Much discussion centers on the importance of the traction force (tension). Our experience after more than 2 decades of use perhaps seems counterintuitive however we’ve found the amount-of-force is only marginally connected to improved outcome but substantially connected to increased pain or iatrogenic (negative) outcomes. Not that there is a direct analogy to the SAID principle however like overtraining, over-stretching or burdening the spinal structures with tensions they cannot easily adapt to is not clinically sound.
When we lie down and eliminate Y-axis compression disc-osmosis begins (in those discs still hydrostatic). Adding a modest axial-tension enhances that effect. In perfectly healthy structures its likely very large forces can be quickly adapted to and no injury results, however virtually every “patient” will have desiccation and degenerative changes, especially in the posterior annulus. This compromised tissue has a poorer adaptation to rotation and axial stretch. A 1/3rd bodyweight (or less in some cases) is still the best starting point. We add 5-10 pounds only after the first 2-3 sessions where full tolerance has been proven but subjective indicators are not changing. You can add the force after the 2nd pull (on most traction units you can do this on-the-fly). The rest force (20-25 pounds needs not be altered…and this remains true irrespective of the pull-force).