Cardiovascular Endurance.
Muscular Strength.
Muscular Endurance.
Flexibility.
Body Composition.
Explanation:
How Age and Exercise Affect Your Max Heart Rate. The relationship between the heart and exercise has been studied for more than six decades and the research is clear: Max heart rate—the highest heart rate you can safely hit during exercise—decreases with age regardless of lifestyle or level of fitness.
I believe that it is a major life change.