second wind

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1. The return of relative ease of breathing after the initial exhaustion that occurs during continued physical exertion.
2. Restored energy or strength.

The sensation of relief from breathlessness and fatigue that occurs at some point during sustained exercise, even though the degree of muscular effort may be unchanged.

— Stuart Judge

See breathing during exercise; fatigue.

A phenomenon characterized by a sudden transition from an ill-defined feeling of distress and breathlessness during the early stages of prolonged exercise, to a more comfortable, less stressful feeling later in the exercise. There is some debate about the physiological reality of second wind, but it may be due to an increase in lactic acid at the beginning of the exercise followed by recovery as a steady state is established. It may also be related to a delay before the correct type and number of muscle fibres are recruited and oxygen-rich blood is diverted to the active muscles.

Restored energy or strength, enabling one to continue an activity or task. For example, I wasn't sure how far they'd get in a week, but now they seem to have gotten their second wind and are making good progress painting the mural. This expression, dating from the late 1800s, was at first (and still is) used for returned ease in breathing after becoming out of breath during physical exertion such as running. It soon began to be applied to nonphysical efforts as well.

A phenomenon characterized by a sudden transition from an ill-defined feeling of distress and difficulty in breathing during the early stages of prolonged exercise, to a more comfortable, less stressful feeling later in the exercise. There is some debate about the physiological reality of second wind, some scientists believing it to be more psychological than physiological. However, second wind may be due to an initial increase in lactate levels at the beginning of exercise, followed by recovery as a steady state is established; or it maybe related to an improvement in the contractility of inspiratory muscles and an improved blood supply to the diaphragm.