We have seen (part 1) that the structure and function of the hamstrings is used to guide the rehabilitation process. To be truly effective, Hamstring rehabilitation must be multifactorial, and a number of factors are important. Let’s begin by looking at changes in the lumbar spine, pelvis, and neural systems.
Lumbo-pelvic manual therapy and neurodynamics
Addressing the lumbar spine and pelvic joints may be important as the presence of pain referred into the leg can change hamstring strength, muscle contraction timing, and willingness to bend. Manual pain provocation tests may be used to clear the lumbo-pelvic region in the hamstring injured patient, and the slump test (also see chapter 8) may be used to differentiate hamstrings and sciatic nerve symptoms as the source of posterior thigh pain. Additionally the slump may be used as a treatment technique to facilitate nerve length and mobility. Neural tension may both increase stretch resistance and limit total movement range.
The slump test is positive where the patient’s posterior thigh pain is reproduced in the final slump position, and reduced with cervical extension, an action which has no effect on the hamstrings, but does change tension in the neural structures of the posterior thigh. The test has been shown to be positive in sportsmen and women (rugby players) who have suffered a number of hamstring tears in the past two years (Turl and George 1998). In addition quality of return to play is enhanced (fewer missed matches) when the test is used as a stretch within a rehabilitation programme (Kornberg and Lew 1989). Including the slump test modified as a neuromobilisation technique (slider exercise) has been recommend for athletes who have suffered a hamstring injury and feel a lack free movement when running even in the presence of a negative straight leg raise (SLR) and slump test (Brukner et al 2014).
Nerve sliding (gliding) of this type involves movement of at least two joints with one lengthening the nerve and the other shortening it. The combination of lengthening and shortening maintains the overall nerve length but improves nerve motility. In the case of the posterior thigh, we move the distal tissues (limb) while maintaining the position of the proximal tissues (spine) and then reverse the sequence. While sustained nerve tension increases intraneural (within the nerve) pressure and reduces local blood flow, sliding, by maintaining overall nerve length avoids these changes.
For the classic slump test or stretch the subject sits on a stool and links their arms behind their back (photo). The action is to gently flex the spine, beginning with the neck. At the same time one leg is straightened and the foot and ankle pulled up (dorsiflexed). Components of this action may be used individually at first, then built up into a full sequence. If one leg is very tight, the knee on that side can be bent and gradually worked towards straightening, easing into the tightness but not forcing the movement. Supporting the foot of the tight leg on the floor by placing it on a shiny piece of paper is also helpful. With the weight of the leg taken through the floor, the subject slides the foot forwards and backwards, again gradually working towards the fully extended position. Maintain this position for 20–30 seconds and then release.
To perform the nerve slide (seated straight leg slider), the subject begins in the classic slump position described above, ensuring that the subjects feet are clear of the floor. Keeping the spine flexed throughout the exercise and the neck is bent (flexed) to bring the chin down towards the breastbone (sternum). At the same time the knee is kept bent and the toes and foot are pointed (plantarflexion). To reverse the action, straighten the knee and draw the foot and toes up (ankle dorsiflexion and toe flexion) and at the same time look up at the ceiling (cervical extension). The sliding action is repeated rhythmically for 10 repetitions. Where there is a high degree of tightness, or where pain occurs the exercise can be performed in two parts. Firstly keeping the head still and moving the leg, and secondly keeping the leg still and moving the head. When both actions are pain free the two actions may be combined.
This straight leg sliding technique has been shown to increase range of motion of the hamstring muscles (measured by straight leg raise) without the need for separate hamstring stretching. Looking at a group of soccer players Castellote-Caballero et al (2013) used straight leg sliding for 3 periods over 1 week. Each exercise was practiced for 60s for 5 repetitions. Average scores for straight leg raise testing for the control group (no sliding) went from 58.9° to 59.1°, while the intervention group (neural sliding) went from 58.1° to 67.4°.
Mobilisation of the lumbar spine has been shown to increase motion range in the SLR test and change sympathetic nervous system activity in the limb (Szlezak et al 2011), and it is recommended that this technique be used to modify patient symptoms with a view to pain modulation. Although lumbo-pelvic examination and treatment may be appropriate for any patient with hamstring injury, it is likely that the MRI negative patient (that is, one where there is no visible muscle damage on an MRI scan) may especially benefit due to the presence of posterior thigh pain in the absence of local tissue change.
Lumbo-pelvic neuromuscular control
Improvement on lumbo-pelvic control has been suggested to reduce hamstring demand and therefore potential for injury (Brukner et al 2014). In addition a trunk stabilisation programme has been shown to reduce hamstring injury recurrence rate (Sherry and Best 2004) and a balance training programme to reduce hamstring injury rate in women’s professional football (Kraemer and Knobloch 2009). Although many athletes successfully compete at very high levels with suboptimal static and dynamic postures, in elite sport where fractions of a second matter, optimising control of the lumbo-pelvic region onto which the hamstrings take attachment would seem logical. Control of lumbo-pelvic alignment in the frontal plane can focus on actions based around the Trendelenburg test (pelvic alignment in single leg standing). In the sagittal plane forward bending and lifting actions (above) can be used to optimise pelvic tilt. These actions should be progressed in terms of overload and complexity, but must be paralleled with good exercise instruction and neurobiology re-education to reduce the chance of hypervigilance following injury.
Eccentric biased strengthening
Consistently research studies have supported the notion that various forms of eccentric hamstring exercise are essential for prevention and rehabilitation of hamstring muscle injury. Injury commonly occurs at the end of the swing phase of sprinting when the hamstring muscles are contracting eccentrically to decelerate the limb, and are at full stretch. Rehabilitation must match this muscle contraction type and joint angle position, so eccentric work (high loads at longer muscle-tendon lengths) would seem logical.
Nordic hamstring exercise
The Nordic hamstring exercise (NHE) has been shown to reduce injuries by 60% and re-injury by 85%, when used in a progressive 10 week programme (Petersen et al 2011). Progressive eccentric strengthening of this type is thought to address eccentric strength deficits, muscle tendon atrophy and scar tissue within the hamstrings (Thorborg 2012). The NHE may shift the optimum angle for torque generation towards a longer hamstring length, mimicking the limb position at terminal swing just prior to heel contact, a point at which injury has been shown to occur (Schache et al 2010).
The NHE is an intense muscle contraction, giving rise to muscle adaptation but with the likelihood of delayed onset muscle soreness (DOMS). Progressive programs should begin cautiously with one session each week initially (weeks 1-3) building to two sessions per week (week 2-5) and finally 3 per week (weeks 3-10) with one session per week for maintenance thereafter. Variation in the prescription is dependent on subject reaction to the exercise intervention.
Although the NHE is a vital component of rehabilitation is should not be used in isolation as it has a number of disadvantages. In general it is practiced bilaterally, not reflecting the unilateral nature of hamstring injury. Also it is a single joint (uniarticular) action whereas the hamstring muscles as a group are biarticular, and normally the NHE is performed at slow speeds. Progression of exercise must include training volume (frequency, intensity, time and type) and velocity at multiple joint angles. Slow controlled eccentrics should progress in parallel with general lower limb and lumbo-pelvic resistance training and motor control complexity. Ultimately power and speed based actions (plyometrics) should be used together with skill based actions reflecting the sport or employment of the subject.
The NHE begins in high kneeling with the ankles fixed (photo). The traditional action is to keep the hip fixed and angle the body forwards from the knee. The aim is to lower the body under control into a prone position, taking the final bodyweight of the final degrees of movement onto the hands. The action may be unloaded using a fixed strap (partner), elastic powerloop (fixed point), or with the subject placing their hands on a swiss ball and rolling it away from themselves.
From the same starting position, a bent knee back extension action may be performed, pulling from the hip and keeping the spine straight to begin. This action targets the hamstring higher up into the buttock, using an active pelvic tilt. It may be combined with or used separately to the traditional eccentric only version.
The straight leg (Romanian) deadlift uses and fixed leg position either with the legs straight (knees locked) or slightly bent (knees soft). The action is to keep the spine straight and lift the body from the hip. Initially bodyweight alone is used (arms behind the tail or behind the head), but resistance may be added from a barbell, kettlebell or dumbells. As an alternative, the arabesque may be viewed as a single leg version of the straight leg deadlift. The leg to be trained stays with the foot on the floor (leg vertical) and the other leg lifts (leg horizontal). There are a number of versions of this action. In yoga this is one of the warrior poses, and the final position is with the lifted leg, trunk, and arms horizontal to emphasise balance. This action may be performed standing on one leg with the arms lifted above the head. The movement is to keep the lifting leg, trunk, and arms rigid and tip forwards into a ‘T’ position. The hands may be placed on a wall for balance. The diver is the same action, but the arms reach downwards to touch a stool or gym bench and then the body is moved back to the starting position focusing on repetitions and strength.
Bridge type movements
Bridging actions use the hip extensors and spine extensors from a supine lying position. For the slide board leg curl the subject lies on their back with their foot on a slide board, piece of shiny paper on a carpet, cloth on a wooden floor, or seat of a rowing machine. The action is to slide the foot out from a bent knee position to straight leg and return. Single leg or bilateral leg action may be used.
The high bridge (gym ball bridge) is performed from a crook (hook) lying position with one heel on a bench or chair, or for an unstable surface a gym ball. The action is to press the heel down to dig into the bench and lift the hips upwards. Again, unilateral or bilateral actions may both be used. Where the unilateral action is used, the pelvis must be kept level, not allowing the hip on the non-active side to trail. This action may be modified into the eccentric leg curl on a gym ball. The action now is to press the heels into the gymball to lift the pelvis and to straighten the legs and then lower the trunk (eccentric only) or to straight the legs and then bend them again (eccentric-concentric).
The loaded bridge may be performed with the shoulders on a gym bench and the knees bent. A weight disc is placed on the lap, or a barbell is placed over the pelvis with the bar (padded) level with the top of the pelvis. The action is to lift the pelvis into a bridge position, finishing with the thigh horizontal. The foot must press directly downwards (hip extension) rather than outwards (knee extension).
Deceleration drills involve dropping into a bent hip and knee (squat) position either on unilaterally or bilaterally. Initially this may be achieved by standing tall and simple dropping into a ½ squat position. Firstly this is performed on both legs together (squat position) and then progressed to one leg leading (lunge position). These actions may be progressed to lunge, hop, and jogging actions to eventually mimic the straight leg heel contact position of terminal swing phase of running.
The flat floor position may be changed to a box drop position, when the action is to jump down and hold the position firstly. This action progressed to drop, land, and move in forward, sideways, or rotary actions. These action represent in-place (staying on one spot), short response (2 or 3 hops or steps) or long response (multiple steps or hops) plyometrics. These actions can emphasise force generation (acceleration) or force acceptance (deceleration) depending on training requirements.
Initially following injury, active muscle lengthening may be imposed by walking (treadmill or set distance / time when land based). At this stage pain tolerance can be used to limit training intensity and volume with short timescales of 5-10 minutes and pain intensity of 3 or 4 out of a maximum of 10 (numerical rating scale). Early activity of this sort (from day 1 with more minor grade 1 or 2 functional injuries) prevents the neuromuscular inhibition which is often seen following muscle injury. Progression can be or time and / or distance, speed, stride length and incline.
Treadmill walking gives way to gentle pain free jogging, and scout pace (walk-jog-walk). Manual resistance is used as isometrics progress to concentrics using both bent leg (prone lying knee flexion) and straight leg (straight leg raise position) actions. The running speed increases gradually ensuring that the subject can tolerate the increase load on the injured leg. Graded exposure is used, increasing and reducing distance and speed depending on symptoms initially. Manual concentric strength work is progressed to assisted bodyweight work using concentrics and eccentrics. Deadlift actions (straight leg and bent leg) are performed to reduced range (bench or stool level) and using band assistance initially. Nordic hamstrings curls can be begun with belt / resistance band assistance, progressing to swiss ball rollout as pain allows. Running gradually increases for pace, distance, and incline. As function improves the symptom contingent nature of training can progress to time contingent work.
Treadmill work gives way to normal running on a runway in the gym or sports field. Longer (50m) runs at slower pace gradually progress to shorer (30m, 20m) at increases pace. The next progression is to focus on acceleration and deceleration drills and to introduce sagittal (side step) and multidirectional (zig-zag and cutting) loading. The final progression prior to return to play (RTP) will depend on the sport and players position, or subjects work time and daily living actions. Functional progressions are used to replicate the actions to be encountered in sport / daily living with the aim of building final load tolerance and confidence in the limb.
Current practice in both prevention and rehabilitation of hamstring injury places less emphasis on stretching than in previous years as the evidence for its importance is limited. Interestingly active straight leg raise (SLR) has been used as an assessment of both flexibility and feelings of general insecurity in the limb following injury. The test (H-test) is performed by the subject lying supine with the upper body and contralateral leg stabilised and the ipsilateral knee locked and held immobile in a brace. The subject performs a maximum number of rapid SLR actions and rates their experience on a VAS scale. The H-test was shown to be sensitive to detect remaining signs of injury in MRI confirmed acute hamstring strain when standard clinical examination (palpation pain, manual strength tests, and passive SLR) had failed to do so (Askling et al 2010).
Range of motion should be restored to that required by the subjects activities to ensure pain free unrestricted movement. The use of range of motion combined with controlled contraction (eccentrics) more accurately reflects the functional requirements of the hamstrings than static stretching alone. A series of three lengthening actions (L-protocol) were compared to traditional contraction and static stretching (C-protocol) in elite sprinters and jumpers (Askling et al 2014). The L-protocol gave a mean time for return to competition of 49 days compared to 86 days for the C-protocol. The three exercises used are shown in table 3.5 Activity specific actions of this type can be designed using basic movement analysis of sports and daily actions with an emphasis on ‘strengthen and lengthen’ exercise. These can progress to functional activities pre-competition which involves all types of muscle work.
Where traditional stretching exercises are used, they must take account of pelvic action and the action of the two-joint muscle. In addition, relative flexibility may dictate that the majority of the stretching force is imposed on the lumbar spine in toe-touching type movements.
Flexibility may begin with active knee extension (AKE) described above. The advantage of this movement is the reciprocal innervation gained from quadriceps action, and the control that the athlete has over the movement. In addition, the back is supported throughout the action. The tripod stretch is also a useful exercise which requires a combination of pelvic stability with hamstring flexibility in a sitting position. The arms support the spine and encourage an upright body position.
Closed chain actions
Closed chain exercises for the hip extensors may be performed by modifying many common exercises. Leg rowing is a useful exercise. The athlete sits on a towel (on a wooden floor) or plastic tray (on a carpeted floor) with the feet fixed. The action is to pull the body forwards by hamstring action, mimicking a rowing position. Sitting astride a gym bench or ‘form’, the athlete digs the heels into the ground and again pulls the body forwards using leg strength alone. Both of these actions may be performed unilaterally or bilaterally. The slide trainer may also be used for sagittal leg pumping actions with the knees straight or bent. The sitting leg press weight training apparatus may be used for the sprint kick exercise. Instead of sitting on the bench, the athlete turns around and places the shoulder against the chair back, and the ball of the foot on the machine pedal. The action is to press the machine pedal with a combined hip and knee extension action. Bridging actions may be performed with the foot on a moving surface (skateboard), bench, or swiss ball as above for variety and resistance increased by adding weight to the hips (barbell) and placing the shoulders on a bench.