Assessing Muscle Quality with MuscleSound

Muscle Quality is only included in the  Data Collection Assessment at this time.

How is Muscle Quality calculated?

MuscleSound has adapted the IntraMuscular Adipose Tissue (IMAT) calculation using ultrasound developed by (Young et al 2015) with permission. IMAT is also normalized for muscle size as a correction. This result is labeled IMAT Index

  • MuscleSound identifies the muscle in the image
  • The echo intensity (brightness) of the muscle is rescaled to match the data from Young's ultrasound.
  • The echo intensity is corrected for adipose thickness.
  • The IMAT is calculated using equation from (Young et al., 2015) for the Rectus Femoris
  • IMAT index is calculated, dividing IMAT by the muscle's area.

The timing of a scan is essential to provide a valid and reliable measure

MuscleSound determines the quality and size of a muscle by measuring its echo intensity and area at predetermined locations. However, the fluid content of a muscle increases both during and following exercise. This will transiently change the muscle echo intensity and volume and resulting in an erroneous assessment of its actual values.

Time frame for scan sessions

During exercise, blood and associated fluids shift into the muscle to meet the increased metabolic demand (Andersen & Saltin), a condition known as "Exercise-induced hyperemia” (Wray et al., 2005). This process, also referred to as “Transient Hypertrophy”, increases the size of the muscle, both during, and for a variable period of time after exercise. While the magnitude and extent of this well-established phenomenon are generally dependent on the mode, duration and intensity of the exercise session, there are wide individual variations in responses (Garton et al, 2014).

Optimal Times to measure Muscle Quality

Muscle Quality should be measured when the subject is rested and/or fully recovered from exercise

Measures are unlikely to be influenced by fluid shifts
Resting measures are the best reflection of a ‘normal’ status for muscle quality
Similar conditions are required for other physiological measures such as blood pressure and pulse rate

Sub-Optimal times to measure Muscle Quality

Muscle Quality should not be measured within 2-3 hours after exercise

If scans are conducted too soon after an exercise session, the subject will not be fully recovered
Muscle Size is likely to be transiently increased as a result of exercise-induced hyperemia
Muscle quality is likely to be changed as a result of exercise-induced hyperemia, and glycogen depletion
Depending on the mode, duration and intensity, these changes can last up to 3 hours after cessation of exercise

What Muscles can be Assessed?

Currently Muscle Quality is assessed only in the Thigh (Rectus Femoris - ‘RF’)

How well does MuscleSound Measure Muscle Quality?

Burton and Stock (2018), recently performed a consistency study using ultrasound to measure echo intensity, muscle area, and IMAT.

Uncorrected and corrected echo intensity, subcutaneous fat and cross-sectional area exhibited excellent consistency.

(P > 005, intraclass correlation coefficients [ICCs] ≥ .900, standard errors of measurement [SEMs] ≤ 726%)

Percent intramuscular fat for all participants also demonstrated satisfactory reliability.

(ICC = 0980, SEM = 307%), with similar findings for males (ICC = 0970, SEM = 363%) and females (ICC = 0968, SEM = 141%

The high ICCs and low SEMs suggest that ultrasonography-derived rectus femoris percent fat may be a reliable tool for tracking changes in lower extremity intramuscular adiposity.

MuscleSound also calculated IMAT and IMATindex on a previous research study where ultrasound reliability was reported.

Subjects included 17 collegiate female (age 18-23) soccer athletes. The female student athlete participants must have been capable of participating in a full range of dynamic activities required to compete. Subjects were currently following a prescribed off-season training program, which included both aerobic and anaerobic components.

A portable diagnostic ultrasound and tablet, Philips Lumify (Koninklijke Philips N.V,Eindhoven, Netherlands) with L12-4 broadband linear array 12 MHz transducer, will be used to capture ultrasound images. Aperture size of this device was 34mm. MuscleSound software (MuscleSound Inc, Denver, CO) will be used to process ultrasound images.

Subjects will be asked to lie supine on a treatment table for ultrasound image capture of the RF. The transducer will be oriented short axis for images collected for all muscles. Ultrasound gel will be applied on the skin for each image capture. Each muscle will be scanned five times consecutively.

IMAT 0.956
IMAT Index 0.871

The high ICCs indicate this process is reliable. Low SEMs suggest that this process is precise.

Ensuring Valid and Reliable Assessments of Muscle Quality

Follow Standard Procedures
This will ensure highly precise and reliable measures
Scan at the appropriate time
For consistent results, the assessment must be taken pre-exercise when the client is fully rested and recovered. THIS IS CRUCIAL!
The scanned thickness of a muscle can transiently (and variably) increase both during and post exercise.  
After High Intensity exercise, scanned muscle size can increase by as much as 25% compared to pre-exercise levels.
Ensure the correct probe location
Probe is located at predetermined positions on the muscle. For example the midpoint of RF is standardized based on the height of the person being scanned.  
Changing the location of probe by as little as +/- 1 inch can result in a muscle size change of up to +/- 12%.
Ensure correct muscle position
Individual must be lying down relaxed on a flat and even surface (use a training table, or yoga mat).  
Sitting up can result in a muscle size change of up to +/- 9% between these two body positions.  
Uneven surface such as lying across a few chairs can result in a muscle size change of up to +/-8%.
Ensure correct probe pressure
NOTE: "Resting" the probe on the muscle is “Standard Protocol”.  
Pressing the probe into the muscle will compress the tissues, resulting in an underestimation of muscle size.
Lifting the probe from the muscle tissues will allow them to expand, resulting in an over estimation of muscle size.
NOTE: It is possible to affect the muscle size by as much as 47% with incorrect probe pressure.
Ensure correct muscle image is displayed
Bottom of the muscle must be visible on the image.  
Increase depth of scan if necessary.

How are the Results Reported?

IMAT is presented as a percentage.

IMATindex is presented as IMAT%/cm2


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