Breathing is the exchange of oxygen and carbon dioxide gases with inspiration (breathing in) and expiration (breathing) in order to maintain the optimum oxygen level in arterial blood. Respiration takes place through respiratory muscles. While inspiration takes place through the diaphragm and accessory respiratory muscles; Expiration takes place passively. Respiratory muscle function is determined by evaluating respiratory muscle strength and respiratory muscle endurance together. respiratory muscle dysfunction; It is a decrease in respiratory muscle strength, endurance, or both, caused by factors such as elongated diaphragm fibers, increased respiratory workload, changes in muscle mass and abdominal weight. Today, respiratory muscle strength are widely used in the evaluation of respiratory muscle function. However, evaluation of respiratory muscle endurance is more effective than respiratory muscle strength in the evaluation of submaximal respiratory muscle contraction, which is valid for daily activities, and in the clinical, functional and prognostic evaluation of respiratory muscles. In chronic obstructive pulmonary disease, respiratory muscle function is associated with pulmonary functions, symptoms, comorbidities, health status, airway obstruction, lung volumes, and physiological disorders. Respiratory muscle dysfunction in chronic obstructive pulmonary disease increases with disease progression. Dysfunction in the diaphragm, which is the most important respiratory muscle, can be evaluated with respiratory muscle strength and endurance, as well as diaphragm thickness. Diaphragm thickness provides information about disease progression in individuals with chronic obstructive pulmonary disease. It is known that diaphragm thickness is associated with respiratory muscle strength and respiratory function parameters in individuals with chronic obstructive pulmonary disease.

The World Health Organization defines health as "a state of complete physical, social and mental well-being and not merely the absence of disease or infirmity". One of the important factors for maintaining health is physical fitness. physical fitness; It is the ability to perform occupational, recreational and daily activities correctly and successfully without fatigue. Physical fitness is also known as the ability to do daily tasks vigorously and carefully, without excessive fatigue, and to allocate sufficient energy for leisure and unexpected emergencies. Physical fitness is divided into two as health-related physical fitness and sports-related physical fitness. While health-related physical fitness parameters are body composition, cardiorespiratory fitness, muscular strength and endurance, flexibility; Sport-related physical fitness parameters are balance, coordination, reaction time, agility, speed and power. Decreased physical fitness in individuals with chronic obstructive pulmonary disease is associated with respiratory problems (such as airway obstruction). It is known that physical fitness is related to the ability to perform physical activity. Low physical fitness occurs in most individuals with chronic obstructive pulmonary disease due to decreased physical activity. There is an important relationship between physical fitness and lung functions.

In the literature, studies evaluating respiratory muscle function, diaphragm thickness and health-related physical fitness parameters together are insufficient in individuals with chronic obstructive pulmonary disease. In the thesis study, which is planned to be done, it is thought that the respiratory muscle function, diaphragm thickness, health-related physical fitness parameters, physical activity and lung functions of individuals with chronic obstructive pulmonary disease can be evaluated together to contribute to the literature.

The aim of this study is to evaluate diaphragm thickness, respiratory muscle strength, endurance, body composition, aerobic exercise capacity, upper and lower extremity muscle strength and endurance, grip strength, flexibility in individuals with chronic obstructive pulmonary disease and compare them with the healthy group.