Assessing Muscle Size with MuscleSound

Which MuscleSound Assessments Include Muscle Size?

We are launching this new service with a single Assessment

  • Monitor Muscle Size

In the future, however, Muscle Size will also be included in a broader range of Assessments, including

  • Physicals and Baseline Health Evaluations  
  • Full Body Assessment Package
  • MuscleHealth Status Assessment
  • Lean Mass Assessment
  • Muscle Symmetry Assessment

When are Muscle Size Assessments best conducted?

At “‘Baseline”

  • To establish a dependable starting point for a muscle prior to the start of a season or a workout program

At “Follow up”

  • To monitor and track changes in a muscle at any point during the season or work
  • To monitor and track changes in a muscle during a rehab program

NOTE: All Muscle Size Assessments should be conducted pre-exercise when the client is fully rested and recovered.

What Muscles can be Assessed?

Currently the Muscles able to be Assessed are

  • Thigh (Rectus Femoris - ‘RF’)
  • Thigh (Vastus Lateralis - ‘VL’)

Future Muscles able to be assessed will include

  • Upper Arm (Biceps Brachii - ‘BB’)
  • Back of Thigh (Hamstring - ‘HL’)
  • Calf (Gastrocnemius - ‘GS’)

How well does MuscleSound Measure Muscle Size?


Ultrasound provides a direct measurement of muscle thickness. This produces valid and reliable results 1, 2, as long as “Standard Procedures” are followed.

Ensuring Valid and Reliable Assessments of Muscle Size

Follow Standard Procedures

  • This will ensure highly accurate and reliable measures
    • Standard error of measure = 0.66mm (Less than 1 mm)
    • Minimum Important Change
      • The smallest change detected that would be considered ‘real’ or ‘important’ = 1.8mm

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%
    • 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 the tissues will allow the tissues 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 is Muscle Size measured?

  • Follow the Standard Procedures (Described above)
  • Identify the correct muscle region (Described above)
  • Calculate the center of mass (depth) of muscle (Described above)
  • Calculate Muscle Thickness = (center of muscle - fat muscle boundary) x 2

How are the Results Reported?

As Muscle Thickness (Size)

  • Displayed in mm

As different Reference categories

  • Based on the MuscleSound database of thousands of muscles scanned
  • Same Muscle, BMI, Age, and Gender are used to determine muscle categories
  • Categories are
    • Small, Average, Large

As Percent difference (Symmetry)

As Change from Baseline

  • Trend, and amount of change

As Change from previous session(s)

  • Trend, and amount of change

As Overall status

  • Based on percent difference and trend

Example of Reported Results

muscle size notification2.png

Comparison of Epidemiological and MuscleSound Data

Research has shown that Muscle Thickness (Size) can be considered a surrogate for Muscle Mass/Volume, particularly in the lower limbs 3-5.

The two graphics in the left hand column below are taken from a study 6 published in the Journal of Applied Physiology that reports on skeletal muscle mass changes  by age and gender. The two graphics in the right hand column below are taken from MuscleSound data on thigh muscle size collected over the last 4 years.

These data show that

  • Age related loss of Total Muscle Mass closely patterns MuscleSound data on age related Muscle Size loss.
  • The pattern of loss is even more evident between Thigh Muscle Mass and Rectus Femoris Muscle Size

  • Age Range is 18-88yrs
  • Data is taken from a heterogeneous population of 468 men and women
  • Whole body muscle mass assessed by MRI
  • Muscle Mass stays relatively stable until around 35yrs, and then declines
  • Similar pattern to MuscleSound data
  • Age Range is 6-79yrs
  • Data is taken from a mainly athletic population of 7000+ men and women
  • Rectus Femoris assessed by ultrasound
  • Male & Female Size peaks between 18-35yrs, and then declines
  • Similar pattern to epidemiological data

  1. Tillquist, M, et al. Bedside Ultrasound Is a Practical and Reliable Measurement Tool for Assessing Quadriceps Muscle Layer Thickness. J Parenter Enteral Nutr. 38:886-890, 2014.
  2. Sanada, K., et al. Prediction and validation of total and regional skeletal muscle mass by ultrasound in Japanese adults. Eur J Appl Physiol. 96: 24–31, 2006.
  3. Abe, T., et al. Morphological and functional relationships with ultrasound measured muscle thickness of the lower extremity: a brief review. Ultrasound 23: 166–173, 2015
  4. Abe, T., et al. Ultrasound assessment of hamstring muscle size using posterior thigh muscle thickness Clin Physiol Funct Imaging 36: 206–210, 2016
  5. Ogawa, M., et al. Ultrasound Assessment of Adductor Muscle Size Using Muscle Thickness of the Thigh. Journal of Sport Rehabilitation 21: 244-248, 2012
  6. Janssen, I., et al.
Skeletal muscle mass and distribution in 468 men and women aged 18-88yr J Appl Physiol 89: 81–88, 2000. 

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