Imagine yourself in the wild: the desert, forest, jungle, or the Great Plains. Your family is depending on you, and if you fail, it may be months before you find food. Now imagine you’ve spotted your target, only it’s got two more legs than you and can run about 15-30 miles per hour faster. Maybe it’s a water buffalo or a majestic antelope buck. Luckily, you practice strength and conditioning regularly, and can pursue your prey until it’s exhausted itself and slows down enough to be captured.

This practice is known as persistence hunting, and can be traced to early human ancestors nearly 2 million years back. In persistence hunting, the hunter can use cardiovascular endurance to exhaust their prey.

Persistence hunting is suggested to be early evidence of the “runner’s high,” or the point at which a person breaks through a mental barrier during heavy doses of strenuous activity — an hour of Fusion class, for instance — due to the release of endorphins.

Endorphins, as you may know, are the chemical released from the pituitary gland when the body is put through moderate to high intensity workouts, for continuous periods of time, where breathing is difficult and the muscles are pushed to their full limit. The athlete’s sense of pain  is known to lessen, and a sense of euphoria can overcome them when experiencing runner’s high.

If you just ripped through a round of 21-15-9-3 only to be met with a mile run immediately after, yet you managed to get that mile in under 8 minutes, it’s very possible that you just reached the runner’s high.

Now, we may not be training for the primal fitness that our ancestors needed for survival, and we probably don’t have to hunt for our dinner anymore in this modern world — unless we really want to.  However, we are training for longevity, whether it’s for a healthier life or for increased stamina on the field or at the office. Hey, walking up stairs can be taxing on a Monday morning. Thankfully, your survival through the next season doesn’t depend on your endurance, but you’re workouts contribute to a practice that has long been a part of human survival.

Now go eat some delicious game. You’ve earned it!