Possible Clues:

• Aerobic workout, briefly
• Aerobic regime, familiarly
• Aerobic regimen, casually
• Spinning, e.g
• Elliptical workout, e.g., informally
• Healthful exercise, informally
• Aerobic exercise, in gym-speak
• High-intensity workout, for short
• Heart opening?
• What spin classes provide, informally