If you like running and are an avid runner, treadmill user, marathoner or the like, then rock on with your bad self. If you run because you like it and enjoy running, then I support you 100%. If you tell me there is another reason you run , then we start to disagree.
So if you think running is the great fitness cure, then you will not like this information. After 25 years of performing arduous cardio training of all types, I am healthier and leaner now that I have given it up.
Many of the cardio type events and training that I did revolved around the military and were purely functional. I was an infantry soldier and I had to get to places and do certain things in a variety of ways. Other things were physical requirements for the job. In the Army, you have to run because they tell you to.
I participated in daily runs, ranging from sprints to anywhere up to half marathon distances. Distance and speed were factors that I had to adapt to because I had to for work. It never got me ripped and it never made my joints stronger. It just wore me down and kept me weak. There was no fitness benefit from running other than being able to run better.
Of course, when I retired from the Army and didn't have to run anymore, I stopped running altogether. My world didn't collapse, I didn't get out of shape and fat and I didn't continue to suffer from joint pain. I got healthier, leaner and stronger by doing exercises and fitness training that were productive.
And from a functional / daily life activity standpoint, in the last 30 years, I've never had to run 5 miles or more for anything. I have had to sprint though, especially when bullets were headed my way.
Long distance, steady state running can impact your hormone levels, keeping you catabolic and can actually lower your T3 levels, killing your metabolism, causing fat to be maintained and stored, while your lean body mass is feasted upon to keep you alive.
Inflammation from repeated, long, steady state running causes cardiac damage and a list of other health issues, not cardiac health. Long, slow, steady state running serves no functional purpose other than to make you better at running.
High intensity interval training, sprinting and walking / hiking have functional fitness value for both body composition and daily life activities. Running 10 miles does not. Sorry.
So like I said, if you enjoy running, then run to your heart's content by all means. But for health and fitness, there are many superior ways to become healthy, lean and fit.
Dempsey's Resolution Fitness