The question, of which type of exercise is better, cardio or weight training, is often asked by beginning exercisers. They often try to determine what exercise they should be doing to lose weight, build muscle, or a combination of the two. The problem is that there is no straight answer to the question. They both have merit in all applications.
To understand the question, and ultimately arrive at an answer for which exercise is best for a particular need, it is important to understand each type of exercise. Cardiovascular exercise is designed to tax the cardiovascular system so that it will become stronger and more efficient. It accomplishes this by increasing the heart rate and making it pump more blood, faster. The lungs are worked because they must bring in more oxygen to feed the working muscles. The heart becomes stronger and more efficient at pumping larger quantities of blood with each pump and the lungs and muscles of the respiratory system become stronger and more efficient. Cardiovascular exercises are usually longer in duration and lower in intensity than weight training activities.
Weight training, or resistance training, is used to strengthen the muscles. It is also used to increase lean muscle mass. The muscles are damaged during weight training, this is the stimulus for growth and development. The body doesn’t like being damaged so it rebuilds the muscle and makes it a little stronger and increases the size of the muscle slightly. This way the next time the same workload is encountered the muscle will not be damaged (or at least not to the same degree.) Increasing the resistance causes more damage the next time and a continuation of the strengthening and building process occurs. Weight training can be done with heavy weights and low repetitions or lighter weights and higher repetitions. The former results in more strength, while the latter results in more endurance.
Neither type of exercise is totally exclusive of the other. The muscles are worked during cardiovascular exercise, which also accounts for some of the fat burning process. The heart rate increases and the lungs must work to pull in more air during weight training, especially during higher repetition sets. Each has benefits in the fat burning game, but they reach it in different ways.
Cardiovascular exercise can result in direct fat burning during the exercise. The body starts out using ATP for energy, then it turns to glucose for energy, and finally at the ten to twelve minute mark (of continuous movement) it begins to burn fats for energy. Cardio exercise that lasts more than fifteen minutes uses this fat for energy. The longer the activity the more fat needed for energy. That is why low intensity cardio is effective at burning fat during the exercise.
Weight training has a more indirect impact on fat stores in the body. Because of the longer duration of the fat burning process, the body uses this for daily energy needs, as well. The body needs a certain number of calories of energy to sustain regular day to day activities. Muscle tissue is very metabolically active because it is constantly using energy to repair and rebuild, plus it needs energy to contract and move, unlike fat stores. This means that the additional muscle built while weight training increases the total number of calories used in a day, which means more fat burned throughout the day just to support daily needs.
Both weight training and cardio have fat loss potential. Cardio exercises directly impact the fat burning process while weight training has a more indirect impact. The best exercise workout routine is one that combines both types of exercise for the most fat burning bang for your buck.