Yudu - sportEX dynamics - 1999-2010

SPORTS MEDICINE HAMSTRING INJURIES

pre-existing lumbar spine pathology’ the second stability and control of the lumbo-pelvic region.

Pre-existing lumbar spine pathology: these problems

can affect the hamstring muscles in two ways to predispose them to injury. First are mechanical based problems, if the inter-segmental motion of the lumbar spine is abnormal this will place increased load on other segments of the kinetic chain. For example, if a lumbar segment is hypomobile (stiff) due to pre-existing pathology, this will shift relative movement onto another area of less resistance to movement. If the lumbar spine cannot fully extend the hip would be required to extend further at the end of the stance phase, increased hamstring muscle activity would be required to achieve this, and the increased use of the hamstrings could cause premature fatigue in the muscle increasing the risk of injury. Alternatively, the increased tone in the muscle from it being over-active may increase the resistance to it being lengthened during the swing phase of gait again increasing the potential for injury. The second mechanism by which pre-existing lumbar spine pathology could influence the predisposition to hamstring injury is through a neurological mechanism, here the efferent (motor) nerve communication with the muscle is affected, this can either be in the form of decreased activity; inhibition of the muscle making it weaker, or increased activity raising its tone (effects of which are discussed above). There are two modes by which preexisting lumbar spine pathology could efferent nerve activity. The first is through direct referral; many structures in the lumbar spine are capable of referring pain to the posterior thigh and so changing efferent nerve activity to the region. The second is through the impingement (putting direct pressure on) the sciatic nerve which supplies the hamstring muscles this alters neural mobility and reduces the nerves ability to communicated effectively with its target tissue (the hamstrings), the poor communication leading to poor control and the potential for injury.

Motion control of the lumbo-pelvic region: Most coaches

and athletes are familiar with the term “core stability” were the deep abdominal muscles (principally Transversus Abdominis), segmental spinal muscles (principally Multifidus) and the Gluteal muscles provide stability to the lumbo-pelvic region and the dampening of been linked to many different musculoskeletal injuries. With regard to hamstring injuries, failure to fully recruit the gluteal muscles during hip extension will increase the load on the hamstrings, the implications of which where discussed earlier.

Running mechanics The key area in running mechanics which has been linked to hamstring injuries is over-striding. The placement of the foot relative to the body’s centre of mass will affect the force the hamstring muscle will have to generate; ideally the foot

should be placed as close as possible to the body’s line of gravity. The further the foot is placed in front of the body’s centre of mass the greater the load placed on the hamstring to brake the knee extension in swing phase and the greater length of the hamstrings at the start of the stance phase (so called increased clawing). Excessive “clawing” will lead to early hamstring fatigue leading to increased potential for injury.

WHAT FACTORS ARE RELATED TO THE REOCCURRENCE OF THE INJURY? To answer this question an understanding of the factors causing the injury is needed, hopefully these have been clearly detailed above. The cause of reoccurrence has often been fairly reported to be due to a failure in rehabilitation of the injury and this cannot be disputed. Too often the patient only receives local treatment in the form of massage and electrotherapeutic modalities to the hamstring muscle. In planning a rehabilitation programme for the hamstring injured patient an assessment needs to be undertaken of all those factors which could have caused the injury and then the correction of any faults found needs to be undertaken and accounted for in the treatment plan.

KEY ELEMENTS IN MULTI-FACTORIAL ASSESSMENT n Assessment of lumbar spine posture and movement: Two key points here first is to establish the presence of any inter-segmental hypomobility and hypermobility within the spine. The second is to establish any deficits in lumbo-pelvic motion control that is the activity of the deep core muscles. n Assessment of neural mobility: mobility of the neural system needs assessing and its role in presenting pathology differentiated through the use of the straight leg raise (Leseages) test and slump tests. n Assessment of muscle strength and activation imbalances: The ratio of strength of the quadriceps to hamstrings needs defining ideally being at least 60:40. This ratio is for concentric strength; more significant would be eccentric hamstring to concentric quadriceps strength. The ability to activate the gluteus maximus and its active participation in hip extension activities should also be investigated.

In order to treat hamstring injuries and prevent their reoccurrence it is crucial that the cause of the injury itself is clearly understood. The injury is often caused by a multitude of interrelating factors all of which will need addressing if a complete recovery and a minimised risk of re-injury are to take place. At the core of this is a thorough assessment of all the underlying predisposing factors which may cause the injury and prevent optimal recovery.