. 2009.
