Eccentric ExerciseInterventions forTendinopathiesDaniel Lorenz, PT, DPT, ATC, CSCS, USAWProvidence Medical Center, Kansas City, Kansas

S U M M A R Y

TENDON INJURIES OR TENDINO-

PATHIES ARE A CHALLENGING

AND PERPLEXING CONDITION FOR

STRENGTH AND CONDITIONING

PROFESSIONALS. TENDON

INJURIES CAN BE DEBILITATING

AND RESULT IN LOST TIME FROM

SPORTS PARTICIPATION. IF LEFT

UNTREATED, TENDON INJURIES

CAN PROGRESS TO AFFECT DAILY

FUNCTION. FURTHERMORE,

TENDON INJURIES AFFLICT ALL

AGES AND SKILL LEVELS. IN THE

PAST 10 YEARS, ECCENTRIC

EXERCISE HAS GAINED SUPPORT

IN THE LITERATURE AS AN EFFEC-

TIVE NONSURGICAL NONPHAR-

MACOLOGICAL INTERVENTION TO

TREAT THESE INJURIES. THE

PURPOSE OF THIS REVIEW IS TO

DISCUSS THE RELEVANT TERMI-

NOLOGY AS WELL AS THE

ANATOMY AND PHYSIOLOGY OF

TENDONS AND TENDON INJURY.

ADDITIONALLY, THE CONCEPT OF

ECCENTRIC EXERCISE IN TREAT-

ING TENDINOPATHIES WILL BE

DISCUSSED, AND EXERCISE

INTERVENTIONS WILL BE

PROVIDED FOR COMMON

TENDINOPATHIES.

INTRODUCTION

Tendon injuries account for30–50% of injuries in sports (16).Specifically, chronic problems

caused by overuse of tendons have

resulted in 30% of all running-relatedinjuries, and elbow tendon injuries canbe as high as 40% in tennis players (26).People of all ages and skill levels, aswell as nonathletes can be afflicted bythese conditions. Tendon pathologiescan not only lead to lost time in sportsbut also can result in long-term damageto tendons that can even affect dailyfunction and let alone sports perfor-mance. There is discrepancy in theliterature about how to manage theseinjuries as well as the proper terminol-ogy to use when referring to them.The term ‘‘tendonitis’’ is often usedas a catchall term for tendon injuries.Histological studies have shown thatoftentimes, no inflammation exists(20,21). The suffix ‘‘itis’’ indicates thatan inflammatory process is present.Leadbetter (19) has previously definedtendonitis as a symptomatic degener-ation of a tendon with vascular disrup-tion and inflammatory repair. Morerecently, the term ‘‘tendinopathy’’ hasbeen used as an all-encompassing termfor tendon injuries, whereas the term‘‘tendinosis’’ has been used to describechronic tendon issues. Leadbetter (19)has also defined tendinosis to be a focalarea of noninflammatory degenerationthat may be asymptomatic. The suffix‘‘osis’’ implies that a degenerative pro-cess is present. Complicating this mat-ter further is that there are significantdifferences in the physiological healingresponses of acutely and chronicallydiseased tendons (15).

Strength and conditioning professionalsoften have to develop training

programs to accommodate the athleteswho have these conditions throughoutthe training cycle and during the com-petitive season. Being able to recognizean ‘‘itis’’ or an ‘‘osis’’ is a crucial stepbecause the management of the ath-lete’s training is vastly different. Aninflamed ‘‘itis’’ often has sharp localizedpain with activity and in the morningor after periods of long rest. Pain mayactually decrease during activity butworsens at rest. On the contrary,a chronic ‘‘osis’’ has fairly constantpain that is more of a dull ache andpoorly localized. Usually, a chronicdegenerative tendon gets worse withactivity. A comprehensive review byNirschl (22) about stages of tendoninjury has been published previously inthe Table.

Within the past few years, eccentricexercise has shown promise in multiplestudies as a potential nonoperative andeffective training modality for tendino-pathies. The purpose of this review is3-fold. First, a brief discussion abouttendon anatomy and physiology willset the foundation for discussing whyeccentric exercise is of physiologicbenefit to tendons. Second, a reviewof the causes of tendinopathies willbe briefly discussed. Finally, exerciseinterventions will be provided forcommon tendinopathies as well asa framework for how to implementthem effectively.

Available at: http://www.nsca-cc.org/ceus/quizzes.html

KEY WORDS :

tendon; tendonitis; tendinopathy;tendinosis; eccentric exercise

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ANATOMY

Tendons transmit force generated bymuscle to bone and act as a bufferby absorbing external forces to limitmuscle damage (27). Tendons them-selves are relatively avascular but gettheir innervations and vascular supplyfrom the paratenon, the sheath aroundthe tendon proper. Tendons are com-posed of 30% type I collagen, gly-cosaminoglycans, elastin, and 68%water (23). Collagen’s role is to resisttensile forces, whereas elastin functionsto increase the flexibility of tendons.The structure of tendons reveals thatthey have a wavelike appearance atrest, indicating that it is susceptible toand allow stretch.

Tendon injuries can happen essentiallyat 2 locations. Tendon injury can bemidsubstance or in the body of thetendon proper. There is also potentialfor injury at the enthesis, which is theattachment of a tendon, ligament, orjoint capsule to the bone (28). Injury atthe enthesis is commonly referred to

‘‘insertional’’ tendinopathy. Regardlessof location, management is very similarand eccentric exercise can be used.

Tendons are prone to injury because ofa ‘‘tendon paradox’’ that exists. Oxygenconsumption is 7.5 3 lower in tendonsand ligaments than skeletal muscle(33). To minimize the risk of ischemia,which is a decrease in blood supply,a low metabolic rate and anaerobicgenerating capacity in tendons areneeded to carry loads and maintaintension for long periods. In the case oftendons, risk of inadequate or deficientblood supply is reduced because of thelower metabolic rate. The lower met-abolic rate indicates that there is lessneed for oxygen for tendons duringfunctional tasks. However, the lowmetabolic rate in tendons results inslow healing after injuries. Thus, thismay explain why tendon injuriespersist or develop chronic issues (32).If an athlete does not rest from theaggravating stimulus or provide thecorrect environment for regeneration,

the tendon will be in a perpetual stateof breakdown and attempted but failedhealing. The end result is pain, dys-function, and, for the athlete, lost timefrom sport.

CAUSES OF TENDON INJURIES

Tendons respond to repetitive overloadbeyond the physiological threshold byinflammation of their sheath, degener-ation of their body, or a combination ofboth (27). There are a host of reasonsthat tendon injuries occur, but theetiology remains unclear, and manycauses have been theorized (27). Typ-ically, there are 2 main types of injurymechanisms that have several potentialsources in each category (5). Intrinsiccauses are factors contributed to anathlete’s makeup. Intrinsic risk factorsinclude, but are not limited to suchthings as anatomical abnormalities ormalalignments (i.e., genu valgum, or‘‘knock kneed’’, and leg length discrep-ancies), age, gender, flexibility, jointlaxity, muscle weakness, biomechanics/

TableNirschl’s stages of tendinopathy

Stage Diagnosis Macroscopic pathology Histologic findings Clinical signs

0 Healthy No inflammation Organized collagen,absent blood cells

Firm tendon, not painful, absentswelling, normal temperature

I Acute tendinitis Symptomatic tendondegeneration, increasedcellularity, vascular disruption,inflammation of paratenon

Degenerative changeswith microtears,inflammatory cells inparatenon, focalcollagen disorientation

Acute swelling, pain, localtenderness, warmth,dysfunction

II Chronic tendinitis Increased tendon degenerationand vascularity

Greater evidence ofmicrotears, increasedlevels of collagendisorientation intissue hypercellularity

Chronic pain with tenderness,increased dysfunction, personvoluntarily unloads structure

III Tendinosis Intratendinous degenerationbecause of microtrauma,cellular/tissue aging, vascularcompromise

Increased cellularity,neovascularization,focal necrosis, collagendisorganizationand disorientation

Palpable tendon enlargement,swelling of tissues, increaseddysfunction with or withoutpain, tendon sheath may beswollen

IV Rupture Tendon failure Complete disruption offibers

Weak and painful muscle testing,inability to move affected joint,positive clinical tests for tendondisruption

Strength and Conditioning Journal | www.nsca-lift.org 91

sport technique, fatigue, and psycho-logical factors. Intrinsic causes may ormay not be adjusted or changed andmay be something that the athletemust learn to live with or possiblymake modifications in training orequipment. The other causes are dueto extrinsic factors. Unlike intrinsicfactors, extrinsic factors can usuallybe easily changed and modified to helpthe athlete. The 2 main extrinsic causesof injury to tendons are overuse andtraining errors (3–6,9,20). Considera-tions under the umbrella of extrinsiccauses include, but are not limited to,faulty equipment, playing surfaces, andshoe wear. Training errors can includea number of factors that the strengthand conditioning professional cansignificantly contribute to either posi-tively or negatively. Doing ‘‘too muchtoo soon’’ or having intensity/volume/load too high; progressions too fast;improper rest and recovery; and repe-titive, asymmetric, specialized trainingare all things that put an athlete atrisk. A properly designed program withprogressive overload helps minimizerisk from these factors.

THE CASE FOR ECCENTRICEXERCISE

As stated previously, the current par-adigm is shifting in favor of eccentricexercise in the treatment of tendino-pathies. Khan and Scott (17) havediscussed the role of mechanotrans-duction as a mechanism for healing ineccentric exercise. Mechanotransductionis the process by which the bodyconverts mechanical loading intocellular responses (17). These cellularresponses lead to cell signaling, aninformational network of proteins,lipids, and ion channels that are partof a physiologic cascade. Mechano-transduction is broken down into 3steps (17). Mechanocoupling is whena physical load (i.e., tension or shear)causes a physical perturbation of cellsthat make up a tissue. These forceselicit a deformation of the cell thattriggers a series of events depending onthe type, load, duration, and magnitudeof loading. The second step is cell-cellcommunication. In this step, stimulus

in one location leads to changes indistant cells, even though the distal celldid not receive the mechanical stimulusdirectly. Mechanotransduction closeswith the effector cell response. Here,the mechanical stimulus on the outsideof the cell promotes intracellular pro-cesses, leading to matrix remodelingthrough alterations in biochemicalpathways and gene expression. In thecase of tendons, load-induced responsesvia mechanotransduction have shownan upregulation of insulin-like growthfactor (IGF-I), which has been asso-ciated with cellular proliferation andmatrix remodeling (17).

In shortening of a muscle, the faster itcontracts, the smaller the tension it canexert (10). Tension is considerablygreater in muscle fibers when length-ened than when shortened (19–21).During negative work (eccentrics), theoxygen consumption rarely rises tomore than twice the resting value(1,2,12,31,32). Studies have shown pre-viously that when a muscle is stretched,the energy requirement falls sub-stantially because ATP breakdownand heat production are both slowed(8,31,32). Clearly, the decreased energyand oxygen requirements needed areof benefit to tendon metabolism basedon the above discussion regardingthe ‘‘tendon paradox.’’ Furthermore,with increased heat generation during

concentric/positive work, there is aconcurrent increase in cellular metab-olism. Thus, more waste productswill be generated, leading to chemicalirritation of nerves and eventually pain.Abbott and Bigland (1) did a studymeasuring oxygen uptake in subjectsusing a bicycle ergometer. Positivework (concentrics) always resulted inmore oxygen consumption than nega-tive work. Abbott et al. (2) did a follow-up study examining the relationshipbetween oxygen consumption andwork. Results of the study showed thatoxygen consumption is many timeslarger at great force and low speed thanat small force and high speed. Lastly,Bigland-Ritchie and Woods (7) foundthat less muscle activity is required tomaintain the same force during nega-tive work, fewer muscle fibers are re-quired to exert a given force, and thereis a substantial reduction in oxygenuptake when fibers are stretched. Theabove studies show that eccentric exer-cise results in less oxygen consump-tion, more force production, and lessenergy requirement than concentricexercise. Put simply, ‘‘you get muchmore bang for your physiologicalbuck’’ with eccentric exercise, bothfor the muscle and for the tendon.

Many studies in the past 10 years havesubstantiated eccentric exercise as atreatment for tendinopathies. In 1998,

Figure 1. Leaning calf raise.

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Alfredson performed, to the author’sknowledge, the first study investigatingeccentric exercise on diseased tendons,and the protocol used in that study hasbeen used in most studies on eccentrictraining (4). In a prospective study of15 athletes with chronic Achillestendinosis, subjects performed 3 setsof 15 repetitions of bent knee andstraight knee calf raises, twice a day, 7days per week over 12 weeks. Subjectswere told to work through pain, onlyceasing exercise if pain became dis-abling. Load was increased in 5 kgincrements with use of a backpack thatcarried the weight once body weightwas pain free. Researchers found thatall 15 patients returned to preinjurylevels of activity. Additionally, theyhad a significant decrease in pain witha significant increase in strength.

Shalabi et al. (25) evaluated 25 patientswith chronic Achilles tendinopathymeasured before and after an eccentricprogram using the protocol of Alfred-son et al. via magnetic resonanceimaging for tendon volume and intra-tendinous signal. Eccentric trainingresulted in decreased tendon volumeand decreased intratendinous signal,which correlated to improved clinicaloutcomes. Reduction in fluid contentwithin the tendon may suggest in-creased collagen deposition. The in-crease in collagen is a possible effectbecause Langberg et al. (18) found thattype I collagen synthesis increased aftereccentric training in a group of 12soccer players with unilateral Achillestendinosis. Ohberg et al. (24) alsofound that in a group of subjects withchronic Achilles tendinosis trainingwith the eccentric calf protocol ofAlfredson et al. resulted in a decreasein tendon thickness and normalizedtendon structure in most patients, bothcorrelated with less pain.

Jonsson and Alfredson (11) did a pro-spective study of athletes with jumper’sknee randomized into either an eccen-tric or a concentric group for 12 weeks.In the eccentric group, 9 of 10 subjectswere pleased with treatment, whereas10 of 10 in the concentric group werenot. At mean follow-up of 32 months,

Figure 2. (a) Beginning of supine calf raise. (b) Eccentric portion of supine calf raise.

Figure 3. Anterior step down.

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the eccentric group was still satisfiedand sports active, but all in the con-centric group had surgery or sclerosinginjections. In another study includingathletes with patellar tendinopathy,Young et al. (34) used 2 differenteccentric programs in elite volleyballplayers using the protocol of Alfredsonet al. but with different exercises. Onegroup did decline squats, whereas theother did a single-leg step down.Results of the study showed that bothgroups improved from baseline at12 weeks and 12 months.

Systematic reviews of literature byWasielewski and Kotsko (30) andKingma et al. (14) examined the effectsof eccentrics in reducing pain andimproving strength in those withlower extremity tendinosis and chronicAchilles tendinopathy, respectively.The systematic reviews revealed thateccentric exercise may reduce pain andimprove strength in lower extremitytendinopathies, but whether it is betterthan other forms of rehabilitation hasyet to be determined and the magni-tude of the effects are equivocal.

IMPLEMENTATION OFECCENTRICS

Kibler et al. (13) has previously statedthat the goal of rehabilitation intendinopathies is relief of the symp-toms from the ‘‘itis’’ to the restorationof function that is lost with the ‘‘osis.’’The previous studies have shown greatpotential in using eccentrics to restorefunction. From an exercise standpoint,regardless of body part, load andvolume should be progressed graduallyand should be dictated by the amountof pain the athlete experiences. Be-cause the athlete is recovering frominjury, it is advised that load used notbe determined by a 1 repetitionmaximum (RM). Furthermore, someof the exercises are for targeted musclegroups (elbow extensors for elbowinjury), and determining a 1 RM isnot practical or advised. The protocolof Alfredson et al. has been used inprevious studies and appears to bea safe and effective method to imple-ment the eccentric training program. Figure 5. Decline squat.

Figure 4. (a) Concentric portion of leg press; (b) Eccentric portion of leg press.

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Curwin (9) has previously proposeda method to determine training load ineccentric training for tendon injuriesthat is based on repetitions completedand the amount of pain experienced.One significant difference betweenCurwin’s program and Alfredson’sprogram is that the athlete performsboth the concentric and eccentricportions of the exercise, with theeccentric portion being performed ata faster rate. In their protocol, theysuggest that the athlete should experi-ence pain and fatigue between 20 and30 repetitions at a given load, perform-ing 3 sets of 10 repetitions. Pain feltbefore that range is generally accom-panied by worsening of symptoms andeither load or speed is decreased. Ifthere is no pain after 30 repetitions, thestimulus is inadequate. Either load isincreased or the speed of exerciseperformance is increased but not both.Pain experienced during the exerciseprotocol should be similar to the painexperienced during the athlete’s func-tional activity with an acceptablemoderate increase from that point. Ifit is the athlete’s first session, load isincreased until symptoms appear. Aftera general warm-up (bike, upper-bodyergometer), the athlete performs two30-second stretches of the involvedmuscle group. The athlete then com-pletes the above exercise protocol.

The author of this article suggests thatonce the athlete can complete 15repetitions over all 4 sets, resistanceshould be increased to perform sets of8 repetitions with the eighth repetitionbeing close to failure. The athlete usesthat load and builds up to 15 repeti-tions before increasing load again.Anecdotally, the author has found thismethod to be progressive yet safe, withless overall volume to help enhancerecovery. Additionally, 3–4 sessions perweek is advocated instead of everyday.The author proposes that ‘‘heavy load’’is a misnomer in the study of Alfredsonet al. because the volume of exercise israther high and the load is low giventhe amount of exercise that is toleratedby the athlete. Ultimately, however,dosing will be based on tendon

Figure 7. (a) Eccentric wrist curl, stretching wrist extensors. (b) Passive return to startposition.

Figure 6. Lateral step down.

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reactivity. Load should be reduced atleast 10% if the athlete has increasedpain or worsening of symptoms, par-ticularly with activities of daily living.Depending on their symptoms, intro-ducing concentric exercise should bebased on whether or not they havepain with nonsporting activities.

Concentrics can be attempted oncenonsport activities, like walking andstair climbing, are pain free. As witheccentrics, the concentric portion ofexercise should involve a gradual pro-gression. Once concentrics are painfree, then the athlete can begin joggingor more sport-specific activities. Aprogression from individual drills toteam activities is a methodical way toreintroduce the athlete to sport. If theathlete has pain, they should regressto the previous regimen until pain free.In the author’s experience, a cooldownactivity (i.e., recumbent bike) followedby stretching of involved musclesshould follow the program. AlthoughThacker et al. (29) found that there isinsufficient evidence to support pre- orpostexercise stretching, lack of flexibil-ity is a common finding in chronictendinopathies (9) and should be a partof the program. Ice to the affected areais advised to limit postexercise pain andpotential inflammation. Athletesshould be warned that eccentric exer-cise may make them sore initially, andthis is to be expected. As a general rule,athletes are instructed to performeccentrics by actively doing the eccen-tric portion of the muscle/joint inquestion while returning to the startposition passively or with assistance ofthe other limb, instead of activelydoing the concentric portion.

ACHILLES TENDINOPATHIES

The athlete could begin with calf raiseson flat ground, plantar flexing withboth legs, and going down with theinvolved muscles only. Once these arepain free, the athlete can be progressedto leaning calf raises with the use ofa physioball (Figure 1). In the leaningposition, there is more ankle dorsiflex-ion, which induces a greater stretch tothe Achilles and thus more force isneeded to plantar flex. Next, the athleteFigure 9. (a) Eccentric supination. (b) Passive return to start position.

Figure 8. Eccentric radial deviation.

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can progress to a staircase. A nicecompliment to these exercises is usinga leg press machine as a ‘‘supine calfraise’’ fashion (Figure 2). Depending onhow much pain the athlete is experi-encing, the supine position may bea more appropriate starting pointbecause the weight can be adjustedto be less than body weight. A veryfunctional addition to the Achillesprogram would be an anterior stepdown (Figure 3). The athlete leads withthe uninvolved muscle, attempting tokeep the involved heel on the step. Asthe reader can see, the ankle is ina dorsiflexed position, thereby placingthe Achilles on stretch because itcontrols the motion. In this position,the soleus muscle is targeted in its roleas a decelerator of the tibia anteriorlyduring gait during the end of stancephase to limit excessive dorsiflexion.To progress, the step can be increasedor the athlete can hold dumbbells.

PATELLAR TENDINOPATHIES

It is suggested that an athlete beginsusing the leg press because the weightcan be adjusted to be less than bodyweight if the athlete cannot toleratebody weight due to pain (Figure 4).Other means include decline squats(Figure 5) or eccentric step downs(Figure 6). The athlete should bereminded to perform the concentric

portion with both legs and the lower-ing phase with just the involvedmuscles. When using the decline boardor step, they should only get back onthe step using the uninvolved limb.

TENNIS ELBOW

Tennis elbow, or lateral epicondylitis, isan irritation of the common extensortendon from its attachment on thelateral epicondyle of the humerus. Onthe extensor surface, the supinatormuscle is also implicated. Therefore,it should be included as part of a pro-gram. The athlete can do ‘‘eccentricwrist extension’’ (Figure 7). Here, theweight is raised by the uninvolved limband then lowered by the involvedmuscles. A hammer or similar devicewith a long lever arm to do eccentricradial deviation (Figure 8) and eccen-tric supination (Figure 9) are additionalexercises. Again, it must be reinforcedthat the athlete cannot raise the weightback to the starting position concen-trically. Although cumbersome toreach across to the involved limb toraise it back to the starting position, itmust be done initially to preventfurther flares. Athletes can be pro-gressed by increasing the lever arm oradding weight. Conversely, if theycannot tolerate a weight at a longerlever arm position, it can be moved toshorten the lever arm, which maymake the exercise tolerable (Figure 10).

CONCLUSION

Eccentric exercise is showing promiseas an effective means to treat tendoninjuries. It is so promising because thebasis for it is centered on muscle andtendon physiology, not a theory. Itshould be a part of a comprehensiveprogram that involves collaboration ofthe health care team and the athlete’scoaches to ensure that all intrinsic andextrinsic risk factors have been ad-dressed as well as other complimentarypain alleviating modalities. It is hopedthat more research will surface further,advocating the use of eccentric exercise.

Dan Lorenz isa sports medicinespecialist atProvidenceMedical Centerand an adjunctfaculty memberat RockhurstUniversity inKansas City,Missouri.

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