While you might think that by this headline you can skip a trip to the gym and hit the sack instead, sadly, that's not quite true. 

But what is true is that sleep is active, essential biology, showing how the brain uses the night to flood the body with growth hormone to repair muscles, strengthen bones and balance metabolism. Researchers have uncovered the neural circuitry that explains why growth hormone surges during shut-eye, and why cutting corners on sleep undermines our physical health.

For the first time, scientists from the University of California, Berkeley (UC Berkeley) have discovered just why growth hormone (GH) surges at night, particularly in deep sleep – something we've known for a while but not the mechanism driving it. In this animal study, the team uncovered a novel feedback mechanism that balances hormone levels to power a range of tasks – including helping to build muscle.

GH isn’t just about children growing taller; in adults, it is crucial for maintaining muscle mass, bone density, healthy fat distribution and blood sugar regulation. Low levels are linked to frailty, weaker bones, belly fat, insulin resistance and higher cardiovascular risk – all hallmarks of aging. The link between sleep and GH is clear, but the precise neuroendocrine wiring that allows one to amplify the other wasn't.

Essentially, we have one set of neurons that releases growth hormone–releasing hormone (GHRH), which stimulates the pituitary to produce growth hormone. While another set releases somatostatin (SST), which inhibits it (this group is further divided into two subtypes that fine-tune the brake on GH output).

If this sounds confusing to you, you're not alone. But the scientists discovered that although SST is described as an inhibitor, it can also act as a timekeeper. In REM sleep, bursts of both SST and GHRH combine to produce sharp pulses of GH, while in non-REM sleep, SST activity drops, allowing steadier hormone release. Together, the two systems ensure GH is delivered in the right rhythm at the right time.

There's a lot more to the story, and a lot more science, but it's safe to say that you should still get a good night's rest following your workout!