# Exhalation effort at max HR?

**URL:** <https://www.trainerroad.com/forum/t/exhalation-effort-at-max-hr/19382>\
**Category:** Training\
**Created:** [August 9, 2019, 4:44am UTC](https://www.trainerroad.com/forum/t/exhalation-effort-at-max-hr/19382 "2019-08-09T04:44:09Z")\
**Posts on this page:** 1\
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**Author:** ![splash](https://avatars.discourse-cdn.com/v4/letter/s/ac8455/32.png) [@splash](https://www.trainerroad.com/forum/u/splash)\
**Post date:** [August 9, 2019, 5:30pm UTC](https://www.trainerroad.com/forum/t/exhalation-effort-at-max-hr/19382/12 "2019-08-09T17:30:15Z")

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I don’t know how medical conditions affect this.  
But in my understanding, when breathing in, the diaphragm and the muscles between the ribs contract, which enlarges the thorax and expands the lungs, which draws air in. When the muscles relax, the thorax reduces in volume, and air is driven out. There isn’t normally an active muscle contraction to breathe out.

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