Final answer:
The upscale gym chain named after the moment when the sun is directly above the equator is called Equinox, reflecting a concept of balance related to health and wellness.
Step-by-step explanation:
The upscale gym chain that is named after the moment when the sun is directly above the equator is Equinox. This term is associated with the two times of the year, the vernal (spring) and autumnal (fall) equinoxes, when day and night are of approximately equal duration all over the planet, marking the start of spring and autumn, respectively. The name Equinox for the gym chain was likely chosen to reflect balance, a concept which is often associated with health and wellness.