Have you ever wondered about the differences between various types of exercise? For example, why should a person have to do aerobic exercise, anaerobic exercise (ie lift weights), and stretch? Is not there a neat, tidy little way to just roll it all into one and get it over with? Well, there's a good reason you should be doing a range of different exercise types. It's known as the 'principle of training specificity'. In plain English that means that your body will adapt quite differently to the three basic types of exercise, and that one can not really substitute for the other. Let's look at each of the three exercise types briefly:
Anaerobic training (Weight lifting): When you perform any type of resistance exercise, such as lifting weights, your muscles (and bones) adapt by getting bigger and stronger. This is beneficial because it allows you to do everyday things better and more safely, such as lifting your child or keeping your balance on the stairs. Also, when your body works anaerobically it is burning fuel (mostly carbohydrates) without using oxygen. This requires a certain metabolic pathway, and specific enzymes. As you perform this type of exercise this pathway and enzymes become more efficient at their jobs.
Aerobic training (Endurance): Muscular and cardiovascular endurance are improved with aerobic exercise, allowing you do go further with less effort. When you exercise aerobically your body is able to supply oxygen to the process of burning fuel it has stored. This allows it to burn fat rather than carbohydrates, and uses an entirely different metabolic pathway along with different enzymes. Just as when you work anaerobically, working aerobically causes this pathway to become more efficient. Want to train your body how to burn fat for fuel? Aerobic exercise is the key.
Flexibility (Stretching): When you do flexibility exercises you are teaching your muscles to move further, more easily, and more freely. This is important to keep you free of injury, as well as to enhance your posture and body alignment. Neither anaerobic nor aerobic exercise put the right type of stimulus on muscles to get them to be more limber in any significant way.
You can see that each of the three types of exercise have their place and that all are important. Any exercise program that does not include all three is simply incomplete and will not be as effective as one that is more well rounded. Take the time to work them all into your fitness routine, and your body will thank you.