Inclusion Criteria:  age within 20-40 yrs, BMI within normal range (18.5-24.9) lack of abdominal obesity lack of chronic musculoskeletal conditions written, conscious consent  Exclusion Criteria:  former abdominal surgery abdominal diseases (i.e. (np. kidney stones, ulcers, irritative bowel sindrome, etc.), pregnancy fever, tumors, blood hypertension, former surgery of respiratory system , condition after surgical procedures in the area of the spine, the occurrence of pain in the spine in the 3 months preceding the research experiment, lack of conscious consent