Following on from part I; part II will outline the function of the posterior chain, how the glutes are involved in this and again why glute inactivity can lead to an increase risk in injuries.
What is the Posterior Chain?
The term posterior chain refers to a linkage of muscles which involves the lower back, the glutes, hamstrings and the calves. It forms the basis of most strength, speed and explosive movements within the body, whether you’re an athlete or the average Joe. However when sitting for long periods of time (daily) it shortens your hamstrings, tightens your hip flexors, causes your glutes to become inactive and allows your lower back to stiffen. The creation of this muscle imbalance and loss of flexibility in the posterior chain, dampens its effectiveness and is a road block to better performance.
Also, like the links in a metal chain, each of these muscle groups are intertwined and work in unison to form part of a stronger and more stable unit. If one muscle forming the posterior chain is underworking, again, similar to the links in a metal chain, it compromises the overall stability and performance. Without a highly functioning posterior chain, it opens you up to injury risks and forms a limitation in your peak performance potential.
#2 Minimise occurrence of acute soft tissue damage
As discussed in Part I, a dysfunction in the glutes, particularly gluteus medius and minimus can cause dynamic valgus within the knee especially during single leg positions. This risk of valgus is heightened when the individual is landing from an elevated position, such as following a jump in basketball or volleyball. This is caused by an increase in ground reaction forces placed on the body, which leads to a greater control required from glute med and min to maintain hip stability to prevent dynamic valgus of the knee.
Knee Valgus with Landing
What can tend to happen when glute med and min are under performing is the reaction forces acting on the knee following landing can strain the soft tissues around the knee which usually prevent knee valgus. This includes structures such as the medial collateral ligament (MCL), medial patellofemoral ligament (MPFL) and the anterior cruciate ligament (ACL).
” A 2008 study by Lawrence et al. demonstrated that the subjects classified within the “weak” hip external rotation group had 146% greater vertical ground reaction forces when landing on a single leg from a 40cm block. The increased ground reaction forces led to increased anterior knee shear forces, external knee adduction and flexor moments causing significantly greater risk of ACL injury. “
Glute strengthening is therefore essential for reducing ground reaction and shear forces on the knee especially if you are involved in sports which involve repetitive jumping and landing, as it significantly reduces the risk of ACL and other ligamentous damage.
#3 Decrease the risk of muscular overuse injuries
Hamstring injuries are the most common condition to affect athletes in the AFL. More often than not, these injuries may be attributed to an inhibition of gluteus maximus’s function, as both muscles form part of the posterior chain.
Since glut max is the primary muscle involved in hip extension and deceleration of the swing leg during running and sprinting, a reduction in its activity will lead to secondary synergists, such as hamstrings to compensate and overwork. This usually isn’t a problem, however due to the design of the hamstrings; it is ideally recruited as a helper rather than the primary driver of the movement. What happens over time is an overuse of the hamstrings can lead to feelings of tightness and can cause an increased risk of hamstring injuries.
Knowing this, recurring hamstring injuries can have an underlying component of inactive glutes, which is why glute strengthening should always be implemented into hamstring rehab protocols, especially when previous programs have not involved it.
Stay tuned for Part III where I’ll discuss the recent research on the best glute rehab exercises to help target your bum.
By William Chin
- Diagnosis and treatment of movement impairment syndromes – Shirley Sahrmann (2002)
- Lawrence R K, Kernozek T W, Miller E J, Torry M, Reuteman P (2008) Influences of hip external rotation strength on knee mechanics during single-leg drop landings in females. Clinical Biomechanics 23: 806-813