Muscle size is measured both at the whole-body and muscle-specific level. In the former, generally fat-free mass or lean mass is distinguished from fat mass and is commonly measured using either dual-energy x-ray absorptiometry (DEXA-DXA|DXA) or bioelectrical impedance analysis (BIA). Other assessment methods include ultrasound, computed tomography, and magnetic resonance imaging.[1]
Muscle strength is most commonly assessed using dynamic resistance exercise in the form of a 1-repetition maximum (1RM) test.[2][3] A higher-repetition maximum test (i.e., a 2–6 RM test) may also be used to assess strength and estimate 1RM. Another option is an isometric strength test, which involves producing a maximal force against an immovable resistance.[4] Unlike dynamic resistance exercise, the muscle length does not change during an isometric muscle action.