The move: Kick downs
Three reasons to do it now:
• They get deep into your core. Many popular core moves, like crunches, hit a superficial layer of muscle while these work those deepest in your torso. They also target the lower abdominal muscles, which usually don't get as much love as those closer to your ribs.
• They build a stronger back. When the muscles of the front and back of your body are balanced, you have a lower risk of injuring your uber-mobile (and therefore injury-prone) low back. Just remember to keep your low back pressing into the ground throughout the move.
• It will make you run faster. How? By strengthening your hip flexors. In a study, participants who followed an eight-week hip flexion resistance-training program decreased their 40-yard and shuttle run times by 3.8 percent and 9 percent, respectively, the Journal of Strength and Conditioning Research reports.