JOURNAL OF APPLIED BtOMECHANtCS, 19^(1, 12,® 1996 by Humnti Kinelics Publishers, Inc,

Kinematic Analysis of the Barbell Duringthe Snatch Movement of Elite Asian

Weight Lifters

Tadao Isaka, Junichi Okada, and Kazuo Funato

The purpose of this study was to describe the kinematic characteristics of the snatchtechnique from the viewpoint of barbell trajectory. Subject.^ included 6 elite male Asianweight lifters who participated in the first Japan International Friendship Tournamentin 1993, Trajectories of the barbell during snatch lifts in the competition were video-taped. Three vertical acceleration peaks of the barbell during ihe pull movement wereobserved and corresponded to the first pull, transition, and second pull pha.ses. Theangle of the resultant acceleration (ARA) of the barbell averaged US" in the first pulland transition pull phases. Lithe second pull ph;ise. the ARA was almost 140°. indicat-ing that the barbell was accelerated anterioriy. away from the lifter. The results of thisstudy suggest that during the firsi pull and transition pull phases, elite lifters pulled thebarbell toward themselves to produce the needed vertical acceleration and that theresulting posterior movement of the barbell was controlled by the forward accelera-tion produced in the second pull phase.

Olympic-style weight lifting consists of two different lifts, the snatch and the clean-and-jerk. Weight lifting contests are judged on the total of the best weight lifted in each ofthe two lifts. These lifts are done very rapidly, with propulsion of the barbell again.stgravity occupying less than 1 s. Weight lifters arc required to generate a great deal ofmuscular power during each lift (Garhammer, 1985. 1993) and to effectively transfer thispower to the barbell. Analysis of top performances during competition produces scientificknowledge about successful lifting techniques and yields information u.seful for coaching.The purpose of this study was to describe the kinematic characteristics of the snatch lifttechnique used by elite male Asian weight lifters from the viewpoint of barbell trajectory.

Methods

Top-level male Asian weight lifters were videotaped during the first Japan InternationalFriendship Tournament in 1993 in Minakami, Japan. There were national team membersfrom China, Korea, and Japan. The best weight lifter in each of six weight categories from76 kg to +108 kg was chosen for analysis. The weight category, body mass, height, andtournament record of each subject are shown in Table 1. Lifts chosen for analysis were the

Tadao Isaka is with the Department of Mechanical Engineering, Ritsumeikan University,Kusat.su. Shiga 525-77, Japan. Junichi Okada is with the Department of Sports Sciences. WasedaUniversity. Tokorozawa, Saitama 359, Japan. Ka/uo Funato is with the Department of Life Sciences(Sports Sciences), University of Tokyo, Meguro. Tokyo 153. Japan.

508

Kinematic Analysis of Barbell 509

Table 1 Weight Category and Best Weight Lifted in Competition Tor Each Subject

Class

76839199

108+ 108

Subject

UNKKBNYCDPH

Mass (kg)

74.0579.2590.1097.85

104.80122.95

Height (cm)

I6I.5161.1174.5178.5182.9181.5

Snatch (kg)

142.5137.5155.0160.0160.0160.0

Jerk (kg)

180.0175.0195.0207.5210.5200.0

Total (kg)

322.5312.5350.0367.5370.0360.0

heaviest successful snatch lift of each subject, which occurred on the third attempt for allsubjects except LJ (76-kg class) and KB (91 -kg cla.ss). who lifted Iheir heaviest weightson their first lift.

The apparatus used for data collection in this experiment was a Video-Tracker Sy.s-tem (OKK Inc., Tokyo) capable of automatically measuring the trajectories of the illumi-nated points through a charge coupled device (CCD) camera. The information obtainedwith the video-tracker system was subsequently sent to a host computer through agenera I-purpose interface bus for calculation of displacement, velocity, and accelerationin the horizontal (X) and vertical (Y) directions. Raw data were transformed to real distanceunits using the calibration scale placed in the field of view. A calibration scale was takenduring an intermission in the competition.

Barbell trajectories during snatch trials in the competition were videotaped at rightangles to the sagittal plane of the lifters. The distance between the CCD camera and thelifter was 10 m. with the camera height adjusted to the middle level of the movement.Barbell trajectories of these weight lifters were sampled at 60 fields per second,

A second-order Butterworth filter was utilized with a cutoff frequency of 3,6 Hz tosmooth the position-time data for the barbell. The filtered displacement-time data weredifferentiated by the finite difference method (Winter, 1990) to determine the velocity-time curve. Barbell acceleration information was obtained by taking a derivative of thevelocity-time data. The angle between the direction of the resultant acceleration vector ofbarbell and horizontal line was defined as the angle of the resultant acceleration (ARA).ARA was calculated from the horizontal and vertical acceleration of the barbell.

Correlation analysis among the obtained data was used, and p < .05 was taken toindicate statistical significance.

Results

Barbell Trajectory

Barbell trajectories for the heaviest successful snatch lifts of each weight lifter are shownin Figure I, together with the corresponding weight categories. Vertical reference lineswere drawn through the center of the barbell disks just prior to lift-off. The subjects werestanding to the right of the vertical reference lines in Figure 1.

The snatch lift requires a barbell to be lifted from the floor to straight arm's lengthoverhead in one continuous motion. The snatch movement is divided into the following

510

Vertical

76kg

tsaka,

r

1

Okada, and Funato

«

1^

8 I?4^

50aii

Horizontal

SOcm

Figure 1 — The harhell trajectories of suhjects during their heaviest successful snatch. Verticalreference liucs were drawn through the barhell just prior to lift-olT.

phases; start position just prior to lift-off, first pull, transition, second pull, catch position,and finish. The barbell trajectories shown in Figure 1 were all similar in one respect: Atthe beginning of the first pull phase, the barbell moved toward the lifter, followed bymovement away from the lifter, and finally toward the lifter again as the bar descendedwith the lifter moving under the bar into catch position. In every case, except for the 76-kgclass, ihe path of the barbell remained to the right ol' the vertical reference line projectedupward from the start position nf Ihe barbell. In the case of the 76-kg class, the bar trajec-tory remained to the lett after the first pull.

Barbell Displacement and Velocity

Vertical displacements from the start position to the highest pull position ranged from1.52 to 1.63 ni in this study, and vertical displacements from start to catch were 0.96 to1.15 m. When the vertical displacement to catch was calculated as a percentage ofdisplacement to highest pull position. LJ (76-kg class) had the lowest value. 62.1%, andCD (108-kg class) had the highest value, 70.8%.

Lifting the resting barbell effectively requires minimizing each of the horizontaland vertical displacements, the maximum height during Ihe second pull to the catch phaseheight, and the vertical drop displacement from maximum height to catch position. Move-ment range of the barbell was defined as the horizontal traveling distance in the pull phaseplus the vertical dropping distance from maximum height to catch position (Figure 2).The minimum horizontal travel distance for the barbell wa.s 8.4 cm, seen in KB (91-kg)and PH {+IO8-kg). The vertical travel distance of the barbell in all 6 lifters ranged from10.1 cm (76-kg class) to 24.3 cm (108-kg). The total travel distance, calculated as hori-zontal plus vertical values, was less than 30 cm in all subjects except CD, the tallestathlete (108-kg class), whose travel distance was 34.9 cm.

Kinematic Analysis of Barbell

40

E

511

0£flCQ

H

20

10t—

11I i

111 •

D

hoHzontal

vertical

total

76 83 91 99 108 +108

200

100

0 soX-displacement (cm)

horizontal

0 50

X-displacemcnt (cm)

vertical

Figure 2 — TVavel range of harbell calculated from the harbell trajectory.

The time-velocity relationship of the barbell, particularly the maximum verticalvelocity, is considered an important parameter in performance evaiuation by coaches andathletes. Figure 3 shows a representative barbell velocity curve from the start to catchposition in NK.The vertical velocity of the barbell increased steadily to a maximum valueduring the second pull phase. The other lifters had velocity-time curves similar to NK's.except for PH, who clearly had two peaks of barbell veiocity because of a decreasingvelocity during the transition phase. The horizontal velocity increased posteriorly untilthe transition phase and then moved sharply in the anterior and posterior directions duringthe second pull phase.

512 Isaka, Okada, and Funato

\ -

200

E 100o

.•t: 50o^ 0

to

-1000.0 0.5 1.0

time (sec)

1.5

horizontal

vertical

Figurt' 3 — Ueprescntative barheil vclocit.v-tinie curve Kf'catch position (Subject NK).

from the start p4>sition to the

In this study, the maximum vertical velocity appeared during the second pull phaseand averaged 186 cm/s. The highest value (195 cni/s) was observed in NY in the 99-kgclass. There was a significant relationship between the horizontal travel distance and themaximum vertical velocity (/• = .916. p < .05).

Angle of Resultant Acceleration of the Barbell

The barbell, from a resting position on the platform, was lifted against gravity with thevertical acceleration provided by the lifter. During the pull movement (Figure 4). therewere three peaks in the vertical acceleration of the barbell. The observed peaks corre-spemded to the first pull, transition, and second pull phases of the lift. The lifter in the 108-kg cla.ss produced a poorly defined second peak of vertical acceleration, while in the otherclasses three peaks of vertical acceleration were clearly seen.

Figure 5 shows the angles of the resultant acceleration (ARAs) of the barbell atpeak vertical accelerations 1. 2. and 3 as calculated according tu the data in Figure 4b.ARA at Peak 1 of vertical acceleration in ail subjects was vertical or slightly toward thelifter; similarly, ARA at Peak 2 of vertical acceleration was almost vertical. !n the second

Kinematic Analysis of Barbell 513

Icm/sec+957.7

2

I

1105.0

Ap1

1

V

Ap3

A/ rA

time

200 r

100

0 50X-displacement (cm)

Figure 4 — (a) Typical sample of vertical acceleration of barbell and fb) calculation of theangle of resultant accekralion at peak vertical acceleration 1, 2. and 3, (The peak verticalaccelerations Apl, Ap2, and Ap3 corresponded to the first puEl, transition, and second pullphases, respectively.)

514 Isaka, Okada, and Funato

•

n

Apl

ApJ

76 83 91 99 108 +108

Figure 5 — The angles of resultant acceleration at peak vertical accelerations 1, 2, and 3.

pull phase. ARA averaged about 1.37° (±16) with a range of 110 to 158", indicating thatthe barbell In all cases was accelerated atiteriorly away from the lifters.

Discussion

The medal awards in weight-lifting contests depend on how much total weight is liftedwith two lifting styles. Movement ofthe barbell is determined by the forces applied by theweight lifter. The relationships between displacement and time, or velocity and time, areoften used at a practical level as the most important indices for as.sessing lifting technique(Baumann, Gross. Quade. Galbierz. & Schwirtz. 1988).

In this study, barbell trajectories, except for one subject, did not cross the verticalreference line projected upward from the start position. Rather, the barbell was pulledtoward the lifter during the snatch movement, especially from the first pull to transitionphase. This technique used during the first pull and transititm phase most likely requiresthe body to be inclined away from vertical, and the resulting barbell trajectory follows theinclination ofthe body. Garhammer (1983) reported a similar pattern of barbell trajectory,but his data showed the trajectory to cross the vertical reference line. He suggested thatthe obtained trajectory may be considered optimal by some experts. The obtained pattemsof barbell trajectory in this study are similar to those of world-class weight lifters at the1985 World Weight Lifting Championship, as analyzed by Baumann et al. (1988), whoindicated that pulling the barbell toward the lifter was widely used as a new technique,and that usually this movement ended with a jump backw;u-d in the drop pha.se under thebarbell, which was previously considered an undesirable technique.

From a mechanical standpoint, it is thought that for effective lifting technique, thebarbel! should move along the vertical reference line in tirder to reduce the horizontalwork and the vertical drop displacement from maximum height to catch position. Manycoaches have advised lifter.'i to pull the barbell straight up and to minimize drop displace-ment from maximum height to catch position. In this sttjdy. there was little difference

Kinematic Analysis of Barbell 515

between the horizontal travel range of the barbell in the various lifters, with a range ofapproximately 10 cm. On the other hand, the vertical travel range of barbell of the liftersvaried widely from K) to 24 cm.

Two typical barbell veloeily curves have been reported (Baumann et ai., 1988;Garhammer, 1985). One type of velocity curve has two velocity peaks, and another onesteadily increases to a single maximum velocity. Top elite lifters have been characterizedlo have the latter type of velocity pattern and seldom show any notable dip in verticalveloeity. This meatis that skillful lifters could pull the barbell more smoothly during thetransition pha.se without a marked deceleratioti of the barbell.

Maximum vertical velocities during the snatch movement were approximately 1.8m/s, similar to those of top world-class lifters (Baumann et al.. 1988). Interestingly, in thisstudy there was a significant relationship between the horizontal travel range of the bar-bell and maximum vertical velocity.

Linear movement, regardless of direction, results from a combination of severaljoint rotations. In lifting, the extensor muscles about the ankle, knee, and hip joints con-tribute to the control of antagonistic muscles in a sequence progressing from the hip to theankle. This sequence is related to the sequence of the three pha.ses of the pull during thislifting task. When these extensor muscles are maximally activated for a brief period oftime, the lifter's body is pulled backward close to full extension because of the largercontribution of hip extensors. These muscle activities induce not only greater verticalvelocity but also a small amount of horizontal travel of the barbell. The horizontal move-ment of the barbell during the pull phase should be considered an effective application ofmuscle power and a reasonable estimate of movemetit iti elite lifters who utilize hip exten-sor resources to contribute to the movement. Therefore, a small amount of horizontalmovement is necessary for good lifting technique provided the proximal to distal sequenceof joint action is followed (Isaka, Mitsushima, & Funato, 1995).

During the pull phase, the elite lifter utilizes the double knee-bend technique, whichrequires considerable practice and demands substantial control of knee joint motion(Burdett. 1982; Enoka. 1979, 1988: Kauhanen, Hakkinen. & Komi. 1984). The doubleknee-bend technique involves a rebending of the knee during the transition phase after thebarbell has been lifted tojust above knee level (Garhammer, 1989). This technique, whichis unique to weight lifting and which has similar effects as observed iti the countermove-ment in vertical jumping (Garhammer, 1992), permits reemployment of powerful kneeexten,wr muscles through their strongest range of motion and may utilize stored elasticenergy and stretch-reflex facilitation of final knee extension to develop the explosive musclepower required during the lift (Boseo, Tarkka, & Komi, 1982: Etioka, 1979; Komi &Bosco, 1978),

Acceleration of the barbell can provide interesting information for evaluation, suchas the timing and direction of the applied force. However, information concerning barbellacceleration has not been published and utilized to the fullest extent. There were obvi-ously three peaks in the venicai acceleration that corresponded to the three phases of thepull movement. Such a pattern is unlikely in a novice lifter, especially the seeotid peak invenicai acceleration during the transition phase. Appearance of the second peak in verti-cal acceleration could be used as a criterion of lifting skill.

If there were no horizontal acceleration during the peaks in vertical acceleration,then the forces produced by the lifter would be completely transmitted in the verticaldirection without any loss of energy. But, if horizontal acceleration occurs, the force trans-mitted to the barbell is away from the desired venicai direction. The angles of the resultantacceleration of the barbell averaged 85° in the flrst pull and transition phases. In the sec-

51 (i Isaka, Okada. and Funato

otid pull phase, the angle of the resultant acceleration averaged about 140°, with a range of110 lo 160'̂ , indicating that in all ca.scs the barbell was accelerated anteriorly, away from

the lifters. The results of this s(udy suggest that during the first pull and transition phases,elite lifters pull the barbell toward themselves to produce effective vertical acceleration.

On the other hand, this posterior movement of the barbell is controlled by the anterioracceleration produced in the second pull phase.

References

Baumann, W., Gross, V., Quade, K., Gaibierz. P., & Schwirtz, A. (1988), The snatch technique ofworld class weightlifters at ihe 1985 world championships. International Joumal of SportBiomechanics, 4. 68-89.

Bosco, CTarkka, !.,& Komi. P.V. (1982). Effectof elastic energy and myoeleclrical polenliation oftriceps surae during si retch-shortening cycle exercise, huemational Journal of Sports Medi-cine, X 137-140,

Burdett, R.G. (1982). Biomechanics of the snatch technique of highly skilled and skilled weightlifters.Research Quarterly, 5i. 193-197.

Enoka, R.M. (1979). The pull in Olympic weightlifting. Medicine and Science in Sports. I I . 131-137.

Enoka. R.M. (1988). Load- and skill-relaled changes in segmental conlributions to a weightliflingmovement. Medicine und Science in Sports and Exercise, 20. 178-187.

Garhammer, J. (1985). Biomechanical proiDes of Olympic weightlifters. Intemational Joumal ofSport Biomechanics, I, 122-130.

Garhammer, J. (1989). Weightliliing and training. In C.L.Vaughn (Ed.), Biomechanics of sport {pp.169-211). Boca Raton. FL: CRC Press.

Garhammer, J. (1992). A comparison of propulsive forces for weightlifting and vertical jumping.Journal of Applied Sport Science Research. 6, 129-134.

Garhammer. J. (1993). A review of power output studies of Olympic and poweriifting: Methodol-ogy, performance prediction, and evaluation tests. Journal of Strength and Conditioning Re-.wm-h. 7. 76-89.

Isaka, T., Mitsushima. R., & Funato, K. (1995). Kinematic analysis on the snatch technique of worldrecords in elite female weightlifters (Abstract). \nXVtli Congress ctf ihe Intemational Societyof Biomechanics (pp. 422-423). Jyvaskyla. Finland: Gummeru.s Priming.

Kauhanen. H., Hakkinen. K.. & Komi. P.V. (1984). A biomechanical analysis of the snatch and cleanand jerk techniques of Finnish elite and di.*itrict level weightlifters. Scandinavian Joumal ofSports Science, 6. 47-56.

Komi. P.V., & Bosco, C. (1978). Utilizationof stored elastic energy in leg extensor muscles by menand women. Medicine and Science in Sports, 10. 261-265.

Winter, D.A. (1990). Biomechunics and motor control of human movement (2nd ed.). New York:Wiley.