You probably already know that exercise is key for reducing depression. But you might not know why.

In his valuable book The Upward Spiral: Using Neuroscience to Reverse the Course of Depression, One Small Change at a Time, Alex Korb, Ph.D, notes that “almost everything that depression causes can be combated by exercise.”

For instance, while depression makes you lethargic, exercise boosts your energy. While depression makes it harder to concentrate, exercise helps with mental sharpness and decision-making. While depression sinks your mood, exercise improves it. And it diminishes anxiety and stress.

Exercise strengthens our brains, writes Korb, also a neuroscientist in the department of psychiatry at the University of California, Los Angeles.

“Exercise increases nerve growth factors, such as brain-derived neurotrophic factor (BDNF), which are like steroids for your brain. BDNF makes your brain stronger, so it’s more resistant to all kinds of problems, not only depression,” he writes.

Any kind of movement boosts the firing rate of serotonin neurons, which triggers the release of more serotonin. Antidepressants actually target the serotonin system to increase motivation and willpower. (Antidepressants also increase BDNF, and exercise does, too.) Movement may be anything from vacuuming to gardening.

Exercise also reduces the stress hormones cortisol and adrenaline, and increases norepinephrine. Korb writes that the difficulties in concentration “are mainly the fault of a lagging norepinephrine system.”

Plus, exercise triggers the release of endorphins, “neurotransmitters that act on your neurons like opiates (such as morphine or Vicodin) by sending a neural signal to reduce pain and provide anxiety relief.”

Maybe you know all these facts. But a bigger fact remains: You don’t feel like exercising, so you don’t.

Depression is a master manipulator. It convinces you there’s no point in doing or trying anything. It batters your body so you’re too exhausted to even get up.

But it’s important not to listen to your depressed brain. Waiting around until you feel like moving may mean that you’ll be waiting a very long time. And exercise is too good of an intervention not to try or practice, even if it hasn’t worked before.

As Korb writes, “… in the complex systems like the brain, the same actions can cause different reactions at different times in your life. It’s like traffic changes — during Friday rush hour, road construction might cause a traffic jam, but on a Saturday, the same construction might barely slow anyone down. Just because something didn’t help at one point in your life does not mean it will never help.”

In The Upward Spiral, Korb demystifies the brain processes that underlie depression and provides clear-cut tips for rewiring your brain. Specifically, he shares suggestions for exercising when you’re depressed. Here are nine of his tips.

1. Change your view of “exercise.”

Forget “exercise.” Instead think: “being active” or “having fun.” This increases your chances of actually moving your body, and gives you a bigger emotional benefit. According to Korb, “”If you bike to work three days a week or play Frisbee with friends in the park, it won’t feel like you’re exercising, but it’ll add up to a lot of activity.”

2. Move with someone else.

Engaging in physical activities with others supports you in doing those activities. And social interaction is important for depression. Ask friends what activities they’re doing or would like to start doing, and join them. Other options include hiring a personal trainer, joining an exercise group or going to a class.

3. Try a trial.

Sign up and commit to going to three exercise classes. Or commit to going to the gym every Monday, Wednesday and Friday.

As Korb writes, “Even if you’re feeling too tired to do any actual exercise, still go to the gym, park your car, walk in, change into workout clothes, and pick up a five-pound weight. If you’re really so tired that you don’t want to do anything else there, that’s totally fine.”

Also check out websites like Groupon for monthly memberships to a yoga or Pilates studio.

4. Take it outside.

Nature has a profound effect on our mood and decreases depressive symptoms. Even just looking at images of lakes and trees helps. Take a walk around your neighborhood or local park. Or walk on a treadmill that’s by a window.

5. Tie it to a why.

According to Korb, “When you connect your exercise to a long-term goal, it helps your brain overlook momentary discomfort and makes your exercise more satisfying.” For instance, Korb started getting active because it made playing sports more enjoyable.

Figure out what’s truly important to you. Remind yourself of your why regularly.

6. Plan for it.

Put exercise on your calendar. Then when you’re done, mark it as complete. As Korb writes, “Planning activates the prefrontal cortex, and checking it off the list releases dopamine.”

7. Keep it small.

It’s a whole lot easier to do something when it’s small and simple. For instance, start with one push-up after checking your inbox. If you’re feeling better, do more push-ups. “But if all you ever do is one push-up, that’s better than nothing,” Korb writes.

8. Keep moving throughout the day.

“Sitting is the new smoking. In other words, it’s bad for you,” Korb writes. Try to incorporate movement throughout your day. If you have a desk job, every hour, get up and walk around (or more frequently, if you can). Every 20 minutes stretch your hands, arms and back.

9. Dismiss “I can’ts.”

According to Korb, a common objection to exercise is “But I can’t …” You might think you can’t go to the gym three times a week, or run a marathon or run at all. That’s OK. As he writes, then go to the gym once a week, run a mile or take a walk.

“Once you stop focusing on all the things you can’t do, you may start to be amazed by what you can do.”

When you’re depressed, the last thing you probably want to do is move your body. In fact, your brain might’ve just come up with five reasons why you can’t or won’t exercise after reading that sentence.

Start small, and keep going. Remember you can do many things, even though your brain may be telling you otherwise. As Korb writes in The Upward Spiral, “Your depressed brain might be telling you to give up. It might be telling you that everything hurts too much to exercise. Thank it for its opinion, and go for a walk.”