When it comes to creating a flat stomach while also reducing low-back pain, few exercises are more effective than the plank. Here are 5 great variations on the plank, which not only use the deep abdominal muscles (which helps flatten the stomach), but also recruit the hip, shoulder and upper-back muscles as well.

The human tendency to think and act in extremes is particularly common in the fitness industry. ACE Fitness Expert Jonathan Ross discusses the tendency for fitness professionals to “ride the pendulum” from one extreme to the other in regards to abdominal and cardiorespiratory exercises, and shares tips on how to avoid this behavior.