Article continues below advertisementDakota Johnson has ignited concern among friends and industry observers after emerging from a Los Angeles gym days after Christmas, with sources warning OK! the "pressure" to achieve a so-called Hollywood "revenge body" following her split from Chris Martin is becoming all-consuming for the star.Johnson's appearance came months after it emerged the 36-year-old actress and Martin, 48, had ended their relationship after eight years together, a breakup insiders say had been unfolding quietly for some time.