Here's a brief summary of an excellent paper by Boudreau et al from Manual Therapy. 

The purpose of this paper was to summarize several important aspects of motor-skill training for enhancing musculoskeletal rehabilitation.

Cortical Neuroplasticity: a dynamic feature of life that encompasses functional or morphological change in properties of neurons (connection strength, represenational patterns, neuron reorganization.

• Positive changes: improvements in motor performance
• Negative changes: decreases in performance, such as in the presence of chronic pain (low back pain resulting in decreased cortical spinal drive in lumbar musculature and subsequent shift in somatosensory representation)

It is hypothesized that motor-skill training can influence the direction of change in cortical neuroplasticity.

• That is, the representation of muscles affected by pain in the sensorimotor system.

Potential effects of motor-skill training:

• Improvements in task performance
• Improvements secondary to very short training intervals.
• Improvements occuring in two stages - 1) fast learning (following a single training session); 2) slower learning (across several sessions of practice)
• Improvements with activation of inhibited/delayed musculature via repeated voluntary contractions.

Methods of Optimizing Rehabilitation:

• Skilled training - skilled/precision tasks (vs strength training) should be performed to facilitate neuroplastic changes, and subsequently improvements in motor behaviour.
• Negative effects of the presence of pain during novel motor skill acquisition - since pain alters excitability of the primary motor cortex in a rapid manner, these responses are generally protective and counterintuitive in the motor-learning process. Negative effects are also demonstrated in the presence of low quality sleep, stress, and attention deficits. Therefore, motor-skill learning should be relatively pain free.
• Protective effect of motor-skill training - training prior to acute experimental pain may prevent unwanted cortical neuroplastic changes.
• Cognitive effort - the greater the complexity of a skilled task and its corresponding intent, results in greater cortical representation and changes.
• Quality - since no difference seems to exist with greater repetitions of within-session skill learning tasks, the primary focus of each rehabilitation session should be quality of performance.

The above information was derived from a multitude of studies and demonstrates that motor-skill training may positively influence cortical neuroplasticity in musculoskeletal rehabilitation
​

An article by Dr. S McGill compared the V-sit flexion endurance test vs the front plank test for endurance.

• The data from this study came from two sources (firefighters and kinesiology students).

• The main objective of this study was to assess the relationship between the V-sit test and the plank test for torso flexion endurance.

• The pearson correlation was r=0.34 (low correlation) as well as the r-squared value. It almost seems obvious that these two wouldn't correlate well as they are two totally different positions.

I think the main reason McGill did this study was because people were using the PLANK test in place of the V-SIT to test flexion endurance (which has plenty of data correlating poor endurance times with low back disorders).
​

• The moral of the story is to use the V-sit when doing your tests for flexion endurance.

• He also cautioned against "training the test" due to the high compressive loads.

DESTRUCTION PHASE:

Initial rupture and necrosis of myofibers

• However, within hours the propagation of necrosis is halted to a local process (similar to a "fire door" mechanism)

Hematoma formation occurs between the ruptured stumps of the myofibers

Blood vessels tear and release inflammatory cells

• Later, inflammation is amplified as “wound hormones” are released by satellite cells and necrotized myofibers – these act as chemotactants, signaling for further inflammation

*Note: Repair and Remodeling Phases Are Concomitant – simultaneously supportive and competitive


REPAIR PHASE:

Phagocytosis of necrotized tissue

• Initially, polymorphonuclear leukocytes are the most abundant cells but within the first day, these are replaced by monocytes/macrophages which proteolyse and phagocytose the necrotic tissue

Regeneration of myofibers

• Pool of satellite cells beneath the basal lamina (present since fetal development) proliferate in response to injury, differentiate into myoblasts, and join together to form multinucleated myotubes (these myotubes then fuse with the injured myofiber that survived the trauma)
• Undifferentiated stem cells which are extralaminally within the connective tissue give rise to determined myoblasts and differentiate to myotubes
• Regeneration of intramuscular nerves is also necessary as a lack of reinnervation of the myofiber results in atrophy

Production of a connective tissue scar

• Initial injury results in a hematoma but within the first day, the hematoma is invaded by inflammatory cells (including phagocytes)
• Blood-derived fibrin and fibronectin cross-link to form a scaffold and anchorage site for the invading fibroblasts
• Fibroblasts then start synthesizing the proteins and proteoglycans of the ECM to restore the integrity of the connective tissue framework
• Fibronectin is followed by Type III collagen. (Type I collagen production is initiated days later).
• The initially large granulation tissue (scar) eventually condenses into a small mass made up mostly of Type I
• The scar is initially the weakest point but infusion of TYPE I collagen (and the cross-link formation with maturation) makes it stronger (tensile strength) than the adjacent myofibers by day 10 post-injury. Therefore, reinjury ISN'T simply the "breaking up of scar tissue"

Capillary in-growth into injured area

• Vascularization is the first sign of regeneration and required for subsequent recovery process
• New capillaries have only a moderate capacity for aerobic metabolism and, therefore, rely on anaerobic means
• BUT during the final stages of regeneration, aerobic metabolism is needed (principle energy pathway) for the regeneration of myofibers - Regeneration does not progress beyond the newly formed thin myotube stage unless a sufficient capillary in-growth has ensured the required supply of oxygen for the aerobic metabolism 

REMODELING PHASE:

Maturation of the regenerated myofibers

Contraction and reorganization of the scar tissue 

• Myofibers that survived form branches as well as try to pierce through the scar on either side. The branches adhere to the connective tissue (scar) to form mini-Muscle Tendon Junctions. As mentioned above, the scar, therefore becomes stronger than its adjacent myofibers, rendering the myofibers more susceptible to injury if reaggravated
• Reinforced lateral adhesions (branches) also form to reduce the movement of the stumps and reduce the pull on the fragile scar. These lateral adhesions are formed as a result of intentional mechanical stress (free/forced mobilizations)
• Overtime the scar progressively diminishes bringing the stumps closer together – until the myofibers become interlaced (though likely not reunited)

Recovery of the functional capacity of the muscle

• Depends on severity of injury and nature of hematoma (intra vs inter muscular hematoma) of the injured muscle

*The above review was a brief summary of Jarvinen's review on Muscle Injuries in the Americal Journal of Sports Medicine

.This week my review on Predictive Factors for Management of Rotator Cuff Tears was posted on Research Review Service.

This review integrated the results of two studies that investigated the effect of pain, tear size, location and humeral head migration on the clinical outcomes and risk of progression in patients with rotator cuff tears.

​As always, for a complete understanding of the study, please read the articles below. To access my review, please visit Research Review Service

The two studies reviewed:

1. Proximal Humeral Migration in Shoulders with Symptomatic and Asymptomatic Rotator Cuff Tears
2. Outcome of Nonoperative Treatment of Symptomatic Rotator Cuff Tears Monitored by Magnetic Resonance Imaging

Main findings:

• Proximal humeral migration was significantly related to rotator cuff tear size and the involvement of the infraspinatus tendon.
• Progression of rotator cuff tears was more likely to occur in patients older than 60 years, those involving a full-thickness tear, and in shoulders demonstrating fatty infiltration upon magnetic resonance imaging.

Clinical application:

​Conservative management alone may not be sufficient in those individuals presenting with the specific characteristics described above. Therefore, simultaneous referral for orthopaedic consultation would be warranted in prudent case management.

The Sleeper Stretch has been one of the most commonly prescribed interventions for athletes presenting with Glenohumeral Internal Rotation Deficit (GIRD) of the shoulder.

But is this the most effective way to apply strain to the posterior capsule?

Using a cadaver-based study, Izumi et al examined and measured posterior capsule strain of 8 different shoulder positions.

What you need to know:

• 3 male and 5 female fresh cadavers were included (74 - 96 years of age)
• Bodies were disected and prepared so that only the posterior capsule was preserved and exposed.
• A displacement sensor (Pulse Coder, Levex, Kyoto, Japan) was used to measure posterior capsule strain
• For specific strain measurements, the posterior capsule was sectioned into 3 parts (upper, middle, and lower)
• Passive internal rotation was used as the primary motion for strain measurement.

Measurement positions:

• Internal rotation + 0 deg. elevation in scapular plane
• Internal rotation + 30 deg. elevation in scapular plane
• Internal rotation + 60 deg. elevation in scapular plane
• Internal rotation + 90 deg. elevation in scapular plane

• Internal rotation + 60 deg. flexion (IR in 60 deg. elevation + 60 deg. horizontal ADDuction)
• Internal rotation + 60 deg. ABDuction (IR in 60 deg. elevation + 30 deg. horizontal ABDuction)
• Internal rotation + 30 deg. extension (IR in 30 deg. elevation + 120 deg. horizontal ABDuction)
• Internal rotation + 60 deg. flexion + horizontal adduction (IR at 60 deg. flexion + 30 deg. horizontal adduction)

More information pertaining to this study's methodology:

• A reference length (R0) was first established and indicated the point at which the stress-strain curve first indicated a sudden decrease in strain
• Strain of the capsule was measured at the terminal range of passive IR. This was determined by grade III mobilization after Kaltenborn procedure.
• Beyond this point, a stretch was applied to the joint for 10+ seconds until no further strain was observed
• To determine the Glenohumeral joint positions that demonstrated significant increases in strain from R0, a one-way repeated measures ANOVA was used.
• The differences in strain among the positions were assessed via paired t-test.

Glenohumeral positions that significantly stretched the posterior capsule:

• Internal rotation + 30 deg. elevation in scapular plane: significantly stretched the UPPER and MIDDLE sections of the posterior capsule

• Internal rotation + 30 deg. extension: significantly stretched the UPPER and LOWER sections of the posterior capsule

Caution:

​It should be noted that joint capsule strain seen in aged cadavers may not be similar to that seen in younger adults. In fact, strain rates in younger populations may indeed be larger.

CERVICAL ZYGAPOPHYSEAL JOINT PAIN PATTERNS II: A clinical evaluation (Aprill et. al., Spine, 1990)

A study testing the reliability of their pain charts by a clinical trial

Guiding principle: if the pain patterns could correctly identify the source of neck pain, they could then be used as diagnostic aids in the clinical assessment of neck pain.

10 subjects used and were administered diagnostic blocks according to the above pain patterns. A positive response was recorded if within 10 minutes, the blocks provided complete relief of pain lasting for the duration of action of the local anesthetic agent used

The diagnostic blocks used were cervical medial branch blocks performed under image intensifier using a lateral approach

In eight cases, there was complete concordance in the predicted levels between the first and second observers

In nine of ten patients, there was complete concordance between the predicted level and the positive response to blocks

Most patients reported areas that were more extensive than those seen in normal volunteers. Therefore, it appears that with stronger stimuli, the pain can spread beyond the core area, overlapping into adjacent zones

Results demonstrated that the segmental pain charts could be used with good accuracy to predict the segmental location of the symptomatic joint

This one's for the manual therapists out there. A brief little review of 2 landmark papers pertaining to fact joint pain and referral patterns.

Part 1A:

CERVICAL ZYGAPOPHYSEAL JOINT PAIN PATTERNS I: A study in normal volunteers (Dwyer et. al., Spine, 1990)

A study determining whether or not pain from a given joint assumed a characteristic distribution…where the pain pattern in a given patient
might be used as an accurate indicator for clinically diagnosing the symptomatic joint

4 asymptomatic subjects were used

A contrast medium was injected into the joints, acting in a prevocational matter (experimental stimulus). Subjects were then examined for tenderness in both the cervical and shoulder regions

The distributions of evoked pain were recorded and a visual analog scale was completed

The medial branches of the dorsal primary rami were also blocked

The pain felt was deep and achy in quality

Pain patterns: 

• C2-3: into the head
• C3-4: (coinciding with the levator scapula) was more rostral than C4-5 (which concentrated by the angle formed by the shoulder and neck)
• C5-6: covered the top of the scapula and shoulder above the level of the scapular spine laterally
• C6-7: extended caudally to the inferior angle of the scapula

Following the analgesic blocks, the subjects unexpectedly demonstrated a slight hypesthesia over the area coinciding with the previous recorded area of invoked pain and tenderness

Concluded that the cervical z-joints can be sources of pain, including referred pain and that a physiological mechanism must exist whereby pain stemming from a z-joint can be referred into the related limb or limb girdle

Further, cervical z-joint pain is distributed in a pattern characteristic of its segmental origin

The Journal of Bodywork & Movement Therapies published an article by Eyal Lederman: The Myth of Core Stability. The following information is a summary of Lederman's conclusions.

ASSUMPTIONS ABOUT STABILITY AND THE ROLE OF CORE MUSCULATURE

Despite the role of the core musculature in creating spinal stability...

• Alterations and damage to the abdominal musculature (i.e. pregnancy, post-partum, post-surgery, etc) does not seem to directly influence low back stability and/or pain.

Despite the exponential number research studies conducted in the last decade...

• Low back pain has yet to be directly related to spinal instability.

TIMING

While the control of specific core musculature has been highly regarded in its "relationship" to low back pain...

• Trunk muscles perform motor reorganization in the presence or expectation of spinal pain, yet this has not been shown to actually cause low back pain
• Traditionally prescribed core exercises do not effectively affect the timing of trunk muscle synergistic contraction nor do they reset onset timing in those suffering from chronic low back pain

STRENGTH

While it is known that trunk muscle strength may decrease as a result of low back pain and injury...

• No evidence exists that demonstrates a lack of trunk muscle strength or endurance actually predisposes one to low back pain
• The findings pertaining to atrophy and a loss of trunk muscle strength resulting from chronic low back pain are still inconclusive
• Traditional core stability exercises do not provide enough of a stimulus to result in actual strength gains

CORE MUSCLE ACTIVATION

There are still many practitioners that still follow the single core muscle activation concept (TrA), unfortunately...

• Core musculature do not work independently from others within the trunk region during normal movements.
• Evidence has yet to show that one can specifically activate a muscle group (within the trunk) in isolation.

THE RELATIONSHIP BETWEEN CORE STABILITY TRAINING AND MOTOR LEARNING

While training for an activity often leads to skill development in that activity (i.e. piano)...

• Trunk control is activity specific (running vs jumping vs throwing), and thus, training to contract the abdominal musculature while on one's back is dissimilar to normal movement and therefore, conflicts with the basic principles of transfer and adaptation.

Although many novel core exercises are now performed in more "functional" positions (i.e. standing, moving)...

• The internal-focus approach of having patients actively concentrate on contracting their abdominal musculature is counterintuitive to motor learning principles. Focusing on tasks external to the body is more conducive to performance improvement.

Furthermore, while individuals are constantly reminded to continuously tighten their core musculature...

• The human body is designed to move efficiently and expend the least amount of energy possible, therefore, it is likely that energy will be wasted if co-contractions of the trunk musculature are continuously performed during normal daily activities. 

CORE STABILITY FOR INJURY PREVENTION AND THERAPY

While an asymptomatic individual may present with weak abdominals...

• Performing core stability exercises does not translate to prevention of injury

While the research on core stability exercises for low back pain treatment seem promising...

• Specific core exercises may be no different from general exercise or manual therapy

CORE STABILITY AND ITS RELATIONSHIP TO THE CAUSE OF LOW BACK PAIN

While our understanding of the aetiology of back pain has increased tremendously over the last decade...

• Chronic and recurrent back pain has been shown to be associated with psychological and psychosocial factors and its relationships to structural factors have been lessened.
• Advising one to "brace" the core while seated is unlikely to offer additional protection against pathology and may in fact increase compressive forces sustained by the spine.
• Core stability may have little preventative effect in those who suffer from acute back injuries (i.e. falls, sports) since these injuries often occur well before the nervous system is able to engage itself and offer protection.

POTENTIAL DAMAGING EFFECTS OF CORE STABILITY

Although compressive forces on the lumbar spine may contribute to low back pain...

• These forces may actually come from core exercises themselves since abdominal co-contraction during movement may provide further increases in spinal compression.
• "Natural" strategies of trunk control have been shown to be more superior to abdominal "hollowing" and "bracing" without the unwanted and excessive spinal compression.

While core training may be aimed at biomechanical dysfunction...

• Continual focus on these methods may shift the focus away from potentially more therapeutic interventions, such as in those suffering from pain associated with biopsychosocial factors.
• Core stability training may actually promote chronicity.

TAKE HOME POINTS

• Musculature weakness and imbalances may actually be a normal variation rather than a pathology
• Isolating the trunk musculature from the entire body may simply act as a means to promoting the "core" industry
• Abdominal weakness/dysfunction may never lead to back pain
• Trunk contraction may provide very little to back injury prevention
• Core stability may not be any more effective than general exercise or manual therapy
• The therapeutic influence may actually be a reflection of general exercise effects rather than stabilization
• Continuous trunk contraction may actually lead to unwanted spinal loads
• Traditional "hollowing" and "bracing" techniques may actually be unnecessary

If accessible, I strongly encourage you to read the paper in full. While Lederman makes some valid points, it was quite interesting that of the 200+ references cited, only one was primarily authored by Stu McGill, a 2003 study at best. Further, much of the points Lederman alludes to have already been elaborated upon by McGill in his book, Ultimate Back Fitness and Performance (also available in my "Educational Resources" above). Again, the above information are merely a summary of Lederman's conclusions.


Make sure you leave a comment and let me know what you think!
Photo source

For those of you who are still using the Smith Machine to Squat, here is another reason why you should set yourself "free".

A recent study published in the Journal of Strength and Conditioning Research, examined the electromyographic activity (EMG) of various muscles during the squat exercise when performed using the Smith machine as well as using free weights. This was performed as a follow up to a 2005 study by Anderson and Behm that demonstrated higher EMG activity of the quadriceps muscles during the Smith Machine squat.

The major difference between this and that of its predecessor was that a weight equal to an 8RM for EACH exercise (to facilitate relative intensity) was utilized in comparison to a fixed, absolute weight for both exercises used by Anderson and Behm.

EMG activity was collected for the following musculature:

• Tibialis Anterior
• Gastrocnemius
• Vastus Medialis
• Vastus lateralis
• Biceps Femoris
• Lumbar Erector Spinae
• Rectus Abdominis

A relatively low "N" was used: 3 men, 3 women.  All were active in sports and familiar with the use of both free weights and the Smith machine.

The average absolute EMG activity for the free weight squat was:

• 34% higher from the gastrocnemius
• 26% higher from the biceps femoris
• 49% higher from the vastus medialis

Interestingly, no significant differences in EMG activity of the trunk musculature were found between the two exercises. I will keep my opinions to myself on this, especially when only 6 subjects were used.

Additionally, I was both surprised and disappointed the authors failed to include the gluteal musculature within this study since hip extension is one major component of the squat exercise.

My Thoughts:

These findings likely represent a increased stabilizing role of the above musculature for the hip, knee and ankle during free weight squats.

• Gastrocnemius for ankle stability
• Gastrocnemius for knee stability (Don't forget that the gastrocnemius not only crosses the ankle joint but the knee as well!)
• Vastus Medialis for knee stability 
• Biceps Femoris for hip stability (Again, its unfortunate Gluteal activity was not recorded)

If you are a strength coach or manual therapist, I can say with 99.9% certainty that you have at one point or another recommended a Standing Wall Stretch to a client or patient. You may have done so for various reasons, including improved triceps surae length, but have you recommended this stretch with external assistance?

The external assistance that I speak of actually comes from a medial arch support.

A recent study published in JOSPT, examined the effect of Standing Wall Stretching on a number of variables in subjects with "neutral" foot alignment and in those with "flat" feet. The variables examined were:

• Displacement of the myotendinous junction (DMTJ) of the medial gastrocnemius
• Rearfoot angle
• Navicular height

The main finding of this study was that following the stretching protocol, the difference in DMTJ was significantly greater in those with flat feet (pes planus). Therefore, for those of you who recommend the Standing Wall Stretch to improve gastrocnemius length, it may be wise to use a medial arch support in those athletes presenting with Pes Planus.