Assessing Muscle Length: Difference between revisions

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=== Documentation ===
=== Documentation ===
The examiner is most concerned about the final, elongated position of the muscle, with the measurement taken in this final position.
The examiner is most concerned about the final, elongated position of the muscle, with the measurement taken in this final position.
== Summary ==
Muscle length is really important for our function, with full range of motion required to enable optimal movement. Thus, assessing muscle length is an important piece in the clinical puzzle. There are different testing options for muscle length, and your choice of test may be influenced by different factors depending on your patient population and each individual’s presentation, including their age, co-morbodities, pain levels and more. Once you decide on a test, you need to be sure to set up your space, so that your patient is able to move through their full range without anything getting in the way, such as pillows. Regardless of the type of test, the key to muscle length testing is to ensure that the tested muscle is in its lengthened position across all the joints it crosses.
If you observe changes in muscle length during testing, it’s important to recognise that this could be because of changes between the agonist and antagonist muscles, so we must always consider our findings in the context of the rest of our assessment, including our movement analysis, as well as posture, range of motion, muscle strength, tone, neural tests and more, and apply our clinical reasoning skills to what we find. Short or tight muscles might be weak or strong, and long muscles might also be weak or strong, so there is no one principle for all muscles. We need to be thorough and consider all aspects of our assessment to be able to go on and select the most appropriate treatment.


== References  ==
== References  ==
<references /> 
<references /> 

Revision as of 00:05, 26 May 2023

Original Editors - Naomi O'Reilly and Jess Bell

Top Contributors - Naomi O'Reilly, Jess Bell and Ewa Jaraczewska      

Introduction[edit | edit source]

Muscle length refers to the ability of a muscle to cross a joint to lengthen, allowing one or more joints to move through the full available range of motion.[1][2] Muscle ability to lengthen is an essential part of everyday movements.[3]This article will discuss methods and principles of muscle length measurement.

Structure of Muscles[edit | edit source]

Skeletal muscles are made up of striated muscle fibres. A muscle connects to bones or joint capsules by connective tissue structures, such as tendons or aponeuroses.[4] Muscle fibres contain smaller units called myofibrils, which are made of thick and thin myofilaments. These filaments are organised longitudinally into units called sarcomeres, which is the basic contractile unit of the muscle fibre. [5]

A muscle belly generates force when the sarcomeres contract, which pulls the origin and insertion of the muscle-tendon complex closer together, so the muscle shortens during a contraction.[4] When sarcomeres contract, the overlap between thick and thin myofilaments increases. The overlap decreases as it lengthens, so the muscle fibre can lengthen.

Kruse and colleagues state, "The force exerted actively by a muscle can be expressed as a function of muscle length.” The length where muscles don’t actively generate force is known as active slack length. The length at which muscles are able to generate their maximal active force is known as optimum muscle length. The difference between the two is the length range of active force exertion. [4]

Mechanism of Muscle Lengthening[edit | edit source]

The lengthening of a muscle fibre begins with the sarcomere, the basic unit of contraction in the muscle fibre. As the sarcomere contracts, the overlap between the thick and thin myofilaments increases. As it lengthens, this area of overlap decreases, allowing the muscle fibre to elongate. Maximal muscle length, therefore, is the greatest extensibility of the muscle-tendon junction. Muscle length testing is done to determine whether the muscle length is limited or excessive, i.e., whether the muscle is too short to permit a normal range of motion or stretched and allows too much range of motion.[6]

Factors Affecting Muscle Length[edit | edit source]

Gender[edit | edit source]

Evidence suggests that biological females tend to be more flexible and have increased muscle length compared to biological males.[7] [8]Research looking specifically at hamstrings length has found that females can have up to 8 degrees more range in their passive SLR [9] and 12 degrees in the knee active knee extension test.[10]

Age[edit | edit source]

Older adults experience increased fibrosis, sarcopenia, decreased force production and a general reduction in flexibility. There may be an association between the range of motion and muscle length of the lower limb and balance performance in older adults with foot deformities. [11] However, as Reese and Bandy [2] point out, there is not much research on age-related changes in muscle length using direct measurement tests, with at least one study on hamstring length using this method showing no difference in muscle length associated with age. [9]

Posture[edit | edit source]

Posture can have an impact on muscle length because our muscles and tissues adapt to how they are used. A common posture seen in clinical practice is a forward head position. [12] Research suggests that a forward head posture can be associated with vestibular deficits, decreased proprioception, abnormal muscle activity, and altered breathing patterns [12], and it has a bearing on muscle length. The cervical flexors and occipital extensors have been found to shorten in a forward head position compared to a neutral spine, whereas the cervical extensors and occipital flexors lengthen. [13] A somatic adaptation in athletes must also be considered when assessing muscle length. Krzykala et al. discuss how athletes with different body structures can react to training loads by developing asymmetries between their right and left arms and legs. [14]

Muscle Length Tests[edit | edit source]

Muscle Length Tests are performed to determine whether the range of muscle length is normal, limited, or excessive. The test results can help identify if these changes in muscle extensibility may be contributing to movement impairment and/or symptoms. Muscle length testing consists of movements that increase the distance between the origin and insertion, thereby lengthening muscles in directions opposite to the muscles' actions while assessing their resistance to passive lengthening.[6]

Precise testing requires that one of the bony attachments of the muscle be in a fixed position while the other bony attachment is moved passively in the direction of lengthening the muscle. To assess and measure the length of a muscle, we need to passively stretch or lengthen the muscle across the joint or joints crossed by that muscle. For the best accuracy and precision, muscle length testing should be performed when the patient is not in acute pain in order to avoid pain inhibition and muscle guarding.[15]

Muscle length testing aims to help determine whether a reduced or increased range of motion at a joint is caused by the length of the muscle being tested or if other structures cause it. [15]

Measurement Methods[edit | edit source]

A review of the literature identifies primarily two methods to assess muscle length.

Composite Measurement[edit | edit source]

Muscle length is commonly assessed through the use of composite tests, which look at movement across more than one muscle or joint. Common composite tests are the Apley’s Test or the Sit and Reach Test, and while frequently used as a measure of muscle length, research suggests that these composite tests do not provide accurate measurements of muscle length as they assess combinations of movements across several joints involving several muscles. Thus, they tend to provide a general idea of flexibility rather than an exact measurement of a single muscle’s length.

Direct Measurement[edit | edit source]

Direct measurement of muscle length is the alternative method where excursion between adjacent segments of one joint is measured. When using direct measurement techniques, we need to consider that muscles are characterised by the number of joints they cross, i.e., one-joint, two-joint, and multi-joint muscles. This will impact the measurement of muscle length.

  • The range of motion and muscle length will measure the same for muscles that pass over one joint only.
  • For muscles that pass over two or more joints, the normal range of the muscle will be less than the total range of motion of the joints over which the muscle passes.[16]

One Joint Muscle[edit | edit source]

One-joint muscle cross just one joint. It typically allows a full passive range of motion at the joint it crosses. If a one-joint muscle is short and limits the range of motion, you’ll notice a firm end feel caused by muscle tension. [2][15]

We can determine the length of a one-joint muscle by measuring the passive range of motion of the joint that it crosses, by positioning the joint where the muscle is lengthened across the joint, and the position of the joint is measured. This represents an indirect measure of muscle length. [2][16]

Effectively we measure the range in the direction opposite to its action. For example, the hip adductors (adductor longus, brevis and magnus) are one-joint muscles. To determine their length, we measure the passive range of hip abduction. [15]

Two-Joint Muscle[edit | edit source]

The muscles that cross two or more joints typically do not allow a full range of motion across all the joints they cover. This is known as passive insufficiency.

"Passive insufficiency occurs when a multi-joint muscle is lengthened to its fullest extent at both joints, thereby preventing the full range of motion of each joint it crosses." [17]

To assess and measure the length of a two-joint muscle, do the following:
  • Position one of the joints crossed by the muscle so as to lengthen the muscle across the joint.
  • Move the second joint through a passive range of motion until the muscle is on full stretch, preventing further joint motion.
  • Assess and measure the final position of the second joint.

This represents an indirect measure of muscle length. [2][16]

Example #1: The biceps brachii crosses the shoulder and the elbow. It flexes and supinates the elbow and is a weak shoulder flexor. Test the length of this muscle as follow:

  • Position the patient in a supine.
  • The starting position is shoulder extension, with the elbow flexed and supinated.
  • Extend the elbow and measure the elbow extension range to determine the biceps' muscle length.

To measure elbow joint extension, position the shoulder joint in neutral to prevent passive insufficiency of the biceps brachii from affecting our results. You can compare the results to see the difference in range when the muscle isn’t on full stretch.

Example #2: Measuring rectus femoris length vs knee flexion range of motion. Rectus femoris crosses the hip and knee, flexing the hip and extending the knee.

Measure knee flexion as follow:

  • Flex the hip to avoid passive insufficiency of rectus femoris.
  • To determine the length of this muscle, position the patient in a prone, which puts the hip in some extension
  • Measure the amount of knee flexion allowed by rectus femoris.

If the hip flexes during the movement, we know this muscle has length limitations. This is also known as Ely's Test. [15]

Multi-joint Muscle[edit | edit source]

Measurement of multi-joint muscles follows the same principles as measuring a two-joint muscle. To assess and measure the length of a multi-joint muscle, position all but one of the joints crossed by the muscle so that the muscle is lengthened across the joints. Then move the remaining joint crossed by the muscle through a passive range of motion until the muscle is on full stretch and prevents further motion at the joint. Assess and measure the final position of the joint; the joint position represents an indirect measure of the muscle length.[2][16]

An example: The flexor digitorum superficialis crosses the elbow, wrist and hand and inserts into the middle phalanges of digits 2-5. It primarily flexes digits 2-5 at the proximal interphalangeal (PIP) and metacarpophalangeal (MCP) joints but is also a wrist flexor.

Assess this muscle (and the other multi-joint finger flexors) as follows:

  • Position the patient sitting with their forearm pronation on a table.
  • The hand rests on the table.
  • Move the elbow and finger joints into extension and then passively extend the wrist.
  • Measure the amount of wrist extension to assess the length of this muscle. [2]

Measurement Tools[edit | edit source]

Measurement of muscle length is assessed using three primary types of instruments, which include the universal goniometer and the variations of this measurement tool, the inclinometer and its variations, and linear forms of measurement such as the tape measure.

Goniometer[edit | edit source]

Fig.1 Goniometer
A goniometer (Fig.1) is a device that measures angles. All universal goniometers have a central "body" with a protractor and fulcrum to centre over the patient's joint and two "arms" to align with the patient's body parts. [1]

Generally, goniometers have been shown to have good to excellent reliability, depending on the motion and joint being measured, with intra-rater reliability higher than inter-rate reliability.[18] [19] The use of standardised positions, stabilisation of the body part proximal to the joint being tested, use of bony landmarks to align the goniometer, and repeated testing conducted by the same therapist all help to improve the validity and reliability of goniometric measurements.[20][21][22]

Inclinometer[edit | edit source]

An inclinometer or clinometer, consisting of a circular, fluid-filled disk with a bubble or weighted needle that indicates the number of degrees on the scale of a protractor, is an instrument used for measuring angles of slope, elevation, or depression of an object with respect to gravity's direction. The majority of inclinometers are calibrated or referenced to gravity, which means that the starting position of the inclinometer can be consistently identified and repeated.[2]

Evidence suggests that the hand-held inclinometer is valid and reliable for assessing muscle length.[23] [24] Intra-rater reliability for the hand-held inclinometer during SLR testing was excellent (ICC, 0.95 to 0.98) with standard error of measurement between 0.54° and 1.22° and the minimal detectable change was between 1.50° and 3.41°.[23] While both intra- and inter-tester reliability were good during the assessment of motion around the knee. [24]

Tape Measure[edit | edit source]

Fig.2 Tape Measure
A tape measure is one of the simplest measurement tools that can be used, which typically measures on a scale with centimetres (cm) or inches (in). The tape is inexpensive, easy to use and readily available in most clinics. [2]

The tape measure has also shown good reliability for muscle testing with good intra-rater reliability (ICC 0.82 0.87) shown within the same day to measure pectoralis minor muscle length.[25]

Principles of Measurement[edit | edit source]

Regardless of the measurement tool being used, the individual employing the instrument must become skilled in the use of the measurement tool to improve reliability in assessing muscle length. Practice in using an instrument should continue until the user has established a high level of intra-rater reliability. [2] Many of the steps involved in measuring muscle length are the same as though used for measuring joint range of motion. The following principles provide the basic framework for muscle length measurement.

Table 1. Principles of Range of Motion and Muscle Length Assessment [2]
Description
Determine the type of measurement to be performed
Explain the purpose of the procedure to the patient
Position the patient in the preferred position for the measurement
Stabilise the proximal joint segment.
Instruct the patient in the specific motion that will be measured
Move the patient's distant joint segment passively through the available range
Determine the patient's end-feel at the end of the range
Return the patient's distal joint segment to the starting position
Palpate bony landmarks for measurement device alignment
Align the measurement device with the appropriate bony landmarks
Move the patient's distant joint segment passively to the end range
Read the scale of the measurement device and note the reading
Document Muscle Length

Instructions[edit | edit source]

Patients should be provided with instructions prior to performing any assessment technique so they have an understanding of what is going to happen. Before beginning the muscle length assessment, describe to the patient what will take place and why the measurement is being completed. Show the patient the measurement tool, and explain, in simple terms, its purpose and how it will be used. Show the patient the position they are to assume, again using simple terms and avoiding medical terminology such as supine or prone.[2][1]

Positioning[edit | edit source]

The muscle to be measured should be placed in the fully elongated position, ensuring maximal lengthening of the muscle from origin to insertion. The examiner is concerned about the final, elongated position of the muscle and not the measurement of the starting position, as would be appropriate for the measurement of the joint range of motion. [1]

The muscle being measured should be isolated across one joint. When measuring two or multi-joint muscles, move the final joint through a passive range of motion until the muscle is on full stretch and prevents further joint motion. [2]

Stabilisation[edit | edit source]

To ensure accurate measurement of muscle length, firmly stabilise one end of the bony segment of the joint being measured, typically at the origin or proximal aspect of the bone. Without adequate stabilisation and isolation of the muscle being measured, the patient may substitute motion at another joint resulting in measurement error.[2]

Speed of Movement[edit | edit source]

Once the patient is positioned and the proximal joint segment is adequately stabilised, the examiner should passively move the joint and lengthen the muscle through the available range of motion. The elongation of the muscle should be performed slowly to avoid eliciting a quick stretch of the muscle spindle and subsequently inducing a twitch response and muscle contraction. [26]

By moving the limb slowly through the range of motion to be measured, the patient is aware of the exact movement to be performed and can cooperate more fully and accurately with the procedure. The examiner can also get an estimation of the patient's available range of motion prior to completing the final measurement, which can provide a check to minimise the possibility of gross measurement error.[2]

Determining End Feel[edit | edit source]

Each joint has a characteristic feel to the resistance encountered at the end of the normal range of motion. Typical end-feels encountered at the end of the normal range of motion are hard (bony), firm (capsular, muscular, and ligamentous) and soft (soft tissue approximation). When assessing muscle length, we are typically looking for a firm end feel when the muscle is on full stretch, and the patient will report a pulling sensation, stretch or pain in the region of the muscle being lengthened. [2][6]

Align Measurement Device[edit | edit source]

Precise alignment of the measurement device relies on accurate palpation of landmarks. Bony landmarks are typically used to align the measurement device since bony structures are more stable and less subject to change in position.

Three landmarks are typically used to align the goniometer, with two landmarks to align the arms of the goniometer:

  1. One landmark for the stationary arm aligned with the midline of the stationary segment of the joint.
  2. One landmark for the moving arm aligned with the midline of the moving segment of the joint.
  3. One landmark for the fulcrum of the goniometer aligned with a point near the axis of rotation of the joint.


Priority should be given to the alignment of the stationary and moving arms of the goniometer for accurate alignment.[2]

Documentation[edit | edit source]

The examiner is most concerned about the final, elongated position of the muscle, with the measurement taken in this final position.

Summary[edit | edit source]

Muscle length is really important for our function, with full range of motion required to enable optimal movement. Thus, assessing muscle length is an important piece in the clinical puzzle. There are different testing options for muscle length, and your choice of test may be influenced by different factors depending on your patient population and each individual’s presentation, including their age, co-morbodities, pain levels and more. Once you decide on a test, you need to be sure to set up your space, so that your patient is able to move through their full range without anything getting in the way, such as pillows. Regardless of the type of test, the key to muscle length testing is to ensure that the tested muscle is in its lengthened position across all the joints it crosses.

If you observe changes in muscle length during testing, it’s important to recognise that this could be because of changes between the agonist and antagonist muscles, so we must always consider our findings in the context of the rest of our assessment, including our movement analysis, as well as posture, range of motion, muscle strength, tone, neural tests and more, and apply our clinical reasoning skills to what we find. Short or tight muscles might be weak or strong, and long muscles might also be weak or strong, so there is no one principle for all muscles. We need to be thorough and consider all aspects of our assessment to be able to go on and select the most appropriate treatment.

References [edit | edit source]

  1. ↑ 1.0 1.1 1.2 1.3 Norkin CC, White DJ. Measurement of Joint Motion: A Guide to Goniometry. FA Davis; 2016 Nov 18.
  2. ↑ 2.00 2.01 2.02 2.03 2.04 2.05 2.06 2.07 2.08 2.09 2.10 2.11 2.12 2.13 2.14 2.15 2.16 Reese NB, Bandy WD. Joint Range of Motion and Muscle Length Testing-E-book. Elsevier Health Sciences; 2016 Mar 31.
  3. ↑ Tomalka A. Eccentric muscle contractions: from single muscle fibre to whole muscle mechanics. Pflugers Arch. 2023 Apr;475(4):421-435.
  4. ↑ 4.0 4.1 4.2 Kruse A, Rivares C, Weide G, Tilp M, Jaspers RT. Stimuli for adaptations in muscle length and the length range of active force exertion—a narrative review. Frontiers in Physiology. 2021:1677.
  5. ↑ Gash MC, Kandle PF, Murray IV, Varacallo M. Physiology, Muscle Contraction. [Updated 2022 May 2]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK537140/ [last access 23.05.2023]
  6. ↑ 6.0 6.1 6.2 Gross JM, Fetto J, Rosen E. Musculoskeletal examination. John Wiley & Sons; 2015 Jun 29.
  7. ↑ Allison KF, Keenan KA, Sell TC, Abt JP, Nagai T, Deluzio J, McGrail M, Lephart SM. Musculoskeletal, biomechanical, and physiological gender differences in the US military. US Army Medical Department Journal. 2015 Apr 1.
  8. ↑ Pawar A, Phansopkar P, Gachake A, Mandhane K, Jain R, Vaidya S. A review on the impact of lower extremity muscle Length. J Pharm Res Int. 2021;33(35A):158-64.
  9. ↑ 9.0 9.1 Youdas JW, Krause DA, Hollman JH, Harmsen WS, Laskowski E. The influence of gender and age on hamstring muscle length in healthy adults. Journal of Orthopaedic & Sports Physical Therapy. 2005 Apr;35(4):246-52.
  10. ↑ Corkery M, Briscoe H, Ciccone N, Foglia G, Johnson P, Kinsman S, Legere L, Lum B, Canavan PK. Establishing normal values for lower extremity muscle length in college-age students. Physical Therapy in Sport. 2007 May 1;8(2):66-74.
  11. ↑ Justine M, Ruzali D, Hazidin E, Said A, Bukry SA, Manaf H. Range of motion, muscle length, and balance performance in older adults with normal, pronated, and supinated feet. Journal of physical therapy science. 2016;28(3):916-22.
  12. ↑ 12.0 12.1 Lin G, Wang W, Wilkinson T. Changes in deep neck muscle length from the neutral to forward head posture. A cadaveric study using Thiel cadavers. Clinical Anatomy. 2022 Apr;35(3):332-9.
  13. ↑ Khayatzadeh S, Kalmanson OA, Schuit D, Havey RM, Voronov LI, Ghanayem AJ, Patwardhan AG. Cervical spine muscle-tendon unit length differences between neutral and forward head postures: a biomechanical study using human cadaveric specimens. Physical therapy. 2017 Jul 1;97(7):756-66.
  14. ↑ Magdalena Krzykała M ,Karpowicz K, Karpowicz M, Bartkowiak S, Demuth A, Czerniak U, Janowski J. Somatic characteristic, morphological asymmetry and postural stability of youth male canoeists compared to control. A cross-sectional study. PLoS ONE 2023; 18(5): e0285997.
  15. ↑ 15.0 15.1 15.2 15.3 15.4 Norkin CC, White DJ. Measurement of Joint Motion: A Guide to Goniometry. FA Davis; 2016 Nov 18.
  16. ↑ 16.0 16.1 16.2 16.3 Conroy VM, Murray Jr BN, Alexopulos QT, McCreary J. Kendall's Muscles: Testing and Function with Posture and Pain. Lippincott Williams & Wilkins; 2022 Nov 23.
  17. ↑ Rogers M, Rogers M. Understanding Active and Passive Insufficiency [Internet]. National Federation of Professional Trainers. 2020 [cited 17 September 2020]. Available from: https://www.nfpt.com/blog/understanding-active-and-passive-insufficiency
  18. ↑ Herrero P, Carrera P, García E, Gómez-Trullén EM, Oliván-Blázquez B. Reliability of goniometric measurements in children with cerebral palsy: a comparative analysis of universal goniometer and electronic inclinometer. A pilot study. BMC musculoskeletal disorders. 2011 Dec;12:1-8.
  19. ↑ van Rijn SF, Zwerus EL, Koenraadt KL, Jacobs WC, van den Bekerom MP, Eygendaal D. The reliability and validity of goniometric elbow measurements in adults: A systematic review of the literature. Shoulder & elbow. 2018 Oct;10(4):274-84.
  20. ↑ Rothstein JM, Miller PJ, Roettger RF. Goniometric reliability in a clinical setting. Elbow and knee measurements. Phys Ther. 1983 Oct;63(10):1611-5.
  21. ↑ Watkins MA, Riddle DL, Lamb RL, Personius WJ. Reliability of goniometric measurements and visual estimates of knee range of motion obtained in a clinical setting. Phys Ther. 1991 Feb;71(2):90-6; discussion 96-7.
  22. ↑ Ekstrand J, Wiktorsson M, Oberg B, Gillquist J. Lower extremity goniometric measurements: a study to determine their reliability. Arch Phys Med Rehabil. 1982 Apr;63(4):171-5.
  23. ↑ 23.0 23.1 Boyd BS. Measurement properties of a hand-held inclinometer during straight leg raise neurodynamic testing. Physiotherapy. 2012 Jun 1;98(2):174-9.
  24. ↑ 24.0 24.1 Romero-Franco N, Montaño-Munuera JA, Jiménez-Reyes P. Validity and reliability of a digital inclinometer to assess knee joint-position sense in a closed kinetic chain. Journal of sport rehabilitation. 2017 Jan 1;26(1).
  25. ↑ Rosa DP, Borstad JD, Pires ED, Camargo PR. Reliability of measuring pectoralis minor muscle resting length in subjects with and without signs of shoulder impingement. Brazilian Journal of physical therapy. 2016 Mar 15;20:176-83.
  26. ↑ Izraelski J. Assessment and treatment of muscle imbalance: The Janda approach. The Journal of the Canadian Chiropractic Association. 2012 Jun;56(2):158.
 
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