Torque is the twist back on impact, measured in units of Newton.meters. See the accompanying remarks, and the explanation of why the torque of the player during impact can be disregarded when writing the conservation equation. A complete description of all variables used in this derivation follows at the end.
Applying Conservation of Angular Momentum, with d and I in centimeters:
Mr2 / I is the Shock Factor, a dimensionless ratio that is a good indicator of general racquet quality. Note that another way of expressing this ratio is r /q. A low mass center radius (small r) is just as important as a high sweet spot (large q) for reducing Torque and Shock from impact. Therefore, a counterweight at the handle end (which gives small r and large q) should be effective, as the performance of the counterweighted Wilson Kannon proves.