Increased fitness in this case refers to the increased capacity of the heart to get blood and therefore oxygen to the working muscles, and the increased ability for the muscles to use the oxygen efficiently. This is known as the aerobic capacity, and is the most important component of any fitness program. It takes into account the fitness level you already have by using the heart rate reserve. A less fit person has a higher resting heart rate and lower heart rate reserve, and so will reach higher heart rates quickly. You can adjust your exercise level to challenge you but not cause burnout or injury.
Heart rate is measured in beats per minute.
Lower Level 6. This is the heart rate range you should have in the middle of exercising and at the immediate end of exercising, that is, between EHR lower level and EHR upper level. In order to complete your log, you will need to know the Calorie content of the foods you eat. You will be given a booklet which provides this information. You will also need to know your basal metabolic rate.