Really? In the UK we have a lot of days where the weather (lighting) is unpredictable.. the sun can be out one minute and in the next.. Why would anyone with half a brain ( let alone more experienced ?) use manual in those conditions?
you can't choose a shooting mode based on the sport/subject.. Choose shooting mode based on the conditions ..
Usually on a running job - 5k, 10k, half marathon, marathon, 24hr ultra marathon or my brief is to try and catch as many runners as possible, usually 2 per runner per position to assist with tagging. They are usually either full length or top 2/3 body shots. Usually two locations, one near the start, and then I have to move to somewhere closer to the finish, whilst there may be other colleagues out on course. If its a rural course there may be shadows cast by hedges and trees, and on an urban course buildings.
The brief usually asks us to shoot at a constant f/4 aperture, whilst maintaining a shutter speed of at least 1/640s to avoid excessive motion blur, to give a 'house style' amongst a team of sometimes one, occasionally ten photogs. The brief usually states to use aperture priority and adjust ISO accordingly to achieve the shutter speed required, applying exposure compensation if necessary to ensure the runner is visible. If the weather is terrible there is leeway to adjust, either f/2.8 or by dropping shutter speed slightly. With possibly 5,000-10,000 runners passing through in quick succession, there is little time to review photos, and if the weather changes you can find yourself shooting and your settings have drifted due to the change in conditions.
The alternative is to use manual mode - dial in the aperture and shutter speed you want and use auto ISO. The problem with this is that many cameras don't allow exposure compensation at the same time, and sometimes its handy to do so.
Whichever mode you happen to be shooting in, you need to be able to quickly review the images during the shoot, without missing any action, in order to present memory cards full of usable images that need little post processing apart from standard recipe, and then go through the tagging phase with race numbers so runners can locate their images easily.
I've shot for a number of agencies in this field and the brief has been broadly similar between each of them.