I hear this statement all the time – “heavy weights with low repetitions will bulk you up while light weights with high repetitions will tone you up.” Is there a difference in these two types of training? Yes, but it’s not about the way you look, it’s about muscle strength vs. muscle endurance. Doing less repetitions with more weight will help you increase your strength. Doing more repetitions with lighter weights will help you build up endurance. And the truth is, in the real world, you need both and use both in your everyday life. Muscle strength is the ability to exert a maximal amount of force for a short period of time. In the gym, that may be bench pressing a heavy barbell 5-8 repetitions. Think about lifting that heavy box when moving – that requires strength.Muscle endurance is the ability to do something over and over for an extended period of time without getting tired. In the gym, that may be doing 50 body weight squats in a row, moving to a rhythm. Skiing, for example, is a sport that uses muscle endurance. When you are going down the slope, bending your knees, firing your quads, and swooshing down that hill or mountain for several minutes to even longer you need endurance.While at the gym, you will see a variety of people doing a variety of strength and endurance exercises. When teaching a strength class, I always incorporate some exercises that will build muscle strength and some that involve muscle endurance to round out the participants training. I do this because as I said above, out in the real world, you never know whether you’ll need strength or endurance to complete everyday tasks.And, ignore the myth that using heavy weight will bulk you up. Men genetically can develop more muscle mass through heavy lifting. However, women, for the most part, do not have the type of testosterone to create that huge muscle bound look. Remember, more muscle is a good thing. The more muscle you have, the more calories your body will burn throughout the day and the more capable you are to perform any activity that comes your way.