One of the best promoted aspects of fitness by far is cardio. People often gravitate to it because the incredible sweating and, often, heavy breathing involved gives a clear and quick physical indication that it is having an effect. But the effects aren't necessarily beneficial in the long run, depending on how you perform it.
Take into consideration a commonly used gym machine: the treadmill. Before beginning a workout, thousands will enter a gym and spend roughly 30 - 45 minutes running on a treadmill, sweating it out, and getting the blood flowing. From what I've seen, most will maintain the same speed and incline for the duration of that time. This can be very detrimental to health.
The effect that constant pounding against a treadmill can have on knee joints is devastating. The knees can become inflamed, which will also have an effect on heart health. In addition, extended cardio exercises like long distance running or treadmill running encourages the development of body fat. When you train your body to endure lengthy bouts of exercise, your metabolism slows down and your body stores more body fat to provide sustained energy for those lengthy runs.
High intensity training, on the other hand, is phenomenal for burning fat and revving up your metabolism. This form of workout requires energy much quicker and more readily than fat can provide, so the fat in your body is instead metabolized as sugars and ATP to power your muscular system. Burning this fat is less of an issue for a body acclimating to a high intensity workout because most animals would not expend that much energy without there being a large food source available. This type of cardio is more suited to a current human's lifestyle of multiple meals a day, generally large meals at that. Training your body to burn these kinds of meals with ease also increases your blood flow, lowers your resting heart rate, and blasts away fat stored on the body.Also, there are great places to run to optimize your health with fresh air, stronger feet, scenery, safety, wherever you would most achieve your goals. Learn more about where to run here.