Not P.D. Mangan
A hallmark of aerobic exercise is a fast heart rate and heavy rapid breathing during the activity. “Aerobic exercise” is things like jogging, treadmill work, stair-stepping, rowing, soccer, serious bicycling, etc.
I’ve never checked my breathing rate during a weight-training workout, but I do occasionally check a heart rate right after a set: 140-150 is common.
P.D. Mangan writes at his blog:
“Of all the misconceptions about strength training and weight lifting, one that comes up a lot is that they have no aerobic component. Therefore, the idea goes, if you do only weight training, you won’t build sufficient cardiorespiratory fitness, which you need to protect your heart and get the benefits of exercise. But weight lifting increases aerobic fitness, all on its own.
On at least two occasions, when a doctor has asked me what i do for exercise — after remarking that I was in great shape — and I told them weight lifting, they said I needed to add some aerobic exercise (cardio).
It’s obvious that these doctors never lifted weights. At my weight lifting sessions, I have to catch my breath after a set and my heart is often going at around 160 to 180 beats per minute.
It’s not just a couple doctors either. The view is widespread that you must do a very special form of exercise, called aerobics or cardio, to improve heart and lung function and raise VO2max, the most common measure of cardiorespiratory fitness.
On the contrary, weight lifting raises VO2max.”
Source: The Big Misconception About Weight Lifting – Rogue Health and Fitness
Steve Parker, M.D.
PS: Check out Mangan’s wonderful books.
PPS: Do you ever wonder what’s your theoretical maximum heart rate? The common heuristic is to subtract your age from 220, and that’s your answer. The formula doesn’t work if you take certain drugs, like beta blockers, the limit your heart rate.
PPPS: If you dislike uncommon words like “heuristic,” you won’t find them in my books.
Advanced Mediterranean Diet 
Except for all of the other proven benefits of cardio. The best fitness program has both. It’s not an either/or.
Liz, especially if one likes cardio, go for it. Even brisk walking is cardio. From my 20s to age 40 I ran at least 20 miles/week. Even ran 2 marathons. That running was sometimes like meditation for me. I made many major decisions while contemplating them As I ran.
-Steve
Exactly (she says while relaxing on her couch after biking 21 miles….)
I do lift weights – heavy weights – twice a week too. 🙂