Dolphin Fitness Clubs, New York

The hiss and clank of weight machines from manufacturers such as Cybex and Precor blend with the whir of recumbent cycles and treadmills to form the perpetual soundtrack at each of Dolphin Fitness Clubs’ 24-hour locations. To augment individual exercise regimens, nationally certified staffers teach aerobic classes throughout the week, with offerings ranging from classic step classes to low-impact yoga and pillow-fighting lessons.