Are you a control freak?

While working with a post surgical ACL patient that has +2 laxity and  graft pain, I was reminded of something Dr. Allen and I were talking about while discussing this case. 

One of the primary goals post ACL is stated as improving range of motion, particularly getting to full extension. If you look at the mechanics of the anterior cruciate ligament, you'll see that placing the knee in full extension places this ligament under stretch. We often will try to increase range of motion by hyper extending the knee, or using it as a fulcrum, which can cause undue stretch to this ligament. This means the burden of oweness is on the musculature surrounding the joint to provide stability, similar to what we are seeing in my patient.

I asked him to perform a one legged stand keeping his knee over his second metatarsal and just hold it. I then had him perform a mini squat, but rather than a traditional knee forward squad I had him do a potty squat (tibia remains vertical, while flexion occurs at the knee by moving the femur and glutes backward). Note that his foot is in a tripod position and his toes are up. (see video here)  He was able to maintain good control of the knee for about the first 10° of flexion and then his motion started to degrade. Our goal will be to keep him in a range of motion where he has good neuromotor (find the first 10° of motion) and expand upon that. We remember from our principles of exercise that isotonic exercises (like a potty squat) have a physiological overflow of 15° on each side of the point of application. If I can get him to flex to 10° and be in control, I'm actually getting effects up to 25° flexion.

Simple? Yes. Important? Incredibly! If you can't control the range of motion that you have, why should you have more? Remember in your rehab procedures, keep it in a safe range.

Lombard's Paradox: A unique look at the cooperation of the quadriceps and hamstrings

Lombard’s Paradox

 In searching our personal archives for neat stuff we came across an oldie but a goodie. We posted this one on the blog for the first time in July 2011 so it was time to revisit it here on the blogs “Rerun Fridays”. This is one to certainly make your head spin. We do not even know where this came from and how much was our original material and how much was someone  else’s.  If you can find the reference we would love to give it credit.  We do now that we added some stuff to this but we don’t even know what parts were ours !  Regardless, there is a brain twister here worth juggling in your heads.  Lets start with this thought……..

When you are sitting the rectus femoris (a quad muscle) is “theoretically” shortened because the hip is in flexion. It crosses the bent knee in the front at it blends with the patellar tendon, thus it is “theoretically” lengthened at the knee.  When we stand up, the hip extends and the knee extends, making the R. Femoris “theoretically” lengthen at the hip and shorten at the knee.  This, it bodes the question…….did the R. Femoris even change length at all ? And the hamstrings kind of go through the same phenomenon. It is part of the  uniqueness of “two joint” muscles.   Now, onto Lombard’s paradox with more in depth thought on this topic.

Warren Plimpton Lombard (1855-1939) sought to explain why the quadriceps and hamstring muscles contracted simultaneously during the sit-to-stand motion.  He noted that the rectus femoris and the hamstrings are antagonistic, and this coactivation is known as Lombard’s paradox.

The paradox is classically explained by noting the relative moment arms of the hamstrings and rectus femoris at either the hip or the knee, and their effects on the magnitude of the moments produced by either muscle group at each of the two joints.

By virtue of the fact that muscles cannot develop different amounts of force in their different parts, the paradox develops.  The hamstrings cannot selectively extend the hip without imparting an equal force at the knee. Thus, the only way for hip extension and knee extension to occur simultaneously in the act of standing (or eccentrically in the act of sitting) is for the net moment to be an extensor moment at both the hip and knee joints. Lombard suggested three necessary conditions for such paradoxical co-contraction:

  • the lever arm of the muscle must be greater at its extensor end
  • a two-joint muscle must exist with opposite function
  • the muscle must have sufficient leverage so as to use the passive tendon properties of the other muscle

In 1989, Felix Zajac & co-workers pointed out that the role of muscles, particularly two-joint muscles, was much more complex than has traditionally been assumed. For example, in certain situations, the gastrocnemius could act as a knee extensor. It is clear now that the direction in which a joint is accelerated depends on the dynamic state of all body segments, making it difficult to predict the effect of an individual muscle contraction without extensive and accurate biomechanical models (Zajac et al, 2003).

 In fact, back to the gastrocnemius another 2+ joint muscle (crosses knee, mortise and subtalar joints), we all typically think of it as a “push off” muscle.  It causes the heel to rise and accelerates push off in gait and running. But, when the foot is fixed on the ground the insertion is more stable and thus the contraction, because the origin is above the posterior joint line, can pull the femoral condyles into a posterior shear vector. It thus, like the hamstrings, needs to be adequately trained in a ACL or post-operative ACL, deficient knee to help reduce the anterior shear of normal joint loading. It is vital to note, that when ankle rocker is less than 90  degrees (less than 90 degrees of ankle dorsiflexion is available), knee hyperextension is a viable strategy to progress forward in the sagittal plane.  But in this scenarios, the posterior shear capabilites of the gastrocnemius are brought to the front of the line as a frequent strategy.  And not a good one for the menisci we should mention.

Andrews J G (1982)  On the relationship between resultant joint torques and muscular activity  Med Sci Sports Exerc  14: 361-367.

Andrews J G (1985)  A general method for determining the functional role of a muscle  J Biomech Eng  107: 348-353.

Bobbert MF, van Soest AJ (2000) Two-joint muscles offer the solution - but what was the problem? Motor Control 4: 48-52 & 97-116.

Gregor, R.J., Cavanagh, P.R., & LaFortune, M. (1985). Knee flexor moments during propulsion in cycling—a creative solution to Lombard’s Paradox. Journal of Biomechanics, 18, 307-16 .

Ingen-Schenau GJv (1989) From rotation to translation: constraints on multi-joint movement and the unique action of bi-articular muscles. Hum. Mov. Sci. 8:301-37.

Lombard, W.P., & Abbott, F.M. (1907). The mechanical effects produced by the contraction of individual muscles of the thigh of the frog. American Journal of Physiology, 20, 1-60.

Mansour J M & Pereira J M (1987)  Quantitative functional anatomy of the lower limb with application to human gait  J Biomech  20: 51-58.

Park S, Krebs DE, Mann RW (1999) Hip muscle co-contraction: evidence from concurrent in vivo pressure measurement and force estimation. Gait & Posture 10: 211-222.

Rasch, P.J., & Burke, R.K. (1978). Kinesiology and applied anatomy. (6th ed.). Philadelphia: Lea & Febiger.

Visser JJ, Hoogkamer JE, Bobbert MF & Huijing PA (1990) Length and Moment Arm of Human Leg Muscles as a Function of Knee and Hip Angles. Eur. J Appl Physiol 61: 453-460.

Zajac FE & Gordon MF (1989) Determining muscle’s force and action in multi-articular movement  Exerc Sport Sci Revs  17: 187-230.

Zajac FE, Neptune RR, Kautz SA (2003) Biomechanics and muscle coordination of human walking - Part II: Lessons from
dynamical simulations and clinical implications, Gait & Posure 17 (1): 1-17.

Stop Doing Kegels: Real Pelvic Floor Advice For Women (and Men)

This web article just came out today and we felt it was important to share. 

Nicole Crawford did a nice job with the article (LINK) and you need to read it.  The pelvic floor is a complicated place. There needs to be balanced muscular contraction and there has to be neutral pelvis and lumbar spine.  We have to agree with her comment:

A Kegel attempts to strengthen the pelvic floor, but it really only continues to pull the sacrum inward promoting even more weakness, and more PF (pelvic floor) gripping. The muscles that balance out the anterior pull on the sacrum are the glutes. A lack of glutes (having no butt) is what makes this group so much more susceptible to pelvic floor disorder (PFD). Zero lumbar curvature (missing the little curve at the small of the back) is the most telling sign that the pelvic floor is beginning to weaken. An easier way to say this is: Weak glutes + too many Kegels = PFD.

 There are too many people who have a shallow lumbar spine lordotic curve. These folks often hold the pelvis as neutrally as they can by keeping a constant squeeze of the glutes to “push” the pelvis “tipped up or levelled up” in the front when in fact the lower abdominals should “hold” them up in the front, to a notable degree.  It is easier for many to push the pelvis up with the glutes particularly when so many individuals are lacking in the abdominal compartment. 

We have so many of our patients learn the “potty squat” where the buttock is pushed backwards in a proper squatting technique.  We do this to reteach gluteal work, hamstring length in an environment of proper abdominal bracing. IT takes time to get the technique down, but it is worth it.  And, Crawford’s article gives it even more validity with its effect on the sacral posturing and impairing pelvic floor tension.

There is much good information in this article by Crawford.  It is worth everyone’s read. If you have been here with us on The Gait Guys for awhile you will know that we hold the mighty glutes on a high pedestal.  They are absolute key in gait and many folks do not use them properly.  After a few rough weeks practicing going gradually deeper as tissue length and strength is earned many of our patients have an epiphany of how little they were using their glutes, and how poorly they squat and how weak they were in the lower limbs.  Even our elderly patients in their 70s and 80s benefit from early shallow potty squat progressions.  We just put a chair behind them in case they fall back. It is never shocking to see what a few weeks of propper “potty-ing” will do to a person.  Do them alot, and do them often.

Good potty-ing to ya’ll.

Shawn and Ivo………Kings of our own Potty Thrones

Here is Crawford’s article link once again.

http://breakingmuscle.com/womens-fitness/stop-doing-kegels-real-pelvic-floor-advice-women-and-men