I kick start many of my morning yoga classes in Spring with Kapalabhati. Kapalabhati is an uplifting, detoxifying and energising practise that is often confused with pranayama. Yes, it works with the breath, but it's actually a kriya - a cleansing practice. It's English translation is "skull shining breath" and it really feels like you've cleansed your frontal lobes after a session of Kapalabhati!
While the exhale is ‘forced’ or ‘explosive’, the inhale is passive. That doesn't mean you don't inhale! Students often forget to inhale, taking one long inhale and snorting out a series of short, sharp exhales without taking a breath in between. Each exhale is followed by a short inhale, it's just that you don't take a long, forceful breath in (that's another practice altogether, called Bhastrkika). You can see a demonstration of Kapalabhati here, with written instructions below. Give it a try!
• Sit up comfortably and take a natural inhale
• Exhale forcefully from the lower abdomen, quickly contracting the lower belly back towards the spine to force air out through the nostrils
• In between each forceful exhale is a short inhale that occurs naturally when the contraction of the lower abdomen is relaxed.
• Repeat 10 times then rest, breathing naturally for a minute.
• Repeat the steps above up to 4 times