Weak abs can limit your ability to keep your spine straight at address. To strengthen, lie supine with knees bent, holding a club over your head. Without moving the club, try to bring your feet up and under the club. This will force a posterior tilt of the pelvis and work the abdominals. Do two sets of 10 reps.
• Breaking 100-90-80: Strengthen Your Tower
ABOUT THE AUTHORS: Co-founders of the Titleist Performance Institute in Oceanside, Calif., Dave Phillips, a PGA professional, and Greg Rose, a golf fitness specialist, host the "Golf Fitness Academy" on the Golf Channel. They have created a comprehensive, free golf and fitness website, mytpi.com