Assessing Muscle Length: Difference between revisions

No edit summary
No edit summary
 
(41 intermediate revisions by 3 users not shown)
Line 1: Line 1:
<div class="pp-no-course-suggestions pp-no-article-suggestions"></div>
<div class="pp-no-course-suggestions pp-no-article-suggestions"></div>
<div class="noeditbox">Welcome to [[Understanding Basic Rehabilitation Techniques Content Development Project]]. Please do not edit unless you are involved in this project, but please come back in the near future to check out new information!! If you would like to get involved in this project and earn accreditation for your contributions, [mailto:[email protected] please get in touch]!</div> <div class="editorbox">  
 
<div class="editorbox">  


'''Original Editors ''' - [[User:Naomi O'Reilly|Naomi O'Reilly]] and [[User:Jess Bell|Jess Bell]]
'''Original Editors ''' - [[User:Naomi O'Reilly|Naomi O'Reilly]] and [[User:Jess Bell|Jess Bell]]


'''Top Contributors''' - {{Special:Contributors/{{FULLPAGENAME}}}}  &nbsp;   
'''Top Contributors''' - {{Special:Contributors/{{FULLPAGENAME}}}}  &nbsp;   
</div><div align="justify">
</div>
 
== Introduction==
== Introduction==
Muscle length refers to the ability of a muscle crossing a joint to lengthen, allowing one or more joints to move through the full available [[Range of Motion|range of motion]].<ref name=":3">Norkin CC, White DJ. Measurement of Joint Motion: A Guide to Goniometry. FA Davis; 2016 Nov 18.</ref><ref name=":4">Reese NB, Bandy WD. Joint Range of Motion and Muscle Length Testing-E-book. Elsevier Health Sciences; 2016 Mar 31.</ref> The lengthening of a muscle fiber begins with the [[sarcomere]], the basic unit of contraction in the [[Muscle Cells (Myocyte)|muscle fiber]]. As the sarcomere contracts, the area of overlap between the thick and thin myofilaments increases. As it lengthens, this area of overlap decreases, allowing the muscle fiber 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 normal range of motion, or stretched and allowing too much range of motion.<ref name=":5">Gross JM, Fetto J, Rosen E. Musculoskeletal examination. John Wiley & Sons; 2015 Jun 29.</ref>  
Muscle length refers to the ability of a muscle crossing a joint or joints to lengthen, thus allowing the joint or joints to move through their full available [[Range of Motion|range of motion]].<ref name=":3">Norkin CC, White DJ. Measurement of Joint Motion: A Guide to Goniometry. FA Davis; 2016 Nov 18.</ref><ref name=":4">Reese NB, Bandy WD. Joint Range of Motion and Muscle Length Testing-E-book. Elsevier Health Sciences; 2016 Mar 31.</ref> A muscle's ability to lengthen is essential for functional activities,<ref>Tomalka A. [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10011336/pdf/424_2023_Article_2794.pdf Eccentric muscle contractions: from single muscle fibre to whole muscle mechanics]. Pflugers Arch. 2023 Apr;475(4):421-435. </ref> so rehabilitation professionals need to consider muscle length when assessing and treating patients. This article discusses the general principles of the muscle length assessment.
 
== Structure of Muscles ==
Muscles connect to bones or joint capsules by connective tissue structures, such as [[Tendon Anatomy|tendons]] or aponeuroses.<ref name=":1">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.</ref>
 
Skeletal [[muscle|muscles]] are made up of striated muscle fibres. These 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.<ref>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]</ref>
 
A muscle belly generates force when the sarcomeres contract. This pulls the origin and insertion of the muscle-tendon complex closer together, thus shortening the muscle.<ref name=":1" /> When sarcomeres contract, the overlap between thick and thin myofilaments increases. The amount of overlap decreases as it relaxes so that the muscle fibre can elongate. Maximal muscle length is, therefore, the greatest extensibility of the muscle-tendon junction.<ref name=":5">Gross JM, Fetto J, Rosen E. Musculoskeletal examination. John Wiley & Sons; 2015 Jun 29.</ref>
 
Kruse and colleagues<ref name=":1" /> state: "The force exerted actively by a muscle can be expressed as a function of muscle length.”<ref name=":1" />


Muscle Length Tests are are performed to determine whether the range of muscle length is normal, limited, or excessive i.e., whether the muscle is too short to permit normal range of motion, or lengthened and allowing too much range of motion and is used to identify if these changes in muscle extensibility may be contributing to movement impairment and/or symptoms. Muscle length testing consist of movements that increase the distance between the origin and insertion, thereby lengthening muscles in directions opposite to the muscles actions, while assessing its resistance to passive lengthening.<ref name=":5" />  
* The length at which muscles do not 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 active slack length and the optimum muscle length is the length range of active force exertion<ref name=":1" />
<br>
For a detailed discussion of these principles, please see Kruse et al. [https://www.frontiersin.org/articles/10.3389/fphys.2021.742034/full#:~:text=The%20muscle%20length%20at%20which,force%20exertion%20(Figure%201). Stimuli for adaptations in muscle length and the length range of active force exertion - a narrative review].


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. This means that 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.<ref name=":0" />
== Muscle Length Assessment ==
The muscle length assessment helps determine whether a muscle's length is normal, decreased or increased. This assessment can help identify if changes in muscle extensibility are contributing to a movement impairment and/or symptoms or if other structures are involved.<ref name=":0">Norkin CC, White DJ. Measurement of Joint Motion: A Guide to Goniometry. FA Davis; 2016 Nov 18.</ref>


The purpose of muscle length testing is to help determine whether reduced or increased range of motion at a joint is caused by the length of the muscle being tested or if it is caused by other structures. <ref name=":0">Norkin CC, White DJ. Measurement of Joint Motion: A Guide to Goniometry. FA Davis; 2016 Nov 18.</ref>
To test muscle length, we must position the muscle so that the distance between its origin and insertion increases - i.e. we lengthen the muscle in the direction opposite to its action.<ref name=":0" /> For example, to measure the length of the hip flexors, we position the hip in extension.  


== Structure of Muscles ==
== Measurement Methods ==
Skeletal [[muscle|muscles]] are made up of striated muscle fibres. A muscle connects to bones or joint capsules by connective tissue structures, such as [[Tendon Anatomy|tendons]] or aponeuroses.<ref name=":1">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.</ref> Muscle fibres contain smaller units called myofibrils, which in turn 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. <ref>Gash, M. C., P. F. Kandle, I. Murray, and M. Varacallo. "Physiology, Muscle Contraction. 2021 Apr 20." ''StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing'' (2022).</ref>
Two main methods are used to assess muscle length: composite tests and direct measurement.


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.<ref name=":1" /> When sarcomeres contract, the amount of overlap between thick and thin myofilaments increases. As it lengthens, the amount of overlap decreases, so the muscle fibre can lengthen.
=== Composite Tests ===
Muscle length is commonly assessed through the use of composite tests (e.g. [[Apley's Test|Apley’s Test]] or the [[Sit and Reach Test]]). These tests look at movement across more than one muscle or joint. However, while frequently used, research suggests that they do not provide accurate measurements of muscle length because they assess combinations of movements across several joints and involve several muscles. Thus, they tend to give a general idea of flexibility rather than an exact measurement of a single muscle’s length.<ref name=":4" />


Kruse and colleagues state that “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. <ref name=":1" />
=== Direct Measurement  ===
In the direct measurement method, the distance between adjacent joint segments is measured. When using this method, we must consider that muscles are characterised by the number of joints they cross, i.e., one-joint, two-joint, and multi-joint muscles.  


== Factors Effecting Muscle Length ==
==== One Joint Muscles ====
One-joint muscles cross just one joint. They typically allow full passive range of motion at the joint they cross. If a one-joint muscle is short and limits the range of motion, you will notice a [[End-Feel|firm end feel]] caused by muscle tension.<ref name=":4" /><ref name=":0" /> To determine the length of a one-joint muscle, we measure the passive range of motion of the joint that it crosses in the direction opposite to its action.


=== Gender ===
'''''Example''''': To measure the length of [[Adductor Longus|adductor longus]], [[Adductor Brevis|brevis]] and [[Adductor Magnus|magnus]]:
In general evidence suggests that biological females tend to be more flexible and have increased muscle length in comparison to biological males.<ref>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.</ref> <ref>Pawar A, Phansopkar P, Gachake A, Mandhane K, Jain R, Vaidya S. A review on impact of lower extremity muscle Length. J Pharm Res Int. 2021;33(35A):158-64.</ref>Research looking specifically at hamstrings length has found that females can have up to 8 degrees more range in their passive SLR <ref name=":6">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.</ref> and 12 degrees in the knee active knee extension test.<ref>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.</ref>  
 
* Position the hip joint so that these muscles are in a lengthened position - i.e. hip abduction
* Measure the degree of passive hip abduction achieved<ref name=":4" /><ref name=":2">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.</ref><ref name=":0" />


=== Age ===
==== Two-Joint Muscles ====
Force production capacity is impacted by reduced muscle fibre length and altered pennation angles, which is the angle between the longitudinal axis of the muscle and its fibers.<ref>Fragala MS, Kenny AM, Kuchel GA. Muscle quality in aging: a multi-dimensional approach to muscle functioning with applications for treatment. Sports medicine. 2015 May;45:641-58.</ref> Older adults experience increased fibrosis, sarcopenia, decreased force production and a general reduction in flexibility. These changes can impact independence and lead to an increase in morbidity and mortality.<ref>Zotz TG, Capriglione LG, Zotz R, Noronha L, De Azevedo ML, Martins HR, Gomes AR. Acute effects of stretching exercise on the soleus muscle of female aged rats. Acta histochemica. 2016 Jan 1;118(1):1-9.</ref> There may also be an association between range of motion and muscle length of the lower limb and balance performance in older adults with foot deformities. <ref>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.</ref> However, as Reese and Bandy <ref name=":4" /> 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. <ref name=":6" />
Muscles that cross two or more joints typically do not allow full range of motion across all the joints they cross. This is known as passive insufficiency.
<blockquote>"[[Active and 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."<ref>Rogers M, Rogers M. Understanding Active and Passive Insufficiency [Internet]. National Federation of Professional Trainers. 2020 [cited 17 September 2020]. Available from: <nowiki>https://www.nfpt.com/blog/understanding-active-and-passive-insufficiency</nowiki></ref></blockquote>To assess and measure the length of a two-joint muscle, we must:


=== Posture ===
* Position one of the joints so that the muscle is in a lengthened position
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. <ref name=":7">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.</ref> In a forward head position, an individual’s chin tends to come forward. They have flexion of their mid-lower cervical spine and extension of their upper cervical spine. This posture is often linked to time spent sitting at desks on computers, laptops and mobile phones. <ref name=":8">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: biomechanical study using human cadaveric specimens. Physical therapy. 2017 Jul 1;97(7):756-66.</ref> Research suggests that a forward head posture can be associated with vestibular deficits, decreased proprioception, abnormal muscle activity, and altered breathing patterns <ref name=":7" /> 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. <ref name=":8" />
* Move the second joint passively until the muscle is on full stretch and prevents further motion at the joint
* Measure the final position of the second joint to determine muscle length<ref name=":4" /><ref name=":2" />
'''''Example #1'':''' Measuring [[Biceps Brachii|biceps brachii]] length vs elbow extension range of motion.


== Measurement Methods ==
Biceps brachii crosses the shoulder and the elbow. It flexes and supinates the elbow and is a weak shoulder flexor. To test the length of biceps brachii:
Review of the literature identifies primarily two methods to assess muscle length.


=== Composite Measurement ===
* Position the patient in a supine
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|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.
* Place the arm in shoulder extension, elbow flexion and supination
* Passively extend the elbow and measure the elbow extension range to determine the length of biceps brachii
To measure extension of the elbow ''joint'', position the shoulder joint in neutral to prevent passive insufficiency of biceps brachii from affecting your results. You can compare your results to see the difference in elbow extension range when biceps brachii is and isn't fully lengthened.


=== Direct Measurement  ===
'''''Example #2'':''' Measuring [[Rectus Femoris|rectus femoris]] length vs [[Goniometry: Knee Flexion|knee flexion]] range of motion.  
D''irect measurement'' of muscle length is the alternative method where excursion between adjacent segments of one joint is measured, and typically are considered a better indicator of muscle length than composite tests. When using direct measurement techniques we need to consider that muscles are characterised by the number of joints they cross i.e. one-joint muscles, two-joint muscles and multi-joint muscles and that this will impact of on the measurement of muscle length.  


* Muscles that pass over one joint only, the range of motion and range of muscle length will measure the same;
Rectus femoris crosses the hip and knee. It flexes the hip and extends the knee. To test the length of rectus femoris:  
* 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.<ref name=":2">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.</ref>


==== One Joint Muscle ====
* Position the patient in prone
One-joint muscles typically allow full passive range of motion at the joint they cross. If a one-joint muscle is short, and it limits the range of motion, you’ll notice a firm end feel caused by muscle tension.  <ref name=":4" /><ref name=":0" />
* Passively flex the knee and measure the angle of knee flexion to determine the length of rectus femoris
* NB: If the hip flexes during the movement, we know there are length limitations in rectus femoris - this is also known as [[Ely's Test]]<ref name=":0" />


As their name suggests, one-joint muscles cross just one joint. 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 the muscle length. <ref name=":4" /><ref name=":2" />
To measure flexion of the knee ''joint'', position the patient in supine and assess knee flexion range (actively and passively). In this position, the hip can flex during the movement, which prevents passive insufficiency of rectus femoris from affecting results.  


Effectively we measure the range in the direction opposite to its action. For example, the hip adductors ([[Adductor Longus|adductor longus]], [[Adductor Brevis|brevis]] and [[Adductor Magnus|magnus]]) are one-joint muscles. So to determine their length, we measure the passive range of hip abduction. <ref name=":0" />
==== Multi-joint Muscles ====
We follow the same principles when measuring multi-joint muscles. To measure the length of a multi-joint muscle, all but one of the joints are positioned with the tested muscle in a lengthened position. We then move the remaining joint crossed by the muscle passively until the muscle is on full stretch and prevents further motion at the joint. We assess and measure the final position of this joint to determine muscle length.<ref name=":4" /><ref name=":2" />


==== Two-Joint Muscle ====
'''''Example''''': Measuring [[Flexor Digitorum Superficialis|flexor digitorum superficialis]] length.  
Unlike one-joint muscles, muscles that cross two or more joints typically do not allow full range of motion across all the joints they cover, which is known as passive insufficiency.  
<br>
<blockquote>"[[Active and Passive Insufficiency|Passive insufficiency]] occurs when a multi-joint muscle is lengthened to its fullest extent at both joints, thereby preventing full range of motion of each joint it crosses." <ref>Rogers M, Rogers M. Understanding Active and Passive Insufficiency [Internet]. National Federation of Professional Trainers. 2020 [cited 17 September 2020]. Available from: <nowiki>https://www.nfpt.com/blog/understanding-active-and-passive-insufficiency</nowiki></ref></blockquote>
To assess and measure the length of a two-joint muscle, position one of the joints crossed by the muscle so as to lengthen the muscle across the joint. Then move the second joint through a passive range of motion until the muscle is placed on full stretch and prevents further joint motion. Assess and measure the final position of the second joint. This represents an indirect measure of the muscle length. <ref name=":4" /><ref name=":2" />
<br>
For example, [[Biceps Brachii|biceps brachii]] crosses the shoulder and the elbow. It flexes and supinates the elbow and is a weak shoulder flexor. To test the length of this muscle, we would position our patient in supine. The starting position is shoulder extension, with the elbow flexed and supinated. We then extend the elbow and measure the range of elbow extension to determine muscle length of biceps. If we want to measure elbow joint extension, we would position the shoulder joint in neutral, to prevent passive insufficiency of biceps brachii affecting our results. We can also compare the results to see the difference in range when the muscle isn’t on full stretch.
<br>
Similarly, if we are considering [[Rectus Femoris|rectus femoris]] length vs [[Goniometry: Knee Flexion|knee flexion]] range of motion. Rectus femoris crosses the hip and knee, flexing the hip and extending the knee. So to measure knee flexion, we must have the hip flexed to avoid passive insufficiency of rectus femoris. If we want to determine the length of this muscle, we can position the patient in prone, which puts the hip in some extension and then we measure the amount of knee flexion allowed by rectus femoris. If the hip flexes during the movement, we know there are length limitations in this muscle. This is also known as the [[Ely's Test]]. <ref name=":0" />


==== Multi-joint Muscle ====
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 and is a wrist flexor. To assess the length of this muscle (and the other multi-joint finger flexors):  
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.<ref name=":4" /><ref name=":2" />


For example, the [[Flexor Digitorum Superficialis|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 it is also a wrist flexor. To assess this muscle (and the other multi-joint finger flexors), we position the patient in sitting with their forearm in pronation on a table. The hand rests over the table. We move the elbow and finger joints into extension and then passively extend the wrist. We measure the amount of wrist extension to assess the length of this muscle. <ref name=":4" />
* Position the patient in sitting with their forearm in pronation on a table
* The patient's hand rests over the edge of the table
* Move the elbow and finger joints into extension and then passively extend the wrist
* Measure the amount of wrist extension to determine the length of flexor digitorum superficialis<ref name=":4" />


== Measurement Tools ==
== Measurement Tools ==
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.  
Three main measurement tools are used to assess muscle length: the universal goniometer and its variants, the inclinometer and its variants, and linear forms of measurement such as a tape measure.  


=== '''Goniometer''' ===
=== '''Goniometer''' ===
[[File:Goniometer measurements.jpeg|frame|'''Fig.1''' Goniometer]]A [[goniometer]] (Fig.1) is a device that measures angles. Goniometers come in a variety of metal and plastic materials in different sizes and shapes. All universal goniometers have a central "body" with a protractor and fulcrum to center over the patient's joint, as well as two "arms" to align with the patient's body parts. <ref name=":3" />  
[[File: Goniometer measurements.jpeg|frame|''' Figure 1.''' Goniometer]][[goniometer|Goniometers]] measure angles. All universal goniometers have a central "body" with a protractor and fulcrum, which you centre over a patient's joint, and two "arms" to align with the patient's body parts.<ref name=":3" /> 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-rater reliability.<ref>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.</ref> <ref>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.</ref> We can improve the validity and reliability of goniometric measurements by:<ref>Rothstein JM, Miller PJ, Roettger RF. Goniometric reliability in a clinical setting. Elbow and knee measurements. Phys Ther. 1983 Oct;63(10):1611-5. </ref><ref>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. </ref><ref>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. </ref>
* using standardised positions
* stabilising the body part proximal to the joint being tested
* aligning the goniometer with bony landmarks
* having the same therapist conduct repeated tests
 
The following video demonstrates how to measure muscle length in the lower limb using a goniometer.
{{#ev:youtube|MQTM7t7wxWc|300}}<ref>Physio Skills. Lower Body Muscle Length Tests. Available from: https://www.youtube.com/watch?v=MQTM7t7wxWc [last accessed 17/11/2023]</ref>
 
=== '''Inclinometer''' ===
An [[inclinometer]] (or clinometer) is used to measure the angles of slope, elevation, or depression of an object. Most inclinometers are calibrated or referenced to gravity, which means that the starting position of the inclinometer can be consistently identified and repeated.<ref name=":4" /> Inclinometers have a circular disc which is filled with fluid and a bubble or weighted needle to point to a number (in degrees) on a protractor scale.<ref name=":4" />
 
Evidence suggests that the hand-held inclinometer is a valid and reliable instrument for assessing muscle length.<ref name=":9">Boyd BS. Measurement properties of a hand-held inclinometer during straight leg raise neurodynamic testing. Physiotherapy. 2012 Jun 1;98(2):174-9.</ref> <ref name=":10">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).</ref> Boyd<ref name=":9" /> found that intra-rater reliability for a hand-held inclinometer to measure a straight leg raise was excellent. Romero-Franco et al.<ref name=":10" /> found that both intra-tester and inter-tester reliability were good when an inclinometer was used to assess motion around the knee.


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.<ref>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.</ref> <ref>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.</ref> 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.<ref>Rothstein,  JM,  et al: Goniometric reliability in a clinical setting: Elbow and knee measurements. Phys Ther 63:1611, 1983.  [PubMed: 6622536]</ref><ref>Watkins,  MA,  et al: Reliability of goniometric measurements and visual estimates of knee range of motion obtained in a clinical setting. Phys Ther 71:90, 1991.  [PubMed: 1989012]</ref><ref>Ekstrand,  J,  et al: Lower extremity goniometric measurements: A study to determine their reliability. Arch Phys Med Rehabil 63:171, 1982.  [PubMed: 7082141]</ref>
=== '''Tape Measure''' ===
[[File:Tape measure and pills.jpg|thumb|200x200px|''' Fig.2''' Tape Measure]]Tape measures are one of the simplest measurement tools that can be used. They typically measure in centimetres (cm) or inches (in). A tape measure is inexpensive, easy to use and readily available in most clinics.<ref name=":4" />


=== '''Inclinometer;''' ===
Rosa et al.<ref name=":11" /> looked at assessing the muscle length of pectoralis minor using a tape measure and found it has good reliability and good intra-rater reliability (ICC 0.82 0.87) with same-day testing.<ref name=":11">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.</ref>
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 gravity using gravity as a reference point means that the starting position of the inclinometer can be consistently identified and repeated.<ref name=":4" />


Evidence suggest that the hand held inclinometer is both a valid and reliable method for assessing muscle length.<ref name=":9">Boyd BS. Measurement properties of a hand-held inclinometer during straight leg raise neurodynamic testing. Physiotherapy. 2012 Jun 1;98(2):174-9.</ref> <ref name=":10">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).</ref> Intra-rater reliability for the hand-held inclinometer during SLR testing was excellent (ICCs, 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°.<ref name=":9" /> While both intra- and inter-tester reliability were good during assessment of motion around the knee. <ref name=":10" />
== Principles of Assessment ==
Following these principles can help improve the accuracy of your muscle length assessment.<ref name=":4" />


=== '''Tape Measure'''; ===
'''Level of Skill:''' Every clinician must be skilled at using measurement tools to improve the reliability of a muscle length test. Clinicians should practise using an instrument until they achieve a high level of intra-rater reliability.<ref name=":4" />  
[[File:Tape measure and pills.jpg|thumb|200x200px|'''Fig.2''' Tape Measure]]A tape measure if one of the simplest measurement tools that can be used, which typically measures on a scale with centimetres (cm) or inches (in). The tape measure can be cloth, plastic or metal, is inexpensive, easy to use and readily available in most clinics. <ref name=":4" />


The tape measure has also shown good reliability for use in muscle testing with good intra-rater reliability (ICC 0.82 0.87) shown within the same day to measure pectoralis minor muscle length.<ref>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.</ref>
'''Communication:'''  Patients should be given detailed information before an assessment so they understand what will happen and what they need to do. Before starting your muscle length assessment, explain what you will do and why. You can show your patient the measurement tool that you will use. Make sure you do not use medical jargon to ensure understanding - e.g. avoid terms like ''supine'' and ''prone'' or ''proximal'' and ''distal.''<ref name=":4" /><ref name=":3" />


== Principles of Measurement ==
'''Positioning:''' In a muscle length test, we are measuring the final, elongated position of the muscle - we do not need to measure the starting position.<ref name=":3" /> Remember to ensure that the tested muscle is lengthened across ''all'' the joints it crosses.<ref name=":5" />
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. <ref name=":4" /> Many of the steps involved in measuring muscle length are the same as though used for measuring joint [[Range of Motion|range of motion]]. The following principles provide the basic framework for muscle length measurement.
{| width="800" border="1" cellpadding="1" cellspacing="1"
|+'''Table 1. Principles of Range of Motion and Muscle Length Assessment'''  <ref name=":4" />
|-
! '''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 ===
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 muscle length assessment, describe to the patient what will be taking 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.''<ref name=":4" /><ref name=":3" />


=== Positioning ===
'''Isolating Muscle:''' We need to isolate the muscle being tested as much as possible (across one or two joints).<ref name=":4" />
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 measurement of joint range of motion. <ref name=":3" />  


The muscle being measured should be isolated across one joint. When measuring two or multi-joint muscles ensure to move the final joint through a passive range of motion until the muscle is placed on full stretch and prevents further joint motion. <ref name=":4" />  
'''Stabilisation:''' During a test, ensure that you fix / stabilise one end (usually the proximal bony segment of the joint being moved) and passively move the other end to lengthen the muscle.<ref name=":5" /> Substitute movements at other joints may occur without adequate stabilisation, which can affect results.<ref name=":4" />  


=== Stabilisation ===
'''Speed of Movement:''' The clinician should move a joint slowly through the available motion to determine muscle length. This means you are more likely to avoid eliciting a quick stretch of the muscle spindle, and inducing a twitch response and muscle contraction.<ref>Izraelski J. Assessment and treatment of muscle imbalance: The Janda approach. The Journal of the Canadian Chiropractic Association. 2012 Jun;56(2):158.</ref>  
To ensure accurate measurement of muscle length, firmly stabilise one end of the bony segment of the joint being measured, typically this is 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.<ref name=":4" />


=== Speed of Movement ===
'''Determining End-feel:''' End feel refers to the resistance to movement at a joint's normal end range of motion.<ref name=":4" /> Common end feels include hard (bony), firm (capsular, muscular, and ligamentous) and soft (soft tissue approximation). We expect a firm end feel when assessing muscle length because the muscle should be on full stretch. The patient may also report a pulling sensation, stretch or pain in the region of the muscle being lengthened.<ref name=":4" /><ref name=":5" /> We can compare sides to get an understanding of what is "normal" for the patient. We can also look at muscle length normative values for each muscle. For examples of normative values for some muscles please see: [[Muscle Length Normative Values]].  
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. <ref>Izraelski J. Assessment and treatment of muscle imbalance: The Janda approach. The Journal of the Canadian Chiropractic Association. 2012 Jun;56(2):158.</ref>


By moving the limb slowly through the range of motion to be measured, the patient is made 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.<ref name=":4" />  
'''Aligning Measurement Tool:''' Bony landmarks are usually used to align our measurement tools when assessing muscle length. This is because bony landmarks are more stable and less likely to experience a change in position from factors like oedema. You will usually need to find three landmarks to align a goniometer:
# One landmark is used to align the stationary arm - this arm is usually aligned with the midline of the stationary segment of the joint.
# One landmark is used to align the moving arm - this arm is usually aligned with the midline of the moving segment of the joint.
# One landmark is used to align the fulcrum of the goniometer - the fulcrum is positioned over a point near the joint's axis of rotation.<ref name=":4" />
'''Documentation:''' Record the results of your muscle length test (and the testing position) in the patient's notes.


=== Determining End Feel ===
'''Acute Pain:''' If a patient has acute pain, muscle length testing may need to be delayed - otherwise, muscle guarding or pain inhibition might impact results.<ref name=":0" />
The most valuable clinical information during the measurement process is the end feel and the location of the end feel. Passive movement of the muscle being assessed allows the examiner to note any limitations to full elongation of the muscle, such as those caused by pain, muscle tightness, or other reasons.


Each joint has a characteristic feel to the resistance encountered at the end of normal range of motion. Typical end-feels encountered at the end of normal range of motion are the hard (bony), firm (capsular, muscular, and ligamentous) and soft (soft tissue approximation). When assessing muscle length typically we are 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. <ref name=":4" /><ref name=":5" />  
== Factors Affecting Muscle Length ==
=== Gender ===
Evidence suggests that biological females tend to be more flexible than biological males.<ref>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.</ref> <ref>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.</ref> Research looking specifically at hamstring length has found that females can have up to 8 degrees more range in their passive straight leg raise<ref name=":6">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.</ref> and 12 degrees more range during an active knee extension test than males.<ref>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.</ref>  


=== Align Measurement Device ===
=== Age ===
Precise alignment of the measurement device relies on accurate palpation of landmarks with bony landmarks typically used for alignment of the measurement device during muscle length assessment whenever possible, since bony structures are more stable and are less subject to change in position as a result of other factors such as oedema or muscle atrophy.
Our muscles also change with age. Older adults experience increased fibrosis, sarcopenia, decreased force production and a general reduction in flexibility.<ref>Zotz TG, Capriglione LG, Zotz R, Noronha L, Viola De Azevedo ML, Fiuza Martins HR, Silveira Gomes AR. Acute effects of stretching exercise on the soleus muscle of female aged rats. Acta Histochem. 2016 Jan;118(1):1-9.</ref> Justine et al.<ref name=":7">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.</ref> note that there may be an association between range of motion and muscle length in the lower limb and balance performance in older adults with foot deformities.<ref name=":7" />


Three landmarks, are typically used to align the goniometer, which is the most common measurement tool used for muscle length assessment, with two landmarks to align the arms of the goniometer;
However, as Reese and Bandy<ref name=":4" /> point out, there are not many studies on age-related changes in muscle length that use direct measurement tests. But at least one study on hamstring length, which does use this method, found no significant difference in muscle length with increasing age.<ref name=":6" /><ref name=":4" />


# One landmark for the stationary arm;  aligned with the midline of the stationary segment of the joint
=== Posture ===
# One landmark for the moving arm; aligned with the midline of the moving segment of the joint.  
Posture can have an impact on muscle length because our muscles and tissues adapt to how they are used. For example, in a forward head posture, the cervical flexors and occipital extensors have been found to shorten compared to a neutral spine while the cervical extensors and occipital flexors lengthen.<ref name=":8">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.</ref>
# One landmark for the fulcrum of the goniometer; aligned with a point that is near the axis of rotation of the joint.
 
<br>
== Summary ==
Priority should be given to alignment of the stationary and moving arms of the goniometer for accurate alignment.<ref name=":4" />
Having adequate muscle length enables optimal movement.  Thus, assessing muscle length is an important piece in the clinical puzzle. When performing your assessment, please remember the following:


=== Documentation ===
* The key to muscle length testing is to ensure that the tested muscle is in its lengthened position across all the joints it crosses.
The examiner is most concerned about the final, elongated position of the muscle, with the measurement taken in this final position.
* There are different testing options to assess muscle length, and your choice of test may be influenced by factors such as the acuity of your patient's injury, their age, co-morbidities and pain levels.
* When we observe changes in muscle length, 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.


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


[[Category:Understanding Basic Rehabilitation Techniques Content Development Project]]
[[Category:Understanding Basic Rehabilitation Techniques Content Development Project]]
[[Category:Course Pages]]
[[Category:ReLAB-HS Course Page]]
[[Category:Rehabilitation]]
[[Category:Rehabilitation]]
[[Category:MOOCs]]

Latest revision as of 00:01, 4 December 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 crossing a joint or joints to lengthen, thus allowing the joint or joints to move through their full available range of motion.[1][2] A muscle's ability to lengthen is essential for functional activities,[3] so rehabilitation professionals need to consider muscle length when assessing and treating patients. This article discusses the general principles of the muscle length assessment.

Structure of Muscles[edit | edit source]

Muscles connect to bones or joint capsules by connective tissue structures, such as tendons or aponeuroses.[4]

Skeletal muscles are made up of striated muscle fibres. These 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. This pulls the origin and insertion of the muscle-tendon complex closer together, thus shortening the muscle.[4] When sarcomeres contract, the overlap between thick and thin myofilaments increases. The amount of overlap decreases as it relaxes so that the muscle fibre can elongate. Maximal muscle length is, therefore, the greatest extensibility of the muscle-tendon junction.[6]

Kruse and colleagues[4] state: "The force exerted actively by a muscle can be expressed as a function of muscle length.”[4]

  • The length at which muscles do not 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 active slack length and the optimum muscle length is the length range of active force exertion[4]


For a detailed discussion of these principles, please see Kruse et al. Stimuli for adaptations in muscle length and the length range of active force exertion - a narrative review.

Muscle Length Assessment[edit | edit source]

The muscle length assessment helps determine whether a muscle's length is normal, decreased or increased. This assessment can help identify if changes in muscle extensibility are contributing to a movement impairment and/or symptoms or if other structures are involved.[7]

To test muscle length, we must position the muscle so that the distance between its origin and insertion increases - i.e. we lengthen the muscle in the direction opposite to its action.[7] For example, to measure the length of the hip flexors, we position the hip in extension.

Measurement Methods[edit | edit source]

Two main methods are used to assess muscle length: composite tests and direct measurement.

Composite Tests[edit | edit source]

Muscle length is commonly assessed through the use of composite tests (e.g. Apley’s Test or the Sit and Reach Test). These tests look at movement across more than one muscle or joint. However, while frequently used, research suggests that they do not provide accurate measurements of muscle length because they assess combinations of movements across several joints and involve several muscles. Thus, they tend to give a general idea of flexibility rather than an exact measurement of a single muscle’s length.[2]

Direct Measurement[edit | edit source]

In the direct measurement method, the distance between adjacent joint segments is measured. When using this method, we must consider that muscles are characterised by the number of joints they cross, i.e., one-joint, two-joint, and multi-joint muscles.

One Joint Muscles[edit | edit source]

One-joint muscles cross just one joint. They typically allow full passive range of motion at the joint they cross. If a one-joint muscle is short and limits the range of motion, you will notice a firm end feel caused by muscle tension.[2][7] To determine the length of a one-joint muscle, we measure the passive range of motion of the joint that it crosses in the direction opposite to its action.

Example: To measure the length of adductor longus, brevis and magnus:

  • Position the hip joint so that these muscles are in a lengthened position - i.e. hip abduction
  • Measure the degree of passive hip abduction achieved[2][8][7]

Two-Joint Muscles[edit | edit source]

Muscles that cross two or more joints typically do not allow full range of motion across all the joints they cross. 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."[9]

To assess and measure the length of a two-joint muscle, we must:

  • Position one of the joints so that the muscle is in a lengthened position
  • Move the second joint passively until the muscle is on full stretch and prevents further motion at the joint
  • Measure the final position of the second joint to determine muscle length[2][8]

Example #1: Measuring biceps brachii length vs elbow extension range of motion.

Biceps brachii crosses the shoulder and the elbow. It flexes and supinates the elbow and is a weak shoulder flexor. To test the length of biceps brachii:

  • Position the patient in a supine
  • Place the arm in shoulder extension, elbow flexion and supination
  • Passively extend the elbow and measure the elbow extension range to determine the length of biceps brachii

To measure extension of the elbow joint, position the shoulder joint in neutral to prevent passive insufficiency of biceps brachii from affecting your results. You can compare your results to see the difference in elbow extension range when biceps brachii is and isn't fully lengthened.

Example #2: Measuring rectus femoris length vs knee flexion range of motion.

Rectus femoris crosses the hip and knee. It flexes the hip and extends the knee. To test the length of rectus femoris:

  • Position the patient in prone
  • Passively flex the knee and measure the angle of knee flexion to determine the length of rectus femoris
  • NB: If the hip flexes during the movement, we know there are length limitations in rectus femoris - this is also known as Ely's Test[7]

To measure flexion of the knee joint, position the patient in supine and assess knee flexion range (actively and passively). In this position, the hip can flex during the movement, which prevents passive insufficiency of rectus femoris from affecting results.

Multi-joint Muscles[edit | edit source]

We follow the same principles when measuring multi-joint muscles. To measure the length of a multi-joint muscle, all but one of the joints are positioned with the tested muscle in a lengthened position. We then move the remaining joint crossed by the muscle passively until the muscle is on full stretch and prevents further motion at the joint. We assess and measure the final position of this joint to determine muscle length.[2][8]

Example: Measuring flexor digitorum superficialis length.

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 and is a wrist flexor. To assess the length of this muscle (and the other multi-joint finger flexors):

  • Position the patient in sitting with their forearm in pronation on a table
  • The patient's hand rests over the edge of the table
  • Move the elbow and finger joints into extension and then passively extend the wrist
  • Measure the amount of wrist extension to determine the length of flexor digitorum superficialis[2]

Measurement Tools[edit | edit source]

Three main measurement tools are used to assess muscle length: the universal goniometer and its variants, the inclinometer and its variants, and linear forms of measurement such as a tape measure.

Goniometer[edit | edit source]

Figure 1. Goniometer

Goniometers measure angles. All universal goniometers have a central "body" with a protractor and fulcrum, which you centre over a patient's joint, and two "arms" to align with the patient's body parts.[1] 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-rater reliability.[10] [11] We can improve the validity and reliability of goniometric measurements by:[12][13][14]

  • using standardised positions
  • stabilising the body part proximal to the joint being tested
  • aligning the goniometer with bony landmarks
  • having the same therapist conduct repeated tests

The following video demonstrates how to measure muscle length in the lower limb using a goniometer.

[15]

Inclinometer[edit | edit source]

An inclinometer (or clinometer) is used to measure the angles of slope, elevation, or depression of an object. Most inclinometers are calibrated or referenced to gravity, which means that the starting position of the inclinometer can be consistently identified and repeated.[2] Inclinometers have a circular disc which is filled with fluid and a bubble or weighted needle to point to a number (in degrees) on a protractor scale.[2]

Evidence suggests that the hand-held inclinometer is a valid and reliable instrument for assessing muscle length.[16] [17] Boyd[16] found that intra-rater reliability for a hand-held inclinometer to measure a straight leg raise was excellent. Romero-Franco et al.[17] found that both intra-tester and inter-tester reliability were good when an inclinometer was used to assess motion around the knee.

Tape Measure[edit | edit source]

Fig.2 Tape Measure

Tape measures are one of the simplest measurement tools that can be used. They typically measure in centimetres (cm) or inches (in). A tape measure is inexpensive, easy to use and readily available in most clinics.[2]

Rosa et al.[18] looked at assessing the muscle length of pectoralis minor using a tape measure and found it has good reliability and good intra-rater reliability (ICC 0.82 0.87) with same-day testing.[18]

Principles of Assessment[edit | edit source]

Following these principles can help improve the accuracy of your muscle length assessment.[2]

Level of Skill: Every clinician must be skilled at using measurement tools to improve the reliability of a muscle length test. Clinicians should practise using an instrument until they achieve a high level of intra-rater reliability.[2]

Communication: Patients should be given detailed information before an assessment so they understand what will happen and what they need to do. Before starting your muscle length assessment, explain what you will do and why. You can show your patient the measurement tool that you will use. Make sure you do not use medical jargon to ensure understanding - e.g. avoid terms like supine and prone or proximal and distal.[2][1]

Positioning: In a muscle length test, we are measuring the final, elongated position of the muscle - we do not need to measure the starting position.[1] Remember to ensure that the tested muscle is lengthened across all the joints it crosses.[6]

Isolating Muscle: We need to isolate the muscle being tested as much as possible (across one or two joints).[2]

Stabilisation: During a test, ensure that you fix / stabilise one end (usually the proximal bony segment of the joint being moved) and passively move the other end to lengthen the muscle.[6] Substitute movements at other joints may occur without adequate stabilisation, which can affect results.[2]

Speed of Movement: The clinician should move a joint slowly through the available motion to determine muscle length. This means you are more likely to avoid eliciting a quick stretch of the muscle spindle, and inducing a twitch response and muscle contraction.[19]

Determining End-feel: End feel refers to the resistance to movement at a joint's normal end range of motion.[2] Common end feels include hard (bony), firm (capsular, muscular, and ligamentous) and soft (soft tissue approximation). We expect a firm end feel when assessing muscle length because the muscle should be on full stretch. The patient may also report a pulling sensation, stretch or pain in the region of the muscle being lengthened.[2][6] We can compare sides to get an understanding of what is "normal" for the patient. We can also look at muscle length normative values for each muscle. For examples of normative values for some muscles please see: Muscle Length Normative Values.

Aligning Measurement Tool: Bony landmarks are usually used to align our measurement tools when assessing muscle length. This is because bony landmarks are more stable and less likely to experience a change in position from factors like oedema. You will usually need to find three landmarks to align a goniometer:

  1. One landmark is used to align the stationary arm - this arm is usually aligned with the midline of the stationary segment of the joint.
  2. One landmark is used to align the moving arm - this arm is usually aligned with the midline of the moving segment of the joint.
  3. One landmark is used to align the fulcrum of the goniometer - the fulcrum is positioned over a point near the joint's axis of rotation.[2]

Documentation: Record the results of your muscle length test (and the testing position) in the patient's notes.

Acute Pain: If a patient has acute pain, muscle length testing may need to be delayed - otherwise, muscle guarding or pain inhibition might impact results.[7]

Factors Affecting Muscle Length[edit | edit source]

Gender[edit | edit source]

Evidence suggests that biological females tend to be more flexible than biological males.[20] [21] Research looking specifically at hamstring length has found that females can have up to 8 degrees more range in their passive straight leg raise[22] and 12 degrees more range during an active knee extension test than males.[23]

Age[edit | edit source]

Our muscles also change with age. Older adults experience increased fibrosis, sarcopenia, decreased force production and a general reduction in flexibility.[24] Justine et al.[25] note that there may be an association between range of motion and muscle length in the lower limb and balance performance in older adults with foot deformities.[25]

However, as Reese and Bandy[2] point out, there are not many studies on age-related changes in muscle length that use direct measurement tests. But at least one study on hamstring length, which does use this method, found no significant difference in muscle length with increasing age.[22][2]

Posture[edit | edit source]

Posture can have an impact on muscle length because our muscles and tissues adapt to how they are used. For example, in a forward head posture, the cervical flexors and occipital extensors have been found to shorten compared to a neutral spine while the cervical extensors and occipital flexors lengthen.[26]

Summary[edit | edit source]

Having adequate muscle length enables optimal movement. Thus, assessing muscle length is an important piece in the clinical puzzle. When performing your assessment, please remember the following:

  • The key to muscle length testing is to ensure that the tested muscle is in its lengthened position across all the joints it crosses.
  • There are different testing options to assess muscle length, and your choice of test may be influenced by factors such as the acuity of your patient's injury, their age, co-morbidities and pain levels.
  • When we observe changes in muscle length, 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.

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 2.17 2.18 2.19 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 4.3 4.4 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 6.3 Gross JM, Fetto J, Rosen E. Musculoskeletal examination. John Wiley & Sons; 2015 Jun 29.
  7. ↑ 7.0 7.1 7.2 7.3 7.4 7.5 Norkin CC, White DJ. Measurement of Joint Motion: A Guide to Goniometry. FA Davis; 2016 Nov 18.
  8. ↑ 8.0 8.1 8.2 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.
  9. ↑ 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
  10. ↑ 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.
  11. ↑ 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.
  12. ↑ Rothstein JM, Miller PJ, Roettger RF. Goniometric reliability in a clinical setting. Elbow and knee measurements. Phys Ther. 1983 Oct;63(10):1611-5.
  13. ↑ 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.
  14. ↑ 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.
  15. ↑ Physio Skills. Lower Body Muscle Length Tests. Available from: https://www.youtube.com/watch?v=MQTM7t7wxWc [last accessed 17/11/2023]
  16. ↑ 16.0 16.1 Boyd BS. Measurement properties of a hand-held inclinometer during straight leg raise neurodynamic testing. Physiotherapy. 2012 Jun 1;98(2):174-9.
  17. ↑ 17.0 17.1 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).
  18. ↑ 18.0 18.1 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.
  19. ↑ Izraelski J. Assessment and treatment of muscle imbalance: The Janda approach. The Journal of the Canadian Chiropractic Association. 2012 Jun;56(2):158.
  20. ↑ 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.
  21. ↑ 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.
  22. ↑ 22.0 22.1 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.
  23. ↑ 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.
  24. ↑ Zotz TG, Capriglione LG, Zotz R, Noronha L, Viola De Azevedo ML, Fiuza Martins HR, Silveira Gomes AR. Acute effects of stretching exercise on the soleus muscle of female aged rats. Acta Histochem. 2016 Jan;118(1):1-9.
  25. ↑ 25.0 25.1 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.
  26. ↑ 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.

 

Retrieved from "https://www.physio-pedia.com/index.php?title=Assessing_Muscle_Length&oldid=347072"