Here is one of my clients who is 63 still killing it. A combo of Strength, power, and metabolic conditioning. Each of these doesn't have to be mutually exclusive.
Online Coaching: www.maximumperformancetraining.net
Youtube Channel: https://www.youtube.com/user/allencresstraining
Off Season Journal: http://www.wannabebig.com/forums/sho...-and-Nutrition