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.
The Physical Activity Guidelines for Americans were created by the Office of Disease Prevention and Health Promotion. This publication recommends that all adults should avoid inactivity to promote good health mentally and physically. For substantial health benefits, adults should participate in at least 150 minutes a week of moderate-intensity, or 75 minutes a week of vigorous-intensity aerobic physical activity, or an equivalent combination of moderate- and vigorous-intensity aerobic activity. Aerobic activity should be performed in episodes of at least 10 minutes, and preferably, it should be spread throughout the week.
An example of a test with average results would be a woman doing between 20-25 push-ups during a muscular endurance test. In all cases of activity, proper precautions should be taken to avoid injuries or other health complications. Consulting with a physician prior to starting an exercise program is recommended. Other professionals, such as personal trainers or exercise physiologists, should also be considered as resources to help create a program that is the best fit based on personal needs.
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.[25] 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.[26] 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.[27] Furthermore, when compared to continuous moderate exercise, HIIT proves to burn more calories and increase the amount of fat burned post- HIIT session.[28] 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.[29]
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.
Centers for disease control and prevention provide lifestyle guidelines of maintaining a balanced diet and engaging in physical activity to reduce the risk of disease. The WCRF/ American Institute for Cancer Research (AICR) published a list of recommendations that reflect the evidence they have found through consistency in fitness and dietary factors that directly relate to cancer prevention.
Sam Ashe-Edmunds has been writing and lecturing for decades. He has worked in the corporate and nonprofit arenas as a C-Suite executive, serving on several nonprofit boards. He is an internationally traveled sport science writer and lecturer. He has been published in print publications such as Entrepreneur, Tennis, SI for Kids, Chicago Tribune, Sacramento Bee, and on websites such Smart-Healthy-Living.net, SmartyCents and Youthletic. Edmunds has a bachelor's degree in journalism.
Possibly one of the most important parts of fitness training is flexibility and mobility. Flexibility is the ability of your muscles to stretch, and mobility is being able to move your joints and tissues through their full range of motion. Both are important to athletic performance and for avoiding injury. Muscles and joints that are flexible and mobile — as well as strong — are much less susceptible to sprains and other injuries.

The US guidelines continue: For additional and more extensive health benefits, adults should increase their aerobic physical activity to 300 minutes (5 hours) a week of moderate-intensity, or 150 minutes a week of vigorous-intensity aerobic physical activity, or an equivalent combination of moderate- and vigorous-intensity activity. Additional health benefits are gained by engaging in physical activity beyond this amount. Adults should also do muscle-strengthening activities that are moderate or high intensity and involve all major muscle groups on 2 or more days a week, as these activities provide additional health benefits.[14]
New (July 2011) guidelines in the United Kingdom include the following points: The intensity at which we exercise is key, and light activity such as strolling and housework is unlikely to have much positive impact on the health of most people. For aerobic exercise to be beneficial it must raise your heartbeat and make you sweat. The more exercise you do, the better. Everyone should do a minimum of 150 minutes a week of moderate-intensity aerobic exercise but that really is the minimum for health benefits. If you can go beyond 150 minutes, you’ll gain even more health benefits. Sedentary time (time spent sitting down to watch TV, use a computer, read or listen to music) is bad for your health, even for those who are achieving 150 minutes of exercise a week. These guidelines, are now much more in line with those used in the US, also include recommendations for muscle-building and bone strengthening activities such as lifting weights and yoga.

Sam Ashe-Edmunds has been writing and lecturing for decades. He has worked in the corporate and nonprofit arenas as a C-Suite executive, serving on several nonprofit boards. He is an internationally traveled sport science writer and lecturer. He has been published in print publications such as Entrepreneur, Tennis, SI for Kids, Chicago Tribune, Sacramento Bee, and on websites such Smart-Healthy-Living.net, SmartyCents and Youthletic. Edmunds has a bachelor's degree in journalism.
These recommendations are also widely supported by the American Cancer Society. The guidelines have been evaluated and individuals that have higher guideline adherence scores substantially reduce cancer risk as well as help towards control with a multitude of chronic health problems. Regular physical activity is a factor that helps reduce an individual’s blood pressure and improves cholesterol levels, two key components that correlate with heart disease and Type 2 Diabetes.[33] The American Cancer Society encourages the public to "adopt a physically active lifestyle" by meeting the criteria in a variety of physical activities such as hiking, swimming, circuit training, resistance training, lifting, etc. It is understood that cancer is not a disease that can be cured by physical fitness alone, however, because it is a multifactorial disease, physical fitness is a controllable prevention. The large associations tied with being physically fit and reduced cancer risk are enough to provide a strategy to reduce cancer risk.[32] The American Cancer Society asserts different levels of activity ranging from moderate to vigorous to clarify the recommended time spent on a physical activity. These classifications of physical activity consider the intentional exercise and basic activities are done on a daily basis and give the public a greater understanding of what fitness levels suffice as future disease prevention.
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