2019 Novel Coronavirus: Emphasis on Maintaining Optimal Levels of Physical Activity Under Self-quarantine Conditions

   Dear Editor, The prevalence of coronavirus disease 2019 in China and subsequently in most countries of the world has become the most important health problem and has declared a state of emergency in many countries. According to the WHO (April 10, 2020), positive cases have been observed in all countries of the world, and its prevalence is increasing sharply, as health systems in many countries have announced a pandemic situation. Finally, as of April 10, 2020, 66220 positive cases and 4110 deaths have been registered, making Iran one of the most infected countries in the world and having the highest number in the region. Given the lack of available vaccines and essential remedies for the virus, numerous articles have been written on providing important scientific information on the virus. Key questions about the modes and mechanisms of transmission, incubation period, level of risk, and effective treatment are still under discussion. Due to the unprecedented outbreak and the state of emergency, many countries including Iran have adopted safeguards including near-total closing of the cities, flight cancellations, closing the schools for long time, and closing the public places such as sport clubs. On the other hand, given China’s successful experience in controlling the epidemic, measures such as self-quarantine are key to the prevention agenda. However, this disrupts the daily activities of millions of people worldwide, as well as in Iran. It is well known that self-quarantine is naturally associated with reduced levels of daily physical activities. Staying home is accompanied by behaviors such as prolonged lying and sitting, watching TV, and using mobile phone. Concurrently, the likelihood of increasing food and calorie intake in inactive conditions is inevitable. Consequently, a reduction in physical activity, and a decrease in resting energy expenditure accompanied by an increase in calorie intake, could increase the risks associated with sedentarism. Hence, while long-term homestay is clearly recognized as an effective and safe preventive measure regarding the spread of virus, inactive lifestyle can lead to detrimental physiological changes including weight gain and metabolic diseases, as well as psychological changes including depression and aggression that may continue until after the end of the disease. Long-term inactivity, which is generally associated with excessive calorie intake, is the major contributor to overweight, followed by increased systemic inflammation. In the current situation where fear of illness causes stress, the combination of stress, overeating, and increased inactivity can severely affect the immune system. In this regard, Dr. Woods, a pioneer in studies of the effects of exercise on the immune system, has shown that regular exercise exerts many anti-inflammatory effects on the body. He has shown in his studies that exercise improves the immune response to the influenza vaccine. Moreover, in his numerous studies on animals and human subjects, he has displayed that endurance exercise has significant anti-inflammatory effects and strengthens the immune system. Therefore, exercise seems to be safe during the coronavirus outbreak and offers many benefits to us. An important issue in the field of exercise in these conditions is the "exercise intensity". If an inactive person wants to start exercising, it is better to start with a low intensity and increase the intensity of the activity over time, as it has been found that intense exercise can have a negative impact on the immunity system of the inactive person. However, if the active person decides to exercise and has already had regular exercise, he or she can continue the exercise at optimal intensity. According to the research, even a single exercise can affect the immune system, but regular exercise has many more benefits, and cellular and molecular changes begin within seconds to minutes after exercise.10 Therefore, in quarantine conditions, continued physical activity and maintaining optimum levels of physical activity to prevent physical and mental disorders, as well as maintaining optimal immune function, is of the utmost importance, while avoiding this has irreparable consequences. Home-based exercise can be performed easily and safely that improves cardiopulmonary and immune function along with maintaining and improving fitness. Balance exercises, stretching, range of motion, stepping, lifting, and moving up the stairs, chair dips, squats, pushups, and planks are examples of home-based exercises, though not limited to these13. Exercises like tai chi, yoga, dumbbell workout, elastic bands, and physioball exercises, as well as some pilates and aerobic exercises can also be performed easily in small space due to the lack of special equipment. In addition to using sports videos, mobile, and web sports software, there are other effective ways to maintain physical function and mental health during the quarantine. Therefore, the restrictions adopted to prevent the outbreak of the coronavirus epidemic should not limit physical activity or exercise, because exercise and physical activity keep people healthy and improve the health of patients with various diseases. It is recommended that physically active people maintain an optimal level of activity and that sedentary people begin their physical activity and increase it over time. Furthermore, individuals staying at home during the coronavirus pandemic can perform 30 minutes of moderate-intensity or 20 minutes of high-intensity physical activities per day. Reducing sitting time and lying down is also highly recommended. Of course, specific groups such as children, the elderly, and people who have experienced the symptoms of the virus or are susceptible to the disease can also ask the advice of sports and health professionals. Given the serious concerns about the increasing prevalence of coronavirus, preventive measures are strongly recommended. Self-quarantine is an important measure to prevent the spread of this infectious virus. Nonetheless, given that long-term quarantine may lead to more sedentary behaviors, increase the anxiety and depression, and lead to increased health risks, maintaining an optimal level of daily physical activity during the coronavirus pandemic is highly recommended.