Just because you’re strong doesn’t mean you’re fit. Dr. Kenneth Cooper, an M.D. in the Air Force, discovered that being strong and being fit are two different things. He found that those who’d done lots of strength training but had not done other fitness exercise did poorly in running, swimming and cycling. He measured sustained performance in terms of a person’s ability to use oxygen and coined the word “aerobics,” which means “with oxygen.”
In 1968, he published Aerobics, the first book to provide scientific exercise programs using running, walking, swimming and cycling. It was the first book that provided a scientific basis for aerobic exercise.
Aerobic exercise involves performing an exercise at a moderate level for an extended period. What’s “moderate”? That’s walking at a pace that gets your heart rate up to sixty percent to seventy percent of your MHR (maximum heart rate) and doing it for at least thirty minutes to get real benefit. It’s going as fast as you can and still carry on a conversation. You have to consciously work at getting to that level, by the way.
There are lots of ways you can do aerobic exercise outdoors; brisk walking (nice if some is uphill), cycling, running, cross-country skiing. All should be done at a pace that’s near the limit of your ability to carry on a conversation.
Gyms are loaded with aerobic equipment — treadmills (as your fitness improves, it’s a good idea to raise the incline at least part of the time), arc trainers, elliptical trainers, stationary bikes, rowing machines. The director of my fitness center in Florida tells me that treadmills get the most usage.