(NEXSTAR) – Viewers tuning in to watch the Super Bowl on Sunday are likely to see plenty of brawn, brute strength and Budweiser Clydesdales. But the one thing that won’t be very visible? The players’ bare legs.

Since 1945, the NFL has mandated that players cover every inch of their legs, via some combination of pants, stockings or socks. The current rules, as outlined in the official NFL rulebook, state that leg coverings “must cover the entire area from the shoe to the bottom of the pants” and conform to the colors approved by the league.

“Skin exposure of the lower leg and ankle area due to improper wear of game socks and/or leg coverings is prohibited at all times throughout the game,” the rulebook states.

The only exception is for kickers who prefer to go barefoot, though there hasn’t been one of those in years.

That doesn’t mean some skin doesn’t peek through from time to time; it happens semi-frequently as the result of strenuous play, and it’s mostly tolerated. But failure to wear the appropriate leg coverings can — and has — resulted in fines.

In 2020, both JuJu Smith-Schuster and James Conner, both of the Pittsburgh Steelers, were fined $5,000 each for wearing stockings that “failed to cover” their lower legs, Sports Illustrated reported at the time. Frank Gore of the San Francisco 49ers, too, was issued a $10,500 fine in 2013 after wearing his socks far too low for the NFL’s liking, the Associated Press reported.

“I was wrong,” admitted Gore, who said he was too preoccupied with the game to pay attention to his socks. “Next time, I’ll do better.”

The NFL’s rulebook doesn’t provide much reasoning for its strict regulations, but safety is likely a factor. Leg coverings can help keep padding in place, provide support and prevent minor cuts and scrapes.

When the rule was instituted by then-NFL Commissioner Elmer Layden in 1945, however, the reasons allegedly had less to do with protection and more to do with aesthetics. Paul Lukas, a journalist who has specialized in sports uniforms for decades, has said on multiple occasions that Layden simply thought players had “unsightly legs.”

“This rule, still on the books, is why NFL players wear high socks while so many NCAA teams still play bare-legged,” Lukas previously wrote in his Uni-Watch column, which appeared on ESPN.com.

Another account shared by notable sports journalist and author Michael MacCambridge suggests Layden’s preoccupation with uniforms resulted in changes that were “largely cosmetic,” MacCambridge wrote in “America’s Game: The Epic Story of How Pro Football Captured a Nation.” (Layden also pushed through a rule that put different referees and judges in color-coded stripey outfits, MacCambridge noted.)

In any case, rules regarding leg coverings have remained on the books for nearly 80 years — meaning it’s not likely that viewers will see much leg at Super Bowl LVIII. Unless, of course, you count the long, lithe limbs of those Clydesdales, who surely aren’t abiding by the NFL rulebook.