Most people know stress is bad. What many people do not realize is that there are different types of stress, and your body responds very differently depending on whether that stress is mental or physical.

The interesting part is that both types of stress can look almost identical on paper. Both can increase heart rate, blood pressure, cortisol levels, adrenaline, and feelings of fatigue. Yet one type of stress generally breaks us down while the other can build us up.

When your body experiences stress, it activates what is commonly called the “fight or flight” response. Hormones such as cortisol and adrenaline are released, increasing alertness and preparing your body to deal with a challenge.

The problem is that your body does not always know the difference between being chased by a bear, worrying about bills, dealing with work deadlines, or running up a hill. At least initially, stress is stress.

Mental stress is what most of us deal with every day. Work, finances, family responsibilities, deadlines, emails, traffic, arguments, and social media all place demands on our attention.

The problem is that your body responds as if something important is happening, but often nothing physical happens afterward. Your heart rate goes up, your blood pressure rises, cortisol increases, and your body becomes more alert. Then you sit, think, worry, scroll, and replay the problem over and over again.

The result is that the stress response stays active without giving your body a reason to adapt or improve. Over time, chronic mental stress can contribute to poor sleep, increased body fat storage, elevated blood pressure, low energy, irritability, and a general feeling of being overwhelmed.

There are very few physical benefits to prolonged mental stress. The exception is when the stress is attached to something meaningful and temporary, such as preparing for an exam, building a business, raising a family, or accomplishing a difficult goal. Even then, recovery is still necessary.

Physical stress creates many of the same immediate reactions. Heart rate increases. Breathing becomes heavier. Blood pressure rises. Cortisol levels increase. Your body is challenged. The difference is that exercise gives your body a reason to adapt.

When you exercise consistently, your heart becomes stronger and more efficient. More capillaries are created to deliver oxygen and nutrients throughout the body. Muscles become stronger, bones become denser, lungs become more efficient, and your body becomes better at handling future stress.

Over time, resting heart rate often decreases, blood pressure improves, energy levels increase, sleep improves, and confidence grows. In other words, physical stress creates positive adaptations.

A physically tired person has challenged their body. Their muscles are fatigued, energy stores are depleted, and recovery is needed.

A mentally tired person may have spent the entire day answering emails, solving problems, worrying about responsibilities, sitting in meetings, and making decisions. Their brain feels exhausted, but their body often has not been challenged at all.

This mismatch is one reason so many people feel exhausted at night but still struggle to sleep. Their mind is tired, but their body is not.

One of the greatest benefits of exercise is that it helps align physical fatigue with mental fatigue. When your body has actually worked, sleep often becomes easier. You fall asleep faster, sleep deeper, and wake up feeling more refreshed because your body finally has a reason to recover.

This is why I often tell people that being tired is not always a reason to skip exercise. In many cases, exercise is exactly what helps solve the problem. The more physically capable and efficient your body becomes, the less taxing everyday activities feel in the future.