Core exercises

Everything I hear anymore has to do with exercising the "core" muscles. I haven't had a chance to do a lot of research, but here are some places with core exercises for older guys like me:

• http://www.menshealth.com/fitness/core-workout-4
• http://www.bestmastersfitness.com/men-over-50-fundamental-core-exercises/
• http://healthyliving.azcentral.com/mens-home-fitness-exercises-men-over-50-1626.html