We are a commune of inquiring, skeptical, politically centrist, capitalist, anglophile, traditionalist New England Yankee humans, humanoids, and animals with many interests beyond and above politics. Each of us has had a high-school education (or GED), but all had ADD so didn't pay attention very well, especially the dogs. Each one of us does "try my best to be just like I am," and none of us enjoys working for others, including for Maggie, from whom we receive neither a nickel nor a dime. Freedom from nags, cranks, government, do-gooders, control-freaks and idiots is all that we ask for.
In the general fitness and endurancecategory of exercises (as opposed to strength and power), bursts of "balls to the wall"* (not sure what term women might use for that) exertion are far more useful than long stretches of less intense cardio. Except for those over 75 or in cardiac rehab, long stretches of "comfortable cardio" advance none of your goals other than plain functional maintenance. Functional maintenance is good, though, for the aging. (Comfortable cardio means you sweat but do not get winded.)
You can watch Social X-Rays, models, and quasi-anorectics jogging or doing cardio exercises for hours all the time in NYC, but they do not look like that because of exercise. They look like that because they don't eat carbs, or anything else much. Creepy.
What most of us regular exercisers do is a combination, eg 20-40 minutes of continuous cardio machines with brief bursts of maximum speed effort - sprints in effect. Distance runners train with sprints, as do swimmers. Other high-intensity sprint-like exercises? Squats, heavy ball smashes, lunges, high steps with weights, burpees, and the like. Basically, any relatively-brief spurts of demand that make you feel like you might drop dead, or might wish to drop dead.
Remember, cardio doesn't burn fat hardly at all, and does not build strength or power either. It can burn some carbs (roughly 2 slices of toast per hour), help mobilize fat-burning somewhat only when combined with low carb, and it puts whatever strength and power you have to work. It is really just about endurance/fitness. If you build your strength and power with other exercises, your effectiveness with high-intensity will obviously increase because your maximum will be more intense.
Losing fat is low-carb diet, improving fitness is demanding cardio, and improving strength/power is resistance. It's simple. Our goal is simple too: to be fit for whatever life offers.
*Thanks to reader for etymology of the balls expression
However the phrase is older than that. Think Steam Power. To go 'Balls to the wall' or 'Balls out' is to go 'Full Steam Ahead'.
Okay, rate my past two days as helping offspring move clinic: agreed, not in a gym, but how much does helping move cat food in and out of containers, binning other bits, and hauling various pieces from Ikea count?
BD, you will get all sorts of comments on balls to the wall, but a very old engineer explained to me when I was a boy (long time ago) that the term referred to the centrifugal governor on steam engines. I can't remembert the technical terms or details but you've seen them, at least in pictures/videos, I'm sure. A vertical rod with two hinged arms hanging down with a weighted ball on the end of each. As the rod spins (engine speed increasing) the arms begin to rise, the balls controlling their speed. At a top or ungoverned speed, the arms are spinning so fast that the balls are horizontal, or pointed to the "wall" of whatever contains the engine. The term way predates airplanes.
Ralph Kinney Bennett