Play middle C on the trumpet and hold the pitch for four beats. Keep your stomach firm but loose. It doesn't require much breath support to play lower pitches.
Slur up to the C one octave higher than middle C and hold the pitch for four beats. When you transition between the lower and higher octave, flex your stomach firmly to help add breath support and push out extra air to achieve a solid sound.
Drop back down to the original pitch, relaxing your stomach and decreasing the airflow slightly. Hold the bottom pitch for four beats. Take a deep breath.
Slur up an octave and a half to the G directly above the staff. Feel your stomach punch air to supply the necessary airstream to play the higher pitch. Hold this pitch for four beats. Slur back down to low C.