Plenty of mystery still remains about the science of recovery: why some methods are supposed to work but don’t; why others feel like they work but have no scientific evidence to support them. And in today’s day and age, there’s no shortage of recovery methods. Just take a two-minute stroll through Instagram: For every shot of an NBA player giving a thumbs-up from an ice bath, you’ll see a soccer megastar with his legs in an oxygen chamber, an elite cycling team wired up to machines between mountain stages, or Dwayne Johnson fueling up after a gym session with enough food to feed an entire Little League team. In fact, you could make the case that Instagram is basically the world’s biggest advertisement forum for elixirs, magical garments, oxygen tents, acupuncture needles, weird bruises, powders, and all manner of wizardry aimed at one singular purpose: recovery.

To better understand recovery—the process by which your body rebuilds itself, your muscles reenergize, your hormones return to balance, and your central nervous system repairs—it’s important to distinguish between its two forms: passive and active.

Passive recovery, of course, occurs when your body is at rest— this includes sleep, diet, and applying compression. Active recovery, meanwhile, happens when your body is in motion: walking, light lifting, having a light go on a stationary bike.

Both forms are equally important for optimizing returns on your workout because they target different aspects of muscle regeneration. The easiest way to think of it is this: Passive recovery helps repair, while active recovery helps deliver the tools necessary to repair—or, as author and personal trainer Harley Pasternak describes it, active recovery “flushes out all the metabolic by-products and brings in nutrient-rich blood that helps heal muscles damaged in the gym.”

Active recovery is the crucial step guys skip. If you’ve just hit the weights hard or rowed for an hour, you can’t just hit the showers, call it a day, and expect your body to magically bounce back in peak form.

“The most effective form of recovery after intense or resistance exercise is active recovery,” Pasternak says. Aside from speeding nutrients and oxygen to damaged muscles, it also helps reduce muscle soreness, which is a good thing.

“Muscle soreness isn’t some badge of honor after an effective session,” says London-based trainer David Kingsbury, the man responsible for getting most of the movie X-Men, including Hugh Jackman, ripped. “Although it can and will be a by-product of training, that’s not what people should be shooting for.”

Of course, before you plan your recovery, you have to decide how often to work out and how to space out those sessions.

“If you come back to train too soon, your body will still be in the recovery phase, and the result will be poor performance in training,” says Keith Baar, professor of molecular exercise physiology at the University of California, Davis. And if you continue to train too frequently, ultimately you’ll experience diminishing returns. “In extreme cases,” he says, “you can even upset your hormonal balance.”

Former U.S. marathon runner Ryan Hall is an example of this. He believes that extreme training—he’d sprint seven miles down a 9,000-foot mountain, then run back up—led to the low testosterone levels that forced him to retire at 33.

So should you go hard three days a week? Five? Seven? What about heavy lifting and cardio?

Generally speaking, when it comes to strength training: “For most people who push themselves hard, two full-body workouts a week are enough, with two days of recovery in between,” Baar says. If you do split-body sessions, it’s two workouts per body part per week.

As for cardio, this type of exercise is crucial. Body-weight exercises—cycling, rowing, swimming—can be done more often than high-impact exercises like running, which cause significant mechanical, not just muscular, fatigue, Baar says. So for those, you’ll need a lower volume of work and even more days off in between to aid recovery.

For guys who want to work out every day, Baar says it’s perfectly all right. After all, elite athletes do it. The trick is to trade out hardcore lift days for occasional days of light cardio.

Finally, some good rules of thumb for endurance training: If you feel like crap—slightly sick or “off ”—or if your resting heart rate first thing in the morning is overly high, you’re not fully recovered. (For this reason we highly recommend using a fitness tracker.)

Bottom line: Find out what works for you. If you find you’re not seeing gains in the gym or on your runs, try adding another day of rest. That way you’ll be sure you’re training at the peak of your adaptation zone, when your body is repaired and ready for physiological gains, rather than when it’s in a recovery phase and still in need of repair.