Sleep

Study: Fish and humans sleep in similar ways

Neural activity in a zebrafish transitioning from waking to sleeping. Credit: Leung et. al. Nature 2019.

Most animals sleep, but scientists still lack a complete understanding of why, the biological factors that regulate sleep cycles and how the behavior evolved.

Driving the news: A new study in Nature on tiny zebrafish finds how humans sleep today may have first evolved in vertebrates more than 430 million years ago.

Endurance athletes have a set energy limit

Photo of two RAUSA ultra athletes running in a desert
Runners on the 3,080 mile Race Across the USA in 2015. Photo: Bryce Carlson/Purdue University

A small study of endurance athletes shows that even the most fit human body can only sustain 2.5 times the person's resting rate of metabolism (RMR), with researchers saying they suspect this is due to the capability of the body to digest food, according to a study published in Science Advances Wednesday.

Why it matters: Human energy expenditure is important because a person's limits affect all their body's systems, including reproduction, thermoregulation and physical activity.