Wearing cycling shorts whilst running - why?

Back when I used to play a lot of football and go running, I’d always wear a pair of lycra cycling shorts underneath whatever else I was wearing. I’ve forgotten the motivation for doing this - it’s certainly comfortable, and many pro-footballers do it, but beyond that are there any good reasons for wearing a lycra-like short whilst running?

Keep the “boys” nice and tight. Don’t want them bouncing around too much. Might help avoid chaffing too.

Some women do it because their legs rub together at the top of their thighs. Or, as smellmywort said, to avoid chafing.

They’re also lighter and dry faster than cotton. Which reduces chafing.

Are you sure you mean bicycle shorts and not generic lycra shorts?

Bicycle shorts have all sorts of whacky padding which make sense if your nads are jammed onto a hard leather seat, but just gets in the way if you’re not on two wheels.

I wear skin tight lycra ‘compression shorts’ to keep my ass fat (which is right under the skin) from bouncing. Running with butt support is quite uncomfortable for me.

I don’t need to do this now, for some reason, but back when I was a runner in high school, I would get severe chaffing/friction burns at the up inside of my thigh, near the boys. The lycra shorts would help with this.

Not so much for the padding as to wick away sweat to avoid chaffing…sweat can’t evaporate where it is blocked by the seat.

IIRC some very muscular football running backs would wear women’s girdles while playing to prevent hamstring injuries as they kept the hamstring muscle from flopping around which (apparently) contributed to potential injuries. Not sure if bike shorts would do the same thing.

There are also products like BodyGlide that help avoid chafing. Good for the nips too.

Actually, it’s for the padding. If you ride for sport, the seats are harder and smaller, and you need the padding for rides longer then about an hour.

The padding can also cause rashes, however, as they hold the sweat, which sits against you skin and can irritate it.

Anyways, back to the subject at hand - I assume it’s as stated above. Compression and/or to prevent friction rashes.

Running shorts are not now made of cotton. They all are made of synthetic material, such as polyester or lycra, which, not only are lighter than cotton, but wick away moisture. In cooler weather, many runners wear running tights, which keep them warm yet are not heavy. I’ve known runners wearing tights even in warmer temps on the same basis that swimmers shave their legs and wear tight trunks: less resistance.

*I meant without butt support

Back in the day, I wore bicycle shorts. They didn’t have padding – just a chamois liner. The saddle on a performance bicycle isn’t supposed to be padded, and padded shorts would detract from efficiency.

Thks for the replies. I meant to refer to lycra shorts in general, rather than cycling shorts with a chammy. I recollect hearing about the support they offer, not just to the sack, but to hamstrings etc. Keep the muscles warm as well - wondered if there was anything substantial to this.

I found this article, which delves into some of the claims of compression gear and concludes:

The marketing wizards at 2XU answer your question of why people wear these sorts of things:
IMPROVED RECOVERY
IMPROVED CIRCULATION
REDUCED FATIGUE
HEIGHTENED AGILITY
REDUCED DAMAGE

If bicycles were powered by your butt bouncing up and down on the seat, yes I could see how padded shorts would reduce your efficiency. Since they are not, care to explain the mechanics on how padded shorts reduce cycling efficiency?

The saddle is narrow and unpadded to allow the greatest possible freedom of movement to the thighs. To add padding to one’s shorts is to sabotage this “engineering” (in other words, you’re spending energy compressing your padding that’s better pushing the pedals). Granted, most people would notice no difference, but “back in the day,” specialty bicycle clothing was the province of racers and a handful of enthusiasts (who, incidentally, had pretty huge thighs). Somewhat later in “the day,” I myself wore padded bicycling underwear under my unlined lycra pants when on long-ish rides – but then, I wasn’t a high-performance rider, just a guy in shape.

**Nametag **is correct - it also affects wind resistance. You’d never see the guys in the Tour - or any professional cycling circuit - wearing padded shorts.

You’re kidding right? It’s impossible to find a good picutre of a cyclist’s arse, but seethis picture. See that bulge in his crotch? It’s padding. Every pro cyclist wears padded shorts. Even if not for the reason that if there was no padding your meat and tackle would be on display for all and sundry.