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There are different categories or types of physical fitness training. Each corresponds to a defined purpose or fitness goal such as the development and improvement of one or more of the five dimensions of physical fitness, or for participation in a particular type of sports and rehabilitation through physical training, among others. Note that the different types of training also correspond to the different categories or types of exercises.
Strength refers to the ability of your muscles to perform work at one time, such as lifting a heavy barbell. You build strength by putting enough resistance against your muscles that you cause damage to them. When your muscles repair themselves in response to this damage, they grow bigger. Since your heart and lungs are muscles, some people refer to your cardio capacity as cardio strength.
To exercise, work, do daily chores and play sports, you’ll need varying levels of cardiorespiratory capacity and stamina, muscle strength and endurance, footwork skills and speed. Training for one type of fitness often requires different types of exercises than training for another type of fitness. For example, strength training uses heavy weights and slower muscle movements than sprint training, which is performed with little resistance and high-speed muscle movements. These different types of fitness workouts recruit different muscle fibers and burn different amounts of fat and glycogen. It's best to focus on strength and endurance exercise during a sport off-season, and work on speed and recovery during the preseason and in season.
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.

Gymnasiums which would seem familiar today began to become increasingly common in the 19th Century. The industrial revolution had led to a more sedentary lifestyle for many people and there was an increased awareness that this had the potential to be harmful for health. This was a key motivating factor for the forming of a physical culture movement, especially in Europe and the USA. This movement advocated increased levels of physical fitness for men, women and children and sought to do so through various forms of indoor and outdoor activity, and education. In many ways it laid the foundations for modern fitness culture.[50]
Physical fitness has always been important part of life. It is theorised that when people left a hunter-gatherer lifestyle and formed fixed communities based around agriculture that physical fitness levels declined. This is not to say that levels of physical labour decreased but that the type of work undertaken was not necessarily as conducive to a general level of fitness. As such, regimented fitness regimes were either invented or became more common. This was especially the case in classical civilisations such as Ancient Greece and Rome. In Greece especially physical fitness was considered to be an essential component of a healthy life and it was the norm for men to frequent a gymnasium. Physical fitness regimes were also considered to be of paramount importance in a nation's ability to train soldiers and field an effective military force. Partly for these reasons, organised fitness regimes have been in existence throughout known history and evidence of them can be found in many countries.
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.