We are always looking for new ways to feel, look and live better. And our approach to fitness has evolved along with our culture, from the charmingly simple Hula-Hoop of the 1950s to the fuzzy leg warmers of the 1980s to today's data-centric activity trackers.
Here are some of the popular fitness trends that have caught on (and, in some cases, held on) over the years.
The hoop is one of humanity's oldest tools for fun and fitness -- the ancient Greeks and Egyptians were among the first to use hoops to play games and hone agility -- but most think of the toy as an iconic symbol of the wholesome "Happy Days" era of the 1950s, when front lawns across America were dotted with fresh-faced tweens swiveling colorful plastic rings around their hips, legs and arms.
After executives at the American toy company Wham-O heard that Australian kids were fashioning hoops out of bamboo for exercise, the company decided to make its own version -- and sold more than 25 million Hula-Hoops in a matter of months.
Although the fad flamed out fast, hoops have continued to be used as whimsical, but effective, exercise tools.
Weighted "fitness hoops" promise to help burn calories and slim your waistline. And reconnecting with your inner child comes with benefits: Just 30 minutes of hip-swiveling action burns about 165 calories for a woman and about 200 calories for a man, according to the Mayo Clinic. (Alas, this doesn't apply to those of us who would spend most of that time retrieving the fallen hoop from the floor.)
These early exercise machines featured a broad strap meant to be looped around the waist (or rear, or thighs, or any part of your body that "embarrasses you most," as one ad helpfully noted).
Turn the machine on, and it vibrated your fat away. The ladies and gentlemen who used this contraption didn't even have to break an unsightly sweat -- they could simply relax while the machine worked its magic.
Except the magic didn't actually work.
Ads in the 1950s and '60s pledged that the machine's vibrations would break down fat so that the body could simply flush it away.
Unfortunately, scientists report that this is not at all how bodies work, and after a while, people started to notice that their flesh wasn't actually getting jiggled into nonexistence.
The belts fell out of favor, but descendants of the original machine are still around, lurking in late-night infomercials and department stores.
When fitness master Jack LaLanne opened what he claimed was the first modern gym -- the Jack LaLanne Physical Culture Studio -- in the mid-1930s, people were aghast: He was charging people just to exercise?
It was the beginning of a trend that wouldn't catch on in earnest for several decades. Although there were men's health clubs, YMCAs and boxing clubs in the 1930s, those were private or specialized -- and so was the first Gold's Gym, opened in 1965 by Joe Gold in Venice, California.The facility quickly became known as the "mecca of bodybuilding," soaring to international prominence in 1977 after it was featured in "Pumping Iron," a documentary starring bodybuilders Arnold Schwarzenegger and Lou Ferrigno (aka the Incredible Hulk).
But gyms weren't just for oiled-up muscle men for long.
The concept of communal exercise began to spread, and Gold's Gym expanded beyond the bodybuilding crowd as it opened new locations in the '80s.
A slew of corporate gym chains got in on the action (24 Hour Fitness -- back then it was known as 24 Hour Nautilus -- and LA Fitness were among the first), and gyms soon became standard fitness fare for both men and women.
In 1969, as people searched for a way to disguise the tedium of exercise in a fun package, a perky dance instructor named Judi Sheppard Missett offered a solution: Jazzercise, a high-octane mash-up of jazz dance, kickboxing, ballet, Pilates and yoga.
It was the dawn of choreographed exercise set to music, and (mostly female) fitness aficionados were psyched. They bought the tapes, took the classes and rocked out to Wham! and Cyndi Lauper in headbands and brightly colored tights.
It's no longer the No. 1 exercise du jour, but Jazzercise is still alive and well with more than 8,300 franchises worldwide.
"You think you know us, but you don't," the company website says -- meaning its fans aren't sporting leopard-print leotards anymore, it swears.
Jazzercise also set the stage for the next wave of dancing-as-fitness trends.
Colombian dance instructor Alberto Perez first used a mix of salsa and merengue to choreograph his aerobics class in the '90s and quickly gained a devoted following.
He called his creation "Rumba" -- derived from a Spanish word for party -- which later became "Zumba," aka one of the biggest workout trends in modern memory, with classes taught at more than 200,000 locations around the world.
You know Jane Fonda and her spandex bodysuits. You know Richard Simmons and his frizzy reddish hair. But what about Kenneth Cooper?
In the late 1960s, the military physician coined the term "aerobics" to describe a regimen he created to prevent coronary artery disease.
After Cooper published a book on the subject, the idea took off in gyms and on VCRs across the country: dance aerobics, step aerobics, sport aerobics, even water aerobics.
Numerous fitness personalities seized on the trend, but the king and queen of aerobics were undoubtedly Simmons, the oft-parodied fitness guru who helped people "party off the pounds," and Fonda, the actress-turned-exercise-maven who sold more than 17 million copies of workout tapes showcasing her famous abs, buns and thighs.
Much like the Jazzercise trend of the '70s and '80s, the goals were straightforward: to be trim and fit, to have fun and (we assume) to emulate Fonda's inexplicable ability to look great even while sweating profusely into a voluminous, heavily hairsprayed coiffure.
If you were alive and anywhere near a television in the '80s, you remember the infomercials: There was Suzanne Somers cheerily touting her Thighmaster. ("Great legs!" one guy shouts at her, because people still thought catcalls were compliments back then.) There was the frazzled, out-of-shape businessman who "gets on track" with his NordicTrack exercise machine. (He'll catch that bus next time!) There was the taut, muscled Bowflex man (sans shirt, always).
These attractive bodies could be yours, the infomercials said, if you bought this equipment, put it in your home and actually used it for exercise.
In an era when everyone was just so busy, the appeal was convenience: You can put it right in your living room! You can watch TV while you work out! You can use the Thighmaster while reading a magazine!
These were the machines of fleeting aspirations and fading New Year's resolutions.
"So it's easy to squeeze, squeeze your way to shapely hips and thighs!" Somers promised. We're willing to bet that most of those Thighmasters have since been squeezed, squeezed into forgotten boxes in dusty basements.
Charismatic karate champ Billy Blanks created his fast-paced cardio workout by combining a little of everything: martial arts, boxing, dance moves and pulsating hip-hop beats.
He taught his first classes in his Los Angeles garage in the '80s, and from there, the workout took off fast: Blanks opened a popular studio, taught Paula Abdul how to keep her abs tight, spent a week recording exercise instructions with Oprah in the Bahamas and suddenly, everyone you knew was talking about Tae Bo.
The infomercials, replete with beautiful people punching their way to rock-hard bods, were convincing.
"Millions of people are losing weight, getting fit and really having fun with Tae Bo!" gushed champion swimmer Dara Torres in one ad. The appeals worked: The company sold more than 500 million videos, created a high-intensity workout empire (Tae Bo isn't just a workout but a life mantra, the company insists) and inspired countless spinoffs.
Looking for a way to train for long-distance cycling races even in bad weather (and to stay home while his wife was pregnant), South African cyclist Johnny Goldberg made his first stationary bike by hand in 1989.
After he started teaching classes for handfuls of friends, the phenomenon began to spread, and Goldberg opened the first Spin Centre in Santa Monica in 1990. By the mid-'90s, he'd trademarked the name: spinning.
As with all popular fitness trends, others were eager to build on his success. Take a stationary bike, add soft candlelight and energetic beats, and you have SoulCycle, a chain of boutique exercise studios that have rapidly spread from California to cities across the East Coast.
Like yoga and Pilates, SoulCycle embraces the idea of exercise as a form of self-care; this is about not only getting your body fit, but balancing your mind and soul, too. Hence the promise of an "inspirational, meditative fitness experience."
The studios have lured thousands of devotees who are willing to fork over upwards of $34 per 45-minute class.
This isn't your typical workout. It's both competitive and communal, and it's intense.
Instructors at CrossFit locations (or "boxes") use whiteboards and timers to keep track of their clients' performances. The regimen emphasizes whole-body fitness and general preparedness (so you're ready when your cat gets stuck in a tree, or your kid gets stuck under a car, or the apocalypse comes, etc.) rather than specializing in one particular discipline.
To accomplish this, the CrossFit method involves a mix of gymnastics, weight lifting, pull-ups and calisthenics. Also, loud grunting.
To make complicated exercise combos more manageable, they're assigned female names: Elizabeth, Fran, Kelly, etc. "The Girls," as they're known, aren't especially friendly. "Cindy," for instance, is code for five pull-ups, 10 push-ups and 15 squats -- as many rounds as you can handle in a set amount of time.
More than any other fad out there, CrossFit -- which launched in Seattle in 2000 and has since spread to thousands of locations around the world -- elicits strong reactions. People tend to love it or hate it.
Detractors say the exercises are dangerous and the community is vaguely cultish. Die-hards laud CrossFit as life-changing, offering a great workout and a meaningful sense of community.
Founder Greg Glassman knows it may not be for everyone.
"It can kill you," he told the New York Times in 2005. "I've always been completely honest about that."
Wearable activity trackers
First came the modern pedometer, those clunky clip-on devices that counted steps and not much else. By the late '90s and early aughts, they were the sort of low-cost perk that companies loved to distribute to employees during annual fitness challenges.
But these rudimentary devices laid the groundwork for the sophisticated step-counters that followed: In 2009, the Fitbit broke into new territory with the goal to "change the way we move" -- mainly by making us acutely aware of how little we move.
Now wearable fitness trackers are everywhere: countless versions of the Fitbit, alongside a growing field of competitors, including Jawbone Up, the Nike FuelBand, the Apple Watch Sport and the Samsung Gear Fit2.
They're used both for solo and social exercise (apps allow friends to compete with one another) and can track not only your steps but also your heart rate, the number of calories you've burned and the quality of your sleep.
Welcome to the here and now, when every aspect of your life can be digitized and quantified!
Of course, all that data can create more than a little pressure.
We all know at least one person who would sooner walk around the living room in circles for an hour than miss hitting the standard goal of 10,000 daily steps.
This can be motivating or overwhelming -- and ironically, your heart-rate-monitoring fitness tracker might just be the first to tell you whether you're feeling a little too stressed.