[T]the principal part of personal beauty is an air of health and vigour, and such a construction of members as promises strength and activity. This idea of beauty cannot be accounted for but by sympathy.
What is beautiful causes attraction; a vigorous, harmonious and active body causes a feeling of beauty; athletic bodies are attractive, generators of passion.
Practising sport, physical activity1 is therefore favourable both for the self and for the passion, because it participates to the notion of beauty in someone. At one end of the spectrum: the trained body of an athlete is agreeable to sight, especially in action. The pleasure caused by observing such performance, the admiration felt towards it, is due to the sympathy one naturally feels towards this show of beauty.
In addition to personal gains (technique, force, movement, etc.) which augment the esteem one has towards themself (by their athletic capacities and their body’s constitution), one also attracts the esteem of others (and their regard, during a performance in competition for instance).
Hume therefore reminds us, in the middle of a philosophy treaty, of the importance of physical culture—and not merely grooming or cosmetic makeup. Physical beauty is, in this sense, largely in connection with a certain athletic functionalism (“health;” “vigour;” “strength;” “activity;”).