Muscle mass measurement

Muscle mass measurement estimates how much of your body is made up of lean tissue, mainly skeletal muscle, rather than fat or bone. It can be done with a DEXA scan (the same machine used for bone density, with a body composition setting), a bioelectrical impedance device like InBody, or more specialized tools like CT or MRI. Results are often reported as total lean mass, appendicular lean mass (arms and legs), or a muscle mass index adjusted for height.

This matters because muscle and bone are closely linked. Muscles pull on bone during movement, and that pulling force is one of the signals bone uses to stay strong, as described by Wolff's Law. Low muscle mass, called sarcopenia, often shows up alongside low bone density, a combination sometimes called osteosarcopenia. Measuring muscle mass helps your doctor understand your overall frailty and fall risk, not just your bones.

A single number isn't the whole story. Many clinicians also look at muscle quality and function, using tests like grip strength, gait speed, the chair stand test, or Timed Up and Go, since strength and performance predict falls and fractures better than muscle size alone. If your muscle mass is low, your doctor may discuss resistance training, protein intake, and fall prevention strategies as part of a broader bone and muscle health plan.