On July 13th, I achieved a personal milestone: I swam for 1.1 miles during my master's class at my Colorado Springs rec center. I wouldn't call it shabby, but in reality, it is more like a series of 25- or 50-yard swims followed by prolonged huffing and puffing. Our coach told me he would not go public with the percentage of time I spent stroking versus gasping. I'd like to be able to swim long and fast. But I am getting older, and the pool is at 6,000 feet elevation. At this elevation, oxygen is pretty precious.

That same morning, two younger and more strapping men were practicing holding their breath at a Staten Island, N.Y., pool to prepare for military training. Today, one of their families will be preparing for his funeral. Bohdan Vitenko, 21, died at a hospital. His Air Force-bound buddy, Jonathan Proce, 21, was resuscitated and is in critical condition.

After my swim, I went to Starbucks, and while I was waiting for my latte, I saw the USA Today image of President Obama reaching to shake the artificial hand of Sgt. 1st Class Leroy Metry, who was just awarded the Medal of Honor. He was shot in both legs, but led other Rangers to cover, radioed for support, and lobbed a grenade to provide cover. One enemy grenade landed, exploded and injured two comrades. A second grenade landed only a few feet away. This father of four did not turn away like a normal person. He lunged forward and grabbed the grenade, which exploded as he was throwing it back.

As I read his story, I felt that I had stopped breathing. I took a deep breath when jerked back to reality by the barista's call. And I realized in that moment how fortunate we all are to be protected by so many who are willing to make the ultimate sacrifice in the heat of battle so we can swim and enjoy enjoy coffee. It is humbling to see the sacrifices that earn the gift and blessing of our freedom.

Even these young heroes are human. They are flesh and blood. They require oxygen to pump through their veins. They may gasp less than the rest of us after swimming, but they cannot escape physics and physiology - that is, that swimmers who practice prolonged underwater breath-holding are particularly at risk of Shallow Water Blackout (SWB), which is what happened to Bohdan Vitenko and Jonathan Proce.

In 2008, we at NSPF reported critical information about this practice:

By rapidly breathing deeply prior to submersion (hyperventilation), swimmers exhale an excessive amount of carbon dioxide. When the oxygen level in the blood runs low before the carbon dioxide level rises to the point that triggers the breathing reflex, the swimmer loses consciousness. The swimmer never actually feels as though a breath is needed.

Anyone who practices competitive, repetitive underwater breath-holding is at risk for Shallow Water Blackout. Once submerged underwater, the swimmer may be hidden from the view of lifeguards by surface glare and ripples/waves on the surface. A series of events is then triggered, including the inhalation of water, possible convulsions and ultimately cardiac arrest and death.

It is tragic when we lose a soldier. It is even more tragic to lose a young man (or woman) who is willing to serve our country, but never got the chance to do so.

Oxygen is precious at any elevation. I like to break the rules in my little ways - and maybe you do, too. But let's not try to defy physics and physiology. Let's never forget that breath holding and hyperventilation will snuff out a life as surely as a hand grenade.