Some muscles are more appreciated than others. Toned abs are proudly displayed in celebrity selfies and on Men’s Health front covers. Bodybuilders show off their pecs and swollen biceps. But deep inside us all, a sheet of muscle quietly gets on with its heroic work. That muscle is the diaphragm, one we are completely dependent on, but take for granted every moment we’re breathing.

In order to inhale, the diaphragm contracts and flattens as the lungs fill up with air.  To exhale, it relaxes and moves back up into its original domed, parachute shape as the air leaves the lungs. The diaphragm delivers oxygen to us a dozen times or more each minute. That’s half a billion times during an 80-year life.

All mammals, from platypuses to elephants, have a diaphragm. But no other animal has one.  Mammals have a very different solution for breathing than reptiles and birds. Before the evolution of a diaphragm, our reptile-like ancestors probably breathed the way many reptiles do today – they used a jacket of muscles to squeeze the rib cage.

Once the diaphragm evolved, breathing changed drastically. Mammals gained a more powerful, efficient way of drawing in a steady supply of oxygen. The evolution of a diaphragm probably made it possible for mammals to evolve a warm-blooded metabolism. Without a diaphragm, humans might not have been able to evolve giant but oxygen-hungry brains.

To experience the diaphragm, try this. Place both hands either side of your rib cage and take a Pilates inhale through your nose laterally into your palms. Can you feel a stretching out to the sides just underneath your ribcage? That’s the diaphragm flattening. Then as you do a Pilates exhale through your mouth and suck your tummy in, you will notice the diaphragm relaxing back into its original domed shape.

Now try this…ease yourself into the downward facing dog pose and hold the position while doing the Pilates breathing. You may find it a little more challenging to take a full inhale when the body is inverted, but a sense of the diaphragm flattening and returning to its dome-shape is arguably even more apparent when holding this pose.

Tips for performing the perfect downward facing dog:

• spread your fingers wide so your weight is distributed evenly on your palms.
• place your head in-between your arms. Don’t let it hang down below them. Your eye-line should be straight down at the mat rather than looking back at your legs.
• actively press your shoulders down and back, squeezing them together.
• here’s the key bit, try to make a straight line with your spine from the tailbone to the crown of the head.
• push your tailbone up and back.
• your knees should ideally be straight, but keep them bent if you have a back issue or are a beginner.