The question is slightly misleading because the Olympics do not disallow a specific stroke. Rather, the competition is governed by specific events, each with its own rules regarding the swimming style allowed. Freestyle is the only event where any swimming style is permitted. All other competitive swimming events at the Olympics have strict technique rules. If a swimmer doesn't adhere to those rules, they are disqualified, but that is not due to a specific style being forbidden, rather the incorrect execution of a stroke.
Here's a breakdown of Olympic swimming styles and regulations:
- Freestyle: Swimmers may use any stroke in freestyle events. This often results in swimmers utilizing the front crawl due to its efficiency and speed. As stated in the reference, it is the only style that allows any stroke.
- Backstroke: Specific rules dictate that the swimmer must stay on their back throughout the race, and they must use alternating arm movements and leg kicks.
- Breaststroke: There are specific requirements on how the arms and legs must move, and the body position of the swimmer.
- Butterfly: This stroke also has strict rules for arm and leg movements, including a dolphin kick.
The important thing to remember is that in every stroke except freestyle, the swimmer must use the specified style correctly to avoid disqualification. Therefore, it isn't that specific strokes are not allowed, instead there are strokes which are only allowed for their named event. If a swimmer were to use another stroke besides the permitted one, then they would be in violation of the rules and be disqualified for their stroke.
Therefore, a more accurate question would be, "Which swimming stroke can be used in all styles within an Olympic swimming competition?", which the answer would be freestyle.
