Let's get two things straight first:
- An hour of physical activity daily, just walking, jogging, or swimming laps, is better than nothing. It's minimal to maintain functionality.
- You can't lose fat through exercise. That's about food.
I've been chatting with doctors lately - my cardiologist for my annual stress test (no symptoms, no problems) and the internist who works out in my gym at 5 am. Oh, and my pure weights friend who is my internist (he is buff at 60). They joke about people who do long/slow exercise instead of weights and HIIT, but they are wrong to disparage people who make the effort to do anything more than sit on their asses.
Of course, though, I know what the docs are talking about.
Let's just talk about cardiac fitness rather than just the ability to hike for 5 or 6 hours. The reasons to do "cardio" exercises are only secondarily for general endurance - they mean to address the heart muscle. That means Cardiac Output when needed, and improving heart vasculature (so you can maybe survive your first heart attack). People who just do "cardio" things do not build or maintain much strength.
That gets us to HIIT. HIIT is a serious cardiac stressor. It's sort-of fun too if you like to sweat. Yes, heavy weights are heart stressors too, but only for seconds. Our Maggie's calisthenics routines are too, to a degree, although they are more oriented to athleticism.
For people who like fitness, one way to do cardio days (assuming you do 2 weights days and 2 calisthenic/sports days) is to use the hour or so to mix in the HIIT with just trucking along. That's how the idea is designed to work anyway.
Low-Intensity Cardio Training: What Is It & How Does It Work? (Note that they assume that low intensity is just one part of a fitness program)
Is High-Intensity Interval Training (HIIT) the Most Efficient Way to Work Out? A simple guide to high-intensity interval training, or HIIT, the fitness trend du jour.
Eventually, we will all break down, get frail, and die (or die before we get frail), but why not make the most of today? Fitness is not about life span.