From the Guidelines
Muscle quality can be assessed using a combination of anthropometric and functional assessments, including dual-energy X-ray absorptiometry (DXA) to evaluate muscle mass and composition, and handgrip strength testing using a dynamometer to assess muscle function 1.
Methods to Assess Muscle Quality
- Dual-energy X-ray absorptiometry (DXA): measures three compartments, including fat mass, lean mass, and bone mass 1
- Bioelectrical Impedance Analysis (BIA): uses hand to foot surface electrodes to determine fluid-related compartments, including fat-free mass (FFM) 1
- Computed Tomography (CT): performed at the level of the 3rd lumbar vertebra to assess fat and muscle areas, with the skeletal muscle index (SMI) calculated as the total skeletal muscle area at L3 normalized to height 1
- Handgrip strength testing: a simple and effective method to detect malnutrition and sarcopenia, with cut-off values of <20 kg for women and <30 kg for men 1
- Mid-arm muscle circumference (MAMC): an indicator of muscle mass, calculated as mid-arm circumference minus triceps skinfold thickness 1
- Muscle ultrasound: a non-invasive technique that measures muscle mass and is scarcely influenced by rapid fluid shifts, making it a potential alternative method for assessing muscle quality in hospitalized patients 1
Key Considerations
- Fluid status: can impact the reliability of lean body mass estimates by BIA and other methods 1
- Hydration status: can influence results of DXA and other methods 1
- Reference values: necessary for accurate interpretation of muscle quality assessments, with different values for men and women 1
- Longitudinal measurements: important for monitoring changes in muscle quality over time 1
From the Research
Methods to Assess Muscle Quality
The following methods are used to assess muscle quality:
- Dual energy X-ray absorptiometry (DXA) to measure appendicular lean mass (ALM) and appendicular skeletal muscle mass index (ASMI) 2, 3, 4
- Handgrip strength (HGS) using a handheld dynamometer to assess muscle strength 2, 3
- Muscle quality index (MQI) calculations using different models, such as MQIRA, MQILA, MQIARMS, and MQITOTAL 3
- Ultrasonography to measure muscle thickness and evaluate muscle mass and quality 5
- Bioelectrical impedance analysis (BIA) to measure fat-free mass index (FFMI) as a surrogate marker of ASMI 4
- Computed tomography and MRI to gain insights into regional and total body skeletal muscle mass 6
Correlations and Relationships
Research has found correlations and relationships between:
- Muscle thickness measured by ultrasonography and appendicular lean mass measured by DXA 5
- Muscle quality index (MQI) and handgrip strength (HGS) 3
- Fat-free mass index (FFMI) and appendicular skeletal muscle mass index (ASMI) 4
- Muscle mass and muscle quality, with higher muscle mass not always associated with higher muscle quality 2
Muscle Quality Index Calculations
Different models can be used to calculate muscle quality index (MQI), including:
- MQIRA: ALM and HGS of right arm and hand, respectively
- MQILA: ALM and HGS of left arm and hand, respectively
- MQIARMS: ALM and HGS of both arms and hands, respectively
- MQITOTAL: ALM of upper and lower-limbs and HGS of left and right hand 3