Merrithew reformers have 3 types of springs – red, blue and white. Red is the heaviest, a 100% spring. Blue is 50% and white is 25%. For most exercises (but definitely not all), more springs are harder / heavier.
When our Pilates instructors plan their workouts, they plan the exercises and the spring tension. They will always call out the springs that should be used for each exercise and they will say how an exercise should feel with the springs. For example, standing side splits on a white is going to work inner thighs; standing side splits on a red will work the hips and booty.
Always pay attention to the spring setting given to your by your instructor. He/she knows the springs and how the exercise should feel. If something is too heavy or too easy, ask before adjusting it yourself. As always, if you have questions, we’d love to hear from you.