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Here’s a brief summary of the study:

Study Purpose:

• To determine the presence of a relationship between hamstring length and PFJ stress at 3 specific knee joint angles of flexion.

Study Population:

• 16 recreationally active males divided into two groups based on knee joint angle-measured hamstring length.

Methodology:

• A biomechanical model incorporating knee joint angle, knee extensor moment, and PFJ contact area was used to quantify PFJ stress.
• MRI and 3D motion analyses were also utilized in this study.
• A one-way ANOVA to determine the variations in PFJ stress between the 2 groups (with and without reduced hamstring length) was used.

Main Findings:

• Patellofemoral Joint stresses differed significantly between the two groups at specific angles of knee flexion.
• No significant differences in hip angles between the two groups.

Clinical Application:

• This study demonstrated that subjects with reduced hamstring lengths have increased PFJ stress during various positions of the squatting movement.  As a result, such a decrease in length MAY contribute to the pathogenesis of various conditions relating to the knee.
• These results enable us to consider another factor when managing those with knee pathology.

For a complete and “evidence-informed” understanding of the study, look out for my review. I have obviously left out specifics from this study in this post as Research Review Service is a paid membership site. However, if you would like more information, please do not hesitate to ask.

Photo source

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What we need:

• Dorsiflexion mobility

Why we need it:

• Minimize stress on knee

How we can get it:

KNEE:
What we need:

• We need to realize that the knee is often an innocent bystander

Why we need it:

• We need to realize this because the research says so

How we can get it

• We can achieve optimal knee mechanics by looking both above (the hip) and below (the ankle) this joint.

HIP:

What we need:

• Saggittal plane mobility
• Extension strength

Why we need it:

• Minimize stress on lumbar spine

How we can get it:

• Glute Bridge
• Glute Bridge – Marching
• Glute Bridge – 1 Leg

What we need:

• Frontal & Transverse plane dynamic stability

Why we need it:

• Minimize dynamic valgus at knee and dynamic internal rotation at knee

How we can get it

• Side Lying Abduction
• Clam Shells (Hip – External Rotation)
• Mini Band – External Rotation
• Airplane (I’ll get a video of this up soon)

LOW BACK / CORE:

What we need:

• Antirotation, Antiextension, Antilateral flexion STABILITY

Why we need it:

• To be able to transfer forces THROUGH not TO the “joint” (aka Core”)

How we can get it:

• Antirotation: “Pig on a Spit” Roll
• Antiextension: Front Plank series including the Body Saw
• Antilateral flexion: Farmer walk / Suitcase carry

What we need:

• Lumbar intersegmental stability

Why we need it:

• To be able to transfer forces THROUGH not TO the “joint” (aka Core”)

How we can get it:

• Effective “core activation” methods

THORACIC SPINE:

What we need:

• Rotation & Extension mobility

Why we need it:

• Lumbar relief & Shoulder mobility

How we can get it:

SHOULDER:

What we need:

• Scapular stability

Why we need it:

• Shoulder mobility

How we can get it:

For those of you who are unfamiliar with this approach of looking at the body, please have a look at Coach Boyle’s The Joint by Joint approach and FITS Toronto’s 5-site Integrity

Anatomical photos courtesy of Primal Pictures

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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)

Your Thoughts?

*Here’s a video I found of squatting with pretty decent technique. The trunk and tibia are parallel, he’s in neutral spine, he doesn’t sandwich, and his weight is relatively back on his heels. Not sure about the guy doing dips in the background though!

Photo source

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“Certain athletes are at higher risk of knee pain and non-contact knee injury than others.”

End of post.

(just kidding)

The above statement is well known but unfortunately, not many of us know exactly why. Thankfully, the American Journal of Sports Medicine gave us some input into the biomechanical reasons some athletes are at risk of patellofemoral pain syndrome (sorry Mike) and potentially at risk of non-contact ACL injury. The information below is taken from two VERY recently published papers from the large scale Joint Undertaking to Monitor and Prevent ACL Injury (JUMP-ACL) study. This study examined the biomechanical variables involved in a jump-landing-rebound task.

Biomechanical Factors Potentially Involved with Risk of Non-Contact ACL Injury

• Lower knee and hip flexion motion (saggital plane kinematics)
• Higher knee valgus and hip adduction angle (frontal plane kinematics)
• Greater internal knee and hip internal rotation moment (transverse plane kinematics)
• Greater internal knee and hip extension moment and anterior tibial shear force (saggital plane kinetics)
• Greater internal knee valgus and hip adduction moment (frontal plane kinetics)
• Greater vertical ground reaction force
• Women

Biomechanical Factors Potentially Involved with Patellofemoral Pain Syndrome

• Decreased hip abduction, knee flexion, and knee extension strength
• Lower knee extension moments
• Greater navicular drop
• Decreased peak knee flexion angle
• Women

This is what I think:

• Women are more important than biomechanical factors (they are actually more important than many things in life)
• Athletes need to learn to absorb the landing (land with the toes and roll back onto the heels in one fluid motion)
• Athletes need to eccentrically control the lower extremity from collapsing in when landing (don’t land knock-kneed)
• Feet should be shoulder width apart
• Spine should be neutral and the core should be stiff
• Athletes need to spend some time on the glute/posterior-chain eccentrics

The preceeding information was derived from the two most recent issues of AJSM. It is strongly suggested that for a complete understanding, readers view the papers in their entirety as Padua et al was based on validating the Landing Error Scoring System and Boling et al interestingly found higher hip ER strength and lower ground reaction forces as risk factors.

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Scientific knowledge expands daily. This article was published in 2008. I started this blog 3 days ago…THEREFORE…the information you are about to read MAY contain concepts that are obsolete…READER DISCRETION IS ADVISED!

The following is a summary of the IOC current concepts statement published in the British Journal of Sports Medicine last year. Contained within this summary are the general principles that were established based on decades of research pertaining to ACL injuries in female athletes.  Since the amount of potential factors associated with injury are plentiful, this review is limited to only those concepts with conclusive evidence.

Epidemiology

• As a whole, ACL injuries most commonly result from non-contact mechanisms
• Although the rates of ACL injury in men and women are similar in professional sports, younger female athletes are at higher risk (than aged- and sport-matched males)
• Along with men’s spring football, women’s gymnastics, soccer, and basketball have the highest injury rates per 1000/athlete exposures.
• Consistent with most sports, injury rates are higher during competition

Risk Factors

• There is an association between intercondylar notch width and risk of ACL injury. Females generally have smaller notches than males and therefore, likely a smaller ACL. It has been suggested that these ACLs may have lower linear stiffness, fail earlier in elongation, absorb less energy, and fail with lower loads.
• The relationships among the presence of sex hormones within the ACL and oral contraceptives with ACL injury risk are still inconclusive.
• Women appear to be at greater risk of ACL injury during the pre-ovulatory phase.

Mechanism of Non-Contact Injury

• Injuries most often occur when landing from a jump, cutting, or deceleration.
• Kinematic analyses have revealed that women land with less knee flexion than men. Women also maintain higher knee extension and valgus during stance phases of running and cutting. Finally, women also display higher quadriceps EMG activity during max loading. Therefore, a straighter knee and higher quadriceps activation likely contribute to the injury mechanism. Other components include anterior translation, dynamic valgus in near extension, increased trunk motion, and a high load placed on the leg or foot that is away from the body’s COM.

Evaluation

• Key components of diagnosis include: sudden knee pain during high intensity activity, inability to resume play, “popping” sensation, haemarthrosis.
• The course of ACL injury classifies the injured into copers, adaptors, and non-copers.
• ACL reconstruction does not warrant surgical management of the injured MCL.
• The meniscus is associated in approximately 50% of ACL injuries. Note: Mike Reinold recently posted an excellent blog (by D. Lorenz) on meniscal testing here.
• A thorough examination searches for articular cartilage, ligamentous, and bony/bone marrow lesions.
• The pivot shift test is best for ruling in ACL injury. The Lachman test is best for ruling out ACL injury. (It is also the most accurate).
• Patient-administered questionnaires should be used as an outcome measure and quantified scores should be kept separate from categorical variables (good/excellent).
• While the incidence of injury in girls increases at puberty, there is a potential risk of growth disturbances with prepubescent operative management.

Rehabilitation

• Although the restoration of full knee extension is important in initial stages of rehab, ROM should be compared with the unaffected knee to determine normal ranges (hyperextension may be the norm in some patients).
• OKC training should be introduced and progressed cautiously, commencing between 90 and 40 degrees.
• CKC exercises recommended at the commencement of rehab. Early weight bearing and mobilzation are safe.
• A minimum of 3-4 functional performance tests should be used for evaluation.
• Return to play should be goal-based (not time-based)

Prevention

• Most prevention programs utilize neuromuscular and proprioceptive training to alter the dynamic loads placed on the tibiofemoral joint
• Henning was the pioneer in neuromuscular training for ACL injury prevention (just thought I’d add that in, dude deserves his props!)
• Program intervention generally takes a minimum of 4-8 weeks in order to impart its desired effect.
• Programs should be implemented as early as possible (age) and those that use minimal equipment are generally more successful
• In jumping sports, proper landing involves softly landing on the forefoot, rolling back to the rearfoot, two-feet landing, and knee and hip flexion engagement.
• In cutting sports, dynamic valgus should be avoided as the “knee over toe” position should be emphasized.
• Programs should be incorporated as a regular warm-up, should also include strength, power, plyometric, and agility exercises
• The drop vertical jump test is a good way to identify those at risk.

There you have it. My generalized summary of the IOC current concepts statement. Since published research on ACL injuries literally come out daily, please be reminded that some of the above concepts may have been updated.

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