Actigraphic sleep parameters before, during and after weekend sleep intervention and psychomotor vigilance task performance before and after the intervention . Shared area indicates the period of the intervention. Filled circles represent weekend sleep intervention condition and open circles represent the habitual sleep condition as control. Lapses were defined as the number of reaction times (RTs) exceeding 500 ms. Error bars represent standard errors. *P < 0.05 from the control condition.