wow, loony tunes that is... could you run alternate laps counter clockwise? during covid lockdown we participated in a virtual ultramarathon (my wife...i just did 15kms) running around our house and garden which was approximately 60 meters.... man does one leg and hip work overtime running permanently one way... so we did 10 clockwise, ten anticlockwise...

well done on enduring 12 hours {removes hat in respect}