A humorous factor occurred when Kameron Lennox revisited the music video for “Physical,” the 1981 pop megahit by Olivia Newton-John, who died on Monday.

For many of the video, Ms. Newton-John bounces round a health club, coaching and terrorizing out-of-shape males whereas carrying a white leotard. In true Eighties style, that leotard was layered over magenta leggings and below a robin’s-egg blue shirt, cinched with a belt and accessorized with thick socks and a sweatband.

As a Hollywood costume designer making ready to work on the Apple TV+ aerobics dramedy additionally known as “Physical,” starring Rose Byrne, Ms. Lennox noticed one thing she hadn’t seen when first watching the silly-sexy music video as a toddler.

The white leotard was “bunching in the groin area,” mentioned Ms. Lennox, who questioned whether or not it was a leotard or one constructed from a big T-shirt. “The bottom kind of looks like a diaper. It looks very homemade. It looks like the fashions, actually, that were about to happen.”

Thanks to the video, which coincided with the daybreak of MTV, “Physical” is remembered as a type of anthem of the aerobics period — regardless of lyrics which might be actually extra about copulation than cardio. Ms. Newton-John’s ensemble, too, has change into a sartorial image of that period — regardless of the rudimentary building of the leotard, which “definitely isn’t a workout outfit,” mentioned Ms. Lennox, who ended up taking her costume design inspiration from lesser-known aerobics instructors like Bess Motta.

In that sense, the “Physical” ensemble can also be an early instance of athleisure, a time period initially used to explain not train clothes however informal clothes that resembled train clothes.

As Ms. Newton-John defined in a video posted to her YouTube channel in December, the video “really helped kick off the entire fitness and aerobic craze of the time. It was the birth of the ’80s headband fashion craze. I should have started a headband and leg warmer company or made fitness videos. Jane Fonda beat me to it.”

It is true that nobody popularized aerobics and the ballet-inspired aesthetic of aerobics greater than Ms. Fonda, who opened a exercise studio in 1979 and revealed the best-selling “Jane Fonda’s Workout Book” in 1981. But “Physical” got here shut, taking an aerosol hairspray can to a health pattern — dance train — that was already poised to mild up the last decade. Not simply due to the dance-centric popular culture phenomena of the last decade (“Fame” in 1980, “Flashdance” in 1983,“Footloose” in 1984) however due to the re-emergence of a textile invented in 1958: Lycra, recognized generically as spandex.

Ms. Newton-John’s video “crystallized, in a short couple of minutes in visual form, what was happening across culture, manufacturing and consumer habits,” mentioned Sonnet Stanfill, senior curator of style on the Victoria and Albert Museum and editor of the 2013 guide “80s Fashion: From Club to Catwalk.”

In the Seventies, the textile business started utilizing Lycra — beforehand used as an alternative choice to rubber in girls’s girdles — to create wardrobes round train. And so girls attending lessons or watching movies from Jazzercise or Jane Fonda had been uncovered to “a whole wardrobe they could buy to feel great when they were exercising,” Ms. Stanfill mentioned, citing leotards and tights in a spread of “almost-violent color tones.” Running bras had been invented and near a decade had handed since Title IX elevated the participation of ladies in sports activities — the choices felt limitless.

“The last quarter of the 20th century in the U.S. was this kind of groundswell of celebrating the benefits of exercise and creating a wardrobe to go along with that,” she mentioned. “Oftentimes changes in fashion are, particularly for women, connected to moments when sport has changed lifestyle.”

In excessive style, the designer Azzedine Alaïa was additionally utilizing stretchy supplies for his body-conscious designs — giving girls a brand new alternative to point out off their toned our bodies, Ms. Stanfill continued.

While the Eighties cardio aesthetic largely feels dated right now, sure parts of that period have briefly come again into style. In the 2000s, earlier than the spectacular fall of American Apparel’s founder, the corporate had reintroduced vibrant leotards and glossy leggings, with advertising that was extra ironic and grungy-sexy than energetic and silly-sexy.

Yet using spandex by no means actually went away, readapting as fashionable yoga pants and leggings, then shapewear-as-outerwear. “The lasting legacy is that elasticated fiber that allows the body to move and can be quite flattering and form-fitting if you’re wanting to show off your figure,” Ms. Stanfill mentioned.

But as Ms. Lennox found whereas making an attempt to trace down Eighties leotards for the present “Physical,” many of the Lycra of that period “did not stand the test of time.” Still, the playful spirit of Ms. Newton-John’s “Physical” continues to encourage clothes and tradition (as seen within the Apple TV+ sequence or the 2020 Dua Lipa track, each of the identical identify).

When Outdoor Voices designed its first studio assortment in 2019, it was influenced by the leotard-over-leggings look (punctuated by ballet wraps and skirts) pioneered by Ms. Newton-John and Ms. Fonda, mentioned Ty Haney, the corporate’s founder and former chief govt.

But the inspiration went deeper: Outdoor Voices helped popularize athleisure within the 2010s by selling motion exterior of conventional train, favoring “doing things” (its tagline) over doing reps, blurring the traces between health club spandex and gardening spandex. Does a leotard should be a efficiency leotard, or can it’s one made for a wacky music video?

There was a “joyous perspective they brought to moving your body,” Ms. Haney mentioned of Ms. Newton-John and Ms. Fonda. “Freeing fitness from performance!”