We derive an effective Rouse model for tangentially active polymers, characterized by a constant active force tangent to their backbone. In particular, we show that, once extended to account for finite bending rigidity, such active Rouse model captures the reduction in the gyration radius, or coil-to-globule-like transition, that has been observed numerically in the literature for such active filaments. Interestingly, our analysis identifies the proper definition of the Peclet number, that allows to collapse all numerical data onto a master curve.