Natural Flexibility: The New Risk-Free Alternative to StretchingNatural Flexibility, a new title by Dr. Charles Kenny, introduces progressive sequential isometrics (PSI for short), a new alternative to traditional stretching, which combines principles of Pilates, Martial Arts, Dance, and Gymnastics into a work out that allows you to strengthen your body and increase your flexibility simultaneously. Traditional stretching has come under scrutiny recently as a possible contributor to injury in athletes. While