Wii Sports Boxing does NOT track motion of your hands (e.g., punches or blocks). There is NO 1:1 motion tracking. The game does not throw your punches (roundhouse, uppercut, etc.) Instead, the game uses 'gestures' of the controllers (tilts, etc.) to throw different punches. This is why I doo not like Wii Sports Boxing. A quick web search will turn up the control scheme.
OTOH, the upcoming Don King Boxing is supposed to track your actual punches.