Decreases the size of your heart
Small muscles use less energy and are more efficient. Consider the difference in energy consumption between a 50cc scooter and a huge V8 4×4 truck. Our heart is a muscle just like the rest of our muscles, if you force the heart to keep running for long periods of time it will naturally shrink to use less energy and become more efficient. Remember that energy is a valuable commodity and the body wants to retain as much as possible.
Causes injury through repetitive movements
When you run 2.5-3 times your bodyweight is transmitted through your joints. Now imagine this type of force being repeated over and over again for long periods of time, eventually your weakest joint will give out. Usually the ankles or the knees are the first to go. Many runners then opt for some kind of support or brace which only exacerbates the problem by moving it on to the next weakest joint whist keeping the old injury still weak.
Slows down your metabolism
The more muscle tone you can maintain, generally the higher your metabolism. Muscle is highly metabolically active and requires constant energy to survive, so the more muscle tone you have the more calories you will be burning at rest. Long distance running will often deplete your energy stores and then start breaking down your muscle tissue to use as energy. If you want some serious muscle wastage and to reduce your metabolic rate then keep running.
Produces more body fat
Fat is one of our body’s favourite sources of energy. The more you run the more your body prepares itself for your next run. You will actually start to hold on to more fat so you can run for longer next time.
Boring and time consuming
Some people run for fun, but lets face it most of us run to get in shape and lose that excess belly fat. The truth is running is very time consuming and there are better ways to get great results in a lot lot less time.
Cardiac distress and heart attacks
Evolving from our hunter gatherer days we had no real necessity to run long distances, in fact the only running we ever did was in short bursts to avoid predators or to catch food. Our body simply isn’t designed to run long distances and the stresses you put your heart under during this time can set you up for a heart attack. It’s a fact that many long distance runners do die of heart attacks.
Fat burning slows right down
The body is an amazing machine and will adapt to anything over time. The more time you spend running the better you become at running and the more efficient you get at using less energy. So what starts off as a great calorie burner quite quickly becomes almost useless at burning excess calories. Ultimately runners then have to run further and further to get the same calorie expenditure that they achieved when they first started.