Related Clues:

• Focus for a core workout
• Fitness centers?
• Muscles worked by side planks
• Core muscles, in brief
• "Six-pack"
• Bustline muscles, informally
• Muscles that get 'crunched' in crunches
• Auto safety feature preventing skidding, for short
• Flutter kicks work them
• Chest bumps, for short?
• Targets of sit-ups
• Core components, for short
• Curl-up muscles
• Muscles used while planking
• Bench targets, for short