There are specific guidelines on how to exercise the most efficient way to build strength, muscle bulk or endurance. It has been generally accepted that to build strength you have to lift heavy weights using few repetitions, for example up to 4 repetitions. To build large muscle bulk it would be more effective to not lift as heavy, but do for example 8-12 repetitions, and if you did higher repetitions like 25-30, you would not build much muscle mass. You would also do several sets of these exercises, and to build endurance you would do many repetitions with very low resistance, for example jogging for a long time or biking for a long time.Some of these practices now need to be questioned looking at recent research in the area of exercise. Having to jog or bike for a long time to build endurance has been proven wrong for a while now. High intensity short interval training is as effective in building endurance and is a lot less time consuming. You can find information on the research related to that if you read earlier blogs.The research reviewed here puts one more training practice into question and that is how to build muscle bulk (Mitchell CJ, et al. 2012). The participants in this study were 21-22 year old men who were assigned to either exercising their legs with weights matching 30% of their maximal strength for 3 sets, exercise with 80% of maximum strength for 1 set, or exercise with 80% of maximum strength for 3 sets. They were able to do 25-30 reps when exercising with weights matching 30% of their maximum strength and 8-12 reps when exercising with weights matching 80% of maximum strength. They exercised 3 times per week for 10 weeks. Strength was measured before starting and after finishing the 10 weeks program, muscle biopsies were also taken and muscle volume was measured by magnetic resonance scans.The results showed that the ones lifting the heavier weights gained more strength than the ones lifting the lighter weights which was no surprise.What was both interesting and surprising was that lifting lighter weights produced similar gains in muscle volume as lifting heavy weights. The researchers concluded that lifting lower weights to failure produced similar muscle hypertrophy as lifting heavy weights to failure.The participants that only did one set of exercises at 80% of maximum strength did not gain as much muscle mass.If you want to gain muscle mass you can use either heavy weights doing 8-12 reps or lighter weights doing 25-30 reps or anything in between, as long as you exercise the muscles to failure (fatigue), that is what the research shows.