The objective of the present study is to evaluate diaphragm activity during three breathing exercises: diaphragmatic breathing (DB), flow-oriented (Triflo II)incentive spirometry and volume-oriented (Voldyne) incentive spirometry.

Seventeen healthy subjects will be studied (8 man and 9 woman).

Right diaphragmatic mobility will be evaluated by determining the craniocaudal displacement of the left branch of the portal vein using a B-mode ultrasound device (Logic 500, Pro Series®; General ElectricMedical Systems, Milwaukee, WI, USA). The ultrasound technician will use a 3.5 MHz convex transducer positioned in the right subcostal region, with the incidence angle perpendicular to the craniocaudal axis, in the direction of the inferior vena cava. Next, an intraparenchymal portal branch will be identified in the field of vision and its position will be traced with the curser during the forced inspiration and expiration. The craniocaudal displacement of these points will be considered to be the amount of right diaphragmatic mobility.

Inclusion Criteria:

• Being 18 to 40 years old
• Having a normal body mass index
• Being a non-smoker
• Not knowing the DB and the IS techniques
• Reporting the absence of respiratory diseases.

Exclusion Criteria:

• Presenting alteration in respiratory function detected by functional analysis of lung volume and capacity
• Inability to understand or perform the procedure.