When you head out for your daily run, with each stride you’re strengthening your quadriceps, your hamstrings and your upper calf muscles. The muscles on the sides of your hips, however, aren’t growing much.

If you have one sport you do regularly, like running, biking or tennis, and rarely do anything else, you run the risk of what’s known as muscle imbalance.

Imbalances happen when one muscle is significantly stronger than another. The two muscles can be on opposite sides of a joint or bone, or even across your body. Imbalances can emerge if, for example, a weightlifter overtrains her biceps and ignores her triceps, or an office worker spends 10 hours a day peering at his computer screen, leading to weak shoulder muscles. This can lead to pain, poor posture and even injury.

Ann Crowe, a physical therapist in Clayton, Missouri, who works primarily with runners and cyclists, said most of her clients’ foot, knee, hip and back pain can be traced to these imbalances.

Runners and cyclists typically focus on the cardiovascular benefits of their sports but neglect strength training, Crowe said. As a result, they often have weak glutes and strong quads.

Studies suggest that muscle imbalance can especially contribute to shoulder, lower back, elbow and wrist injuries in athletes who play sports with overhead movements, such as water polo, tennis and basketball. Another study found that professional soccer players with strength imbalances were four to five times more likely to suffer a hamstring injury as compared to those with no muscle imbalance.

Muscular imbalance is also caused by sitting in a chair for hours on end. When experts have studied office workers, they have found muscle imbalance tied to neck pain in as many as 70% of subjects.

While muscle imbalance does not always cause pain in the short term, experts say it’s important to focus on strengthening all the major muscle groups in your body, which over time can help prevent pain and injury by improving your body mechanics.

When is muscle imbalance a problem?

Opposing muscles around a joint or bone need to work together to function, but occasionally one muscle becomes too weak, too strong, too tight or even too loose. That’s not always a cause for concern, and everyone has some degree of muscle imbalance in their body, said Darren Calley, a physical therapist at the Mayo Clinic specializing in orthopedic physical therapy.

For instance, experts don’t typically worry as much about left-to-right muscle imbalance, said Aimee Diaz, clinic director at University of Southern California Physical Therapy. A pitcher might have a wickedly strong right arm, but the contrast with their left side is not an issue unless they experience pain. However, front-to-back imbalance, like tight hip flexors paired with weak abs and glutes (often caused by too much sitting), can lead to low back pain.

Although we can isolate some muscles and train them independently, our muscles need to work together for everyday movements, said Jessica Curran, a physical therapist at Shirley Ryan AbilityLab, a nonprofit rehabilitation research hospital based in Chicago.

“They need to be equally strong and flexible,” she said.

What are the signs?

Symptoms of a muscle imbalance differ from person to person (and from muscle to muscle), but Curran said one sign might be aches and pains that don’t seem to dissipate, or if you feel sore in the same general area even when you aren’t working those muscles. The only way to know for sure, she said, is to visit a doctor or physical therapist for an evaluation.

The pain might also show up differently in each region of the body. Someone who has stronger chest muscles and a weaker back could experience a pinching sensation in the shoulder, and a muscle imbalance in the lower body could show up as low back pain, Diaz said.

How can you prevent it?

Preventing and addressing a muscle imbalance usually requires strength training, especially if you focus on one activity or sport.

“All runners should do strength training, whether they’re new to running or they’re doing really high mileage,” Crowe said.

For runners, she recommends single-leg squats with one leg elevated, holding onto a table if necessary, because those target the muscles on the sides of your hips, which are often weak for them. For cyclists, who often have weak glutes, she recommends reverse sliding lunges or step-ups, either weighted or unweighted.

People who develop muscular imbalances from habitually sitting at a desk should work on strengthening the upper back, which can become weak when hunched over. Some exercises to try include bent-over rows, kettlebell swings or Romanian deadlifts.

Ultimately, whether you are a weightlifter, an endurance athlete or a deskbound worker, you should vary your movement at least a few times a week. Long-distance cyclists could try swimming or hiking, and office workers should take breaks during the day to change positions and move around.

Fortunately, it doesn’t take long to address the problem, Calley said, if you are intentional about strength training and regularly vary your movements.