We investigate the suppression of the turbulent transport associated to the emergence of spontaneous internal transport barriers, due to the combined collective effects played by trapped electrons and energetic passing ions. Numerical experiments performed with a 'particle mode' model based on a double gyro-average over the fast cyclotron phase and over the bounce (or transit) phases are used to show the role played by energetic particles in the suppression of the ion-temperature-gradient driven turbulence. We show this occur via phase locking in a Kuramoto-type synchronization process.