Cardio May Be A Waste of Time Without This Knowledge

Cardio May Be A Waste of Time Without This Knowledge: "The most important factor for improving cardiorespiratory fitness (cardio or CR) is the intensity of the workout. Changes in CR fitness are directly related to how 'hard' an aerobic exercise is performed. The more energy expended per unit of time, the greater the intensity of the exercise, the greater the effect on cardiorespiratory fitness."