Yesterday, the website Active.com posted a link to an article called “The incredible unaging triathlete” from the blog Sweat Science. The article pointed to a study that found zero loss of muscle mass and integrity among recreational competitive athletes (runners, bikers, and swimmers) from ages 40 to 79 years old — in dramatic contrast to their sedentary counterparts:

Which do you want your leg to look like?

I mention this to you as a source of encouragement — or fear, if that’s more where you’re at! I also mention it because I suspect I won’t be breaking all those existing 60+ age group records after all, once the rest of my well-trained age group gets there with me. I’m guessing that middle picture was resized from much larger thighs, but even if you enlarge it to show greater area, I don’t think anyone wants to be the owner of that shrivelly steak in the middle of that sea of fat.

The study authors did observe a small strength (vs. mass) decline among the athletes in their sixties, but no strength loss after that all the way through their entire seventies. They mention two more studies that showed “no significant decline in the running performance times of top senior athletes … until age 75 years,” and the same finding among masters swimmers.

The authors conclude that what we in our society (and medical community) have accepted as the inevitable decline of aging, is actually due to disuse and a sedentary lifestyle. Exercise prevents the muscle loss of aging!

That’s heady stuff. Prevents. Erases. 100%. Nada. Not “slows,” “decreases,” or “delays.” Wipes it out. Doesn’t have to happen at all. Look at the thighs.

So, okay, there’s a trick. These were masters athletes that are often winners in their age groups. They work out four to five days a week at a competitive level. The trick is not that you have to be as fast as them. The trick is that you have to work out as often as them, at the same intensity level (for you).

I’ve been loathe to mention this before. I’m trying to encourage people new to exercise or who haven’t been at it regularly for awhile. (“Chronic exercise,” the study authors call it, which sounds like a disease: “Doctor, I’ve been suffering from chronic exercise!”). My  experience is that when you’re starting, the very first thing you need to do is establish pleasant associations to what you’re doing and form a habit of doing it.

But I know many people who hope to continue a light level of exercise indefinitely, and while that’s infinitely better than being sedentary, it doesn’t have the same fat loss or anti-aging benefits. Those benefits come from intensity. This is why Jillian is such a hard ass (well, that and her inherent personality). Intensity itself comes primarily in the form of short interval cardio workouts that get your heart rate up several times in a row, and lifting heavier weights for lower numbers of repetitions.

It ain’t my old Jane Fonda workout.

Something a friend said had made me realize there is a discrepancy between how gently I tell people to begin, and what I describe myself actually doing in my own training — my “intensity paradox.”

Partly that’s because I’m in my sixth year of doing this. I didn’t even compete until I’d been running, walking and biking for three years already (and I think most beginner runners try to compete way too early). But I also personally enjoy the feeling of physical intensity, which can sweep away stress hormones like cortisol and adrenaline. Some people dislike the feeling of breathlessness or burning muscles, or even have a fear that it’s hurting them. (I’ve noticed this especially among women in my mom’s generation, who weren’t taught how to work out.) And there is definitely too intense; most boot camp style instructors like Jillian fall into that category for me, and I’m still leery of Cross-Fit (sorry!). For example, if my heart rate is over 95%, my runner’s instinct is to lower it; Jillian says she wants it up to 100%! Also, if you’re already suffering from adrenal burnout, or currently have a high stress level in your life, it is not the time for more intense exercise!

On running plans, I don’t rack up much weekly mileage (yet), but I’m often doing something hard or fast. This is the key to performance as a masters athlete. Athletes who put in more slow mileage as they age suffer both slowed race times and symptoms of aging. So far my “low volume” (but high intensity) programs have worked well in getting me faster. (Note: it’s also important to understand that not every day should be intense. I do one or two intense runs a week, maximum. Slow cardio causes an entirely different set of adaptations, which you also need.)

So I will try to address the reality of the need to increase intensity in exercise, once you have gotten started — what that means to a beginner, a recreational exerciser, and an athlete. In the meantime, take a look at those leg pictures one more time.