This is Scientific American 60 Second Science.

I'm Christopher in Tagata.

Got a minute?

Most carbon dioxide that travels from your muscles to your lungs for exhalation

does so not as CO2 proper but as part of bicarbonate

HCO3. Bicarbonate's vital to maintaining your blood pH and it also aids and

digestion but it turns out bicarbonate also tweaks the activity of rod cells in your retina.

In everyday vision, photons flood your rod cells, setting off a chemical cascade that eventually translates into an electrical message about

what you saw. But in lab tests, higher than normal levels of bicarbonate, allow the

rods to recover from that photon response, 30% faster. A 30%

higher refresh rate essentially,

meaning your ability to detect movement would improve.

The downside, this rapid reset of the rod cells

means they're less sensitive to light.

If you're sitting in darkness and you turned on a steady light,

you might now take brighter light for you to say,

I can see that. Study author Clint McKeino of the Massachusetts Eye and Ear Infirmary in Harvard

med school.

Or if the light's already on, it would take a larger increment in the intensity for you to say,

okay, it looks brighter now now the results are in the

Journal of Biological Chemistry. McIno says that heavy exercise which causes a

boost in CO2 might even alter the body's but carbonate enough to trigger a measurable effect on the eye.

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