Look at my biceps.

These anastomoses exist between the femoral artery or profunda femoris and the gluteal vessels.

He repeated several times it was a three wheeled manual wheelchair, which means he was using his strong biceps to push himself up the gradient.

Because this is blood returning from our legs if we're running, or returning from our brain, that had to use respiration or maybe we're working out and it's returning from our biceps, but it's de oxygenated blood.