Sunde et al. 2010 and their graph to the right clearly demonstrated the benefits over weight strength training in power (rate of force development, RFD 17%), work efficiency (4.5%) and endurance (pre-intervention maximal aerobic power, MAPtime 17%).

Training should be varied and there appear to be no negatives of weight training. 

The mechanism of action for these improvements is that weight training postponed activation of less efficient type II muscle fibers, conversion of fast twitch type IIX fibers into more fatigue-resistant type IIA fiber, and improved musculo-tendin stiffness [Ronnstad and Mujika 2014]. 

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