This is the 1648th most frequent Spanish word.
mantienen
"Maintaining" or "they maintain."
In this sentence, 'mantienen' is used reflexively to indicate that the subjects maintain their own state of health.
Ellos siempre se mantienen saludables haciendo ejercicio.
They always stay healthy by exercising.
Here, 'mantienen' describes the action of holding or keeping attention.
Los estudiantes mantienen la atención durante la clase.
The students keep their attention during the class.
In this example, 'mantienen' refers to the act of preserving or upkeeping something, specifically the structural condition.