Biomechanical analysis of the deadlift duringthe 1999 Special Olympics World GamesRAFAEL F. ESCAMILLA, TRACY M. LOWRY, DARYL C. OSBAHR. and KEVIN P. SPE-ERMichael W. Krzvzewsk-i HBumanz Perfrmance Laboratoro. Division qf Orthopaedic Surgern, Duke University MedicalCeenter, Durhain. NC

ABSTRACTESCAMILLA. R. F., T. M. LOWRY, D. C. OSBAHR. and K. P_ SPEER. Biomechanical analysis of the deadlift during the 1999Special Olymnpics World Games. Med. Sci. Spors Exer:.. Vol. 33. No. 8. 2001. pp. 1345-i353 Purpose: Improper lifting techniquesmas increase injuiy risks and decrease performance. The aim of this study, was to compare and contrast biomechanical parametersbetween sumo and conventional style deadlifts and between high- and iow-skilled lifters who participated in the powerlifting eventduring the 1999 Special Olympics World Games. Methods: Two synchronized video cameras collected 60 Hz of data from 40 subiects.Parameters were quantified at barbell liftoff tLO). when the barbell passed the knees MKPI and at liff compietion. Results: Comparedwith the conventional group. the sumo group had a 100*% greater stance width. 20% smaller hand width. 10% less vertical bar distance.a more vertical tink at LO. a more horizontal thigh at LO and KP. a less vertical shank at KP. and greater forefoot abduction, Thesumo group generated ankle dorsiflexor. knee extensor, and hip extensor moments0, whereas the conventional group produced ankleplantar flexor. knee flexor and extensor, and hip extensor moments. Compared with low-skilled lifters, high-skilled lifters hiadl a 40%greater barbell load. 15% greater stance width (surno group only). greater knee flexion at LO tconventiona! group only}. greater kneeextenson at KP. a less vertical shank: position at LO (sumo group only{, 15% less vertical bar distance, less first peak bar velocitybetween LO and KP (conventional group oniv. smaller plantar flexor and hip extensor moment arms at LO and KP. and greater kneeextensor, moment arms at LO. Conclusions: The sumo deadlift may be more effective in working ankle dorsiflexors and knee extensors.whereas the conventional deadhtft may be more effective in working ankle plantar flexors and knee flexors. High-skilled lifters exhibitedbetter lifting mechanics than low-skilled lifters by keeping the bar closer to the body, which may both enhance performance andminimize injury risk. Key Words: POWERLIFTING. JOINT MOMENTS. JOINT MOMENT ARMS, JOINT ANGLES. SEGMENTANGLES. KINEMATICS. KINETICS, MECHANICAL WORK

T he deadlift is one of three lifts in powerlifting com-petition. This exercise, which measures overall body

rr strength. begins with the lifter in a squat position.arms straight and pointing down, and an alternating handgrip used to hold a bar positioned in front of the lifter's feet.The deadlift is performed using either a conventional orsumsy style (Figs. I and 2). The primary differences betweenthese two styles are that the feet are positioned further apartand turned out in the sumo style, and the arms are positionedinside the knees for the sumo style and outside the knees forthe conventional style (5).

There are eight known studies that have examined bio-mechanical variables during the barbell deadlift (1-3.5-8.] 1). Three studies examined lumbar spinal loads (2.3.6).two studies ,nvestigated the effects of intra-abdominal andintra-thoracic pressures (7,8). one study quantified joint andsegmental angles (II ). and two studies calculated joint andsegment angles and joint moments (1,5). However. onlythree of these studies compared kinematic or kinetic param-eters between sumo and conventional deadlifts (3.5.1 1).Escamilla et al. (5). who conducted the onlv known three-

0195-9131/011330- 1345!$300/10MEDICINE & SCIENCE IN SPORTS & EXERCISE,Copyright e 2001 by the American College of Sports MedicineSubmitted for publication April 200(1)Accepted for publication No ember 20N00.

dimensional (3-1D) biomechanical analysis of the deadlift,examined kinematic and kinetic variables between sumoand conventional deadlifts during a national powerliftingcompetition. These authors found several significant kine-matic and kinetic differences between the sumo and con-ventional deadlifts, They also reported that a two-dimen-sionalf (2-D) biomechanical analysis was adequate whenanalyzing kinematic and kinetic parameters during the con-ventional deadlift. but a 3-D analysis was needed to accu-rately calculate these parameters during the sumo deadlift.McGuigan and Wilson (11) performed a 2-0) kinematicanalysis using male lifters from two regional powerliftingchampionships. The only significant differences they ob-served were that the sumo group had a more upright trunkand less hip flexion at liftoff. and the shank range of motionwas greatest in the sumo group. Cholewicki et al. Q3) quan-tified lumbar loads and hip and knee moments between thesumo and conventional deadlifts during a national power-lifting championship. They found significantly greaterL4.1L5 shear forces and moments in the conventional group,whereas hip and knee moments were not significantly dif-ferent between the two deadlift styles.

In the three known studies that have compared biomechani-cal parameters between sumo and conventional deadlifts,skilled powerlifters without mental retardation were utilized.There are no known studies that have examined biomechanicalparameters for athletes with mental retardation. such as in the

1345

FIGURE 1-High (top)- and low (bottom)-skilled sumo deadlifts.

Special Olympics powerlifting competition. All participants ofthe 1999 Special Olympics World Games had varying levels ofmental retardation, with an intelligence quotient generally lessthan 80. Although all powerlifters in the Special Olympicshave coaches, most of these coaches are not experts on theproper techniques of performing the deadlift, but rather volun-teers who have an interest in supporting athletes with mentalretardation. It is believed that results from the current study willaid coaches and volunteers in teaching proper lifting mechanicsto powerlifters competing in Special Olympics powerliftingcompetition.

Since powerlifting is one of the events in Special Olym-pics competition, it was the purpose of the current study toquantify and compare joint and segment angles, ankle, knee,and hip moments, and ankle, knee, and hip moment armsbetween sumo and conventional deadlifts during the 1999Special Olympics World Games. These biomechanical pa-rameters are important because improper lifting mechanicscan both increase injury risk and decrease performance. Itwas hypothesized that significant kinematic and kinetic dif-ferences would be found between sumo and conventionaldeadlifts. In addition. high- and low-skilled lifters werecompared with each other for both sumo and conventionaldeadlifts, with skill level determined by normalized bodyweight and load lifted. High- and low-skilled lifters per-forming the deadlift were biomechanically analyzed byBrown and Abani (l) in a study of powerlifters withoutmental retardation during the 1981 Michigan Teenage Pow-erlifting Championships. These authors reported several sig-

1346 Official Journal of the American College of Sports Medicine

FIGURE 2-High (top)- and low (bottom)-skilled conventionaldeadlifts.

nificant kinematic and kinetic differences between low- andhigh-skilled lifters. It was hypothesized that the high-skilledgroup would maintain a more erect trunk and generate asmaller hip extensor moment arm and vertical bar distancecompared with the low-skilled group.

MATERIALS AND METHODSSubjects. Over 200 powerlifters from 22 countries par-

ticipated during the powerlifting competition (squat, benchpress, and deadlift) of the 1999 Special Olympics WorldGames, which was held in Raleigh. NC. Approximately150-175 of these lifters performed the deadlift. Becausemost of these lifters were male, the current study waslimited to male subjects. Forty male powerlifters, 20 sub-jects performing the conventional deadlift and 20 subjectsperforming the sumo deadlift, were randomly selected fromthe 150-175 lifters to serve as subjects. These 40 subjects,who represented 13 different countries, all wore a one-piecelifting suit during competition. Written informed consentwas obtained and approved by the Special Olympics WorldGames organization committee and by the institutional re-view board of Duke University Medical Center. Mean age,body mass, body height, and load lifted are shown inTable 1.

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TABLE 1. Anthrooometric. temporai. and worK comparisons Imean t SD) between sunmo and conventional deadlift groups and betveen high- and iow-skilled deadlift groups,Sumo Group Conventional Group High-Skilled Group Low-Skilled Group

-- ____ (P1= 20) (N{= 20) (NP= 20) (N =20)Age (yri 24.9 5.5 25,2 - 4.2 24.8 4.5 25.3r 5.2Body height itcmBody mass (kg)Barbell load tkgiSchwartz score (pis)Stance width (cm'iStance width (% shoutfer width)'Hand width tcmi

Total lift time is}Time from liftoff to knee passing (s;Time at sticking point (s;

-68875.t- 19.2

125.5 31.987.9 t 20.5

73 + I2F194 t 30Q50 10

2.39 a. 0.710.38 Q.191.59 0.31

167 - 4076.1 .- 13.0

137.8 49.391,9 - 26.9

37 _ 10D93 _ 2563 101

2.36 0.700.74 0.201.63 t 0O50

154.3 U 8.571.6 t 13.9

154.3 _ 41_5't09.0 . 15.40

58.1 1 24.3'.52.2 66.554.7 - 1 0.9

2.36 + 0.660.75 . 0.161.58 0G42

156.9 ' 9.880.3 + 17.4

109.0 - 26.870.7 t 1 1.93

51.8 - 18.7134.3 + 47.557.8 ' 13.3

2.38 10 0.740.80 t 0.231.65 0- 0.42

Total vertical bar distance l%4 height} 27.7 1 3.50 30.2 + 2,3 27.2 2.54' 30,7 - 2 gbTotal vetical baF distance (cm) 46.6 4.73 50.6Q 5.8a 45.2 - 5.20 51.9 + 6.1'Total mechanical work on bar 13 338 886 402 + 103" 413 + 1190 328 - 85b

The sumo and conventional groups consisted of both high- and low-skilied lifters combined whereas the high- and low-skilled groups consisted of both sumo and conventional lifterscombined.

Significant differences (P < 0.01) betw een sumo and conventional groups.tSigreficant differences ;P < 0.01) between high- and low-skilled groups'Significant interactior Wdeadlift style x skil] level" (P < 0.01).

The Schwartz score. which is used in powerlifting com-petition to normalize the barbell load to each lifter's bodymass, was used to compare relative loads lifted betweensumo and conventional groups. The Schwartz score is de-termined by multiplying the load lifted by a body mass-dependent coefficient. These coefficients range between1.2803 and 0.4796 for corresponding body masses between40.9 and 164.5 kg. Therefore, small body mass individualsare assigned a high coefficient, and large body mass indi-viduals are assigned a low coefficient. A complete list ofSchwartz coefficients for any given body weight can befound in official powerlifting rulebooks. The Schwartz scorewas also used to rank from high to low the 20 subjects in theconventional group and the 20 subjects in the sumo group.Subjects with the top 10 Schwartz score rankings in thesumo and conventional deadlift groups were classified ashigh-skilled lifters, and those with the bottom 10 Schwartzscore rankings in the sumo and conventional deadlift groupswere classified as low-skilled lifters. Therefore. both thehigh-skilled and low-skilled groups had a total of 20 sub-jects. High- and low-skilled sumo and conventional liftersare shown in Figures I and 2.

Data collection. Two synchronized gen-locked PeakPerformnance video cameras (Peak Performance Technolo-gies, Inc., Englewood. CO) were used to collect 60-Hz videodata. One camera faced the subject's left side and the othercamera faced the subject's right side, with each camera'soptical axis forming a 45' angle to the sagittal plane of thelifter. The cameras were positioned approximately 12 mnapart and faced perpendicular to each other. with eachcamera approximately 8 m from the subject. To minimizethe effects of digitizing error. the cameras were positionedso that the lifter- barbell system was as large as possiblewithin the viewing area of the cameras.

Approximately 10 flights itwo flights per day) of thedeadlift competition were videotaped over a 5-d period. withapproximately 10-15 lifters in each flight. For each camera

BiOMECHANICAL ANALYSIS OF THE DEADLIFT

view, videotaping began approximately 3 min before a lifterstarted his lift and ended approximately 2-3 min after thecompletion of the lift. An event synchronization device(Peak Performance Technologies, Inc.) was used- to generatea time code directly onto the video signals, thereby allowingcorresponding time-synchronized video frames between thetwo videotapes to be determined. Before and just after thesubjects were videotaped, a 2 x 1.5 X 1-rn 3-D calibrationframe (Peak Performance Technologies. Inc.). surveyedwith a measurement toierance of 0.5 cm., was positioned andvideotaped in the same volume occupied by the lifter-barbell system. The calibration frame was composed of 24spherical balls of known spatial coordinates. with the x- andz-axes positioned parallel to the ground and the v-axispointing vertical.

Data analysis. According to the International Power-lifting Federation rules at the time of the current study, asuccessful deadlift involved the barbell being lifted upwardin a continuous motion until the lifter was standing erectwith knees locked and the shoulders thrust back in line withthe torso. Causes for disqualification included lowering thebarbell before the referee's "'down" signal at the completionof the lift, any downward movement of the bar once the barleaves the lifting platform, failure to stand erect with lockedknees and shoulders thrust back, any shifting of the feet, andany "hitching," bouncing, or resting of the bar aeainst thethighs during the lift. All deadlift trials analyzed in thecurrent study were in accordance with these InternationalPoerlifting Federation rules.

In powerlifting competition, a lifter is given threeattempts during the deadlift to maximize the amount ofweight they can lift. A lifter's first attempt is usuallysubmaximal; their second and third attempts are near themaximal weight they are capable of lifting. Therefore.only second and third attempts that were successfullycompleted (i.e., ruled a "good lift" by at least two of thethree judges) were analyzed. Twenty-four of the 40 lifts

Medicine & Science in Sports & Exercises 1347

analyzed were third attempts. The 16 second-attempt liftswere used because the third attempts were unsuccessfuldue to the lifter attempting a weight that was beyond theirone repetition maximum (1 RM), or the lift was disqual-ified due to a rules infraction. Therefore, it was believedthat all lifts analyzed were near each lifter's I RM.

Three events were defined during the deadlift. The firstevent was barbell liftoff (LO), which was defined as the firstpicture in which the barbell disks on both sides of the barwere no longer in contact with the lifting platform. Becauseboth sides of the bar typically remained symmetricalthroughout the lift, the left- and right-side barbell disks leftthe lifting platform at approximately the same time. There-fore, at LO the lifter was supporting the entire barbell load.The next event was at the instant the bar passed the knees(KP), which was defined as the first picture when the ver-tical position of the bar was higher than the vertical positionof the knees. The last event was lift completion (LC). whichoccurred when the lifter was in an upright position with theknees and hips fully extended and the shoulders thrust back.At this time, the head judge gave the "down" command,signaling the end of the lift. Total lift time was defined fromLO to LC.

A 3-D video system (Peak Performance Technologies,Inc.) was used to manually digitize data for all 40 subjects.A 15-point spatial model was created, comprising the top ofthe head and centers of the left and right mid-toes, ankles,knees, hips, shoulders, hands. and end of bar. All pointswere seen in each camera view. Each of these 15 points wasdigitized in every video field (60 Hz), which was adequatebecause of the slow movement of the lift (1,3,5.10). Digi-tizing began 15 video fields (0.25 s) before LO and ended 15video fields after LC.

A fourth-order, zero-lag Butterworth digital filter wasused to smooth the raw data with a cutoff frequency of S Hz(4,5,1 11). Using the direct linear transformation method(15,16), 3-D coordinate data were derived from the 2-Ddigitized images from each camera view. An average re-sultant mean square calibration error of 0.3 cm produced anaverage volume percent error of 0. 121.

The origin of the 3-D orthogonal axis system was firsttranslated to the right ankle joint and rotated so that thepositive x-axis pointed to the left ankle joint, the positivez-axis pointed anteriorly in the direction the lifter was fac-ing, and the y-axis pointed in the vertical direction (5). Thevertical positions of the digitized left and right ankles werewithin 1 cm of each other. This axes system was initiallyused to calculate all joint moments, joint moment arms, andjoint and segment angles. Because hip flexion and extensionduring sumo and conventional deadlifts occur primarily inthe y-z sagittal plane about the x-axis, hip moments werecalculated about the x-axis and hip moment arms werecalculated in the z-axis direction. Because the feet wereturned approximately 15-25' during the deadlift, ankle andknee flexion and extension occurred in a plane between they-z sagittal plane and x-y frontal plane established above.Therefore, erroneous moment arm measurements would oc-cur if the above axes system were used for a 3-D analysis,

1348 Official Journal of the American College of Sports Medicine

because ankle and knee movements do not occur in thesagittal plane during the sumo deadlift (5). Therefore, theaxes system was translated to each ankle joint center androtated so that the positive z-axis pointed in the direction ofthe mid-toes, the y-axis pointed vertical, and the x-axis wasorthogonal to the y- and z-axes. Hence, for both sides of thebody, ankle and knee moments were calculated about thex-axis, and ankle and knee moment arms were calculated inthe z-axis direction.

Linear and angular displacements and velocities werecalculated for both the left and right sides of the body andthen averaged (5). Escamilla et al. (5) have previouslydemonstrated the symmetrical nature of the deadlift. show-ing negligible differences between left- and right-side kine-matic measurements. Relative knee and hip angles andabsolute trunk, thigh, and shank angles were defined inaccordance with previous studies (1,5,1 1). Trunk, thigh, andshank angles were measured relative to the x-z horizontalplane (i.e., relative to a sagittal view of the lifter's rightside). Knee angles were measured relative to the thigh andleg segments. Although the hip angle is actually formedbetween the pelvis and the femur, this measurement cannotaccurately be determined without external markers affixedto these segments. Therefore, the hip angle was defined asthe relative angle between the trunk (hip to shoulder seg-ment) and thigh (hip to knee segment). As long as the trunkremains rigid and straight, this relative angle approximatesthe true hip angle. However, during the deadlift the trunkdoes not remain rigid and straight, because spinal flexioncauses the back to round to some extent, especially whenmaximum weight is used. As the spine flexes during thedeadlift. the shoulders drop downward, causing the hipangle measurement to decrease and underestimate its truevalue. Foot angle was defined as the angle formed betweenthe foot segment and the y-z sagittal plane. Stance widthwas defined as the linear distance between the left and rightankle centers, and hand width was defined as the lineardistance between the left and right hand centers.

Escamilla and colleagues (5) have shown that during theI RM deadlift the barbell initially accelerates at LO to a firstpeak velocity (acceleration phase), then decelerates to a mini-mum velocity (sticking region), accelerates again to a secondpeak velocity (maximum strength region), and finally deceler-ates until l C (deceleration phase). These lifting phases andregions were calculated in the current study.

Because segment and barbell accelerations are very smallwhile lifting maximum or near maximum loads, joint mo-ments can accurately be calculated using quasi-static models(9,10,12-14). Lander et al. (10) found that joint momentsvaried less than I % between quasi-static and dynamic anal-yses during the squat exercise with near maximum loads.Left and right hip, knee, and ankle moments and momentarms were calculated at LO, KP, and LC and then averaged(5). Escamilla et al. (5) have previously demonstrated neg-ligible differences between left- and right-side kinetic mea-surements. Joint moments and moment arms were calcu-lated relative to the barbell center of mass (COMbar) (5). Thegeometric center of the barbell represented COMbar. The x-,

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TABLE 2. Joint and segment angles ,mean t SD) between sumo and conventional deadlit groupc and between high- and low-skillea deadlift grouns.Sumo Group Conventional Group High-Skilled Group Low-Skilled Group(N =20) (1 = 20) l# = 20) ( = 20)

LiftoffHip (l? 59 9 56 - 8 59 -7 55 -10Knee e 12. _ 12 12. 12 121 t 7 120 t 16Truntkl 0 16-62 11 7 1 5-7 12-0Th igh; 143t 6 136 6 139 5 1409 0Shank !73-5 74-5 72 4 74-6

Knee passingHip 101 -3 1C1 -11 104 11 98 13Knee l 158 tI 159-6 162-6D I55- 7Trunk I') 36 8 32.7 36 8 32 8Thigh .23-6D 111--67 115 8 116 8ShankfX 74 7 62 3 4 77- 8 80 6

Littoff to knee passing rangeHip fE 42 --7 45t9 44 8 43 9Knee - 37 -14 38 12 4 - 9 36 -16Trunk. j' 20 -8 2.6 21-7 20 8Thigh (l 23 8 25- 24-6 23- 0Shank( 16i g I7a 5 8 67Minimum bar veiocit, (sticking poincIHip (~1 147 16R 157 t ga 151 t 8 53 t 17Knee ( 168 6 168 - 6 1695 6 f67 6TrunKt 73 11 735 74 4 72 11Thigh 109- 7 99 -4 105 t.7 103 8Shank (Y,c 694 41 814 75 9 75 -5Fool argie ( _ - 25 _ 6 15 -6 _ 20? 8 21 t 8

The sumo and conventional groups consiste of both high- and low-skilled lifters combined. whereas the high- and low-skilled groups consisted of both sumo and conventiona' lifterscombined.

Significan; differences WP< 0.01) between sumo anG conventional groups.tSignificant diffeences (F < 0.01) between high- and low-skilled groups.

Signifficant interaction (deadlift styie x skill leve!) (P

TABLE 3. Select events (M : SD) between sumo and conventional deadlift groups and between high- and low-skilled deadlift groups.Sumo Group Conventional Group High-Skilled Group Low-Skilled Group

(N =_20) (N =20) (N= 20) (N = 20)First peak bar velocity

Velocity (m -s-1) 0.503 0.117 0.536 + 0.168 0.493t 0.138 0.546 + 0.147Time occurred (i total time) 34.5 + 13.3 33.2 + 15.7 31.6 12.4 36.1 16.1Vertical bar position (% total vertical 48.7 - 13.8 47.5 + 18.4 46.8 + 14.7 49.4 17.6bar distance)

Minimum bar velocityVelocity (m * s-1) 0003 + 0046 0.015 0.041 0.016 0.033 0.002 0.052Time occurred (% total time) 70.0 _16.9 70.6 + 13.4 68.5 + 14.2 72.1 ii 16.0Vertical bar position (% total vertical 92.4 i 14.2 95.7 5.0 94.9 5.5 93.1 14.1bar distance)

Second peak bar velocityVelocity (m s) 0.113 0.086 0.091 + 0.044 0.104 0.061 0.099 + 0.075Time occurred (% total time) 78.7 + 14.7 79.1 13.0 74.8 13.3 82.8 t 13.3Vertical bar position (% total vertical 96.0 t 7.5 97.9 3.9 96.9 4.5 97.1 t 7.1bar distance)

The sumo and conventional groups consisted of both high- and low-skilled lifters combined, whereas the high- and low-skilled groups consisted of both sumo and conventional lifterscombined. There were no significant differences (P < 0.01) observed between sumo and conventional groups and between high- and low-skilled groups.a Significant interaction (deadlift style x skill leve!) (P < 0.01).

low-skilled conventional group (123 5). Knee angle atLO was not significantly different between high- andlow-skilled sumo groups.

Select events and lifting phases are shown in Tables 3 and4. Vertical bar velocity remained low throughout the lift.MVB occurred at 70% of the total lift time and 90-95% ofthe total vertical bar distance. No significant differenceswere observed between sumo and conventional groups andbetween high- and low-skilled groups. The ANOVA re-vealed a significant deadlift style X skill level interactionfor first peak bar velocity between LO and KP, which wasapproximately 25% less in the high-skilled conventionalgroup (0.465 0.133 m-s- l) compared with the low-skilledconventional group (0.607 + 0.147 m-s 1>. In contrast,there was no significant difference in first peak bar veloc-ities between high- and low-skilled sumo groups.

Joint moments and moment arms, which are relative tobarbell loads, are shown in Table 5. Positive moment: armsare anterior to a joint, producing positive hip flexor, kneeextensor, and ankle dorsiflexor load moments. Hip extensor.knee flexor. and ankle plantar flexor resuitant muscle mo-ments are needed to counteract these load moments. Nega-tive moment arms are posterior to a joint. producing nega-tive hip extensor, knee flexor, and ankle plantar flexor loadmoments. Hip flexor, knee extensor, and ankle dorsiflexorresultant muscle moments are needed to counteract theseload moments. At LO, KP, and LC, ankle and knee momentsand moment arms were significantly different betweensumo and conventional groups. The sumo group generatedankle dorsiflexor moments exclusively, whereas the con-

ventional group generated ankle plantar flexor momentsexclusively. Although at LO both groups generated kneeextensor moments, at KP and LC the conventional groupgenerated knee flexor moments, whereas the sumo groupgenerated knee extensor moments. Although both sumo andconventional groups generated hip extensor moments, hipmoments and moment arms were not significantly differentbetween the groups. At LO, the high-skilled group hadsmaller hip extensor moment arms, larger knee extensormoments and moment arms, and larger ankle dorsiflexormoment arms compared with the low-skilled group. At KP,hip extensor moment arms were smaller in the high-skilledgroup compared with the low-skilled group. There were nosignificant deadlift style x skill level interactions.

DISCUSSIONOn the average, the total lift time was approximately 2.4 s

for both sumo and conventional groups (Table 1), which issimilar to the total lift times of 1.9-2.1 s reported byMcGuigan and Wilson (1 1) and 2.4 s reported by Brown andAbani (1). However. 2.4 s is approximately 35-40% lessthan the 3.6-4.1 s reported by Escamilla et al. (5) andCholewicki et al. (3). Since the lifters in the studies byEscannilla et al. (5) and Cholewicki et al. (3) were national-level powerlifters, thev may have been more experiencedthan the regional-level lifters in McGuigan and Wilson (I1l),the teenage lifters in Brown and Abani (1), and the SpecialOlympic lifters in the current study. A nmore experiencedlifter can better predict their 1 RM in competition compared

TABLE 4. Lifting phases (mean SD) between sumo and conventional deadlift groups and between high- and low-skilled deadlift groups._Sumo Group Conventional Group High-Skilled Group Low-Skilled Group

_ __ ___ ____ ___ ___

(= 20) (N4 201 _N =20) l(N= 20)Acceleration phase (% total time) 34.5 13.3 33.2 + 15.7 31.6 + 124 36.1 + 16.1Sticking region (% total time) 35.5 + 8.8 37.4 9.1 36.9 + 6.8 36.0 10.7Maximum strength region (% total time) 10. C 7.2 8.5 + 4.3 7.8 3.3 13.7 + 7.3Deceleration phase f(% total time) 21.3 t 14.7 20.9 + 13.0 25.2 t 13.3 17.2 + 13.3

The sumo and conventional groups consisted of both high- and low-skilled lifters combined, whereas the high- and iow-skilled groups consisted of both sumo and conventional lifterscombined.There were no significant differences (P < 0.01) observed between sumo and conventional groups and between high- and low-skilled groups. There were no significantinteractions (deadlift style x skill level) (P < 0.01).

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TABLE 5. Joint moments and moment arms (mean t SD) between sumo and conventional deadlifi groups and between high- and low-skilled deadlift groups.Sumo Group Conventional Group High-Skilled Group Low-Skilled Gmup(N = 20) (N = 20) (N = 20) (R = 20)

Moment arms at liftotf (cm)AnkleKneeHiu

Moments at liftoff (JN -AnkleKneeHip

Moment arms at knee passing ,cm-AnkleKneeHip

Moments at knee Dassing IN -m)AnkleKneeHiCt

Moment arms at lif completion irtmlAnkleKnee

Moments at hil completion (N m ml

-4.3 _ ---13.2 - sQ

27.9 - 6.2

-59 67- -'70 -Q- 1252

339 . 106

-5.2 t 5.3-4.8 5A423.5 5.4

-68 -742-66 ! 80V286 92

-4.2 5.28--7.6-- 5.76

7.4 t 2.5

6s . 3.71- 3.3 t 5.2227.9 5.2

83 +_ 57-5-v t 781376 -t 136

2.9 4,063.2 3.2P

2.1 t 3.6

42 t 60a45 jt 49

281 _ 9'.

4. 1 + 2,7P2,6 - 38a8.3 + 2.3

-10.5 t 6.9 25.9-i 3.21-

-2 t 104-157 108"

396 t 131

-2.5 6.0-1.6 - 6120.9 t 3.8E

-31 + 92-21 t 96313 82

-1.4A 5.8-2.4 t 6.5

7,7 t 2.1

2.67.'.t-6.0 t 7,1b29.9 z 5.9

27 t 84- :E t- t 41314 _ 97

0.3 6 6.20.0 5,9

23.8 - 4.2L

4 80-1 i 76

253 t 89

1.3 5.7-2.6 7.7

8.0 t 2.8

Ankle -54 68' 56 44' -13 t 89 14 68Knee -98 832 38 59A -32 t 101 -28 9 99ilip 92 38 115 73 12' - 7s 86 38

The sumo and conventional groups consistec ot both nigh- and low-skilled lifters combined, whereas the higS- and low-skilled groups consisted of both sumo: and conventiona. titterscombined. Positlve moment arms are anterior to joint, producing positive hip flexor, knee extensor. and ankle dorsitlexor load moments, Hip extensor. knee flexor. and ankle planrarflexor resultant muscle moments are needed to counteract these load moments. Negative moment arms are posterior to joint, producing negative nip extensor, knee flexor. and anklepiantar flexor ioad moments. Hip llexor. knee extensor, and ankle dorsiflexor resultant muscle moments are needed to counteract these load moments.

Significant differences (P < 0.01) between suno and conventiona: groups.Significant differences (P < 0.0,' between high- and low-skilled groups

There were no signrficant: interactions (deadlift styte x skill level) (P < 0.01).

with a less experienced lifter. Therefore, the subjects in thestudies by McGuigan and Wilson (I 1) and Brown and Abani(1) and those in the current studv may have slightly under-estimated their I RM. This implies that the amount ofweight the Special Olympics athletes lifted may be closer to95% of their I RM, which may slightly affect both liftingkinematics and kinetics compared with I RM lifting.

Two studies are known to have compared kinematic pa-rameters between sumo and conventional deadlifts (5,11).Whereas McGuigan and Wilson (' 1.) conducted a 2-D ki-nematic analysis. Escamilla et al. (5) conducted the first 3-Danalvsis of the deadlift. Escamilla et al. (5) demonstratedthat: erroneous results occur, especial during the sumo dead-lift, from a 2-D analysis of the deadlift. This is because thelower extremities move both in a sagittal and frontal planeduring the sumo deadlift. In comparisons of 3-D kinematicsbetween the Special Olympics powerlifters and the elitenational powerlifters from Escamilla et al.(5). the nationallifters maintained a more vertical trunk and shank and flexedthe hips less at LO and KP but had a less vertical trunk, moreknee and hip flexion. and a more horizontal thigh at MBV.The latter occurred because MBV occurs at approximately40-45% of the total lift time in national powerlifters (5,1 1)but at approximately 7 0% of the total lift time in the SpecialOlympics lifters. This implies that the percent time in eachof the four lifting phases is different between national andSpecial Olympics lifters. Compared with the percent totattimes the Special Olympics lifters spent in each lifting phasetTable 4), the national lifters spent approximately 10-15%less time in the acceleration phase and sticking regions andapproximately 10-15% more time in the maximum strength

BIOMECHANICAL ANALYSIS OF THE DEADLIFT

region and deceleration phase. This implies the nationallifters are more efficient and effective throughout the dead-lift, because spending less time in the sticking region andmore time in the maximum strength region enhances thelikelihood that a successful lift will occur.

MBV during the deadlift has previously been referred toas the "sticking point' (5). The Special Olympics liftersreached the sticking point at approximately 90% of verticalbar distance (Table 3). compared with approximately 60%of vertical bar distance by the national-caliber lifters inEscamilta et al. (5). Because bar velocity is minimal at thesticking point. this appears to be the most difficult part of thelift and is often where powerlifters fail in their attempt at asuccessful lift. This implies the most difficult part of the liftfor Special Olympic lifters was near LC. In contrast, thesticking point occurred just after KP in national lifters (5),The sticking point phenomenon mav be due in part tomechanical principles of skeletal muscle, such as to thelength-tension relationship, or to decreasing muscle momentarm lengths from KP to LC.

The lifters in the current study performed the sumo andconventional deadlifts with 5-15% wider stance and handwidths compared with the lifters from Escamilla et al. c5).Since the arms are positioned outside the legs during theconventional deadlift (Fig. 2), a wider stance may force awider hand width. If the stance widens excessively. the armsare forced to deviate from a vertical position (Fig. 2, bot-tom), causing the lifter to have to bend over to a greaterextent to grip the bar. Optimal arrn position is with the armsvertical (Fig. 2, top). because this will decrease vertical bardistance from LO to LC. The wider stance and hand widths

Medicine & Science in Sports & Exercises. t1351

may have resulted in the lifters in the current study having20-25% greater vertical bar distance from LO to LC com-pared with the lifters in Escamilla et al. (5).

Optimal stance and hand widths also allow the trunk to bein a more vertical position at the beginning of the lift. Thewider stance and hand widths in the current study may havecompromised good lifting mechanics at LO (Fig. I, bottom).because the 16 90 and 1 1 7 trunk positions measuredfor the sumo and conventional groups, respectively, areconsiderably less than the 25-33 and 17-24' trunk posi-tions, respectively, reported by other deadlift studies thatused skilled elite lifters (1,5,1 1). The increased forwardtrunk tilt at LO in the current study resulted in a 10-20'decrease in hip angles compared with several other studies(1.5.1 1). The increased forward trunk tilt at LO may pre-dispose the spine and back musculature to an increased riskof injury (123,6). Cholewicki et al. (3) reported that a moreupright trunk at LO resulted in less anterior shear force atthe lumbar L4/L5 joint. This was especially true in theconventional group, which had significantly greater forwardtrunk tilt than the sumo group at LO. since there is approx-imately 10% greater shear force and moment generated atthe L4/L5 joint in the conventional deadlift compared withthe sumo deadlift (3).

Escamilla et al. (5) conducted the only known 3-1) anal-ysis that quantified ankle, knee, and hip moment arms forsumo and conventional style deadlifts. Compared with thesumo deadlift in the current study, at LO, Escamilla et al. (5)reported 25-30% smaller hip moment arms, 30-35%greater knee moment arms, and three times greater anklemoment arms. This implies that the national lifters fromEscamilla et al. (5) used their hip extensors less and theirknee extensors and ankle dorsiflexors more compared withthe Special Olympic lifters. These hip, knee, and anklemoment arm differences occurred because the national lift-ers maintained the barbell mass closer to the body comparedwith the Special Olympics lifters. As the center of mass ofthe barbell load moves closer to the body in the sumndeadlift. hip moment arms and monments decrease and ankleand knee moment arms and moments increase. In the sumodeadlift. the greater the feet turn out (i.e.. forefoot abduc-tion). the closer the barbell can be positioned to the body.The national lifters were able to keep the barbell closer tothe body partially because they had 170 greater forefootabduction compared with the Special Olympics lifters. Thisimplies that a forefoot abduction of 40-45c may be optimalin the sumo deadlift in minimizing hip moment arms andmoments. The smaller hip moment arms and moments thatresult by keeping the barbell mass closer to the body alsoresult in smaller L4/L5 joint moments and shear forces (3).This implies that the Special Olympics lifters may increasetheir risk of injury to the low back by keeping the barbellmass further away from the body. In addition, perfornancemay also be compromised, since increasing hip and L4/L5moments may also result in less weight being able to belifted. However, performance is also dependent on the kneeand ankle moments and moment arms that are generated,which increase as hip moments and moment arms decrease.

During the sumo deadlift, the ankle dorsiflexors. kneeextensors, and hip extensors were primarily responsible forcausing or controlling ankle, knee, and hip movements.respectively. During the conventional deadlift, the ankleplantar flexors, knee flexors, and hip extensors were pri-marily responsible for causing or controlling movements atthe ankles, knees, and hips, respectively. From these data, itis hypothesized that the lower-extremity muscles involvedduring the conventional deadlift are the hamstrings. gluteusmaximus, gastrocnemius, and soleus, and the lower-extrem-ity muscles involved during the sumo deadlift are the glu-teus maximus, hamstrings, quadriceps, and tibialis anterior.Electromyography should be used during these two deadliftstyles to test these hypotheses.

At KP and LC during the conventional deadlift, smallknee extensor moments were generated by the barbell centerof mass, which attempts to extend the knees. This occurredbecause the barbell center of mass was slightly anterior tothe knee joint. To counteract this knee extensor moment,increased activity from the knee flexors is needed to gen-erate the knee flexor moment needed to control the rate andextent of knee extension. This is one reason it is hypothe-sized that the hamstrings are more active and the quadricepsless active during the conventional deadlift compared withthe sumo deadlift. Because the knee flexors are also hipextensors, they attempt to extend the hip and flex the kneesimultaneously. In contrast, because the barbell center ofmass is posterior to the knee axis during the sumo deadlift,a large knee extensor moment is needed to counteract thelarge knee flexor moment generated by the barbell load.This implies that the quadriceps may be more active duringthe sumo deadlift compared with the conventional deadlift.

In comparisons of high- and low-skilled lifters, it wassurprising that not rmore significant kinematic differenceswere observed. From the 21 kinematic variables in Table 2,only knee angle at KP was significantly different betweenhigh- and low-skilled groups. Brown and Abani (1) con-ducted the only other deadlift study that compared biome-chanical variables between high- and low-skilled lifters,with their teenage subjects performing the conventionaldeadlift. Uiniike the current study, at LO, these authorsreported significant differences in shank, thigh, hip, andknee angles between high- and low-skilled lifters. However,their results were the same as the current study at KP, withgenerally no significant differences occurring.

From LO to KP, high-skilled lifters have demonstratedlower peak bar velocities compared with low-skilled lifters(1,5), which is in agreement with peak bar velocity datafrom the current study. The greater first peak bar velocity inlow-skilled compared with high-skilled conventional lifters isprobably due to differences in body position between thesegroups. At LO, lifters often attempt to minimize hip and trunkflexion and knee extension in order to better utilize hip andthigh musculature. For example, if the knees extend prema-turely and excessively at LO, the lifter will be in a position toperform what is referred to as a "straight-leg" deadlift, whichoccurs when the knees are at or near full extension. Thisposition may result in a decrease in quadriceps activity and

1352 Official Journal of the American College of Sports Medicine http:J/www.acsmmsse.org

effectiveness, an increase in hamnstring activity (17). and anincrease in erector spinae activity due to the spine being in amore bent and rounded position. This places the lumbar spinein a more vulnerable position. with a higher risk of injurv (3.The low-skilled conventional lifters in the current study hadgreater knee extension at LO compared with the high-skilledconventional lifters. A rapid knee extension and forward trunktilt can occur near LO if a lifter attempts to "jerk" the weightoff the floor. Brown and Abani (1) have reported that low-skilled lifters attempt to "jerk" the weight off the floor at LO,althouoh these authors did not find greater forward trunk tiltand knee extension in low-skilled lifters compared with high-skilled lifters.

The greater vertical bar distance for the low-skilled groupcompared with the high-skilled group may be one reason whythe relative loads lifted by the low-skille.d groups were smallercompared with the relative loads lifted by the high-skilledloads, as shown bv the Schwartz scores. This greater verticalbar distance for the low-skilled group implies that if the loadslifted were the same for both the low- and high-skilled groups,the low-skilled group would have to perform a greater amountof mechanical work: on the bar compared with high-skilledgroup. However., since the loads lifted were greater in thehigh-skilled group compared with the low-skilled group,greater mechanical work was performed by the high-skilledgroup.

The smaller hip extensor moment arms and larger kneeextensor and ankle dorsiflexor moment arms imply thatthe high-skilled aroup kept the bar closer to the bodycompared with the low-skilled group. Keeping a weightclose to the body during lifting is important in minimiz-ing injury potential. especially to the lower back, becausehip and spinal moment arms will decrease. This impliesthat the low-skilled group may have a higher risk of

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injury compared with the low-skilled group. Keeping theweight closer to the body also may enhance lifting perfor-mance. In addition, ankle. knee, and hip moment arm datasuggest that the high-skilled group may use the hip extensorsand ankle plantar flexors to a lesser extent and the knee ex-tensors to a greater extent compared with the low-skilledgroup. An electromyographic study of high- and low-skilledgroups nmay be helpful in testing this hypothesis.

CONCLUSIONSThere were numerous kinematic and kinetic differences ob-

served between sumo and conventional style deadlifts andbetween high- and low-skilled lifters. The sumo deadlift wasperformed with a more upright trunk and a wider stance comn-pared with the conventional deadlift. which may decrease in-jury risk in the sumo deadlift and increase injur) risk in theconventional group. The sumo deadlift mav be more eftectivein developing the ankle dorsiflexors and knee extensors.whereas the conventional deadlift may be more effective indeveloping the ankle plantar flexors and knee flexors. High-skilled lifters exhibited better lifting mechanics than low-skilled lifters by keeping the bar closer to the body. which mayboth enhance performance and minimize injury risk.

The authors extend a special thanks to Herbie Bohnet, BrianPullin, and Bolu Ajiboye for all their assistance in digitizing the data.They also acknowledge the Special Olympics World Games Pow-erlifting Committee, competition manager Richard Frazier, technicaldelegate Chip Hultiquist, the International Powerlifting Federation.and the staff personnel of Stuart Theater for all their help andsupport throughout the data collection period. They also acknowl-edge Lee Todd, Vice President of Sports and Competition Depart-ment, for all his support in this project.

Address for correspondence: Rafael Escamilla. Ph.D.. C.S.C.S.,Duke University Medical Center, P.C. Box 3435. Durham. NC 27710;E-mail: rescamil@duke.edu.

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Medicine & Science in Sports & Exercise. 1353BIOMECHANICAL ANALYSIS OF THE D-EADLIFT

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TITLE: Biomechanical analysis of the deadlift during the 1999Special Olympics World Games

SOURCE: Medicine and Science in Sports and Exercise 33 no8 Ag2001

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