Prety much full force depending upon the shin guard.Of course if you insist on getting caught upon the thigh or head its still gonna hurt ...!
What are you gonna be using them for also makes a difference.Purely stand up or will you be training stand up and ground work together?If you doing both you may want some that are thinner and neoprene backed rather than some that have straps as a fastenening system.
Shin Guards?