The guy is a professional. He rented a Canon 500 f/4L lens for the weekend. The lens was introduced in 1999 (not only it was the previous century, it was the previous millennium).
There’s an IS (Image Stabilization) built in the lens. It’s OK for ‘kind of stabilizing’ the lens but… It’s not that good. The lens is just above 4kg/just above 9lbs, plus the camera, only supported by the left arm. Impressive!
I know that I can’t. I have tried. I get decent results with a monopod, which is what I used on this day.
Handholding a Canon 1DMk4 with a Canon 500mm f/4L
Camera: Canon 7D ISO 400 and 1/1250
Lens: Sigma 120-400mm f/4.5-5.6 @120mm and f/7.1
Processed with Darktable 2.2.3: http://www.darktable.org/