RSSHamstring Strains and Core Stability
September 16, 2009 by David Fitzgerald
|
| Print
Filed under Physiotherapy Blog
The link between hamstring strains and poor core stability is frequently casually referred to in rehabilitation and strengthening conditioning literature. In fact it appears that there is no injury these days that is not associated with impaired “core stability”!
Has it taken over from excessive pronation as the ubiquitous explanation for intrinsic overuse injuries?
However, rarely do we see discussed the postulated mechanisms between impaired trunk control and potential hamstring overload. Here we will consider these hypotheses, the clinical testing methods and rehabilitation strategies to address these functional control deficits.
Mechanism of hamstring overload in “core” instability.
The basic premise of impaired trunk controls involvement in hamstring overload is that compromised proximal trunk control (muscular control above the pelvis) leads to a compensatory overstrain of muscles more distant in the chain, in this case muscles attaching to the lower end of the pelvis. The analogy of a triangle standing upside down is a useful visual concept to explain this phenomenon. In this situation we have the hamstrings posteriorly and the quadriceps anteriorly acting with the knee as a point of fixation and trying to balance the pelvis in an antero-posterior direction, almost like reins horse riding.
Importantly the control requirement is not entirely in an antero-posterior direction i.e. a sagittal plane but is in fact all 3 planes of motion:
Sagittal Plane
Coronal Plane
Transverse Plane.
However, it is easier to consider in each individual plane and build up the elements.
Simultaneous Concentric & Eccentric Loading
So the concept of excessive hamstring activity in order to balance the pelvis “from below up” is complicated by the fact that the hamstring muscle group crosses two joints – namely the hip and knee and in many sporting situations there are simultaneous but different movements occurring at the hip and knee. This is thought to predispose the hamstrings to alternating patterns of concentric and eccentric activity which maybe required simultaneously depending on the position of the respective hip and knee.
Primary & Secondary Hip Muscle Function
The situation is further compounded by the frequent clinical observation of impaired hip joint extension function i.e. inhibition of the prime one joint hip extensors- gluteus maximus in particular. Vladimir Yanda described this many decades ago as part of the “cross pelvic” syndrome and although this was reported in a context of tight hip flexors causing secondary gluteal inhibition, the clinical observation in my experience is just as frequent in patients without tight hip flexors – (as measured by Thomas test).
So What?….
So the practical implication of this scenario is an increased loading through the hamstrings by combining both a stability and a mobility challenge. If we explore this further in terms of functional consequences for muscle recruitment this is often evident as a poor coordination of hip extension (as measured in Yanda’s prone hip extension test). Here the prone patient is asked to extend the hip an inch off the supporting surface and the clinician observes for the pattern of motion. First one is looking for the timing of contraction between glutes and hamstrings on the lifting leg with the hypothesis being that the gluteus maximus should initiate the hip extension pattern followed closely by the hamstrings. In regards to the torso contribution, the proximal pelvis needs to be stabilised in order to allow the 15 to 25kgs of leg to be lifted. In the presence of hamstring substitution for gluteus max and compromised trunk control this leg extension is often accompanied by a hyper- lordosis of the lumbar spine and then associated anterior pelvic tilt. This represents a shift in compensation above the pelvis where the movement of hip extension is enhanced by excessive contribution of lumbar lordosis and paraspinal muscle activation. A critical point to bear in mind with this movement pattern is that lumbar lordosis associated with paraspinal hyperactivity has the complicating effect of relative inhibition of the anterior abdominal wall, which perpetuates the cycle of global core instability.
Clinical Solution
Previous posts outlined the sequence of progressions for proximal trunk control in this plane. I don’t need to reiterate them here but follow the link provided for further explanation. One of the most useful clinical exercises/tests is what I often refer to as tri- bike hip extension. In this position the patient is in a crouched kneeling position (as a triathlon bike rider) with one leg trailing back behind. The trailing knee is then bent and the test/exercise is to lift the leg by driving the heel towards the ceiling. Most importantly – the lower the crouch position the greater the degree of difficulty on lift.
I find this an extremely potent test for evaluating hip extensor function and it also yields good information about trunk stability and compensatory strategies but more on that another time.
P.S. When patients cramp in the hamstring, doing this exercise, you can bet your bottom dollar they are still trying to use the hamstring as opposed to gluteus maximus to execute this movement. In that event one needs to revert to a less challenging position.
Enjoy the clinical challenge.
David
