When I walk around the gym, talking to members and clients about "weight" lose, most of the time people ask if they should "run" more. Simple answer, no.
I'm quite a big fan of trying to keep my body as close to it's original genetic expression. As in the last few thousand years we haven't changed on the genetic level. I very rarely run, unless it's for the bus, and I lift pretty heavy a couple of times a week. This is what I do with my clients too.
There are many forms or training out there that are good for very short term gains. like following a resistance programme for under a month or even running, BUT after 30 days it makes sense to slow it done or your body wont last. Yes certain factors do play a role in you staying injury free, for now. The biggest one is age. the younger we are the more durable we are. For example, you run 5-10 miles every day starting from the age of 20. okay fine. 10 years later you're still doing that, now though you find you have knee problems or are having issues with your feet. Another ten years you could be having surgery to correct those problems. you're now 60 years of age, walking has now become a problem, and you need to use a cane to help you get around, it even hurts every time you stand or sit.
If you are an athlete, and you are paid a lot of money to run about (football, rugby, American football players and so on) you expect to retire in your 30's, you get into these fields knowing what could happen as you age. Just look at players over 30 and see how often most of them get injured.
To have any positive effect on your body, you need to put it under some stress (exercise) but the wrong kind of stress can have a negative effect, such as chronic cardio. When we exercise we deplete glycogen stores from our muscles and liver. Our body will break down excess fat stores and have that converted into glycogen and stored back into our muscles and liver. With cardio, you will replace that fuel with large amounts of carbohydrate foods. Your body will breakdown muscle tissue to keep you moving during endurance runs.
As muscle tissue is used up, the negative impact of this is, lack of muscle size and strength, speed and power. Think of it this way, when a body builder wants to lean up what does he do more of? Cardio.
As a species w have been moving about under our own power for over 2 million years. Hunting and gathering for survival. one thing we did most, was stalk our prey. No running after it, if we did we surly would have been killed by it. We stalked our prey as most of the things we hunted were quadrupeds (four legs) and could clearly out run us.
Bone fractures, shin splints, tendonitis, bursitis, muscle cramps, ligament injuries, plantar fasciitis, cardiac arrhythmias, atherosclerosis and oxidative stress and over training, and many other joint and feet problems that can come with chronic cardio. Yes you can be injured from weight training too, if done incorrectly, and trust me I see a lot of this in the gym.
One thing you might want to compare are sprinters and endurance runners and see the difference in their physicality.
Cardio is just an abbreviation of cardiovascular, which in it's simple term just means heart and lungs. There are other ways to work those.
I'm not trying to get to deep on this, just wanted to throw up (as simply as possible) my thoughts on this subject and maybe just have that grey matter expand a little.
If you run for fun, cool, just don't rely on it to much as a way to stay/become healthier, there are safer ways.
Eat smart, Train hard
