The Importance of Isometrics

An isometric contraction is a static form of exercise in which a muscle contracts to produce force without an appreciable change in muscle length and without visible joint movement1 We learn these basic concepts in school and are told to provide these types of interventions during the early phases of rehabilitation, but do we truly understand the benefit of these seemingly simple exercises?

Eccentrics versus Isometrics

While eccentric exercise is the mainstay of most rehabilitation programs for tendinopathies, some patients find them painful to complete and difficult to perform.2 In these cases, patient compliance suffers due to increased pain, leading to underwhelming outcomes.3

Conversely, the impact of isometric contraction on pressure pain thresholds (PPTs) yields promising results. When asymptomatic volunteers held a quadriceps isometric contraction at 21% MVIC until exhaustion (maximum of 5-minute duration), patients demonstrated a significant increase in PPT at the start of contraction. PPT continued to increase until the middle of the contraction period and stayed increased for up to 5 minutes post-intervention.4

Reduced Perceived Pain

In a similar study, PPTs were determined after 14 healthy women completed 2 sets of submaximal (40-50% MVIC) isometric exercise consisting of squeezing a dynamometer for 2 minutes with their dominant hand.5 This trial demonstrated a positive contralateral and ipsilateral hypoalgesic effect with elevated PPTs and a reduction in self-perceived pain rating for both hands following isometric exercise. While this provides a good foundation of support, it does not provide information regarding isometric exercise’s effect on individuals with a painful condition

To answer this question, Rio and associates performed a randomized cross-over study to investigate the hypoalgesic impact of a single bout of isometric contractions on individuals with patellar tendinopathy.6 Those in the intervention group performed 5 sets of 45 second isometric quadriceps contractions (70% MVIC) with a 2 minute rest break between each set. Those in the control group performed 4 sets of 8 repetitions (100% 8-repition maximum) of an isotonic leg extension exercise with a 4 second eccentric phase and 3 second concentric phase.

At the conclusion of the study, isometric contractions reduced pain during single-leg decline squat from 7.0 to 0.17 on an 11-point scale and increased MVIC by 18%. Both values were maintained for 45 minutes post-intervention. Also, cortical inhibition increased from 27.5% to 54.9%, which may factor into the underlying mechanism of this hypoalgesia.7

Further supporting the hypoalgesic properties of isometric contractions, Rio and colleagues once again added to the depth of literature in this area. They used a within-session randomized controlled trial to compare isometric leg extension at 60 degrees of knee flexion to isotonic leg extension in volleyball or basketball players with patellar tendinopathy. At the conclusion of the study, those randomized to the isometric knee extension group demonstrated significantly greater immediate analgesia throughout the 4 weeks trial.8

Back to the Basics

Isometrics are not simply an introductory exercise for patients following a post-operative procedure (i.e. quad sets following ACL reconstruction). Their hypoalgesic effects are far more impactful then most of us recognize. Although we are not sure why isometrics are efficacious in these tendinopathies, they give us an intervention that is successful.  Clinicians often get too caught up in complex and intricate treatment philosophies when in reality all we have to do is go back to the basics!

References

1. Kisner, Carolyn, and Lynn Allen. Colby. Therapeutic Exercise: Foundations and Techniques. 5th ed. Philadelphia: F.A. Davis, 2007. Print.

2. Alfredson H, Pietila T, Jonsson P, et al. Heavy-load eccentric calf muscle training for the treatment of chronic Achilles tendinosis. Am J Sports Med 1998;26:360–6.

3. Visnes H, Hoksrud A, Cook J, et al. No effect of eccentric training on jumper’s knee in volleyball players during the competitive season: a randomized clinical trial. Clin J Sport Med 2005;15:227–34.

4. Kosek E, Ekholm J. Modulation of pressure pain thresholds during and following isometric contraction. Pain 1995;61:481–6.

5. Koltyn KF, Umeda M. Contralateral attenuation of pain after short-duration submaximal isometric exercise. J Pain 2007;8:887–92.

6. Rio E, Kidgell D, Purdam C, et al. Isometric exercise induces analgesia and reduces inhibition in patellar tendinopathy. British Journal of Sports Medicine. 2015;49(19):1277-1283. doi:10.1136/bjsports-2014-094386.

7. Rio E, Kidgell D, Moseley GL, et al. Tendon neuroplastic training: changing the way we think about tendon rehabilitation: a narrative review. British Journal of Sports Medicine.2015.

8. Rio E, van Ark M, Docking S, Moseley GL, Dawson K, Gaida J, van den Akker-Scheek I, Zwerver J, Cook J. Isometric Contractions Are More Analgesic Than Isotonic Contractions for Patellar Tendon Pain: An In-Season Randomized Clinical Trial. Clinical Journal of Sport Medicine. 2016.

Evidence-Based Strength Training: Gluteus Maximus

To build upon my previous post regarding Evidence-based Strength Training of the Gluteus Medius, I wrote the following article for MedBridge Education

Pain and Gluteal Strength

The gluteal musculature has been implicated in many different pathologies due to its potential impact on lower extremity biomechanics. During weight bearing, the femur moves about a fixed patella and therefore excessive femoral internal rotation and adduction results in increased contact directed primarily at the lateral facet of the patella1. Just 10° of IR can lead to a substantial decrease in PFJ contract area and a 50% increase in joint stress. Coinciding with these findings, Souza et al.2 found that females with patellofemoral pain syndrome (PFPS) demonstrated greater peak hip internal rotation compared to the control group during running, drop jump, and step down. The PFPS group also demonstrated 14% weaker hip abductor strength and 17% weaker hip extensor strength. Wilson et al3, Noehren et al4, and Nakagawa et al5 found that individuals presenting with PFPS demonstrated increased hip adduction during running, jumping, and single-leg squats. This excess femoral adduction creates an increased valgus force about the knee joint, which in turn causes increased loading of the lateral patellofemoral joint. In addition to patellofemoral pain, a hip etiology or influence has also been implicated in iliotibial band syndrome6, anterior cruciate ligament rupture7, and achilles tendinopathy8. More specifically, impaired gluteus maximus function has been demonstrated in individuals diagnosed with femoroacetabular impingement9.

Gluteal strengthening and Rehabilitation

In support of a gluteal etiology, several studies have found the effectiveness of gluteal strengthening in the treatment of lower extremity disorders. A recent systematic review conducted by Santos and colleagues9 found gluteal strengthening decreased the highest intensity of pain experienced during the previous week, pain when ascending and descending stairs, and pain while squatting or sitting for prolonged periods amongst individuals diagnosed with PFPS. Additionally, with regards to rehabilitation following anterior cruciate ligament reconstruction, the inclusion of hip strengthening appears to improve sagittal plane dynamic balance at three months post ACLR as compared to traditional rehabilitation10.

EMG Activity and Exercise Goals

According to Reiman et al.11 and Escamilla et al.12, moderate electromyographic activity (EMG) activation (21-40% MVIC) is best used to facilitate endurance and neuromuscular re-education; high activation (41-60+% MVIC) in order to promote strength gains.

From Biomechanics to Exercises

Gluteus Maximus

Origin: Ilium posterior to posterior gluteal line; dorsal surface of sacrum and coccyx; sacrotuberous ligament

Insertion: Iliotibial tract and gluteal tuberosity

Primary Function: Extends thigh and assists in hip abduction and external rotation; steadies thigh and assists in rising from sitting position

Among introductory exercises, the gluteus maximus achieves the highest EMG levels during:

  1. Front-plank with Hip Extension
  2. Gluteal Squeeze
  3. Side-plank with Hip Abduction
  4. Quadruped with Contralateral Arm/Leg Lift
  5. Uni-lateral Bridge

screen-shot-2016-09-19-at-2-51-18-pm

Additionally, you must consider the interaction of other muscles acting with or against the gluteus maximus when determining exercise prescription. It has been proposed that individuals who demonstrate excess femoral internal rotation during functional tasks may be relying too heavily on the tensor fasciae latae to control their pelvis in the presence of weak or inhibited gluteus medius musculature.

Selkowitz and colleagues determined that the following exercises achieved the best Gluteal to Tensor Fasciae Latae Activation Ratio:

  1. Clamshell
  2. Side-step with resistance band
  3. Single-leg bridge
  4. Quadruped hip extension with knee extended
  5. Quadruped hip extension with knee flexed

screen-shot-2016-09-19-at-2-55-12-pm

Finally, when progressing your patient towards more functional closed kinetic chain and sport/activity-specific exercises, the following exercises achieve the highest gluteus medius activation:

  1. Cross-over Step-up
  2. Hip Thrust Variations (Barbell, Band, American)
  3. Rotational Single-Leg Squat
  4. Skater Squat
  5. Single-Leg Squat

screen-shot-2016-09-19-at-2-56-43-pm

Exercise prescription is a multi-faceted decision, which is driven by the individual patient’s goals, functional limitations, and the evidence supporting the treatment of these factors. Using EMG studies to drive the selection of exercise is highly valuable, especially during early stages of rehabilitation or when attempting to isolate individual muscles and/or groups of muscles. However, there are limitations when comparing different studies due to methodological differences (type of EMG, patient population, data analysis, etc.). Additionally, due to the cost and time to conduct these studies, there are thousands of exercises that have not been evaluated in the literature. In light of this information, these studies should be used to guide your decision making, it should not override your clinical expertise when accompanied by biological plausibility.

VMO: An Update

The following is an article written for the online, video-based physical therapy continuing education company MedBridge

Patellofemoral pain syndrome (PFPS) is among the most common sports injuries and yet the current treatment protocols are not optimal. In particular, the latest research questions our ability to selectively recruit vastus medialis obliquus (VMO) and affect its timing and suggests that VMO may have nothing to do with the PFPS.

Prevalence of Patellofemoral Pain Syndrome

PFPS has an astounding prevalence according to a retrospective case-control analysis by Taunton et al. They analyzed 2,002 running-related injuries seen at a primary care sports injury facility – and 42.1% (842/2,002) were knee injuries. Of these knee injuries, 39.3% (331/842) were due to patellofemoral pain syndrome (PFPS), which made PFPS by far the most common diagnosis found in this large-scale study.

Similarly, in an older study (1984), Devereaux et al found that over a five year period, 137 patients presented with PFPS – accounting for 25% of all knee injuries seen at this sports injury clinic.

These two studies were conducted 17 years apart, giving support to the consistently high prevalence of this disorder. Now the most important question is, how are we treating these patients?

How are we treating patients with PFPS?

Imbalance of LV and VMO

The biomechanical study by Lieb et al made the VMO the mainstay of most physical therapy protocols and treatment approaches for PFPS.

Conducted in 1968, the study found that VMO’s fibers are oriented at 55° from the longitudinal axis of the femur. This orientation alone makes VMO the primary restraint to lateral subluxation of the patella. The study further postulated that VMO was able to counterballance the pull of the much larger vastus lateralis (VL) due to the discrepancy in mechanical advantages.

As a result of this study, an insufficient balance between the VL and VMO has long been considered the primary contributing factor in developing patellar subluxation, or maltracking.

VL:VMO timing

A study by Cowan et al found that subjects with PFPS have an imbalance of VL:VMO timing. The VL typically begins to fire approximately 15-20 ms prior to the VMO.

Due to this understanding of the biomechanics, the treatment strategy typically involved correcting the potential VMO atrophy, hypoplasia, inhibition, and impaired motor control.

Now, this all seems logical in theory, but can we actually selectively train the VMO? Is this relatively small muscle affected differently than the rest of the quadriceps musculature in the presence of pain?

New research questions…

Does VMO atrophy relative to the rest of quadriceps?

A recent study by Giles and colleagues refutes one of the cornerstones of the VMO theory; namely, that this small muscle tends to atrophy relative to the rest of the quadriceps during or following surgery. They performed a cross-sectional study of 35 participants diagnosed with PFPS.

The results showed atrophy of all portions of the quadriceps muscles – and no selective atrophy of the VMO – present in the affected limb of people with unilateral PFPS.

Can we selectively activate VMO?

Even if the atrophy was present, the literature is not very kind to the ability to preferentially activate this musculature either.

Cerny et al evaluated the ability to preferentially recruit the VMO during 22 different quadriceps exercises. Through electromyographic analysis, they determined that VMO activity was not higher in any exercise compared to VL.

In a randomized controlled trial, Song et al found no evidence that VMO can be activated separately. They compared the change in VMO cross-sectional area after 8 weeks of unilateral leg press and unilateral leg press with subsequent hip adduction. The two groups showed no significant difference between the change in VMO cross-sectional area (the standard leg press actually yielded better results).

Thus, selective isolation of the VMO in everyday clinical practice is highly unlikely. In all reality, if we consider inability to selectively recruit their target, most of the ‘VMO programs’ are merely strengthening the quadripceps as a whole. If we could selectively recruit these fibers, according to Grabiner et al, it would take approximately 60% of maximal voluntary contraction to stimulate hypertrophy of the VMO.

Does VMO training have advantages over general quadriceps strengthening?

In 2010, Bennell et al investigated how VMO retraining compares to a general quadriceps strengthening program in relation to vasti onset.

The VMO retraining group used EMG biofeedback during the following series of exercises:

  • isometric VMO contractions at 90° of knee flexion
  • standing mini squats to 40°
  • isometric contraction of the VMO in combination with hip abduction and hip external rotation during an isometric wall contraction in standing
  • step downs

The quadriceps group performed:

  • isometric quad sets
  • straight-leg raises
  • SAQs
  • side-lying hip abduction

At the conclusion of the training programs, the retraining group actually did create more significant changes in stair descent activation in the short-term. However, at the 8-week follow-up, both values were nearly identical. The initial improvement may have been due to the use of ‘step downs’ in the retraining group, which most closely simulates the functional and muscular demands of stair descent.

During stair ascent, on the other hand, the quadriceps strengthening group caused a much more significant alteration in VMO:VL timing and was the only group that caused the VMO to fire prior to the VL.

A study conducted by Laprade et al showed similar results using isometric exercise. This study compared the EMG activity in individuals with PFPS and asymptomatic controls during 5 isometric exercises. There was no significant difference in the ratio of VMO:VL firing between the two groups.

Given these results, I find it hard to support the use of VMO training in everyday clinical practice.

Does VMO strengthening make a difference for PFPS?

Suppose it was possible to selectively recruit the VMO. Would it reduce patellofemoral contact stress sufficiently to relieve the pain?

Sawatsky et al say no. They conducted a biomechanical study using New Zealand white rabbits. Although this is not a direct human study, the muscular alignment and pull of the quadriceps is very similar: the fibers of the VMO and VL are oriented at 45-50° and 14-19°, respectively, in relation to the longitudinal axis of the femur.

They transected VMO at varying levels of knee flexion (30°, 60°, and 90°), measuring patellofemoral joint contact pressures before and after the transections.

There were no significant differences between peak pressures, average pressures, contact areas, or contact shapes before and after transection.

If the contact area and pressure are not altered when the muscle is removed from the equation, then why do we continue thinking VMO training is the gold standard in PFPS treatment?

Evidence-Based Strength Training: Gluteus Medius, An Update

To build upon my previous post regarding Evidence-based Strength Training of the Gluteus Medius, I wrote the following article for MedBridge Education

Pain and Gluteal Strength

The gluteal musculature has been implicated in many different pathologies due to its potential impact on lower extremity biomechanics. During weight bearing, the femur moves about a fixed patella and therefore excessive femoral internal rotation and adduction results in increased contact directed primarily at the lateral facet of the patella1. Just 10° of IR can lead to a substantial decrease in PFJ contract area and a 50% increase in joint stress. Coinciding with these findings, Souza et al.2 found that females with patellofemoral pain syndrome (PFPS) demonstrated greater peak hip internal rotation compared to the control group during running, drop jump, and step down. The PFPS group also demonstrated 14% weaker hip abductor strength and 17% weaker hip extensor strength. Wilson et al3, Noehren et al4, and Nakagawa et al5 found that individuals presenting with PFPS demonstrated increased hip adduction during running, jumping, and single-leg squats. This excess femoral adduction creates an increased valgus force about the knee joint, which in turn causes increased loading of the lateral patellofemoral joint. In addition to patellofemoral pain, a hip etiology or influence has also been implicated in iliotibial band syndrome6, anterior cruciate ligament rupture7, and achilles tendinopathy8.

Gluteal strengthening and Rehabilitation

In support of a gluteal etiology, several studies have found the effectiveness of gluteal strengthening in the treatment of lower extremity disorders. A recent systematic review conducted by Santos and colleagues9 found gluteal strengthening decreased the highest intensity of pain experienced during the previous week, pain when ascending and descending stairs, and pain while squatting or sitting for prolonged periods amongst individuals diagnosed with PFPS. Additionally, with regards to rehabilitation following anterior cruciate ligament reconstruction, the inclusion of hip strengthening appears to improve sagittal plane dynamic balance at three months post ACLR as compared to traditional rehabilitation10.

EMG Activity and Exercise Goals

According to Reiman et al.11 and Escamilla et al.12, moderate electromyographic activity (EMG) activation (21-40% MVIC) is best used to facilitate endurance and neuromuscular re-education; high activation (41-60+% MVIC) in order to promote strength gains.

From Biomechanics to Exercises

Gluteus Medius

Origin: External surface of Ilium between anterior and posterior gluteal lines

Insertion: Lateral surface of greater trochanter

Primary Function: Abduction of the hip joint; the anterior fibers contribute to hip flexion and hip internal rotation, and the posterior fibers to hip extension and hip external rotation. Additionally, the gluteus medius is responsible for preventing the opposite side of the pelvis from dropping during the stance phase of gait and plays a major role in providing frontal stability for the entire pelvis during walking and other functional activities.

The gluteus medius achieves the highest EMG levels during13,14:

  1. Side-lying plank with hip abduction
  2. Reverse clamshell with hip abduction and extension
  3. Prone plank with hip extension
  4. Reverse clamshell with hip abduction
  5. Single-leg Bridge

Screen Shot 2015-07-26 at 3.30.35 PM

Additionally, you must consider the interaction of other muscles acting with or against the gluteus medius when determining exercise prescription. It has been proposed that individuals who demonstrate excess femoral internal rotation during functional tasks may be relying too heavily on the tensor fasciae latae to control their pelvis in the presence of weak or inhibited gluteus medius musculature.

Selkowitz and colleagues determined that the following exercises achieved the best Gluteal to Tensor Fasciae Latae Activation Ratio15:

  1. Clamshell
  2. Side-step with resistance band
  3. Single-leg bridge
  4. Quadruped hip extension with knee extended
  5. Quadruped hip extension with knee flexed

Screen Shot 2015-07-26 at 3.23.48 PM

Finally, when progressing your patient towards more functional closed kinetic chain and sport/activity-specific exercises, the following exercises achieve the highest gluteus medius activation13,16,17,18:

  1. Walking lunge with dumbbell in contralateral hand
  2. Unilateral mini-squat
  3. Skater squat
  4. Unilateral deadlift
  5. Unilateral wall squat

Screen Shot 2015-07-26 at 3.24.37 PM

Exercise prescription is a multi-faceted decision, which is driven by the individual patient’s goals, functional limitations, and the evidence supporting the treatment of these factors. Using EMG studies to drive the selection of exercise is highly valuable, especially during early stages of rehabilitation or when attempting to isolate individual muscles and/or groups of muscles. However, there are limitations when comparing different studies due to methodological differences (type of EMG, patient population, data analysis, etc.). Additionally, due to the cost and time to conduct these studies, there are thousands of exercises that have not been evaluated in the literature. In light of this information, these studies should be used to guide your decision making, it should not override your clinical expertise when accompanied by biological plausibility.

Should we stop blaming the glutes for everything?

Below is an article written for MikeReinold.com… 

Anterior cruciate ligament (ACL) rupture1,2 and patellofemoral pain syndrome (PFPS)3,4,5 are two of the most common lower extremity complaints that physicians or physical therapists will encounter. In addition to the high incidence of these pathologies, with regards to ACL injury, very high ipsilateral re-injury and contralateral injury have also been reported6,7,8. With the importance of treating and/or preventing these injuries, several researchers have taken it upon themselves to determine what movement patterns predispose athletes to developing these injuries. This research indicates that greater knee abduction moments9,10, peak hip internal rotation11 and hip adduction motion12 are risk factors for PFPS development. Whereas, for ACL injury, Hewett and colleagues13 conducted a prospective cohort study identifying Knee abduction angle at landing as predictive of injury status with 73% specificity and 78% sensitivity. Furthermore, as the risk factors for developing both disorders are eerily similar, Myer et al performed a similar prospective cohort study finding that athletes demonstrating >25 Nm of knee abduction load during landing are at increased risk for both PFPS and ACL injury14. With a fairly robust amount of research supporting a hip etiology in the development of these injuries, it would make sense that weakness of the hip musculature would also be a risk factor, right?

A recent systematic review found very conflicting findings on the topic. With regards to cross-sectional research, the findings were very favorable with moderate level evidence indicating lower isometric hip abduction strength with a small effect size (ES) and lower hip extension strength with a small ES15. Additionally, there was a trend toward lower isometric hip external rotation and moderate evidence indicates lower eccentric hip external rotation strength with a medium ES in individuals with PFPS15. Unfortunately, the often more influential prospective evidence told a different story. Moderate-to-strong evidence from three high quality studies found no association between lower isometric strength in hip abduction, extension, external rotation or internal rotation and the risk of developing PFPS15. The findings of this systematic review indicated hip weakness may be a potential consequence of PFPS, rather than the cause. This may be due to disuse or fear avoidance behaviors secondary to the presence of anterior knee pain. Regardless of its place as a cause or consequence, hip strengthening has proved beneficial in patients with both PFPS16,17,18 and following ACL Reconstruction19, but does it actually help to change the faulty movement patterns?

Gluteal strengthening can cause several favorable outcomes, from improved quality of life to decreased pain, unfortunately however marked changes in biomechanics is not one of the benefits. Ferber and colleagues20 performed a cohort study analyzing the impact of proximal muscle strengthening on lower extremity biomechanics and found no significant effect on two dimensional peak knee abduction angle. In slight contrast however, Earl and Hoch21 found a reduction in peak internal knee abduction moment following a rehabilitation program including proximal strengthening, but no significant change in knee abduction range of motion was found. It should be noted that this study included strengthening of all proximal musculature and balance training, so its hard to conclude that the results were due to the strengthening program. Potentially, gluteal endurance may be more influential than strength itself, so it would make sense that following isolated fatigue of this musculature, lower extremity movement patterns would deteriorate.

Once again, this belief is in contrast to the available evidence. While fatigue itself most definitely has an impact on lower extremity quality of movement, isolated fatigue of the gluteal musculature tells a different story. Following a hip abductor fatigue protocol, patients only demonstrated less than a one degree increase in hip-abduction angle at initial contact and knee-abduction angle at 60 milliseconds after contact during single-leg landings22. In agreement with these findings, Geiser and colleagues performed a similar hip abductor fatigue protocol and found very small alterations in frontal plane knee mechanics, which would likely have very little impact on injury risk23. The biomechanical explanation for why weakness or motor control deficits in the gluteal musculature SHOULD cause diminished movement quality makes complete sense, but unfortunately, the evidence at this time does not agree.

While the evidence itself does not allow the gluteal musculature to shoulder all of the blame, this does not mean we should abandon addressing these deficits in our patients. As previously stated, posterolateral hip strengthening has multiple benefits, but it is not the end-all-be-all for rehabilitation or injury prevention of lower extremity conditions. Proximal strength deficits should be assessed through validated functional testing in order to see its actual impact on lower extremity biomechanics on a patient-by-patient basis. Following this assessment, interventions should be focused on improving proximal stability, movement re-education, proprioception, fear avoidance beliefs, graded exposure, and the patient’s own values, beliefs, and expectations.

Evidence-Based Strength Training: Scapulothoracic Musculature, Part 2

Scapulothoracic Muscles and Pain

As I mentioned in Part 1, weakness or poor neuromuscular control of the periscapular muscles has been implicated in subacromial impingement1,2, lateral epicondylalgia3-5, cervicogenic headache6, and neck pain7,8.

Specifically, insidious onset of neck pain and whiplash associated disorder (WAD) have been linked with a significant delay in and shorter duration of serratus anterior activity bilaterally during arm elevation9. A similar study found decreased serrates anterior activation in individuals with acromioclavicular osteoarthritis and rotator cuff disease.10

Although a cause-and-effect relationship cannot be confirmed, this preliminary evidence still lends support for targeting the periscapular muscles in individuals with neck or shoulder pain.

EMG Activity and Exercise Goals

According to Reiman et al.11 and Escamilla et al.12, moderate EMG activation (21-40% MVIC) is best used to facilitate endurance and neuromuscular re-education; high activation (41-60+% MVIC) – to promote strength gains.

From Biomechanics to Exercises

Serratus Anterior

Primary Function: scapular upward rotation, external rotation, posterior tilt at the acromioclavicular joint, protraction of the clavicle at the sternoclavicular joint.

Origin: External surfaces of lateral aspect of 1st-8th ribs

Insertion: Anterior surface of medial border of scapula

The SA is often activated with scapular protraction. The exercises yielding the highest MVIC for the serratus anterior include:

  • dynamic hug13
  • push-up plus13
  • scaption with external rotation14
  • diagonal PNF (shoulder flexion, horizontal flexion, external rotation)15
  • shoulder abduction in scapular plane above 120 degrees15

The upper trapezius (UT) often compensates for a weak or inhibited serratus anterior, so it’s beneficial to selectively activate the SA in lieu of the UT. According to Cools and colleagues, the best SA:UT ratio is achieved in:

  • high row
  • forward shoulder flexion
  • scaption with external rotation14
Serratus Anterior
Prone Push Up with Plus
Serratus Anterior
Dynamic Hug with Resistance
[Table] MVIC values for SA exercises

Levator Scapulae

Primary Functions: scapular elevation, glenoid cavity inferior tilt through upward scapular rotation

Origin: Posterior tubercles of transverse processes of C1-C4 vertebrae

Insertion: Medial border of scapula superior to root of scapular spine

These muscles have received little attention in the literature compared the SA or trapezius. In a study, Moseley and colleagues discovered that the levator scapulae achieves the highest activity in:

  • rowing
  • horizontal abduction
  • shrug
  • horizontal abduction with ER
  • prone shoulder extension16
[Table] MVIC values for Levator Scapulae exercises

Rhomboids

Primary Functions: Retraction of the scapula; upward rotation to depress glenoid cavity; scapular attachment to thoracic wall

Origin: nuchal ligament; spinous processes of C7, T1 and T2-T5 vertebrae

Insertion: smooth triangular area at medial end of scapular spine; medial border of scapula from level of spine to inferior angle

The rhomboids achieve the highest MVIC during:

  • ER at 90° of abduction17
  • ER at 0° of abduction17
  • horizontal abduction16
  • shoulder extension17
  • scaption16
Levator Scapulae
Prone Shoulder Row
Rhomboid
Shoulder External Rotation at 90° Abduction with Dumbbell
[Table] MVIC values for rhomboid muscle exercises

Choosing the Best Exercise

These studies give us a glimpse into properly selecting exercises, yet very few exercises have been or will ever be studied.

When choosing an exercise for your patient, be sure to consider:

  • the biomechanics of the movement,
  • current evidence for or against the exercise,
  • your patient’s presentation, and goals for treatment.
  • aggravating movement(s) or comparable signs

Evidence-Based Strength Training: Scapulothoracic Musculature, Part 1

In the next installment of the Evidence-Based Strength Training Series for MedBridge Education, we are going to take a look at the often-neglected scapulothoracic musculature. Typically when considering the management of painful upper quarter conditions, local exercise and manual therapy interventions are employed judiciously. However, when utilizing a proper movement assessment or regional interdependence philosophy, impairments in the scapulothoracic musculature are often found to contribute to pain in distal or proximal joints. Weakness or diminished neuromuscular control of the peri-scapular muscles has been implicated in Subacromial Impingement4,18, Lateral Epicondylalgia2,7,12, Cervicogenic Headache10, and Neck Pain3,16. Additionally, in a prospective cohort study conducted by Clarsen et al.6, the presence of scapular dyskinesis led to an 8.4x greater risk for developing a shoulder injury during the course of an elite male handball season. Furthering the support for interventions focusing on the peri-scapular musculature, Lawrence and colleagues11 found that in the presence of shoulder pain due to subacromial impingement, patients demonstrated significantly reduced scapulothoracic upward rotation at lower angles of humerothoracic elevation and significantly reduced sternoclavicular posterior rotation throughout humerothoracic elevation.

With the knowledge of the scapulothoracic musculature’s impact on potentially injurious altered biomechanics and the deficits seen in many common musculoskeletal disorders, healthcare providers need to ask themselves, “What are the best exercises to recruit these muscles?”

Before delving into specific exercises, it is necessary to understand the basic biomechanics of the scapulothoracic and glenohumeral joints. During humeral elevation, the scapula upwardly rotates 1° for every 2° of humeral elevation until 120° humeral elevation is achieved. After this point, scapular rotation contributes 1° for every 1° humeral elevation until maximal arm elevation is met. Also, the scapula typically tilts posteriorly between 20° and 40° in the sagittal plane and externally rotates between 15° and 35° in the transverse plane17. This complex movement pattern relies on coordinated and balanced contributions from the trapezius, serratus anterior, levator scapulae, rhomboid, and pectoralis minor musculature.

Trapezius Musculature

The broad posterior musculature known as the trapezius originates at the medial third of superior nuchal line, external occipital protuberance, nuchal ligament, and the spinous processes of C7-T12 vertebrae and its distal insertion is at the lateral third of clavicle, acromion process, and spine of scapula. This muscle is divided into three distinct portions with the Upper Trapezius (UT) providing scapular elevation, Lower Trapezius (LT) proving depression, and the Middle Trapezius (MT) causing scapular retraction. Additionally, the UT and LT act together to rotate the glenoid cavity superiorly, which is a very important and often dysfunctional action for individuals suffering from shoulder impingement or pain11.

The primary action of the upper trapezius musculature involves elevation of the scapula and, predictably, the exercises that provide the highest Maximal Isometric Voluntary Contraction (MVIC) are those that involve this motion. Additionally, during scapular abduction, upper trapezius activity progressively increases from 0° to 60° and from 120° to 180° of abduction1. With this knowledge in mind, researchers have found that the highest electromyographical (EMG) activity occurs during the uni-lateral shoulder shrug9, rowing14, scaption8, and shoulder abduction in the scapular plane above 120°9. Due to the infrequency of UT weakness (unless secondary to neurological involvement) strengthening of this portion of the trapezius is often not the focus during the rehabilitation of painful upper quarter conditions. Instead, clinicians have learned to focus on improving middle and lower trapezius strength and normalizing the ratio of UT to the lower two portions of the trapezius activation.

[Table] Click to see MVIC values for UT exercises

Similar to the UT, the middle trapezius, with its primary function being scapular retraction, is often activated during exercises involving this action. The highest MVIC percentages for the MT have been recorded during horizontal abduction14, prone full-can9, horizontal abduction with external rotation14, and scaption8. Additionally, as the UT often compensates for a weak MT or lower trapezius, it is likely beneficial to utilize exercises with a good upper trapezius to middle trapezius ratio (UT:MT) when attempting to strengthen this musculature. Exercises shown to provide this ratio are side-lying forward flexion, side-lying external rotation, and prone shoulder extension5.

[Table] Click to see MVIC values for MT exercises

 

Due to its impact on scapular upward rotation, external rotation, and posterior tilt, the lower trapezius is of more importance than the aforementioned UT and MT during rehabilitation17. There have been a multitude of studies investigating lower trapezius weakness and its association with painful conditions and most do find this connection. Due to this fact, there have also been many studies looking into maximal EMG activity of the lower trapezius during upper extremity strengthening. The results show that significantly high MVIC values have been recorded during arm raise overhead in line with the LT muscle fibers9, ER at 90° of abduction9,15, horizontal abduction with ER5, and prone shoulder abduction5. While choosing exercises with a relatively high MVIC is important, it may be more important to choose those exercises that provide an optimal upper trapezius to lower trapezius ratio (UT:LT). As these are the two primary muscle groups involved in upward rotation of the scapula, having adequate and relatively equal contributions from each is important in maintaining normal biomechanics. In a study conducted by Cools and colleagues, it was determined that side-lying forward flexion, side-lying external rotation, and horizontal abduction with external rotation had the best UT:LT ratios5. In addition to this study, McCabe et al. conducted a similar study and found that the seated press-up, uni-lateral scapular retraction, and bilateral shoulder external rotation provided UT:LT ratios that showed a preferential activation of the lower trapezius over the upper trapezius13. While these studies do give a glimpse into proper exercise selection, not every exercise has been studied to date and never will. When choosing an exercise for your patient/client, it is important to take into consideration the biomechanics of the movement, current evidence supporting/refuting, and your patient’s presentation and goals for treatment.

[Table] Click to see MVIC values for LT exercises

 

The trapezius musculature is a very important piece of the puzzle, but contributions from the Serratus Anterior, Rhomboids, and Levator Scapulae also play a large role and will be discussed in Part 2.