Bed yoga is a series of stretching and breathing exercises done on your bed. Because a mattress is a softer surface than the floor, you cannot do standing or balancing postures that require a solid feeling of the ground. But this soft surface can be beneficial if you have pain in your knees, wrists or other joints. Bed yoga is usually done just before bedtime or immediately after waking up. Bed yoga practices include calming and soothing postures that are invigorating if done at night or in the morning.