DAVE MCGILLIVRAY, for Cape Cod Times

For the better part of my life, I thought I was as close to invincible as was humanly possible. With all the running I have done, I thought no physical challenge was insurmountable.

Editor’s note: Dave McGillivray is director of the New Balance Falmouth Road Race, the Boston Marathon and dozens of other events through his company, Dave McGillivray Sports Enterprises. In 1978 he ran from Medford, Ore., to Medford, Mass. — 3,452 miles — to raise money for the Jimmy Fund. He has run every Boston Marathon since 1973 and has competed in eight Hawaii Ironman Triathlons.

First, this is a “good story” with a happy far.

For the better part of my life, I thought I was as close to invincible as was humanly possible. With all the running I have done, I thought no physical challenge was insurmountable.

It took 59 years, but recently that all changed in a “heartbeat.”

For over a year now, I’ve been experiencing difficulty breathing as soon as I start my workout. For the first 10-15 minutes, I’ve had to run and then walk just to be able to catch my breath. This has been embarrassing to say the least.

It felt like I was running at altitude. It seemed like angina-type symptoms. After about one to two miles, the discomfort seemed to either go away or at least became less painful. I seldom ran with others, choosing rather to run alone because I didn’t want anyone else to know “my little secret.”

Like most people, I know my body very well and knew something wasn’t right, that something was very wrong. I proceeded to have all the normal tests done — pulmonary, heart, EKG, inhalers, echo tests, stress tests and on and on.

The good news, nothing was detected. The bad news, nothing was detected.

In fact, although my fitness level isn’t close to what it used to be when I was in my 20s and 30s, I am much fitter now than most folks my age, or any age for that matter, and as such the stress test showed nothing out of the ordinary.

Then, what the heck was causing this nagging, non-stop breathing issue?

Unfortunately, I come from a family with a history of heart disease, in particular, a higher than normal cholesterol level. It is simply in the gene pool. I only realized this about 10 years ago and started taking a cholesterol-lowering statin.

However, I had a bad reaction (mainly muscle cramping) and got frustrated, and stopped taking the medication for quite some time. I eventually experimented with different ones until I came up with the one that worked best.

Through a methodical process of elimination, I tried valiantly to determine what the cause of my condition was, but kept coming up with no answers. Was it hot weather or cold weather, running up hills, running after eating or drinking? What was causing this?

I even went on a run with my cardiologist, Dr. Aaron Baggish, but, of course, I could not replicate the problem for him to diagnose first-hand.

After a year-and-a-half of this, I had had enough and Dr. Baggish ordered a CAT scan. The result, in his words: “severe blockage and chronic ischemic heart disease.”

The word that jumped out at me was “severe.” Really? I was devastated and really scared. 

How can this be me? I’ve run across the darn country averaging 45 miles a day; I’ve run hundreds of marathons; I’ve run over 140,000 miles; I’ve done the Ironman in Hawaii numerous times and just ran 59 miles on my 59th birthday in August. Really, severe?

Dr. Baggish immediately scheduled me for an angiogram at Massachusetts General Hospital on Oct. 9. I thought, OK, go in, maybe get one stent, leave and start running again the next day ”» all fixed up. Problem solved.

Not so fast.

As I lay on the operating table, I nervously looked at the monitor and saw the image of my arteries looking like the twisted branches of an oak tree. My jaw dropped as the doctor pointed out “all” the blockages and narrowing in many of the arteries ... no, not just one. I started counting them on one hand and then stopped when I ran out of fingers.

The doctors determined it would be more risky to operate than not and wheeled me out of the room. As I was leaving, I was thinking to myself, how much more time do I have? Is this possibly terminal? I usually don’t get emotional, but I broke down uncontrollably.

So much for being Superman anymore.

After some “heart-to-heart” discussions with my doctors, it was decided that since I probably put myself in this position, it would be up to me to get myself out of it.

Have I followed the best nutrition plan all my life? Hardly. A few of my mottos have been, “Anything and everything but in moderation” and “sleep is over rated.”

I realized for the first time in my life that these just might be flawed statements. I always rationalized that whatever I ate, I burnt off. However, it’s like putting a bad grade of gas in your car. The car will still run, but your engine will “gunk up” in no time. And I always thought I’d sleep enough when I’m dead. There is even a song that says so.

I’ve also been told that stress can be a factor. I guess you could say this past year in Boston (with the marathon bombings) has been a little stressful for many of us. There seemed to be a confluence of factors coming into play here.

I can name a half dozen friends who were really good athletes who, in the past 10-15 years, went for out for a run and never came back. That could have happened to me, but how lucky am I that I am now getting a second chance.

I never believed that I would drop on a run, but now I wonder. People often use the expression, “at least he died doing what he loved.”

I’m sorry, but I don’t want to die doing what I love, which is being out for a run. Dying in my sleep when I am 110 seems like a better option.

Only a few weeks ago, a 52-year-old man dropped to the ground in my Thanksgiving Day race, the Feaster Five in Andover, and lucky for him our medical people saved his life. He later found out he had 100 percent blockage in a major artery and he didn’t know it. If he went down in his back yard shoveling snow, he probably wouldn’t be with us today.

The biggest lesson I’ve learned from all this is that being fit doesn’t necessarily mean being healthy.

I’ve spent my entire life focused on being fit, but not really focused on being healthy because I thought one meant the other. That’s all changed now. I only need one warning.

Interestingly, being fit saved my life. My other arteries were healthy and developed enough to overcompensate for the blocked arteries, but my fitness also seemed to “mask” my underlying problem, something all “fit” people should take notice of.

It’s been two months since my “rude awakening.” I’ve done a complete 180 degrees in my lifestyle. I totally changed my diet (no meat, no fat, no soda, no beer, no anything that is bad for you) and have lost 21 pounds.

I’ve started swimming again, lifting weights and hooked up with a personal trainer and a nutritionist, and have been taking dietary supplements. My cholesterol level has dropped 65 points from 212 to 147.

When my doctor gave me these results all he said was “you over achiever.”

This has nothing to do with overachieving. I just want to stay alive a little longer and I got the message loud and clear!

And, guess what? I now no longer have the breathing issue. Yahoo! My running has felt the best in the past 15 years. However, I do take my cell phone with me every time I go for a run now.

I’m thinking of doing another Ironman triathlon, which I haven’t done in 25 years. And today I actually passed someone jogging while I was running, first time in a long time. He was probably 90 years old, but you take what you can get.

At first, I didn’t want to tell anyone this story. I was embarrassed and didn’t want to burden anyone with it. And I’m not good with sympathy and all that stuff.

However, after now processing it all, and talking with close friends, I’ve realized a few things. First, I needed a support group myself, of family and friends who care. They actually “rescued” me.

My wife, Katie, has been my biggest supporter. A number of others have helped educate me on all of this, which has made a huge difference.

I’ve also realized that there are many people out there just like me who are in the same boat, some who have caught this just in time, and others who don’t even have a clue that they are currently in big trouble. They deserve a second chance, too, but they need to take action right away.

Maybe my story can help bring some awareness to this. Could this be you?

That is the second lesson here. No matter how fit you think you are, get checked before it’s too late. We are not invincible.

I’m no Superman, but even Superman went down when he came up against his weakness, kryptonite.

I have a beautiful wife and five children, the youngest 4 years old. I want to be around when she graduates from college and has her own family.

Frankly, I’m still praying that I haven’t missed the “health bus,” but I’m grateful that my destiny is now in my own hands, right where it should be.

After I finished my cross-country run in 1978, my brother put a slide show together which included the Bee Gees hit, “Stayin’ Alive.”

I loved that song. I love it even more now.