Make no mistake about it, regular exercise is probably the biggest factor in living a long and healthy life (not discounting healthy eating). But with boot camp-style workouts, triathlons, marathons and even ultra-marathons becoming increasingly popular, more athletes — both professionals and weekend warriors — are at risk for overtraining.

Here are several ways to tell that you’re working out too hard. The first five are acute, short-term symptoms, while the second group comprises more uncommon long-term consequences of overtraining.

Here are the obvious ones:

  • Dizziness
  • Trouble breathing or maintaining a conversation
  • Disorientation, foggy mental processing
  • Rapid heart beat
  • Dehydration
Dr. Guy Hornsby, director of the human performance lab at West Virginia University, adds another obvious sign that you’re working out too hard: injury.

“Many of us have gone out to the track and tried to sprint without properly training and have developed an acute musculoskeletal injury,” says Hornsby, who adds that when people work out in competitive, high-endurance environments like Crossfit and beach boot camps, many people may not pay attention to signs that they are overtraining or improperly executing movements.

“Take an Olympic lift like snatches,” he says. “The form may be fine for the first two or three repetitions, but when performed for an extended period of time, the nervous system begins to shut down, and if you keep going beyond your threshold, you’re setting yourself up for an injury like a long-term stress fracture.”

Here are some other not-so-obvious signs that you’re training too hard:

Disrupted or skipped menstrual cycles: An article in Journal of Family Practice suggests that excessive exercise could be one cause of secondary amenorrhea, which occurs when a woman who has been having normal menstrual cycles stops getting her periods for six months or longer.

Myocardial fibrosis: A thickening of the heart valves may occur with excessive training. A study published in the Mayo Clinic Proceedings says “long-term excessive endurance exercise may induce pathologic structural remodeling of the heart and large arteries.” If you don’t have a medical degree, it may seem innocuous — or even beneficial — if your heart and arteries go through some restructuring. Could it be that this restructuring improves blood flow? According to the study, “chronic training for and competing in extreme endurance events such as marathons, ultra-marathons, ironman distance triathlons, and very long-distance bicycle races, can cause … after months and years, patchy myocardial fibrosis. … Additionally, long-term excessive sustained exercise may be associated with coronary artery calcification, diastolic dysfunction and large-artery wall stiffening.” Even without a medical degree, you know this sounds bad. But endurance athletes can find solace in this: the study’s authors admit that endurance athletes generally have low mortality rates and excellent functional capacity.

Withdrawal symptoms: Excessive exercise can be addictive, and according to a study in Behavioral Neuroscience, lab rats that were given a drug that produces withdrawal in heroin addicts — naloxone — went into withdrawal after running excessively in exercise wheels. Rats that ran the hardest had the most severe withdrawal symptoms. The study’s authors argue that excessive running causes physiological responses in the brain’s reward system, similar to those associated with drug-taking behavior.

Hormonal imbalances: In addition to disrupting the female sex hormones and adversely affecting menstruation, training too hard can produce excess levels of cortisol, the so-called “stress hormone.” One study, published in the Journal of Strength and Conditioning Research, concluded, “Significant increases in salivary cortisol concentration occur in response only to long-duration, high-intensity exercise.” Excessive cortisol levels may lead to a decrease in testosterone and a weakened immune system, to name a couple of adverse reactions.

Immune function: Speaking of a weakened immune system, a study in the Journal of Applied Physiology concluded, “Post[-]exercise immune function depression is most pronounced when the exercise is continuous, prolonged [greater than an hour and a half], of moderate to high intensity (55–75 percent maximum oxygen uptake), and performed without food intake. Periods of intensified training (overreaching) lasting one [week] or more can result in longer-lasting immune dysfunction.”

Not seeing any of the signs above? If you’re experiencing any of the following remaining five symptoms, you may also be exercising too hard:

  • Moody, easily agitated or depressed
  • Apathetic, lethargic and averse to competition
  • Decreased appetite accompanied by weight loss, particularly muscle mass
  • Frequent sickness or flu-like symptoms
Last but not least, the #1 sign you’re overtraining

“Overtraining is marked by cumulative exhaustion that persists even after recovery periods,” says Dr. Mark Jenkins, associate team physician for Rice University and a contributor to Runner Triathlete News. If you’re too beat to function at work or finish those chores around the house, you may have overdone it.

How much is too much?

Everybody is different, but the American Heart Association currently recommends that adults stick with 150 minutes per week of moderate exercise or 75 minutes a week of vigorous activity. Stay within that zone and you’ll likely avoid any symptoms of overtraining.

Judd Handler is a health writer in Encinitas, Calif.

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