Rehabilitation of Rectus Femoris Injuries in Kicking Athletes

Rehabilitation of Rectus Femoris Injuries in Kicking Athletes Chris Morgan 1, Matt Konopinski 1 , Andrew Dunn 1 , Jordan Milsom 1

Rehabilitation | Case study | Rectus Femoris

Headline sub-group RF injuries into those which typically take longer he Rectus Femoris (RF) is one of the most important to rehabilitate and finally to present a complete rehabilitation Tmuscles in sports which require repetitive kicking; this process for this particular type of injury with a particular em- would include any of the football codes including Rugby, Aus- phasis on ‘kicking progressions’ for use in the those sports for tralian Rules Football (AFL) and in particular Soccer where it which a return to a full strike or “shot” will ultimately be has consistently presented as one of the most injured muscles the final mechanical criteria to allow a return to sport (RTS) since epidemiological data started to be collected. Quadriceps (figure 1). injuries typically make up 7% of the total injuries sustained As part of this kicking progression we will introduce the use by an elite soccer team during the course of a season with RF of an eccentric progression carried out on the Isokinetic Dy- injuries making up the vast majority of those injuries (1). namometer (IKD) which we feel is unique and show how this During a recent season our shared club sustained an unusu- can be integrated into functional loading and strengthening of ally high number of RF (Eight) injuries whilst simultaneously the injured tissue to allow isolation of the injured tissue within sustaining a historical low number of Hamstring injuries (Five) a full strength program. which goes against the published data of Hamstring > Quadri- ceps.(1) It is beyond the scope of this paper to present reasons as Anatomy and Action to why there would be such a switch in the number of Ham- RF is a bi-articular muscle located within the anterior aspect string and Quadriceps injuries within a season and there is of the quadriceps muscle group; it works to extend the knee, nothing to suggest that the events are related. Whilst there flex the hip and stabilise the pelvis on the femur in weight- are some similarities in terms of injury mechanism when com- bearing.(2) paring Hamstring and RF injuries which occur during high It is an extremely long muscle, is innervated by the Femoral speed running or deceleration the majority of RF injuries oc- nerve and has two proximal heads of origin. The direct head cur during kicking and occasionally when sprinting whereas originates from the anterior inferior iliac spine and the indi- the majority of Hamstring injuries occur during sprinting and rect head arrises from the superior acetabular ridge running occasionally during stretching or kicking. parallel to the direct tendon; these origins then converge down The purpose of this paper is to re-visit the RF in terms of to from the proximal aspect of the RF muscle with the indi- its unique anatomy and suggest reasons as to why the struc- rect tendon situated medially within the proximal part of the ture of the muscle contributes to its susceptibility to injury, to muscle and is cord like in appearance.(3,4) This interaction of direct and indirect heads results in the so-called “muscle within a muscle” configuration in which an outer unipennate muscle surrounds an inner bipennate muscle. This unique anatomical variation was best described in a paper by (5) “A unipennate muscle is one in which the muscle fibres originate from one side of the tendon and that tendon remains on one side of the muscle, sometimes blending with an aponeurosis on the surface of the muscle, as is the case for the direct portion of the RF. A bipennate muscle is one in which the muscle fibres originate from two sides of a tendon, as is the case of the indirect portion of the RF, and form an intramuscular central tendon or central aponeurosis . Because of the complex “muscle within a muscle” anatomy, injuries to the RF may not always fit into the traditional grading system of describing muscle injuries.

Types of Injury As with all muscle injury it is important that an accurate diagnosis and prognosis is made at the time of injury. This is particularly important in the RF due to the complex nature of the anatomy as described above. There is obviously a clear clinical diﬀerence between players who present with a gradual onset of tightness with maintenance of power and a slight loss of range versus those who have acute sudden onset pain and immediately display the typical clinical signs of a more significant muscle injury such as pain, loss of strength and reduced range. Fig. 1. sportperfsci.com 1 SPSR - 2018 | June | 31 | v1 Rehabilitation of Rectus Femoris Injuries in Kicking Athletes

The use of imaging can give specific details of which area of a functionally limited scar that requires collagen synthesis and the muscle is injured and this can certainly help when diag- remodelling for return of tensile strength. nosing and prognosticating but it is also vital to be guided by The tendon remodelling phase, which occurs from around the clinical signs; this is particularly important with the lower 6 weeks after injury, replaces the early type III collagen and grade injuries (clinically and radiologically) to reduce the risk extracellular matrix with longitudinally orientated type I col- of injury extension. lagen. This is necessary to restore the tendon stiffness and The RF isn’t a muscle that athletes are typically able to function required for athletic activity such as sprinting or kick- continue with if they still have clinical signs of a problem - ing function. even if these signs are fairly minor. Its vital that athletes are With this in mind and similar to our clinical experience it is clear from a clinical perspective “on the bed”, are confident in suggested that RF injuries which include Tendon involvement the muscle and are also able to reproduce pre-injury objective are likely to require a recovery period of 8-12 weeks depending scores of strength and length before they are exposed to any on the length and degree of damage. sort of explosive activity, if not there is a significant risk of the injury extending. Bails et al (6) investigated central aponeurosis tears of the Mechanism of Injury RF in 35 players, they concluded that RF central tendon in- 3 distinct types of injury mechanism are recognised when deal- jury at the proximal level (injury located above the intersec- ing with injuries to the RF; they are Acceleration, Deceleration tion created between the lateral edge of the sartorial muscle and Kicking. and the medical edge of the RF) is associated with a greater During acceleration the RF reaches its maximum length RTS time than at the distal level, that players with a grade during early swing phase when the hip-flexor muscles generate II injury have an RTS time longer than those with a grade force at the same time as the knee-extensor muscles absorb en- I injury whether the injury is located proximal or distal and ergy through an eccentric muscle action. During deceleration that greater injury length corresponds to longer RTS time. mechanisms of injury the body adopts a more up-right posture (Proximal = RTP of 45.1 when injury length is 4cm - RTS and a large eccentric force is passed through the quadriceps increases by 5.3 days with each 1cm increase. Distal injury = muscle group with the biarticular nature of the RF placing it RTS of 32.9 when injury length is 3.9cm - RTS increases with under the most stress. each 1cm increase. As muscle injury will typically happen during a lengthened Recently attempts have been made to further sub-classify state it has been proposed that the injury mechanism during the grade of muscle injuries by including information on loca- “kicking” actually occurs during the cocking phase of the action within the muscle, Pollock et al (7) classified injuries as tion when the hip flexors work to decelerate the femur as it myofascial, musculotendinous junction (MTJ) and intratendi- approaches terminal hip extension and at the same time the nous, they described 4 grades of muscular damage according to RF has to work eccentrically distally to decelerate the flexing image findings based on cross-sectional area (CSA) and length tibia - essentially both ends of the RF are working eccentri- of injury within the muscle or tendon. Although this work was cally to control the end of the cocking phase of kicking before based on Hamstring injuries it is likely that this grading sys- the leg is then accelerated forward to strike the ball - in prac- tem can be extrapolated to include the RF. tice however the player will typically feel that the injury has This is important as intratendinous tears have been shown occurred at the moment of ball strike. to take longer to recover and have a higher recurrence rate meaning that accurate initial diagnosis of tendon involvement would impact upon prognostication and early management. Brukner and Connel (8) warned of the “difficult thigh mus- Degloving injury cle strains” related to intrasubstance quadriceps strains re- The muscle within a muscle anatomy described above also re- sulting from a tear of those fibres originating on the tendon of sults in a type of ‘degloving’ injury which is unique to the the indirect head of the muscle, other variations include those RF and is described by Kassarjian (11) whereby the inner tears which disrupt the myofibrils from the central tendon but bipinnate intramuscular portion of the indirect myotendinous the tendon itself remains intact whilst the central tendon itself complex is separated from the surrounding outer unipennate can fail to create a fluid filled defect. They describe a clinical portion of the muscle, this results in dissociation of the inner experience of athletes initially recovering fairly quickly only to muscle belly from the outer belly and in some cases retraction sustain a reinjury, this time with failure of the intramuscular of the inner muscle belly and a palpable dip in the normal tendon. anatomy. These type of injuries have a mean RTS of 39 days Hughes et al (9) postulated that the indirect (central ten- although they can take up to 8 weeks. don) and direct heads of the proximal tendon begin to act The myotendinous junction (MTJ) of the indirect head of independently, creating a shearing phenomenon in contrast to the RF appears susceptible to a longitudinally orientated in- what occurs in the normal RF. This hypothesis was then used jury giving rise to the separation of the inner bipennate com- as a potential explanation for the longer rehabilitation associ- ponent of the muscle from the surrounding unipennate muscle. ated with acute injuries involving the central (intramuscular) This appears to occur in the periphery of the fibres of the inner tendon. bipennate muscle belly. Pollock et al (10) gave a possible explanation for the longer recovery time required for tendon injury. Tendon healing occurs in a very different way to muscle repair. Muscle injury Bulls eye sign induces a satellite cell response and early scaffold on which Another commonly found injury to the indirect component of muscle regeneration can occur enabling early return of muscu- the RF is an MTJ injury centred along the indirect intramus- lar function whereas Tendon repair initiates an inflammatory cular tendon which is referred to as a Bullseye sign (9) due response characterised by extracellular matrix deposition and to the distinctive MRI appearance (Fig.2A). In these cases increased signal seen around the RF tendon is likely to represent evolving stages of injury with early oedema and haemorrhage followed by later increased vascularity and scarring, whereas sportperfsci.com 2 SPSR - 2018 | June | 31 | v1 Rehabilitation of Rectus Femoris Injuries in Kicking Athletes

Fig. 2.

Fig. 5.

a “bulls eye lesion”. Linear interfascicular haemorrhage and minor partial tears are present surrounding the haematoma within the peripheral unipennate portion of the muscle belly (small arrows). The sagittal image in Fig.2B of the same injury shows the degree of retraction (large arrow) of the central bipennate muscle belly that surrounds the central tendon. Note the minor partial tears in the deeper unipennate portion Fig. 3. of the muscle extending distally to contact the deep aponeurosis (small arrows). The coronal in Fig.2C illustrates the “muscle within a muscle” morphology of the torn, retracted central bipennate portion of the muscle and the minor partial tears outlining he interface with the peripheral unipennate portion of the muscle.

Fig. 6.

Fig. 4. a Bulls eye sign with secondary atrophy and fatty inﬁltration of the muscle around the tendon reﬂects an old injury (12).

Common image findings There are a number of common image findings which can help Fig. 7. guide the clinician in terms of diagnosis and prognosis when marrying them together with clinical findings, these are shown in the following section. Fig.2 – Axial image Fig.2A shows a cross section through the intramuscular haematoma (large arrows) formed by retraction of the central bipennate portion of the muscle due to a tear at the distal end of the central intramuscular tendon. This produces a characteristic appearance sometimes referred to as Fig. 8. sportperfsci.com 3 SPSR - 2018 | June | 31 | v1 Rehabilitation of Rectus Femoris Injuries in Kicking Athletes

Fig.3 – Axial image showing a longitudinal tear of the an- sue (large arrows) throughout the anterior aponeurosis and the terior aponerosis with associated loss of tension and buckling, direct head tendon contribution to the more anterior fibres with minor partial tearing of the muscle belly at the myotendi- of the central intramuscular tendon located in the proximal nous junction. The anterior aponeurosis arrises from the di- third of the muscle. Note the central tendon is poorly defined rect head tendon contribution to the muscle-tendon unit. Note as it has become retracted towards the mass of scar tissue that the central intramuscular tendon is intact. (small arrows). Fig.9B shows thick mature scarring follow- Fig.4 – In contrast to Fig.3, this axial images shows a mod- ing tear involvement of the deep aponeurosis (large arrows). erate partial tear of the deep aspect of the RF that involves Intermuscular haematoma commonly forms between the RF the deep aponeurosis (large arrow). The aponeurotic tear in- and the vastus intermedius following deep aponeurotic tears, volvement also produces loss of tension and buckling of the which may further contribute to scar formation. The sagit- normally taught aponeurosis (small arrow). tal image in Fig.9C demonstrates the anatomical relationship Fig.5 – The axial image in Fig.5A shows a high grade par- of the proximal anterior aponeurtotic scarring (large arrows) tial tear involving the central and deep fibres of the central and the more distal deep aponeurtoic scarring (small arrows), tendon (large arrows) within the mid third of the tendon. relative to the longitudinal extent of the muscle-tendon unit. The accompanying coronal image of the same injury in Fig.5B Fig.10 – This figure shows acute avulsion of both proximal demonstrates the high grade nature of the injury with a long tendon origins of the RF. The axial image in Fig.10A shows the craniocaudal extent of the central tendon tear and laxity of avulsed and retracted direct head tendon (large arrow) and the the central tendon distal to the tear site (small arrows), both deeper more laterally located indirect or reflected head tendon of which are adverse imaging prognostic features. (small arrow). The sagittal image in Fig.10B illustrates the re- Fig.6 – The axial image in Fig 6A shows complete non- tracted direct head tendon, avulsed from the anterior inferior visualization of RF muscle or tendon with high signal iliac spine, with the retracted indirect head tendon in Fig.10C haematoma (large arrows) replacing the expected space of the avulsed from the lateral acetabular rim. Note both retracted muscle indicating a complete rupture of the muscle-tendon tendon footprints are closely related as they merge to form the unit in a goal keeper following a place kicking drill. The superficial and deep components of the central intramuscular coronal image in Fig.6B shows the rupture has occurred on tendon. a background of extensive chronic scarring of the central tendon (small arrows) which show laxity with muscle retraction. Fig.7 – Coronal MR image in Fig.7A illustrating an acute avulsion of the origin of the indirect (reflected) head tendon of Management of Injury RF from its insertion on the supero-lateral acetabular rim fol- The early treatment following RF injury would follow the prin- lowing an injury sustained during kicking (large arrow). The ciples of soft tissue injury management and be guided by the sagittal image in Fig.7B demonstrates the intact direct head healing continuum of inflammation, proliferation and remod- tendon inserting on the anterior inferior iliac spine (large ar- elling. The use of NSAID’s would be contraindicated in the row) and the thickened , retracted indirect head tendon (small first 5 days due to its negative effect on inflammation and thus arrow). The 3D CT reconstruction in figure 7C performed 8 the trigger to efficient healing. An emphasis would be placed weeks following the original injury shows heterotopic bone for- on allowing the injured tissue to rest and settle employing pas- mation (large arrows) at the site of tendon avulsion and at the sive modalities such as Crutches, Ice, compression, PSWD and end of the retracted tendon reflecting the associated acetabu- Muscle stimulation. lar periosteal disruption. Within elite sport this early management phase would be in- Fig.8 – The axial MR image in Fig.8 shows an acute tear corporated into a complete “return to performance” program of the deep free edge of the central tendon with associated aimed at reducing the effects of both relative immobilisation moderate partial tearing of the surrounding muscle fibres of and time out of training by incorporating fitness and condi- the myotendinous junction (large arrow). Note the low signal tioning elements away from the site of injury from as early as thickening of the central tendon indicating that the acute tear Day 1 (the only stipulation being that the program should not has occurred in a region of mature scar tissue (small arrows) result in the aggravation of any symptoms). following earlier tendon injury. The key variable in allowing a kicking athlete to RTS fol- Fig.9 – The images in figure 9 illustrate the locations and lowing injury to the RF is the ability to kick and in order to do patterns of scar tissue that may form following RF tears. The this full range, strength and power will need to be achieved. axial image in Fig.9A shows thick, mature low signal scar tis- Within the rehabilitation setting progression is criteria driven rather than stipulated by time - essentially once they have achieved certain objective markers they are clear to progress to the next stage. Whilst keeping the key variables of “reducing pain, increasing length, increasing strength and maximising function” in mind with every intervention applied to the athlete the aim is to impact positively upon each of these elements as soon as possible within the rehabilitation process. In the early phases this is likely to include pain relieving Fig. 9. modalities, gentle ROM exercises (painfree), functional movement patterns (initially in a pool if accessible) and and as soon as the athlete is able to withstand force through the muscle (assessed manually) then loading of the muscle can begin; initially this is likely to be isometric contractions but as soon as possible light eccentric work (in various position of hip and knee flexion) can and should be started. The achievement of full ROM and the ability to withstand eccentric force in a prone (hip extended position) then be- Fig. 10. sportperfsci.com 4 SPSR - 2018 | June | 31 | v1 Rehabilitation of Rectus Femoris Injuries in Kicking Athletes

comes the key objective criteria to trigger eccentric loading on of injury associated with low levels of eccentric hamstring the IKD and the unique kicking progression we introduced. strength (22, 23, 13). Recently, eccentric overload training has Alongside this OKC progression the athlete will also be pro- been shown to accelerate or optimise quadriceps endurance, gressing functional strength, closed chain strength, proprio- isokinetic and isometric strength (24) – justification for in- ception and multi directional movement patterns and those clusion in RF rehabilitation irrespective of associated injury progressions will run alongside the kicking rehabilitation. data. Collectively this phase could be considered the mid-stage of Takagi et al (25) investigated the repeated bout effect of ec- the rehabilitation and is based on the principles of protecting centric contractions in the gastrocnemius muscle of rats. The the healing scar whilst exposing it to length and strength chal- CG completed one bout of eccentric contractions (EC’s) at lenges which will positively impact upon its maturation to a week 4 whilst the EG completed a bout of EC’s at week 1 functional and repaired tissue ready to withstand the powerful and week 4. The initial bout caused the muscle in the EG to actions expected of it at the time of RTS. become resistant to the injurious effects of the second bout. Type I collagen was increased in the EG prior to the second

Eccentric Training Eccentric muscle contraction potentially offers a number of advantages during RF rehabilitation, in particular: fascicle lengthening; optimising improvements in muscle strength; and increasing collagen synthesis. Retrospective evidence suggests that individuals with a his- tory of hamstring strain injury possess shorter fascicles (13). A subsequent prospective cohort study concluded that short biceps femoris fascicles and low eccentric hamstring muscle strength significantly increased the risk of future hamstring injury (14). Although there are no studies investigating the Fig. 12. IKD prone eccentric quadriceps protocol - *eccentric PT limit controlled association of fascicle length and RF injury there is compelling by isometric hold if athlete exceeds set PT **rehabilitation must be pain-free at all evidence to suggest a similar concept applies. times – maintaining PT limit over consecutive sessions is acceptable Concentric muscle training has been shown to reduce muscle fascicle length in vastus lateralis (15). Conversely, eccentric muscle training using an isokinetic dynamometer revealed significant increases in fascicle length for vastus lateralis and RF (16). Brughellii et al (17) performed a RCT to assess the out- come of a 4-week eccentric strength training intervention for RF using 28 professional football players. The experimental group (EG) had an increase in optimum length – likely due to fascicle lengthening - compared with the control group and also incurred no RF injuries that season – the control group suffered 2 RF injuries. There is a paucity of evidence related to eccentric strength Fig. 13. and RF injury. Research on hamstring injuries lends support to inclusion of eccentric strength work within muscle rehabilitation. Eccentric hamstring conditioning is arguably the most effective means of preventing hamstring injury (18,19, 20, 21). Three large-scale prospective studies have shown that high levels of eccentric strength offsets the inherently greater risk

Fig. 11. Fig. 14. sportperfsci.com 5 SPSR - 2018 | June | 31 | v1 Rehabilitation of Rectus Femoris Injuries in Kicking Athletes

bout. Eccentric exercise may enhance muscle rehabilitation Kicking Progressions via increased collagen synthesis. Typically muscles incur strain injury in relatively lengthened This isokinetic dynamometer (IKD) provides a unique mode states; however it is our experience that RF is commonly in- of eccentric contraction during RF rehabilitation. The athlete jured during ball contact phase. Although the RF is in a can complete the EC in prone (Fig.11), which permits eccen- shortened position during ball contact there is huge variation tric muscle activity throughout a large range of motion, which potential for ball-contact forces and kicking technique. may optimise fascicle lengthening. We propose a model whereby kicking is initially compart- Isolating knee flexion range allows good RF excursion and mentalised from bi-articular to uni-articular motion at the hip EC in comparison to combined hip and knee flexion (e.g. and knee using knee drives (fig.14) and seated IKD concen- squatting) whereby the muscle remains fairly isometric during tric knee extensions respectively (fig.15). The kicking protocol contraction. The angular velocity of isokinetic contraction can evolves to include bi-articular kicking biomechanics, which is be controlled at a slow velocity – we incorporate 10°/s. This not only provides reassurance for the athlete rehabilitating an injured muscle but may also delay short-term anoxia associated with isokinetic exercise at faster angular velocities, and improve muscle metabolism (26). A tablet computer provides the athlete with live torque data throughout each repetition. Strength training that is externally paced and replicates a skilled movement task has been shown to increase cortico- spinal excitability and reduce cortico-spinal muscle inhibition compared to self-paced strength training. (27). Tendon involvement is common in RF injuries and modulation of muscle activity in this manner potentially restores corticospinal control of the muscle-tendon complex. (28) Our IKD protocol is shown below (fig.12 and fig.13) and commenced at the earliest clinical opportunity alongside traditional gym-based loading. The athlete is educated that this is a component of their strength work rather than an isolated rehabilitation intervention and it will be completed alongside other CKC strength exercises including squat, step-up and split-squat variations before progression into plyometric work.

Fig. 16.

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commenced in the pool utilising the resistive properties of the We describe the velocity bands as low, medium and high water (fig.16) and progressed to incorporate pneumatic pulley when explaining kicking intensity to athletes. It is acknowl- resistance on dry land. Progression of the velocity component edged that there will be kicking variability associated with is vital - the thigh can reach speeds of 500 degrees/second playing styles, game situations, formations and leagues. during kicking (29). When the athlete is clear to commence pitch-based kicking progressions we recommend a graduated velocity-based interval kicking progression. A recent study found a velocity-based Pre-Activation approach to be more reflective of the true demands of soccer The premise of this phase of training must be individualised to compared to a distance-based approach (30). the athlete. For the purpose of this article a general overview The authors examined match analysis data from the US Ma- of elements specific to RF injury will be discussed. Recently, jor League soccer during the 2012 season. The number and it has been established that gluteal activation exercises re- type of kicks were allocated to three discreet velocity bands (0- 6m.s-1; 6-12m.s-1; >12m.s-1) and shown to vary dependent on playing position. This data acts as a reference enabling prac- titioners to grade the volume, intensity and type of kicking within rehab to be reflective of the demands of a particular playing position.

Fig. 18. Fig. 20.

Fig. 19. Fig. 21. sportperfsci.com 7 SPSR - 2018 | June | 31 | v1 Rehabilitation of Rectus Femoris Injuries in Kicking Athletes

C R Y S T A L P A L A C E F O O T B A L L C L U B

PLAYER INJURY D.O.I Flexibility/Mobility Pain Nil/quad stretch Prone Knee Bend Range L=R Pain Nil/quad stretch Modified Thomas Range L=R Pain Nil/L=R Neural- Femoral Slump Range L=R Strength Ecc. 10*/s Nil IKD Con 60*/s L=R Functional Progressions/Tests Height Within 1 STDEV of pre-injury Ecc RFD <10% LSI Pk Landing Force Asymm <10% LSI DL CMJ Conc Force Asymm <10% LSI Height <10% LSI SL CMJ Pk Power <10% LSI RSI >2 Pk Drive Off Force Asymm <10% LSI DL Drop Jump Pk Landing Force Asymm <10% LSI >1 RSI <10% LSI Height <10% LSI SL Drop Jump Pk Drive Off Force Asymm <10% Asymm Single Hop for Distance <10% LSI, within 10% of pre-season screen Horizontal Hops Triple Hop for Distance <10% LSI, within 10% of pre-season screen Pitch Mechanical Tests Side-foot pass No pain, no apprehension Crossing/Clipping No pain, no apprehension Kicking Shooting No pain, no apprehension Return to Training GPS/Training Markers TD HSR Sprint A+D % Max Speed Target Actual Target Actual Target Actual Target Actual Target Actual Last Rehab Week = Ave. Training Week Prognosis Predicted Days to RTT: Actual Days to RTT:

Fig. 22. duce cortico-spinal inhibition, increase cortico-spinal excitabil- subject to. ‘Drop jumps’, ‘alternating split-squat jumps’ and ity and improve gluteal muscle efficiency (31). ‘forward deceleration steps’ are useful exercises to prepare for One can surmise that similar neuro-physiological processes the eccentric demands associated with deceleration (fig.18). occur following activation of alternative muscle groups. During swing phase Iliopsoas produces approximately 4x RF does not play a significant role in generating positive the muscle forces of rectus femoris when normalised for body- work during running rather it acts to facilitate energy transfer weight. Iliopsoas muscle forces increase relative to increments from the hip to the ground during the braking component of in running speed (33). stance phase (32). Insufficiency of the iliopsoas may increase the demands on During the first half of swing phase the RF is designed to RF to produce concentric hip flexion force, in particular areas absorb energy (eccentric contraction), however computational derived from the direct head. At the end of swing phase the modelling has demonstrated that these forces are low relative rectus femoris muscle-tendon unit is at it’s maximal length to Iliopsoas (33). and thus susceptible to injury (34). The ‘leaning tower wall series’ is a selection of exercises that Lewis et al (35) used computational modelling to demon- replicate the stance phase function for RF (fig.17). Emphasis strate that a 50% reduction in iliopsoas force during hip flex- is triple extension through the stance leg replicating the strong ion resulted in increased anterior hip joint forces - RF force activation of RF during the stance phase. increased to compensate. One of the common RF injury mechanisms via eccentric In addition, a lack of iliopsoas flexibility will compromise hip loading is deceleration. Trunk posterior lean further increases extension and potentially the efficacy of the stretch-shortening the horizontal braking forces and eccentric load that the RF is cycle (SSC) which contributes to iliopsoas force development. A lack of hip extension during running gait could also lead

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to a compensatory increase in lumbar lordosis and potential In order to reduce anterior hip joint forces in the early femoral nerve root compression. Knee drives serve to repli- phases of rehab, gluteal activation and strength exercises are cate and enhance the efficacy of the iliopsoas SSC. Varying advocated in hip flexion initially (fig.20). Gluteal exercises speed of contraction as well as resistance is recommended in should subsequently be progressed into more extended hip po- order to replicate the biomechanical demands of running. The sitions (fig.21). ‘leaning tower step-to-box series’ encourages hip extension in The rectus abdominis and oblique muscles prevent exces- the stance leg whilst also supplementing RF activation work sive anterior pelvic tilt at toe-off during running. Amongst (fig.19). the many negative effects associated with insufficient control of Decreased gluteus activity in hip extension increases ante- pelvic tilt, the length-tension range of iliopsoas is sub-optimal. rior hip joint forces. During running Gluteus Maximus ex- As previously highlighted, this will increase anterior hip joint tends the hip with high force and speed during flight and loading and subsequent RF forces. Strong abdominal contrac- stance phases. Gluteus Medius stabilises the SIJ by enhanc- tion should be coached in all activation exercises and specific ing force closure and also contributes to preventing Trende- high volume lower abdominal sessions should be included to lenburg’s sign (36). train this aerobic muscle group (fig.22). Pitch based rehabilitation with special reference to the RF Exercise selection, volume and intensity will have a significant impact on the success of any rehabilitation program; players will only overcome the anxieties of injury once they have completed a significant volume of unique rehabilitation tasks associated with performance (37). Before commencing pitch based rehabilitation the players training and match outputs for external loading were anal- ysed. This information provides targeted loads for RTS with a gradual increase in volume (duration and total distance) and intensity (velocity) throughout the rehabilitation period. Figure 24 provides a graphical representation of volume and intensity progressions achieved. The acute tolerance of the player, reflected by his maximum completed session, resulted in 77% of game total distance, 81% of high speed running and a maximum speed reached equivalent to 95% of recorded maximum speed whilst working at match intensity for metres per minute. This information provides the practitioner with the confi- dence that the tissue can withstand significant stresses reflective of competition whilst conditioning them to a level which will reduce the likelihood of an acute:chronic loading spike at the time of return to competition.

RTS The RTS criteria used at the end stage of of rehabilitation to formalise the markers used to trigger a return to full activity is Fig. 23. shown in Figure 22 and is a combination of clinical, isokinetic, functional and pitch loading parameters.

Percentage of Maximum Game Data Summary Session Total Distance Average Speed High Speed Peak Speed Running Injuries to the RF present a unique challenge to the clinician (M) (m/min) (M) (m/s) working in the kicking sports; its bi-articular nature, length 1 23% 97.4% 0% 50% and ability to generate huge torque whilst performing move- 2 29% 125% 0% 65% ments which make up a critical component of performance 3 33% 98% 0% 73% within these sports mean effective rehabilitation has to incor- 4 48% 103% 2% 75% porate both open and closed chain rehabilitation variations. 5 49% 95% 6% 64% Accurate diagnosis and prognosis as a result of detailed clin- 6 38% 90% 0% 71% ical assessment and the recognition of specific image findings 7 45% 87% 4% 65%

8 56% 91% 0% 81% which will impact upon the time scales imposed upon recovery

9 50% 96% 39% 64% whist following a task based criteria driven progression make 10 53% 97% 0% 88% up a vital component of the assessment phase of the injury. 11 44% 87% 70% 66% We have presented a kicking progression which utilises early 12 31% 73% 0% 54% eccentric training delivered on the IKD before incorporating 13 43% 94% 0% 90% more functional strength and movement tasks and believe this 14 50% 85% 47% 65% to be a unique way of combining the beneﬁts of eccentric 15 33% 85% 0% 66% strength training of injured tissue on the IKD within a generic 16 77% 109.9% 81% 95% lower limb anterior biased strength and power rehabilitation program and pitch based kicking progression. Injuries to the RF central tendon present a particularly dif- ﬁcult clinical challenge but the use of objective data in terms Fig. 24. sportperfsci.com 9 SPSR - 2018 | June | 31 | v1 Rehabilitation of Rectus Femoris Injuries in Kicking Athletes

of both strength and pitch based loading markers give the 16. Baroni, B.M., Geremia, J.M., Rodrigues, R., Franke, clinician the best chance to return these injuries back to full R.D.A., Karamanidis, K., Vaz, M.A. Muscle architecture competition and pre-injury levels of performance whilst min- adaptations to knee extensor eccentric training: rectus femoris imising the risk of re-injury. vs vastus lateralis, Muscle & Nerve. 2013;48:498-506. 17. Brughelli, M., Mendiguchia, J., Nosaka, K. Idoate, F., Ar- cos, A.L., Cronin, J. Effects of eccentric exercise on optimum length of the knee flexors and extensors during the preseason in professional soccer players, Physical Therapy in Sport. References 2010;11:50-55. 1. Ekstrand, J., Hägglund,M., and Waldén,M. Epidemiol- 18. Arnason, A., Anderson, T.E., Holme, I., Engebretsen, ogy of muscle injuries in professional football (soccer.) The L., Bahr, R. 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