A Cessna 172 Instructor Pilot reported that his seat slid all the way back as the aircraft was rotated for takeoff. This event resulted in a loss of aircraft control; and an excursion from the runway surface as the takeoff was aborted.

Narrative

I was cleared for takeoff on Runway XXL. At rotation my seat slid to the rear. My feet were unable to reach the rudder pedals & the airplane veered left. I pulled the throttle to idle. The plane was heading towards the VASI. I slid the seat forward; regained direction control; and steered left of the VASI. I stopped the plane just beyond the VASI and told the tower what had happened and needed no assistance. I was cleared to exit Runway XXL at Taxiway 1; cross Runway XXR and the contact ground control. Ground cleared me to taxi to the run up area for Runway XXR and phone the tower; which I did. Next; airport security drove up and I submitted my drivers license and pilot certificate. I then restarted and taxied back to parking where I was met by our maintenance crew. The tower phoned me to verify there was no damage or injuries. Maintenance readjusted the seat. I test flew the plane once around the pattern on Runway XXR and then continued with my intended mission.I was fortunate with 2 things. First; the conditions were dry; so I had no issues with direction control and braking in the grass. Second; in choosing my departure on Runway XXL; I had the least likely chance of hitting people; vehicles or aircraft to the left of that runway. While I had maximum braking and significant rearward seat pressure during the magneto check; I will be more diligent in checking that my seat is locked in place.