In my last video, I noted how lying at a slight six-degree head-down tilt for a few hours

can boost fat burning.

Now, obviously, you wouldn't want to lie tilted back if you had a heart condition,

such as congestive heart failure, as many as 8 to 12 cups of blood may be displaced into the torso

from the extremities at a tilt like that, so you have to have the cardiovascular fitness to handle

it.

Acid reflux could also be a problem.

In fact, we typically tell heartburn patients to do the reverse,

put a few bricks under the posts at the head of their bed,

to have gravity work in their favor to keep stomach acid down where it belongs.

But for those without medical problems,

is there a harm to lying tilted back for a few hours?

Well, it could give you a space headache.

In movies, astronauts are shown practicing underwater, but the gold standard

for simulating the physiological effects of the weightlessness of outer space is

HDBR, head-down bedrest.

On Earth, our blood tends to collect in our legs, so our body is designed to force blood

headward.

In outer space, our body is still trying to push our blood up, so without Earth's gravity,

blood pushes upwards to our head and chest, just like it does

when we lie tilted back. This realization came from cosmonauts, returning from the space station,

feeling as though they were slipping towards the foot of the bed and only feeling, quote-unquote,

...