Why Your Muscles Shake During a Hard Workout

... to injury if you're not careful to use proper form. Let's explore why your muscles may quiver during a barre class, Pilates, strength workout, or other type of exercise-and what to do about it. 1. Inadequate sleep. If you are heading into a cardio ...

http://www.shape.com/blogs/fit-list-jay-cardiello/why-your-muscles-shake-during-hard-workout