Plank
Start with both hands and knees on mat with your back straight and head looking forward. Raise opposite arm and leg straight out and alternate.

Crunches on the Ball
Lie on your back with your shoulder blades on the ball. Cross your arms across your chest. Keep your hips level with the ball. Now slowly roll up contracting your abs (abdominal muscles). Slowly return to starting positions and repeat.

Lumbar Stretch
Lie on stomach with head down and arms bent in push-up position. Raise upper body with arms straight and hips on the mat. Hold for 20-30 seconds.