Bio Mechanics of the Tennis Ground Strokes

Biomechanics of theTennis Groundstrokes:Implications for StrengthTrainingE. Paul Roetert, PhD,1 Mark Kovacs, PhD, CSCS,1 Duane Knudson, PhD,2 and Jack L. Groppel, PhD3

1United States Tennis Association, Boca Raton, Florida; 2Department of Health and Human Performance,San Marcos, Texas; and 3Human Performance Institute, Lake Nona, Florida

S U M M A R Y

THE PURPOSE OF THIS ARTICLE

WAS TO SUMMARIZE RECENT RE-

SEARCH RELATED TO THE BIO-

MECHANICS OF TENNIS

TECHNIQUE IN GROUNDSTROKES

AND THEN TO RECOMMEND SPE-

CIFIC STRENGTH AND CONDI-

TIONING EXERCISES THAT WOULD

TEND TO IMPROVE TENNIS PER-

FORMANCE AND PREVENT INJURY.

BASED ON THE AVAILABLE

RESEARCH, IT WAS DETERMINED

THAT TRAINING EXERCISES

SHOULD EMULATE THE SEQUEN-

TIAL COORDINATION INVOLVED IN

GROUND STROKE PRODUCTION,

AS WELL AS STABILIZING MUS-

CULATURE THAT MIGHT BE IN-

VOLVED IN DEVELOPING FORCE

OR IN PROTECTING BODY PARTS

FROM STRESSFUL ACTIONS. SPE-

CIFIC EXERCISES BASED ON THE

FINDINGS IN THE RESEARCH LIT-

ERATURE WERE THEN OFFERED.

INTRODUCTION

The game of tennis has changeddramatically in the past 30years. This is probably most

evident in groundstroke techniqueand strategy. Modern players oftenhit aggressive high-speed ground-strokes to overpower their opponent.

This strategy places extra stress on theplayer’s body that strength and condi-tioning professionals should considerin designing training programs. Thisarticle will summarize recent researchrelated to the biomechanics of tennistechnique and propose specific condi-tioning exercises that logically wouldtend to improve performance and re-duce the risk of injury in tennis.

CHANGES IN TECHNIQUE

Traditional tennis groundstrokes werehit from a square or closed stance witha long flowing stroke using simulta-neous coordination of the body. Themodern forehand and even the back-hand (particularly the 2-handed back-hand) are more often hit from an openstance using sequential coordination ofthe body. Elite tennis always had these2 styles of groundstrokes (1), but sincethat time, there has been a reversalfrom primarily simultaneous to sequen-tial groundstroke technique. Thischange in the coordinated use of the‘‘kinetic chain’’ suggests that the load-ing and injury risk to major segmentsof the body may have changed intennis (11).

It is not possible to uniquely track thetransfer of mechanical energy in a 3-dimensional movement of the humanbody, but it is generally accepted thatmost of the energy or force used toaccelerate a tennis racket is transferred

to the arm and racket from the largermuscle groups in the legs and trunk(5,15,21). While it is believed thatoptimal use of the kinetic chain willmaximize performance and reduce therisk of injury (6,11), the transfer of forceand energy to the small segments andtissues of the upper extremity do placethem under great stress. For example,medial elbow pain is on the rise intennis players most likely because ofthe transfer of energy from the legsand trunk in forehands and serves. Thisfocuses stress on the medial elbowregion in the bent-arm sequential co-ordination in these strokes. The nextsections will summarize recent re-search on technique issues specific toeach groundstroke that are importantto consider when planning condition-ing programs. Several reviews of thebiomechanics of tennis are available forinterested readers (5,15,18).

FOREHAND

Vigorous extension of the lower ex-tremity in classic closed stance fore-hands creates greater axial torques torotate the pelvis and hips than notusing the legs (9). While this transfer ofenergy has not been tested in open

KEY WORDS :

kinetic chain; tennis-specific training;technique analysis

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stance forehands, it is logical thatvigorous leg drive also transfersenergy to trunk rotation. Knudsonand Bahamonde (16) reported non-significant differences in racket pathand speed at impact between open andsquare stance forehands of tennisteaching professionals. As stated byRoetert and Reid (20), there are 2things to remember related to theseforehand stances: (a) open stances areoften situation specific and (b) bothstances use linear and angular momen-tum to power the stroke. Situation-specific forehands refer to the need toproduce different types of forehandsdepending on where the player is in thecourt, the purpose of the shot (tactics),amount of preparation time available,as well as where the opponent is duringthe same scenario. Tennis players needto create differing amounts of force,spin, and ball trajectories from a varietyof positions, and this has resulted inadaptations of stroke mechanics andstances. The most common situationswhere open stance forehands areapplied include wide and deep ballswhen the player is behind the baselineor requires greater leverage to producethe stroke.

Vigorous axial hip and upper-trunkrotation allow for energy transfer fromthe lower extremity to the upperextremity in the square stance fore-hand. The upper trunk tends tocounter-rotate about 90 to 100� fromparallel to the baseline and about 30�beyond the hip in the transverse plane(22) in preparation for the stroke.Forward axial torque to rotate the hipsachieves its peak at the initiation ofthe forward stroke (8). Forward rota-tion of the upper trunk coincides witha lag in the upper extremity resisted byeccentric muscle actions and large peakshoulder horizontal adductor andinternal rotation torques (3). Well-coordinated sequential rotations upthe kinetic chain through the trunkand upper extremity take advantage ofthe stretch-shortening cycle of muscleactions.

The forearm flexors and grip muscula-ture are also important in the tennis

forehand. Not because these musclescreate a great deal of joint rotation toaccelerate the racket (4) or becausegrip forces increase ball impulse (13),but because the energy from the lowerbody and trunk must be transferred tothe racket in the later stages of thestroke. In fact, the preferred style ofgrip and height of the ball at impactused by the player significantly affectsthe potential contribution of thehand/wrist rotation to racket speed(4). The main kinetic chain motionsthat create racket speed in the fore-hand are trunk rotation, horizontalshoulder adduction, and internal rota-tion (4). Modern forehand technique(typically utilizing grips ranging be-tween eastern and western grips)clearly involves sequential coordina-tion that takes advantage of stretch-shortening cycle muscle actions.Training exercises should, therefore,emulate this sequential coordination,as well as stabilizing musculature.Following impact in all tennis strokes,the racket and arm retain the vastmajority of the kinetic energy frombefore impact, so the eccentricstrength of the musculature active inthe follow-through should also betrained. Eccentric strength both inthe upper and in the lower body canassist in maximizing tennis perfor-mance as well as to aid in the pre-vention of injuries (12). Particularly, thecatching phase of the medicine ball(MB) tosses in Figures 4–7 helps inimproving both upper- and lower-body eccentric strength.

Figure 1a–c show the preparationphase of the open stance forehand.The player’s weight transfer from hisright leg to his left leg (he is lefthanded) shows the horizontal linearmomentum used to preload the left legfor a stretch-shortening cycle action toinitiate the stroke. Some of the energystored in this leg is converted topredominantly upward (vertical linear)momentum but also forward (horizon-tal linear) momentum. This leg driveutilizes ground reaction forces and iscritical for linear to angular momentumtransfer and the development of high

racket speed. In Figure 1d–f, we can seethe forward swing. The pronouncedhip and shoulder rotation from Figure1c–f is evidence of the use of angularmomentum. Energy from the left legis transferred as the hips open up first,followed by the shoulders. The com-pletion of the swing shows a follow-through in the direction of the targetuntil well after contact is made fol-lowed by the racket swinging backover the head as a result of the forcefulrotational component of the swing.This follow-through, where the racketactually finishes over the head, is anadaptation that many players haveimplemented, and although the follow-through is initially still toward thetarget (Figure 1e), the overall pathwayof the stroke (Figure 1f ) ending upover the shoulder allows the playerto impart greater spin on the ball.This adaptation is partially the resultof technology changes in the tennisracket and strings allowing for morepower and spin generation resultingin more margins for error on thestrokes.

ONE-HANDED AND TWO-HANDEDBACKHAND

Training the wrist extensors is partic-ularly important for tennis playersusing a 1-handed backhand. Torquesabout the wrist in 1-handed backhandsare greater than direct force loading(14) and can create a rapid stretch ofthe wrist extensors that is more pro-nounced in players with a history oftennis elbow (17). This is strongretrospective evidence that trainingof the wrist extensors and grip maybe useful to reduce the risk of thecommon overuse injury of the lateralepicondyle.

There are differences in the use of thelegs, trunk, and upper extremity be-tween the 1- and 2-handed backhands.One-handed backhands have the hit-ting shoulder in front of the body andrely less on trunk rotation and moreon coordinated shoulder and forearmrotations to create the stroke (Figure2a–f ). Front-leg extensor torques arelarger in the 1-handed backhandthan the 2-handed backhand (19).

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Biomechanics of the Tennis Groundstrokes

Two-handed backhands have largerextension torques in the rear leg, whichresult in larger axial torques to rotatethe hips and trunk than 1-handedbackhands (2,10,19). Greater upper-trunk rotation has been observed in2-handed backhands than in 1-handedbackhands (19). Note the hip and trunkrotation in the 2-handed backhand(Figure 3a–f ).

Despite these differences, skilled play-ers can create similar levels of racketspeed at impact in 1- and 2-handedbackhands (19). In general, there are2 styles of coordination in 2-handedbackhands. One essentially involvesstraight arms and 4 major kinetic chainelements (hips, trunk, shoulder, and

wrist), while the other adds rotationsat the forearm (7,19). Whatever thetechnique adopted, the strength andconditioning professional should workwith the tennis coach to customizetraining programs for the specifictechniques used by players.

EXERCISES

Examples are described for forehands(right-handed players), but they shouldalso be performed on the opposingside to mimic movements required forbackhand strokes.

MEDICINE BALL DEEPGROUNDSTROKE

The purpose was to train the athlete tomove efficiently to deep balls behind the

baseline and to be able to producegreater energy transfer from openstance position that will translate intogreater weight transfer, trunk rotation,and more effective stroke productionfrom deep in the court (Figure 4).

The athlete starts on the center servicemark and the coach/trainer throws theMB about 3 to 5 feet behind and to theright. The athlete will need to moveback and across quickly to catch theMB (loading phase) and then whilemaintaining dynamic balance producea forceful hip turn and throw that willmimic the muscle contractions andmovements required for a deep de-fensive forehand stroke (for a right-hander).

Figure 1. (a–f ) Forehand groundstroke—(a–c) illustrates the preparation phase of the open stance forehand, while (d–f ) illustratesthe forward swing.

Strength and Conditioning Journal | www.nsca-lift.org 43

MEDICINE BALL SHORTGROUNDSTROKE

The purpose was to train the athlete tomove forward and in a balanced fash-ion transfer energy from the lowerextremities (open or square stance) toweight transfer and hip/trunk rotationfor more effective stroke production(Figure 5). In Figure 5, the athlete isdemonstrating a closed stance catchingposition. This movement can also beperformed using an open stance catch-ing position.

The athlete starts on the center serviceline and the coach/trainer throwsthe MB about 3 to 5 feet in front andto the athlete’s right. The athlete will

need to move forward and acrossquickly to catch the MB (loadingphase) and then while maintainingdynamic balance produce a forcefulhip and trunk rotation to throw theMB. This will mimic the movementand muscles used during a short at-tacking forehand.

MEDICINE BALL WIDE

The purpose was to train the athleteto move sideways and to be able toproduce greater energy transfer froman open stance position (Figure 6).This position will produce greaterweight transfer, trunk rotation, andmore effective stroke production onwide balls.

The athlete starts on the centerservice line and the coach/trainerthrows the MB about 5 feet to theright of the athlete. The athlete willneed to move laterally (utilizing eitherthe shuffle or the crossover step) tocatch the MB (loading phase) and thenwhile maintaining dynamic balanceproduce a forceful hip and trunkrotation to throw the MB. Thismovement sequence will mimic themovement and muscles used in a wideforehand.

MEDICINE BALL WALL OPENSTANCE

The purpose was to develop rotationalhip and core strength in movement

Figure 2. (a–f ) One-handed backhand groundstroke—(a–c) illustrates the preparation phase of a 1-handed closed stance backhand,while (d–f ) illustrates the forward swing.



patterns and planes that are most usedduring tennis strokes (Figure 7).

The athlete starts about 5 to 8 feetfrom a solid wall and loads the hips

and core while also putting the

oblique muscles on stretch. From

this loading position (Figure 7 demon-

strates an open stance loading

position), the athlete forcefully

rotates the hip and upper body to

release the MB as hard as possible

against the wall.

Figure 3. (a–f ). Two-handed backhand groundstroke—(a–c) illustrates the preparation phase of a 2-handed open stance backhand,while (d–f ) illustrates the forward swing.

Figure 4. Medicine ball deep groundstroke drill.


CABLE ROTATION IN THETRANSVERSE PLANE

The purpose was to develop rotationalcore strength in the transverse plane(Figure 8).

The athlete grasps the handle of a cablepulley machine at the height of thewaist. The athlete takes 3 to 5 stepsfrom the machine to increase thetension and lowers the body intoa quarter squat position. From thisposition, the athlete slowly rotatesthrough the transverse plane as far asthe athlete’s flexibility allows. Thismovement is then repeated on theway back to the starting positionfocused on developing decelerationability in this same plane of motion.

WRIST ROLLER

The purpose was to increase gripstrength and endurance via forearmflexion and extension (Figure 9).

The athlete grasps the wrist rollerdevice with both hands at shoulderheight. The athlete flexes and extendsthe wrist to lower the weight. Once theweight is lowered as far as possible,the athlete then flexes and extends thewrist to lift the weight back up to thestarting position.

WEIGHTED FOREARMPRONATION AND SUPINATION

The purpose was to develop forearmstrength and endurance in pronationand supination (Figure 10).

Figure 5. Medicine ball short groundstroke drill.

Figure 6. Medicine ball wide groundstroke drill.

Figure 7. Medicine ball wall open stance groundstroke drill.



The athlete places their forearmon a table or bench while graspinga head heavy instrument (a weightedbar and hammer are both goodoptions). Figure 10a demonstrates

a forearm pronation movement, andFigure 10b demonstrates a forearmsupination movement. Both thesemovements are used during tennisgroundstrokes.

SUMMARY AND APPLICATIONSFOR COACHES

The purpose of this article was to helpcoaches recognize the unique aspectsof tennis groundstrokes, with specificimplication for how they can train theirathletes. Again, the 2-fold approach ofthis article was to help practitionersrealize the types of training that will (a)improve performance by creating moreforce within muscle groups, improvecoordination between various bodyparts involved in each stroke, anddevelop overall power in the athlete’sstroke production and (b) developstrength in the various body partsand across joints that would protectthe athlete from injury.

Practical exercises have been offeredthat will emulate the stroke coordina-tion to improve the efficiency of strokeproduction as well as exercises that willimprove the athlete’s ability to deceler-ate specific body parts to assist inrecovery after the execution of thespecific stroke. The exercises denotedin this article are designed to help thecoach with on-court and off-courttraining so that various training sitescan be utilized for effectiveness intraining. For example, MB drills areoffered to help the athlete, not onlymove and get in position properly but

Figure 8. Cable rotation (in the transverse plane) drill.

Figure 9. Wrist roller drill.


also to execute the form of the stroke inthe proper pattern. Coordination ofbody weight transfer is discussed as well.

Finally, there is a demonstration ofhow the legs, hips, and torso shouldmove in synchrony as well as in-struction on how to develop coordi-nation so the athlete can utilize thekinetic chain more effectively. It isanticipated that coaches will be able toprovide a safer yet more productiveand effective strength training regimenfor their athletes.

E. Paul

Roetert isManagingDirector ofCoachingEducation andSport Science atthe United StatesTennis Association.

Mark Kovacs isSenior Managerof Strength andConditioning/Sport Scienceat the UnitedStates TennisAssociation.

Duane

Knudson isChair of thedepartment ofHealth andHumanPerformance atTexas StateUniversity.

Jack Groppel isco-founder of theHumanPerformanceInstitute.

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Documents

Bio Mechanics of the Tennis Ground Strokes