i know that Martial Arts practice requires General Warmup.
for Knife Martial Art, Arms Stretching & Warmup should be important part, i think.
but one should not neglect legs' warmup & whole body's, as they are important as well.
Martial Artists fight using whole Body, even if arms carry the strike.
legs & hips for example add Momentum (product of mass & velocity vector) to the Strikes & other Moves.