Coronavirus (COVID-19) was first developed in Wuhan, China in December 2019 and spread rapidly around the world (1, 2). In late January 2020, the disease was recognized as the sixth international public health emergency (3). The infection is transmitted from person to person through respiratory secretions and contact with surfaces or people (4). In general, infectious diseases constantly threaten human health; especially if they are new, because they are always a potential challenge for the healthcare system around the world (5). Health personnel, like other infectious diseases, are at the forefront of the fight against coronavirus. A high percentage of these personnel work night shifts with high workload (6). Work-related stress, lack of sleep, and shift work in health care personnel cause sleep disorders and poor sleep quality (7). Sleep is a specific behavior and each person is aware of its importance and its appropriate duration, and is rotated by waking up. Also, one of the most important parameters in assessing the quality of life and health status of each person is the quality of sleep (8). Sleep is a key factor in a person's physical health and related disorders including poor sleep quality, difficulty sleeping at night, waking up early, circadian rhythm disorders, parasomnia, sleep-related movement disorders, and sleep-related respiratory disorders (9). Sleep disorders are physical and mental conditions that cause adverse effects due to poor sleep quality (10). Sleep disorders have many negative effects on people's lives and lead to physical complications such as increased risk of obesity, diabetes, high blood pressure, increased heart rate, heart attack, and stroke (11). Therefore, during the COVID-19 epidemic and with the increase of work pressure in health care workers, there is a possibility of increasing sleep disorders and consequently increasing physical diseases. Healthcare personnel are the most important group in dealing with the COVID-19 epidemic; therefore, increasing the number of medical staff and reducing the number of work shifts can relieve fatigue and maintain energy levels in them and reduce physical complications in them.
Among the treatment methods for insomnia, we can mention medication; however, because sedatives have side effects such as drowsiness and decreased accuracy, they are not recommended for people such as nurses who always need full alertness during their shift; instead, non-pharmacological therapies such as relaxation techniques can be used. Because relaxation is a relative state of relief from the mental and physical effects of stress which can improve the sleep quality by regulating the hypothalamus and reducing sympathetic and parasympathetic functions (12). The progressive muscle relaxation technique introduced and used by Jacobsen is an easy, cost-effective method without the need for special equipment; it is one of the best complementary therapies to reduce the effects of mental illness such as anxiety because people in this method, by contracting and relaxing a specific muscle, cause relaxation in different target muscles and increase concentration and pleasant emotions (13). In order to improve working conditions, it is also suggested that the chronobiological characteristics of individuals should be considered when planning work shifts and classifying individuals accordingly. This type of chronotype classification is a simple method and takes into account issues such as individual circadian differences, sleep habits and performance on a particular day, and ultimately helps to plan work shifts based on these chronobiological characteristics (14). Another suggestion that can be made in this regard is physical activity because physical activity promotes physical and mental health with the biological and biochemical changes that follow. As a result, they improve the quality of sleep. In addition, physical activity, if repeated frequently, reduces the risk of physical illnesses such as cardiovascular disease, cancer, diabetes, and hypertension by boosting the  immune response in the body (15).