Answer to Question 1
Overall, you can burn twice as many calories during vigorous-intensity exercise and, subsequently, more fat as well. Another benefit is that the metabolic rate remains at a slightly higher level longer after vigorous-intensity exercise, so you continue to burn a few extra calories following exercise. Researchers believe that the extra caloric expenditure following vigorous exercise is because (a) the body uses more fat and less carbohydrates following a hard exercise session, (b) additional energy is required to replenish glycogen stores used during intense exercise, and (c) hormones released during vigorous exercise remain high, maintaining an elevated metabolism for several hours thereafter.
Answer to Question 2
a