  We have investigated the global dynamical state of the Integral Shaped
Filament in the Orion A cloud using new N$_2$H$^+$ (1-0) large-scale, IRAM30m
observations. Our analysis of its internal gas dynamics reveals the presence of
accelerated motions towards the Orion Nebula Cluster, showing a characteristic
blue-shifted profile centred at the position of the OMC-1 South region. The
properties of these observed gas motions (profile, extension, and magnitude)
are consistent with the expected accelerations for the gravitational collapse
of the OMC-1 region and explain both the physical and kinematic structure of
this cloud.
