"Endorphins" is the last of four works commissioned by and dedicated to 78 adventure-seeking tubists representing 30 states and three countries, who fearlessly joined the 2001 Solstice/Equinox Commissioning Consortium to commission James Grant to write four new recital pieces. As each Solstice and Equinox approached during the year 2001, a new piece was sent out to the participants. All four pieces (Stuff, High Autumn, Just a Thought and Endorphins) now exist in multiple versions for orchestral and band instruments and are programmed frequently at conferences and on student and faculty recitals throughout the year. Endorphins is marked "aerobic" and features, in its middle section, a recap of principal themes from the first three recital pieces in the set, as well as a brief yet dramatic cadenza for the tuba.