I went out for a 5K run. I jogged for 5 minutes as a warm-up. Then started running. After about 2.5 kilometers, I got really tired and had to stop. So I then walked for about 1 kilometer. Then I started running again, and, weirdly enough, I was now running way faster and with way more energy than I did for the first 2.5 kilometers.

What happened here? How come I was FASTER during the 2nd stint?

1 Answer 1


It sounds like the phenomenon of a second wind. There is no clear proven reason for the second wind to my knowledge.

A couple possibilities:

  • It may be that your body's pain relieving endorphins start kicking in and you don't feel the pain anymore.
  • The most common theory comes from the fact that second winds are more widely reported by amateurs than pros. The idea is that your body takes some time before it begins clearing lactic acid and its use of oxygen is optimized, and once that kicks in your fatigue lessens. Highly trained athletes tend to be more efficient at this so they clear lactic acid from the start and as a result they don't feel the second wind.

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