A workout is supposed to make a person feel energized and strong. It’s expected that there may be some fatigue or soreness after exercising, but prolonged sluggishness or feeling ill after working out could each be a red flag indicating a person is overdoing it.

The terms “exercise fatigue” and “overtraining” may be used interchangeably. The Hospital for Special Surgery says exercise fatigue occurs when athletes ignore signs of overreaching and continue to engage in workouts. It may cause a viscous cycle where overtraining impacts performance, and then a person perceives this weakness or poor performance as a signal that they need to train even harder, which only compromises the body further.

Exercise fatigue can occur when participating in any type of sports or fitness program. The 2022 edition of the National Academy of Sports Medicin’s “NASM Essentials of Personal Fitness Training” defines overtraining syndrome as “a condition in which an athlete or fitness client experiences fatigue, declining performance and burnout.” Some people do not realize they have overtrained, but the following signs suggest exercise fatigue is setting in.

Unusual muscle soreness after workouts that persists with continued training.

A plateau or decline in fitness performance.

Excessive sweating or overheating while working out.

Unusual feelings of heaviness or stiffness in muscles.

Delays in recovery from training.

Thoughts of skipping workout sessions, or at the least cutting them short.

Persistent exhaustion or low energy throughout the day.

A drop in self-confidence.

A lack of enjoyment of previous hobbies or interests.

New problems with sleeping, including poor sleep quality.

Unplanned or undesired weight loss or weight gain.

Digestive issues, including loss of appetite, constipation or diarrhea.

Repeated bouts of illness, such as colds and upper respiratory infections.

Increased blood pressure and at-rest heart rate.

The National Academy of Sports Medicine says individuals can log their workouts and be mindful of body changes to determine if they are experiencing exercise fatigue. However, there is no test to diagnose overtraining. Taking time off from workouts, fueling the body with healthy foods, and getting sufficient sleep is often advised for people confronting exercise fatigue.