Some types of photography require the photographer to be physically fit, to a certain degree. Shooting extreme sports, such as rock climbing, for example, naturally requires one to be proficient enough in the sport in order to be able to keep up with the athletes (if they are climbing in the actual mountains and not in a gym, where a photographer does not have to do any climbing.) Underwater photography is another obvious example, where physical ability is crucial.
However, even in less obvious situations, such as travel, street or action photography, physical fitness is a definite asset. Endurance, in particular, enables one to cover larger distances on foot, carry more gear and minimize camera shake while hand-holding heavy “fast” lenses. There many ways, of course, to compensate for the lack of strength or endurance, for example, by using some form of transportation, carrying less or lighter gear, shooting from a tripod, etc. (BTW, in my experience, a carbon fibre tripod is a must for travel use.) Over time, however, there would be certain situations where lack of endurance would result in missed shots.
I have recently heard an interview with Kelly Starrett, a trainer of high-profile athletes a the author of “Becoming a Supple Leopard.” He mentioned that the key element in improving endurance and physical mobility in general is to improve one’s posture. According to him, there are several fundamental postures and basic movements that are common in many types of activities (e.g. standing, squatting, etc.) Training to improve (or correct) these postures allows one to utilize the skeleton, rather than muscles, to absorb most of the stress of the motion (or lack thereof. )
Following this advice, I try to be conscious of my posture while hand-holding a 300mm f/2.8L IS lens during a soccer game or shooting from a sitting position at the side of a basketball court.