The validity of the perturbative analysis during inflation imposes bounds on the inflationary parameters. For single field inflation, the current experimental bounds on non-Gaussianity necessarily imply that the physics is weakly coupled at CMB scales. In this talk, I will show that for models with a scale dependent sound speed, the system can become strongly coupled at lower scale. I will also discuss multiple field models which can produce non-Gaussianity at CMB scales. In these scenarios, the extra scalar fields are strongly coupled in a large part of the parameter space.