Fitness does not only refer to being physically fit, but also refers to a person’s mental state as well. If a person is physically fit, but mentally unwell or troubled, he or she will not be able to function optimally. Mental fitness can only be achieved if your body is functioning well. You can help relax your own mind and eliminate stresses by exercising regularly and eating right.
These types include cardiorespiratory endurance, which is how long or fast a person can perform an activity and how this impacts heart rate and oxygen consumption. Muscular strength, which is how much weight can be moved in relation to repetitions and muscular power, which is how much force can be generated during a given activity. There is also flexibility, how far a muscle group can be stretched or joint can be moved. Balance how long a particular position can be held with or without some type of activity being performed. Speed, how quickly an individual can move from one point to another. And body composition, the amount of fat on the body versus other tissues such as muscle, bones and skin.
Before the industrial revolution, fitness was defined as the capacity to carry out the day’s activities without undue fatigue. However, with automation and changes in lifestyles physical fitness is now considered a measure of the body's ability to function efficiently and effectively in work and leisure activities, to be healthy, to resist hypokinetic diseases, and to meet emergency situations.[4]
Physical activity boosts the immune system. This is dependent on the concentration of endogenous factors (such as sex hormones, metabolic hormones and growth hormones), body temperature, blood flow, hydration status and body position.[37] Physical activity has shown to increase the levels of natural killer (NK) cells, NK T cells, macrophages, neutrophils and eosinophils, complements, cytokines, antibodies and T cytotoxic cells.[38][39] However, the mechanism linking physical activity to immune system is not fully understood.