It’s one of those days—an I-can’t-seem-to-fit-everything-in-today day. We’ve been there. When the thought of fitting in a workout just seems impossible, remember this inspiring news: Even a brief cardiovascular exercise session can help you maintain a healthy weight, improve your heart health and keep you energized to take on the rest of your to-dos.

Whether your free time—albeit short—falls early in the morning, midday, or later on, make the most of it with one of these three cardio options that offer an effective workout in just 20 minutes:

GO FOR A WALK OR RUN. Whether it’s indoors or out, putting one foot in front of the other for 20 minutes will get your heart pumping. Consider making it a high-intensity interval workout, which ups the challenge and burns more calories in a short amount of time. Start with a five-minute warm-up, walking or jogging slowly. Then really push it for 30 seconds, walking briskly or sprinting, before slowing down for a 90-second recovery (until your heart rate returns to normal). Use the entire recovery period, even if you feel like you may not need it. Repeat that cycle four more times, and then end with five minutes of cool-down stretches.

You can also perform incline intervals. Plan an outdoor walk that includes hills, challenging you to climb for a bit and then walk an even stretch to recover. If you’re on a treadmill, begin your warm-up on a one percent incline since there’s no wind resistance and the belt moves for you. Increase the incline to a more challenging level for your 30-second burst and then lower it back down to one percent for your 90-second recovery. If you’re comfortable, increase the grade or experiment with inclines during your intervals.

CLIMB THE STAIRS. Working out on a stair-stepping machine can burn just as many calories as running (sometimes more). Try alternating your pace to challenge your body in the short time you have: Step up at a moderate speed for the first flight, at a faster clip the next, back to moderate pace after that, and so on. As you move, make sure you press through your heels to target the muscles in your thighs and glutes, as opposed to stressing your calves by stepping through your toes. Don’t have access to a climbing machine? Tackle any flight of stairs at work, at home or at the park.

HOP ON A BIKE. When you bike at a moderate-to-fast pace, you can burn up to 700 calories an hour, so even 20 minutes of hard pedaling makes a difference. Watch your speed on a stationary bike, however, because relying on momentum can prevent your heart and legs from getting an effective workout. Keep your revolutions per minute (RPMs) between 60 and 110, aiming for the lower number when you’ve selected a high resistance and reaching the higher RPM when you’re sprinting.