Myofascial pain syndrome (MPS) is defined as sensory, motor, and autonomic symptoms caused by myofascial trigger points. Trigger points are defined as tender points in discrete taut bands of stiffened muscle that cause local and referred pain, among other symptoms. The mechanical and psychological stress of the muscle can activate trigger points and cause pain over a wide area. MyofascialPainSyndrome (MPS) is considered one of the most common chronic musculoskeletal pains. Various studies have shown that it is often associated with depression and anxiety. It is important to focus on modifiable biopsychosocial factors, while paying attention to aspects that cannot be changed, such as attitudes, neuroticism, and trait anxiety, which are known to be somewhat stable over time. Knowing these factors is necessary to improve patients' quality of life and regain their functions.

Pain in patients with MAS can cause sleep disorders such as non-restorative sleep or difficulty initiating or maintaining sleep. It is estimated that 70-80% of patients with MAS experience sleep disorders. Patients with insomnia, especially those living in urban affluent areas, are at risk of developing MAS later in life. Morning-evening preference is an inter-individual difference, also known as diurnal or circadian preference.

The circadian rhythm is controlled by the endogenous circadian clock, which has a genetic basis and is affected by exogenous factors. Due to these individual differences, individuals' energy levels during the day vary so much that people prefer to be active at different times of the day. Morning Type individuals prefer to be active early in the day, while evening type individuals prefer to be active later in the day. Individuals who are between these types and morning or evening preference are called intermediate types. Morning preference is affected by biological factors (e.g., body temperature, cortisol, melatonin), technological and social factors (e.g., electronic media, lighting, TV screens, daily life activities), and environmental factors (e.g., climate, latitude, longitude). In addition, morning preference is related to personality, health, eating habits and psychological well-being. Morning people are more conscientious and more prone to healthy behaviors. On the other hand, evening preference can lead to behavioral problems (e.g., depression, loneliness), personality disorders (substance abuse, eating disorders, internet addiction, daytime sleepiness) and poor academic performance. A study in which 1548 people with fibromyalgia (FMS) were assessed with an online survey that included questions about sleep quality, well-being, pain, chronotype and FMS showed that late chronotypes were more affected by fibromyalgia.

Another study investigating the relationships between chronotypes and musculoskeletal pain showed that evening and intermediate chronotypes were associated with musculoskeletal pain, but mental distress, insomnia, and comorbidities also played a role in these relationships. The aim of this study is to examine chronotype preferences in myofascial pain syndrome and to investigate its relationship with pain severity, disability and quality of life.