sorry but smiling and standing up straight is not the same physical exertion as flexing all muscles from calves to traps simulaneously as hard as you can for extended period 
being confident is not physically demanding
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Sucking in your stomache, maintaining perfect posture, maintaining the most attractive look on your face possible, portraying desired personality, putting forth the effort and discipline necessary for rigorous pre-competition preparation including diet and training
do involve achieving a physical form and expressing muscle control similar to bodybuilding.
Bodybuilding is a beauty pageant.
I would agree with where you said "the same" here in bold in the quote above, but just because one sport is more physically demanding than another doesn't disqualify it as a sport altogether.