Feeling sluggish? Experiencing low energy by midday? Many factors can cause a drain of energy, but there are just as many ways to boost energy levels when you’re feeling foggy and finding it hard to concentrate.

These 10 natural energy boosters will keep your engine humming throughout the day.

1. Eat an apple. Apples contain natural sugars, which your body can turn into energy. “An apple will have the same effect as a cup of coffee without the side effect of an energy crash,” says Kathi Casey, wellness coach, author, trainer, and owner of Healthy Boomer Body Center in Otis, Mass. “Any kind of apple will do, and there is a wide variety of apples to choose from, so you can pick the one you like best.”

2. Do five or more push-ups. It may seem counterintuitive to exert energy when you’re already tired, Casey says, “but it’s amazing what a couple of push-ups will do for you if you have low energy.” Push-ups get your blood circulating through your body, she explains. Your blood brings oxygen to your brain and your tissues, making you more alert and energetic.

3. Take a power nap. A power nap will help you feel refreshed, says Jini Cicero, a fitness and nutrition expert based in Los Angeles. Between 15 and 30 minutes is best. “You don’t want to get into deep REM sleep, or you’ll be groggy afterward,” says Cicero. “I believe 20 minutes is ideal — just enough to refresh your body’s systems.”

4. Have a cup of green tea. One of the reasons people feel as though they have low energy is that they’re really dehydrated, Cicero says. Staying hydrated is a natural energy booster. “I recommend replenishing your fluids by sipping a cup of green tea or white tea, which is the younger plant of green tea.” Green tea has a small amount of caffeine and white tea even less, but it’s the fluid that will perk you up. Even drinking water can help, Cicero says.

5. Step outside. Sunshine gives you energy because you’re getting vitamin D, and vitamin D can help boost your mood and mental performance. However, keep your face out of the sun and don’t bake — always protect yourself from the sun’s harmful UV rays. Take just 10 to 15 minutes to step outside for some fresh air and sunshine and you’ll go back to work feeling refreshed, Cicero says.

6. Phone a friend. Social connections are another natural energy booster, Cicero says. Studies have shown that people gain enormous amounts of energy from having friends, helping others, and giving of themselves. If you’re feeling down or have low energy, take a few minutes to call someone whose voice will perk you up. Even better, make plans to do something positive for someone else, such as volunteer at a shelter or help an elderly neighbor.

7. Meditate. A mini-meditation break of 5 to 10 minutes can be a great natural energy booster. “There is a lot of clinical evidence that people who meditate are less stressed and have higher energy levels,” says KC Craichy, nutrition and fitness expert in Tampa, Fla., and author of SuperHealth: 7 Golden Keys to Unlock Lifelong Vitality. Find a quiet place where you can get comfortable. Sit down and concentrate on your breathing. Clear your head and forget about your work or whatever was on your mind. After meditating, get up, stretch, and go back to whatever you were doing, feeling refreshed and more energized.

8. Eat high-energy foods. We’re not talking power bars or energy drinks. While they can provide quick energy, they also can cause you to crash when they wear off, Craichy says. Instead, choose high-energy foods that have essential vitamins and minerals. Vitamins B1, B2, and B6 in particular help your body convert carbohydrates into energy. Foods rich in B vitamins that will work as pick-me-up snacks include yogurt, whole grains, and sunflower seeds. Minerals in nuts, whole grains, and dairy products also enhance energy by assisting metabolism.

9. Take the stairs. Like doing push-ups, a quick flight up the stairs in your office building will provide aerobic exercise and help you feel more energetic, Casey says. Exercise not only helps your body function better, it also increases the amount of oxygen in your blood and causes your heart to beat faster, which increases blood flow to your muscles and back to your lungs. Exercise also releases endorphins, hormone-like substances that promote an increased sense of well-being.

10. Stop multitasking. “People are really doing themselves a disservice by trying to do too much at once,” Casey says. “You’re causing way too much stress on yourself and you’re not able to focus as well as you could were you to give each task your undivided attention.” If you do your day’s activities one at a time, you can devote more energy to each one. It will make you feel as though you have more energy overall.

Most of these natural energy boosters are easy to work into your day. They take 10 to 15 minutes at most, and the benefits can last for hours.