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.
High intensity interval training (HIIT) consists of repeated, short bursts of exercise, completed at a high level of intensity. These sets of intense activity are followed by a predetermined time of rest or low intensity activity. Studies have shown that exercising at a higher intensity has increased cardiac benefits for humans, compared to when exercising at a low or moderate level. When your workout consists of an HIIT session, your body has to work harder to replace the oxygen it lost. Research into the benefits of HIIT have revealed that it can be very successful for reducing fat, especially around the abdominal region. Furthermore, when compared to continuous moderate exercise, HIIT proves to burn more calories and increase the amount of fat burned post- HIIT session. Lack of time is one of the main reasons stated for not exercising; HIIT is a great alternative for those people because the duration of an HIIT session can be as short as 10 minutes, making it much quicker than conventional workouts.
Calisthenics. There's nothing fancy about a calisthenics workout, but just because it's basic doesn't mean it's not effective. A 2017 study in Isokinetics and Exercise Science put a group of untrained individuals through a calisthenics program to test the effectiveness of an exercise method that uses no equipment. Participants did a brief workout consisting of four or five exercises three days a week for eight weeks. At the end of the trial, all participants had significant improvements in posture, strength and body composition.
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. 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. However, the mechanism linking physical activity to immune system is not fully understood.