April Bowling, a Level 1 certified coach with USA Triathlon and owner of TriLife Coaching, knows a strong core improves performance in all three disciplines of swimming, cycling and running, in addition to overall fitness. The chair suitcase, she says, targets all the main abdominal muscles except the obliques. You'll need to:
- Sit on the edge of the chair seat and lean back until your upper back touches the back of the chair. Tuck your tailbone under, and hold onto the arms of the chair for support.
- Bring your knees up -- with your shins parallel to the floor -- so that your torso and thighs make an "open suitcase."
- Close the "suitcase" by bringing your chest and knees toward one another.
- Open and close for 10 to 20 repetitions, two to three sets.
The sole caveat, she says, is to maintain good posture and keep your back straight, supporting your upper body on the arm rests.
"You never want to arch your back," Bowling said. "As soon as your back begins to arch, it means you need to take a break and rest" [source: Bowling].