I have been adjusting my strength training to reflect an approach that does higher intensity, heavier weights with lower reps, lower volume, and longer rest periods. Doing this recruits not only the slow twitch fibers and fast twitch fibers but the fast twitch glycocytic fibers which are used in life and death type struggle. This may involve an isometric contraction to failure at the end of the last maximum repetition. Efforts of this intensity will usually require 6-7 days of rest to fully recover before again stressing the muscles.
It is important to feed your muscles with a smoothie consisting of E3 Live, bee pollen, hemp seed oil, micronized creatine, micronized glutamine and branched chain amino acids within 45 minutes of completing exercise of this intensity. For more information hit the following link on my website to order the book Serious Strength for Seniors and Kids Under 65 by Peter Ragnar .
I am also starting to include interval training by running up a 35 degree incline hill. This stimulates lean muscle mass and is big for cardio development.