Abstract: Split Hopkinson pressure bar apparatus capable of generating a compression wave or pulse in an input bar or member, said apparatus comprising an input bar or member, actuator means, a fragile or frangible component and an impactor bar or member held, in use, adjacent one end of the input bar or member and supported to resist movement in a direction away from said input bar/member when the impactor bar/member is pre-loaded in said direction by actuator means, the apparatus being such that, in use, the pre-load force can be quelled suddenly so that the impactor bar/member is released into impact or energy transfer with the input bar/member thereby transmitting a compression wave or pulse through the input bar to a specimen under test.