In the broadest sense, physical fitness is your body's ability to perform physical activity. There are several ways to judge your level of fitness.
Functional Fitness
One of the most basic measures of physical fitness is your functional fitness: your ability to perform daily activities — such as walking, bending, lifting and climbing stairs — without pain or discomfort. Functional fitness comes from having healthy lungs, heart, muscles, bones and joints, and it influences your risk of disease and early death. Good indicators of your functional fitness are the number of minutes you engage in physical activity each week and the number of calories you burn in the process.
Physiological Determinants
Physical fitness can also be measured using a series of physiological assessments that chart how effectively your body rises to the demands of physical activity.
Cardiorespiratory endurance. Cardiorespiratory endurance, also known as aerobic fitness, is perhaps the best-studied gauge of fitness. Measurements of cardiorespiratory function indicate how efficiently your heart, lungs and blood vessels can supply oxygen to your cells during extended bouts of physical exertion.
Muscle strength and muscle endurance. Measurement of muscle strength assesses the amount of power your muscles are able to exert. Your muscle endurance indicates how long your muscles can work before becoming fatigued.
Flexibility. Flexibility is the ability of your joints to move easily through their entire range of motion. As you age, flexibility becomes increasingly critical for avoiding injury and maintaining independence.
Body composition. Also relevant to your overall fitness is your body composition — the proportion of fat you carry in relation to your lean muscle mass. Many diseases, including cancer, heart disease and diabetes, are linked to the accumulation of extra fat, particularly in the abdominal area.
