People often ask me what is the best way to improve their ability to equalize and feel more comfortable at depth. My answer is always the same: Practice your stretching! And in particular, peak inhalation stretches and negative diaphragm stretches—the same ones you learned in class if you’ve taken a PFI course.
As most freedivers will discover when they get deep enough, it is not breath-hold ability that limits how deep you can dive. It’s the simple fact that at a certain depth, because the increased water pressure has decreased the volume of air in your lungs, you lose the ability to bring up enough air from your lungs to equalize your ears and you need to turn around and head back to the surface. It takes time for the body to adapt so that you can equalize deeper and deeper, and it also takes experience—meaning you have to get “reps at depth.” You have to spend time at depth working your equalization technique and manipulating your “mouth fill” so that you finally succeed and move on to a deeper depth. The problem is, however, that it’s hard to get reps at depth. Think about it: after a day of doing target dives, say 5 of them, how much time have you actually spent at the depth where you can no longer equalize? Mere seconds, because when you reach that depth, you typically don’t hang out there to work on your equalization technique! So one or two attempts at depth, meaning just seconds, per dive is not a lot of time to practice. And it’s often difficult to get in good open water training time depending on where you live and your other responsibilities in life.
So I have found that perhaps the greatest tool for working on my equalization is to practice inhalation and exhalation stretches. You can simulate great depths and in a 10-minute session, you can get a lot more “reps at depth” than you will in a whole day of diving.
These are great for increasing flexibility of the thoracic cavity and rib cage and lead to increased lung volume over a relatively short time. To perform them, you can kneel down resting your hands on your knees while you sit back over your ankles. Perform a peak inhalation, hold it, extend your arms overhead in proper freedive position, and then stretch to the left for 10 seconds, then the right for 10, then back for 10 lifting your chest high in the air, and then finally bend over forward and place your hands on the ground way out in front of yourself so you can really feel a good side stretch. After that last 10 seconds, come back up to the starting position and perform 6 cleansing recovery breaths. You can repeat this stretch several times while alternating with the negative diaphragm stretches described below.
NEGATIVE DIAPHRAGM STRETCHES
This is where the magic happens! At depth the lungs compress as we get deeper because of the effect of Boyle’s law on the air in our lungs—as pressure increases, volume decreases. While stretching on the surface, though, we’re not under any water pressure, so we can simulate the effects of depth by performing “negative pressure” or “negative diaphragm” stretches. To do these, start in the same position as the prior stretch, and also take a peak inhalation, but then immediately release it to a 1st Level Exhalation (which you learned about in class). Now, while you have relatively negative lung capacity, you draw up your diaphragm as high up inside you as you can for a count of 3 seconds. Then release the diaphragm for three seconds, pull it up again for 3, release it, and repeat one more time. You may feel a very intense urge to breathe during these stretches, but just remember, as you learned in class, that is not a true urge to breathe caused by either low oxygen or high CO2—it is simply the “Lying Bastard”—the urge to breathe created by the brain’s reaction to the stretch receptors that are attached to the diaphragm being stretched beyond their usual capacity. The brain recognizes the lungs are very empty and tries creates an urge to breathe so that you will stop what you’re doing and take a darn breath! But you don’t need to at this point, as you’ve only been doing the drill for less than 15 seconds and you know you’re not hypoxic. What you are, though, is in a state of negative lung volume and significant discomfort—exactly the same as when you can no longer equalize at depth! The perfect time and place to get some “reps at depth.” So now work on your equalization technique by attempting 3 to 5 equalizations after you’ve released your diaphragm for the last time. It should be very difficult, but that’s where the practice comes in. Keep at it—it will get easier as your body becomes more familiar with (and less freaked out by) the “interesting” sensations you’ll be encountering.
So, alternate these two stretches by doing one Peak Inhalation stretch followed by one 1st level exhalation stretch, and then repeat but follow the next Peak Inhalation stretch with a 2nd level exhalation this time. And so on, until you have done a 3rd level exhalation/diaphragm stretch—you should feel miserable during that one! After a week or two of practicing those stretches, you may want to add a few “packs” on the inhalation stretches and “reverse packs” on the negative diaphragm stretches to enhance the stretches. But just remember to add packs/reverse packs slowly over time and just a couple additional per week as your body takes time to expand and adapt, and you certainly don’t want to risk an overexpansion or compression injury to your lungs or trachea.
With practice, you can really work on your depth equalization technique without even getting in the water, and you’ll be very pleasantly surprised the next time you dive!
Enjoy the ocean and dive safe and always with a trained buddy!