Table 2.

Advantages and disadvantages of methods that can be used to measure muscle mass and strength. The methods that are commonly used in research and clinical settings are shown in italics [9, 10]

Measurement methods	Advantages	Disadvantages
Muscle mass
DXA	Three component model combining protein and minerals into “solids”	Unable to evaluated intramuscular fat
Anthropometry	Simple to measure	Lack precision and prone to overestimation Inter-observer variation may occur
Urine metabolites	Provides a useful approximation of muscle mass	Unsuitable for research and clinical practice
Isotope dilution methods	Administration of tracers and collection of samples is simple	Unsuitable for research and clinical practice
Bio-electrical impedance	Easy to use in both research and clinical settings	Lack of standardised methodology May be considered more as a surrogate muscle mass measure than a direct measurement
Air-displacement plethysmography	Highly reproducible	Relies on an assumption that the density of fat mass and fat-free mass are the same in all patients
MRI and CT	More sensitive to small changes than DXA	Large amount of radiation involved
Muscle strength
Isometric/isokinetic	Recognised gold standard for measuring muscle strength	Cost and availability of equipment
Grip strength	Simple to measure	Variation in methodology makes comparisons between studies difficult Use of standard Jamar dynamometer may be difficult for some patients, e.g. Advanced arthritis