When health journalist Christie Aschwanden was traveling the world as a competitive ski racer in the 1990s and 2000s, recovery between training sessions basically meant doing nothing — taking a day to sleep in or lie around with a good book.

About a decade ago, she noticed something had changed: recovery became a thing athletes actively performed — with foam rollers, cryotherapy, or cupping — as part of their training routines. These recovery tools were heavily marketed to athletes, including amateur ones, as a means to boost performance and bust muscle aches.

In a new book, Good to Go: What the Athlete in All of Us Can Learn from the Strange Science of Recovery, Aschwanden walks through all the biggest recovery fads of the past decade — and exposes the shoddy science backing most of them.

It’s an intelligent and entertaining tour of fitness research for anyone who exercises, with clear advice on what actually works to aid recovery. I won’t give away all the juicy details in the book, but I did ask Aschwanden to walk me through three of the most dubious recovery methods she uncovered. Here’s what she told me.

1) Athletes should be more concerned about overhydration than dehydration

There’s a lot of fear about dehydration during exercise, and the need to replenish fluids with electrolyte-rich beverages. Big beverage companies (like Pepsi) peddle sports drinks (such as Gatorade) with the promise that they’ll replace the fluids we lose via sweat and help us “tackle recovery.” But Aschwanden finds there’s just no science to support those claims.

“We’ve created this situation where people are told they need to drink early and often” during exercise, she told me. “We’re taught we can’t trust our bodies and that it’s not enough to listen to your thirst.” But it turns out thirst is a great indicator of dehydration.

“You really can use [thirst] to know whether it’s time to drink or not,” she said. And sports drinks aren’t necessary in most cases. “The exception might be if you’re doing an endurance event — it might be helpful to get some calories. But you have to be exercising for over an hour, and most of us aren’t exercising like that.”

Instead, athletes should be more concerned about overhydration — when you take in so much fluid that sodium concentrations in the blood drop to dangerously low levels. “There’s never been a case of a runner dying of dehydration on a marathon course,” Aschwanden writes, “but since 1993, at least five marathoners have died from hyponatremia [overhydration] they developed during a race.” (It’s difficult to say precisely how much water is too much, since it depends on a person’s health status, but the Merck medical manual suggests a healthy young adult would have to drink more than 6 gallons — 22 liters — of water a day on a regular basis to run into trouble.)

2) Cold therapy after exercising can hamper recovery

From icing sore muscles to dipping your entire achy body into a cryotherapy chamber (like this one featured on Dr. Oz), cold has become synonymous with recovery. Yet according to Aschwanden’s research, cold exposure after exercise can actually impair the body’s ability to heal.

Here’s how to think about it: When you challenge your muscles during exercise, you create tiny tears in your muscle fibers. “Your body responds to this injury by mobilizing a cleanup crew to remove damaged tissues and rebuild the muscles,” she writes. That process involves inflammation, and it heals and makes your muscles grow stronger. But icing sore muscles actually hampers inflammation.

“When you reduce that process [by cooling the muscles], you’re impeding your training effects and reducing the benefit you’ll get from the exercise,” Aschwanden told me.

(Side note: The American Academy of Orthopedic Surgeons still endorses icing for soft tissue injuries, like sprains and strains, but there’s some disagreement about whether ice is truly helpful.)

So why do many people use cold for recovery, anyway? Aschwanden chalks it up to the placebo effect. “A lot of [recovery tools] work via the placebo effect, and there’s good evidence that placebos that are painful are more effective than placebos that aren’t painful,” she says. “So the cold makes it a really good placebo.”

3) There’s no good evidence that cupping therapy works

When Michael Phelps competed in the 2016 Brazil Summer Olympics, he had big, circle-shaped bruises spread across his back. He got the marks from cupping therapy, the traditional Eastern medicine practice that some athletes now use to try to speed recovery and soothe sore muscles.

Cupping involves pressing plastic or glass cups against the body and using them to suck up the skin, breaking capillaries. A vacuum is created through a mechanical pump or by heating the cups.

But again, there’s no good evidence that cupping is doing anything helpful. “You’re basically giving yourself a bruise,” said Aschwanden.

Vox’s Brian Resnick also dove into the science and came to a similar conclusion: “The practice isn’t harmful — but the studies on it are too weak to come to solid conclusions about whether it really works,” he wrote. “There’s no good data to prove cupping helps, but, likewise, there isn’t data to disprove it either. Meanwhile, you have celebrity endorsements to propel the fad forward.”

So what actually works to speed recovery?

One of the most fascinating findings in Good to Go is that soreness or injury from exercise can be exacerbated by psychological stress. “The psychological component of recovery is underappreciated among athletes,” Aschwanden said, pointing to studies of college football players who had a higher risk of injury during stressful periods of the academic calendar. But helping athletes learn to be mindful about their stress, and cope and respond to stressors, can go a long way.

Aschwanden says she realized she often failed to listen to her body during training and when it was telling her to rest, which only raised her risk of injury and limited her performance.

So, she advises, any good recovery program should include elements that focus on mindfulness and easing psychological stress. That might involve meditation, yoga, or listening to music. For Aschwanden, a float tank did the trick. Floating, another popular form of recovery, involves relaxing in an Epsom salt solution in a quiet room or pod.

According to Aschwanden, it wasn’t the water that healed her but the hour in silence that helped her meditate, and calm her mind and body. “True recovery requires nurturing a recovery mindset,” she writes, “one that fully honors the body’s need to recuperate and senses when it’s time to chill.”