The health benefits associated with resistance training are not under debate and include decreased gastrointestinal transit time, reduced risk of colon cancer, increased resting metabolic rate, improved glucose metabolism, improved blood-lipid profiles, reduced resting blood pressure, improved bone mineral density, pain, and discomfort reduction for those suffering from arthritis, decreased lower back pain, enhanced flexibility, and improved aerobic capacity. What has been under debate is how to do it best. 1 The American College of Sports Medicine, long considered the expert in resistance training, has dispensed poor advice over the years, largely unsupported by rigorous science. 

In 2011, researchers used existing studies that employed rigorous science to more fully understand how we should work out. They included intensity, the number of repetitions, the length of training sessions, the volume of work, whether core exercises were as important as we think, the speed of repetitions, rest time between sets, and whether free weights are better than machines. Their findings might surprise you.