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Decades ago, fitness consisted of two workouts: all-out, all the time; and “LSD”—long, slow distance training. Then fitness went high-tech. Personal-metrics devices from companies like Polar, Garmin, Nike, and others became a billion-dollar industry. Nutrition took wild turns, too. Rocky-style raw-egg shakes were replaced by beet juice smoothies as the (legal) performance-enhancing drug of choice. At last, science-based training had replaced superstition.

But along with the research came the meaningless buzzwords, pseudo-science peddlers, and gimmicks (Shake Weight, anyone?). What’s more, every age-grouper suddenly seemed to be an expert in exercise physiology. We’ve been following this stuff for a long time (37 years, to be exact), and we know how challenging it is to ferret out rules that actually work. Here are the 12 you need to know—and apply—starting now. Welcome to the new rules of fitness.

#1: Stop Overdosing on Vitamins and Supplements

The multivitamin industry is widespread and lucrative—but it’s always been difficult to demonstrate that taking supplements offers a real benefit, says Thomas Sherman, an associate professor of pharmacology and physiology at Georgetown’s Medical Center. For years, multivitamins were considered a low-level insurance policy and performance upgrade. Pop one if you’re worried you’re not getting the right nutrients, and you’ll be healthier—perhaps even stronger and faster. The problem: “There is a lot of theory, but no real data,” Dr. Sherman says. To make matters worse, a string of recent studies suggests that antioxidants get in the way of training adaptations, making them detrimental to performance.

#2: Go the F*ck to Sleep

Somewhere along the way, Americans, with their Puritan work ethic, decided sleep was a bad thing. But if you’re an athlete (or, hell, just a human), you need to take sleeping as seriously as you do training and eating. “In the past, many athletes would continue to train well past their body’s physical ability,” says Michael Breus, Ph.D., author of��The Sleep Doctor’s Diet Plan: Lose Weight Through Better Sleep. Less sleep theoretically means more time for PRs, but your body doesn’t see it that way. Performance rests on a good night’s sleep, when your body chemistry shifts, and all kinds of beneficial bodily repair gets underway.

Need proof? In a recent study, 11 Stanford varsity basketball players maintained their sleep schedules for 2 to 4 weeks then slept as much as possible at night for 5 to 7 weeks—aiming for about 10 hours. Researchers measured timed sprints, shooting accuracy, and reaction times after every practice, and levels of daytime sleepiness, and mood throughout. The results: Athletes sprinted faster, shot more accurately, and felt better.��

#3: Get Away from Your Chair

You probably go above and beyond the American Heart Association’s guidelines for 30 minutes of moderate exercise five days a week, but that may not be enough if you’re planted in a seat all day. That’s according to a new study that found an hour of sedentary behavior increased people’s risk of being unable to perform basic functions—like doing household chores—by 46 percent even if they still met the exercise requirements. “We don’t like to be idle,” says Allen Lim, Ph.D., founder of .

There are ways to lessen the blow, though—without having to actually train more. Research by James Levine, Ph.D., M.D. of the Mayo Clinic found small movements throughout the day—fidgeting, walks, or getting up to go talk to someone instead of hitting send on an email—can work toward counteracting the effects of sitting.

#4: Train Specific to Your Sport

Ten thousand hours of practice may not make you an expert—if you’re training at the wrong intensity. A recent study in the that studied Olympic medal-winning speed skaters and their fitness regimes reached an interesting conclusion: While performance increased throughout the years, there was no increase in training or skating hours. The shift, instead, was to polarize training—training at a very high intensity in this case.

“It’s important to ask yourself what you’re training for,” says Lim. “Speed skaters do short, high-intensity events, so it makes sense that they train specifically for that,” he adds. But if you’re training for a century—and need the fitness to survive six hours in the saddle—then you need to put in that time. After a disappointing showing at the 2010 Tour de France, Bradley Wiggins revamped his training to meet the exact demands of the 2012 Tour. Forgoing many of the early season races, Wiggins spent time on the island Tenerife, preparing for the races’s high-altitude summits. And his approach paid off: In 2012, he became the first British cyclist to win the race.

#5: Quit Flexing in the Mirror

The media has driven home the same message for years: If you look good with your shirt off, you’re healthy. The truth? “You can be protected from disease if you exercise—even if you are over eating and gaining weight. Unfit and skinny may be worse than fit and fat,” says Lim.

The new mantra is simple: “Beat yourself up over whether or not you are getting enough daily physical activity not over how you look,” says Lim. “Thin man syndrome”—or being skinny, but lacking muscle and having a high percentage of body fat—can put you at an increased risk for cardiovascular disease, says Stacy Sims, MSc, Ph,D., co-founder of . Carrying a little extra weight—so long as you have the muscle—won’t negatively impact your hormone profile or appetite like being scrawny, she says. Fit versus fat is an ongoing debate—and the jury’s still out on how much fat you can have without being “unhealthy.” The bottom line: Lean muscle is critical for overall health—even if the mirror isn’t reflecting those results yet.

#6: Be a Little Salty��

“Sweat sodium is much more variable than we thought with a stronger genetic link than previously known,” says Lim. What he means: When you sweat and lose salt, there’s huge variability between you and the guy next to you. “Someone can lose 200 milligrams (mg) of sodium per liter of sweat an hour and someone else could lose 2,000 mg per liter of sweat per hour,” he says. That’s like having a shoe store and needing to stock size 2 to 200 to accommodate everyone.

The practical application of this is listening to your body—and not assuming that salt is always so bad for you. “Our own mechanism for taste can be affected by how much you salt you lose,” he says. So if you’re athletic, you sweat, and you crave salt, eat salt,” Lim says. The “salt is unhealthy” mantra probably doesn’t apply if you workout frequently.

#7: Stop Playing the Age Card

There’s a common misconception about aging that needs to be laid to rest—and it’s that you get old, and you lose your ability to move. Some research suggests that you lose 8 percent of your muscle mass each decade after age 40 and muscle loss increases significantly after age 75. But in a recent University of Pittsburgh study of 40 competitive athletes ages 40 to 81 who worked out four to five days a week, researchers found that athletes in their 70s and 80s had similar thigh muscle mass as those in their 40s. The 40-somethings were also just about as strong as the athletes in their 60s.

Those results make sense when you look at people like Kelly Slater—the 42-year-old pro surfer, the oldest to ever win the Surfing World Championship—or American cyclist Chris Horner, who last fall became the oldest��champion of one of cycling’s three-week grand tours. Though a calendar would tell you their time has passed, a lifestyle of movement has kept them in the game.��

“As you get older, you simply have to take training in a different approach,” says Sims. Plyometric work and pure strength workouts help maintain neuromuscular connections and muscle mass and help generate speed and power.”��

#8: Minimize the Junk Miles

Give those long, slow jogs a break. According to a 2008 study in the��, one and a half hours a week of high-intensity intervals will improve arterial structure and function just as much as five hours a week of lower-intensity workouts. Even more: When��highly��trained recreational cyclists reduced their distance��from 200km per week, swapping it with 12 x 30s sprints a few times a week and four minute intervals, their performance improved.

With intensity, your body learns to recognize stress, and overcome it without taking hours out of your day. Being more responsive to immediate stress increases your aerobic capacity, decreases bad cholesterol, works to build lean mass—much more than a long, slow fat-burning workout can offer, says Sims.

#9: Experiment on Yourself

“There’s a tendency to say, ‘This is the average result, so this is the result,’” says Lim. But at the end of the day, we are our own experiment, Lim adds. Take research that looks at how different athletes respond to variables like altitude. In a recent Australian study of 16 highly trained runners with maximal aerobic power who simulated “live high, train low,” . Some people have no response at all—others have a massive response.

Another noteworthy study that discovered great variability in results was the A to Z study, which tested people on four different kinds of diets. While statistically, all diets yielded similar weight loss after a year, a closer look at the data reveals incredible variation. “People who were outliers in one group did better on a different kind of a diet,” Lim explains. When it comes to diet performance, it’s—again—so particular. What works for you may not work for everyone else—and vice versa.��

#10: Embrace a New Era of Hydration

In 1965, when Gatorade was introduced to the sidelines of a University of Florida football game, a craze was born. “The typical mindset is to replace carbs and electrolytes,” says Sims. “But the bottom line is that anything’s that over a 4 percent carbohydrate solution can dehydrate.” Why? Water goes from a low concentration to a higher concentration, she explains. So drinks that are too sugary can force your body to move water out of your blood and muscles instead of into them, she says.

Hydration should be about just that: Hydration. And as research continues, low-concentration approaches to hydration like Nuun, SOS, and Sims’ own OSMO, have become popular.

#11: Workout Before Breakfast

Breakfast may be the most important meal of the day, but if you’re waking up to a fast sweat, it can wait. In a recent study, two groups performed a high-intensity workout before or after eating the same morning meal. The results? The group that sweat before eating lost more weight, says Lim.

One reason: When you wake up, you have plenty of fuel stored from the night for a short workout—your blood glucose levels are stable and your body is in fasting mode. “Your workout stimulates muscle sensitivity to insulin, so when you eat, most of the food goes back into muscle rather than fat,” Lim says.

#12: Train Your Brain��

Ten years ago, hardly anyone trained their minds like they trained their bodies. Now, just about every serious athlete practices visualization or specific relaxation techniques—arousal control or pre-performance routines. “Everyone on the world class stage is closely linked when it comes to physical capabilities and technical proficiencies,” says Michael Gervais, one of the best sports psychologist’s in the business who coaches the likes of Olympian Kerri Walsh and professional daredevil Felix Baumgartner.

That’s why the U.S. Olympic Committee staffs five full-time sports psychologists: In order to win a gold, you must have a mind-body connection that’s strong enough to stop worrying about the crowd, failure—or arguably worse, brimming success. Take Team USA Swimmer Eric Shanteau: After receiving a cancer diagnosis weeks before the Beijing Olympics, he spent days at a facility near his home undergoing brain training simulations for focus. While Shanteau didn’t medal at Beijing, he set a personal best in the 200-meter breaststroke and went on to earn a gold medal four years later at the 2012 London Olympics.