NOOOOOO!
Aerobic conditioning occurs when you keep you heart rate between 60-85% of maximum. I would advise each of you over 50 and just starting out on a program to see your doctor. Especially if you have hypertension or diabetes. A treadmill exercise stress test will 1. make sure you have no issues with asymptomatic heart disease (33% of people still drop dead as their first sign of heart disease) and 2. give you an idea of your baseline exercise capacity. The second thing you may want to consider is a heart rate monitor. I recently started exercising with one myself, despite the fact I've exercised regularly since I was 13, and I find it helps me keep my heart rate within the 60-85% of my maximum
To find your maximum, take 220-age. You ideal heart rate for aerobic exercise is going to be 60-85% of that number.
As for running/jogging v. walking, you gain no real aerobic benefit from running when compared to walking, you have an exponential increase of training related injuries if you run over 30 miles a week, and you put 8 times your body weight in terms of stress to your joints, especially knees and hips. I used to run religiously until my second knee recon cost me my right medial meniscus, now I bike religiously and walk for the weight bearing exercise-gotta maintain that bone density! Also, a rheumatology collegue of mine told me he didn't think anyone over 35 should run for fitness because of the wear and tear issues...
As for triathletes, I can tell you, as a former collegiate swimmer, they all pretty much suck at swimming...
I can't tell you how much "pop science" I've heard passed down through the years as fact. It seems to spread in waves. The real medical facts are what I've just laid out. Lactate testing is not a viable option for 99.99% of athletes out there, so, stick with the tried and true (and supported by medical evidence ) methods.
FYI, I'm a board certified general internist, with 20 years practice experience...





. . . for thought. (Pun intended.)
