Good posture while seated: the trumpet player’s feet are flat against the floor and his back is straight. He is not leaning against the chair, even though he is seated towards the back. Notice that the shoulders are relaxed and the neck is not bent, and the horn is held slightly below parallel. Some players will need to hold the trumpet at a lower angle because of their dental structure, but the weight of the instrument itself is never a reason to forgo this objective.
Good posture while standing: the trumpet player’s upper body looks identical to his posture while seated; he does not need to lean back or tense his neck muscles. Practicing while standing up is usually conducive to healthy air support, as it eliminates the tendency to slouch.