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Everyone knows that exercise in general makes you happier, stronger and more energetic. We hear it ad nauseam, especially this time of year.

But what if fitness did the very opposite? In other words, if exercise brought on depression, injuries and lack of motivation. If that happens, what’s going on?

It’s called overtraining syndrome, said Sabrena Jo, a senior exercise scientist for the American Council on Exercise. “The first sign of overtraining is when the performance of the exercise starts decreasing,” she says. “Additional symptoms can be things like sleep disturbances, lack of motivation and moodiness.”

But don’t bag your recently kicked-off 2018 fitness routine just yet. Overtraining syndrome mostly happens to elite athletes, said Joe Park, an orthopedic surgeon with the University of Virginia Health System. But it can also strike dedicated amateur athletes, such as long-distance runners.

Park, who frequently treats Achilles tears and stress fractures of the feet, said we can all benefit from learning the warning signs of overtraining — such as pain.

Deciphering warning signs

“What I tell patients is to observe the trajectory of pain,” Park says. “Is it better today than it was last week?”

Sometimes with overtraining injuries related to running, the pain subsides during the run as the soft tissue, like muscles and tendons, loosens up during movement. So instead of examining the pain only during the activity, watch for it after the activity is done, he says.

If pain doesn’t subside in 10 to 14 days, something might be amiss and should be assessed by a doctor, he says.

Kendall Black, a Washington physical therapist, said another warning sign is when the pain subsides, but the area in question feels tight. “Take note if there is stiffness and a decrease in range of motion,” she says. “That can be a problem.”

The next level of warning signs — but please don’t feel compelled to wait that long — is when injuries start accumulating, Park said.

“The same person might have a hamstring tear, an Achilles tear and a stress fracture,” he says. “It might be time to ask if it’s really the right sport for you.”

Sleep disturbances, moodiness and lack of motivation may all be due to hormonal changes that can occur with overtraining. But the area is not well understood, Jo says.

“Cortisol — the stress hormone — plays a role, but it is not clear how.”

For female athletes, missed menstrual periods can also be a sign of overtraining and should not be taken lightly, Park said.

“That’s associated with bone-density loss and should be addressed. It’s not a small matter,” he said, noting that many female collegiate athletes he sees consider missed periods a relief rather than a problem.

Same with the other hormone-related symptoms. If you experience them while ramping up physical activity, keep an eye on them and seek out medical help if they persist, he says.

Prevention: Progression, balance, rest

One way to avoid symptoms of overtraining is to ramp up exercises gradually, the experts agree.

There are rules of progression whether the sport is endurance-focused or strength-focused, Jo said. “The rule of progression is to increase no more than 5 to 10 percent every few weeks whether it’s distance traveled, weight load or intensity,” she said.

If you fall behind on a training schedule by a week or more due to illness, there is no way to make that up, Black said. “You just have to skip it. You can’t just double up the next week.”

For example, say you’re in a run training program in preparation for a race and you didn’t do your assigned 10 miles one week. That doesn’t mean you should do 20 miles the next week.

Black said overtraining is often due to biomechanical imbalances. In runners, for example, these imbalances can include poor ankle range of motion and tightness or weakness throughout the back of the leg (posterior chain).

To avoid injury, then, make sure to both strengthen and stretch these muscles: gluteus, hamstrings, calves and Achilles.

Rest is also key in preventing overtraining symptoms. Rest includes good sleep (7-9 hours) and not repeating the same activity too often.

“You want give yourself 48 hours of rest between intense activities,” Jo said.

To circle back around, fitness should be about health first and foremost, Park said. If there are negative consequences such as moodiness, sleep disturbances, recurring injuries, decreased performance and other overtraining symptoms, you should ask yourself: “What are the health benefits of this?”

Because, he says, there is an ideal fitness routine for you out there — one that gives you the mental and physical rewards you seek without causing mental and physical pain.

“Wear and tear is not necessary. There is a sweet spot.”

Boston is a fitness trainer and freelance writer. She can be found at gabriellaboston.com.