Effektiveness of training with the book / App
A study of the Department of Sports Science of the Univeristy of Tuebingen, Germany showed, that the exercises caused an improvement in 76% of the body areas by 52% on average.
A swiss study on spinal posture of high school students during lessons showed, that the training caused the students to go from 45% to 67% sitting upright: Obrist J. Maturitätsarbeit.