Jenny Cheng/Business Insider Making time for a solid arm workout isn't always easy, especially if you're in need of weights and other equipment. But when you're on the road or have a few minutes to spare between events, it can be nice to have some quick, virtually equipment-free arm workouts up your sleeve. We asked New York University physical-therapy professor Marilyn Moffat, who also wrote the book "Age Defying Fitness," for some of her favorite arm workouts that don't require weights. Here are the nine she gave us, including modifications to help personalize your workout.