Thirty years and 50 pounds of blubber ago, between various teaching jobs and being fired from computer companies, I wrote for a New York-based magazine called The Runner, which was long ago absorbed by Runners World. I took the gig to force myself to get in shape and it worked, which is why one year I ran the Boston Marathon. Understand that my editor at the time, a guy named Amby Burfoot, had won the Boston Marathon, so my finish well back in the pack was professionally meaningless, but that memory gives me some sense of the scene yesterday in Boston when those bombs went off. I know what the air was like, what the runners were feeling, and from my earlier stint in Beirut I knew the adrenalin rush that follows an unexpected explosion.

One of the Boston runners interviewed today on television spoke of being unable to reach his family on the phone (they were spectators near the finish line) but he was able to get through by texting them. If, like me, you’ve been there and done that, hit the wall at 20 miles and nearly lost your will to run on Heartbreak Hill, the first thing that came to mind was “he carried a mobile phone for 26 miles???”

Here come the four technical paragraphs in this column and they may surprise you: the total energy required to run a marathon is not dependent on the speed of the runner. You’d think the winners would be putting out way more energy than the stragglers but that’s not true: they just expend the same energy (per unit mass — this is important) in the shorter time it takes for them to win the race.

Don’t take my word for it.

For male runners it generally requires one kilocalorie per kilogram for each kilometer run. Since a marathon is 42.195 kilometers that means an average 170-lb male runner will expend 3,260.52 kilocalories to finish the race. What lets the winners win is higher foot speed, the ability to expend the same amount of energy at a higher rate per unit time, and — most importantly — they are little skinny guys.

An iPhone 4 weighs 137 grams which means carrying it the length of the race course requires 5.78 kilocalories and will slow down that 170 lb runner by 0.177 percent. If he’s a natural three hour marathoner, carrying the phone will slow his finish time by 19.11 seconds. If he’s a 120-lb Ethiopian and can run a 2:10 marathon, carrying that iPhone will slow him down by 20.37 seconds, which this year was the difference between first and fourth place making it a very expensive iPhone indeed given the associated reduction in prize money.

That’s why elite runners don’t carry mobile phones or much of anything else on the race course. But even three hour marathoners are competitive and 19 seconds are still 19 seconds too many in a race.

Which explains why so many companies are now planning to introduce lighter smart phones built into wristwatches.

This advance in mobile phones, which is expected in the next year from Apple, Samsung and others, couldn’t have happened with any elegance before now. It has taken Moore’s Law, better battery technology, and the deployment of hundreds of thousands of cell sites to make such a tiny thing possible. I know, because I thought of doing it myself.

A year or so ago, when it became clear to me that blogging for ad dollars would end for me in personal bankruptcy, I started considering things I could sell on this page to make money. There were only two products I explored in any detail and one was a mobile phone. That specific idea was to offer a Bob Lee Signature Edition Android Phone.

Bob Lee, if you don’t know him, is a great guy who currently works as CTO at Square, the mobile payments company. Before Square he was the lead developer for Android at Google. Bob is a friend of mine so my idea was to build and sell his ideal Android phone, one with the best mix of parts and apps to create a supreme Android experience. Putting Bob’s name on the phone, rather than mine, was obvious since I’m nothing in this space: not even my Mom would pay a premium for a Bob Cringely phone.  But a Bob Lee phone — now there’s some geek cachet!

Of course it didn’t happen and that was for three reasons: support costs, (lack of) economies of scale, and those damned wristwatch phones.

I’d have to build a support organization no matter how many or few phones I sold. The big phone manufacturers I went to didn’t want to both make my phones and absorb the support obligation.

With the small volumes I expected my phones would always be expensive — too expensive I feared. Prada could pull off a luxury phone, but I’m not Prada, as my wife is constantly reminding me.

Finally, I got hints of these looming watch phones with technology I couldn’t access at any price, so the idea was doomed.

For a watch phone to be a breakout hit and more than just a short-lived fad it has to be even more powerful than the phone you are using now. That’s because the screen is inherently so limited that the watch will have to have superb audio controls. Siri and Siri-like interfaces are not enough. Wristwatch smart phones will require Bluetooth earpieces combined with Siri’s younger, smarter sister whom I’d call Seven of Nine. At present this could only be accomplished with full time cloud integration, which may be the interim deal-killer for these things.

An alternative to a brilliant audio interface could be something like retinal scan displays or even Google Glass, but I don’t expect that this year. Why? Because then you wouldn’t bother with the wristwatch form factor and would instead build the entire phone into the display.

As long as they are calling it a watch it won’t be shooting lasers in your eye.

All of this mobile phone speculation has taken us away from the somber subject at the start of this column — the violent events yesterday in Boston. Readers who like to get pissed-off at me (you know who you are), please hold your wrath for another day because tomorrow’s column will discuss technologies we could use to make such violent episodes less likely in future.

It’s not that I’m insensitive, then, just that these things take time to research and write.