Maximal oxygen consumption, VO2max, is the gold standard to evaluate human aerobic fitness, which stands for the maximal capacity of cardiorespiratory system and musculoskeletal system to transport and utilize oxygen. Previous study showed that there is significant correlation between maximal oxygen consumption from cardiopulmonary exercise test and strength and endurance of lower extremities. In people with sedentary lifestyle, they often limited by the lower limb muscle performance during cardiopulmonary exercise test. Their breathing patterns are more irregular than athletes during cardiopulmonary exercise test. However, there is no study comparing the activation pattern of respiratory muscles between these two groups. Whether the breathing pattern in people with lower exercise capacity is less efficient under exertional activities still unknown. The purpose of this study is to investigate the relationship between maximal oxygen consumption and inspiratory muscle activation pattern in healthy adults.

Inclusion Criteria:

• Healthy adults (age > 20 years old)
• Be able to cooperate with the measurements of this study

Exclusion Criteria:

• any clinical diagnosis that will influence the measurement, including any history of neuromyopathy
• angina, acute myocardial infarction in the previous one month
• pregnancy
• history of syncope during exercise
• any musculoskeletal system disorder that unable to perform cardiopulmonary exercise test

Healthy population is free from abnormal breathing pattern caused by disease. Their terminals of cardiopulmonary exercise test are not limited by symptoms of disease.