The aim of this study is to describe the movement of the diaphragm during postural activation of the trunk muscles in comparison with tidal breathing.

Diaphragm movement will be measured by m-mode ultrasonography in a standing position. 30-35 healthy subjects will participate in the study. The movement of the diaphragm will be measured during tidal breathing then, during holding a load corresponding to 20% of the subject´s body weight and finally, during voluntary contraction of the trunk muscles. Trunk muscles contraction will be measured by a special device with pressure sensors placed on a trunk surface. Breathing activity will be measured by spirometry.

Inclusion Criteria:

• Signed informed consent form
• Able to comply with the study protocol, in the investigator's judgment
• Aged 20-40 years, inclusive
• Healthy as determined by the Investigator based on medical history, physical examination, vital signs and neurological examination
• Waist-to-height ratio < 0,59

Exclusion Criteria:

• Low back pain (acute or chronic)
• Previous abdominal or spine surgery
• Acute or chronic respiratory or musculoskeletal disorder
• Any clinically significant illness, medical/surgical procedure or trauma within 4 weeks before initiation of the study
• Pregnancy

Healthy Subjects