for, well, boxers.

This underwear was loose around the legs,

giving boxers the freedom that they needed

to move around the ring.

Then, about a decade later,

briefs came into the world,

offering a sleeker, tighter-fitting option

and sparking a now-classic question.

Boxers or briefs?

And as it turns out, there may be a clear winner after all.

You heard that right,

wearing tight underwear can lower your sperm count.

Turns out if underwear is too tight,

it pushes the testicles closer to the body,

increasing their temperature in the process,

and that's bad news for the sperm inside.

You see, a man's sperm production is at its best

when his testicles are cooler

than his core body temperature.

Two to 4 degrees Celsius cooler, to be exact.

That's why the testes hang down

away from the body

for most mammals.

So when you wear tight underwear,

the resulting increase in temperature can damage the sperm

and potentially your fertility as well.

Scientists have been studying the link

between body heat and fertility for years.

Several studies show that men who work under hot conditions,

like bakers and ceramic oven operators,

are more likely to have fertility issues

than men who work cooler jobs.

But ovens, of course,

are much, much warmer than the human body.

So it wasn't until recently

that researchers discovered that, yes,

even small increases in temperature

from wearing tight underwear can cause problems.

In 2018, Harvard researchers released

the largest study on the subject to date.

They analyzed 656 men

seeking treatment at fertility centers

and recorded their daily underwear preference,

boxers or nonboxers, like briefs and Jockeys.

Sure enough, men who wore boxers had 33% more mobile sperm.

You know, the kind that can swim

and successfully fertilize an egg.

They also just had more sperm in general,

about 25% more in their collected samples.

But researchers also found something they weren't expecting.

Men in the nonboxers group had higher levels

of something called a follicle-stimulating hormone, or FSH.

FSH is released by the pituitary gland

to help boost sperm production in the testes.

So researchers think that an increase in FSH levels

could be the body's way of compensating

for low sperm production.

And while both groups of men

still had plenty of sperm needed to conceive a child,

researchers found that tight underwear

could jeopardize the fertility of men

who already suffer from low sperm counts.

Luckily, young, healthy men

tend to produce sperm continuously.

So it's possible to reverse damage

caused by wearing tight underwear

simply by switching to a less confining option.