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INTERNATIONAL JOURNAL OF SPORT BIOMECHANICS, 1988, 4, 68-89

The Snatch Technique of World Class Weightlifiers

at the 1985 World Championships

Wolfgang Baumann, Volker Gross, Karl Quade, Peter Galbierz, and Ansgar Schvvirtz

The purpose of this study was (a) to describe the snatch technique in terms of kinematic and external and internal kinetic parameters, and (b) to com- pare the results for athletes of different groups and weight categories. By means of three-dimensional film analysis and measurements of ground reaction forces during the 1985 World Championships in Sweden, it was possible to analyze the spatial movements and to calculate joint moments of force in each leg. Concerning the kinematics, a snatch technique starting with a strong pull toward the lifter could be established. The most interesting kinetic results are that the knee joint moments are relatively small (one third of the hip joint moments of force) and do not correlate very well with the total load. The best lifters seem able to limit the knee joint moment by precise control of the knee position with respect to the ground reaction force. Al- together, the results concerning the internal kinetic parameters question the logic of the classical division of the lifting technique into phases according to external kinetic parameters.

Until now, research in weightlifting has been predominantly concerned with the kinematics of competitive techniques, particularly the two-dimensional analysis of the trajectory of the bar itself (Garhammer, 1979, 1981, 1985), occa- sionally including selected parameters with respect to actual body movements (Enoka, 1979; Ono, Kubota, & Kato, 1969). The external kinetics of lifting techniques have been investigated in detail by Vorobyev (1978) and reported in his textbook, Weightlifting. Similarly, the work of Kauhanen, Hakkinen, and Komi (1984) concerned itself with selected kinematic and external kinetic parameters of training techniques. In most studies, however, the movements have been confined to the sagittal plane corresponding to the preferred observation perspective of the trainer. To date, no known studies have been conducted considering the

The authors are with the Institut fiir Biomechanik, Deutsche Sporthochschule, Carl-Diem-Weg, D-5000, Koln 41, Federal Republic of Germany.

SNATCH TECHNIQUE OF WEIGHTLIFTERS 69

features of (a) three-dimensional data collection, @) measurements of ground reaction forces, and (c) movements under competitive conditions, that altogether would have allowed the determination of joint moments of force of competitive techniques in weightlifting. Lacking, therefore, is essential information on the fac- tors governing specific techniques and conditioning practices. Through this investigation, we attempted to overcome this lack of scientific information.

Subjects

Methods

At the 1985 World Weightlifting Championships in SMedje , Sweden, virtually all lifts in the snatch and in the clean and jerk in all weight categories were recorded using video techniques. In addition, 20% of these were also filmed and ground reaction forces were measured for about 80% of the lifts.

Kinematic parameters of the movement of the bar were determined from video recordings. With respect to these, two extreme groups were formed using four weight categories (i.e., 60, 75, 90, and 110+ kg), the furst comprising the 10 best lifts of the four first-place Group A athletes and the second comprising the 10 poorest lifts from Group B. In all, 82 lifts were studied.

The three-dimensional kinematic and kinetic analysis, including a calculation of the joint moments, was obtained directly from film and the measurement of ground reaction force (GRF). Chosen were 17 attempts in three weight categories (i.e., 60,82.5, and 110+ kg). Among these were Shalamanov's world record lift and the best lifts of gold medalists Vardanyan and Krastev. Six unsuccessful lifts were also included in the analysis.

Definition of Variables

The present analysis focused on the snatch technique from the beginning of the movement to the point at which the lifter dropped under the barbell. This phase is considered to be the most important and technically most difficult part of the whole movement and is treated accordingly in the literature. The initial choice of parameters was based on a theoretical and practical approach by considering the kinematics of the movement of the bar and of the lower limb, and external kinetics in the form of ground reaction forces. Then certain variables associated with muscular control, namely net joint moments of force in the lower extremity, were investigated. Table 1 shows the selected variables.

Data Acquisition and Processing

Kinematics. In order to determine the kinematic parameters of the movements of the bar and the lifter, video and film techniques were employed. Video was chosen because it provides a suitable, low cost means for collecting data on all the lifts while providing adequate precision for quantitative analysis. The two cameras used were semiprofessional JVC triple-tube color models (PAL 50 Hz, 625 lines) which were set up in the horizontal plane at an angle of 90" to each other (see Figure 1) in order to allow the movement to be viewed from the side and from the front. The pictures were recorded on U-matic recorders via a com- mon timer. The films were taken using two phase-locked synchronized 35-mrn Arritechno 150 cameras, which were placed at 45" angles to the frontal plane

70 UMANN, GROSS, QUADE,. GALBIERZ;x AND SCHWIRTZ

RFt * N1s"'maximum

the films ,using the well established (Abdel-his & Karara, 1971). This

SNATCH TECHNIQUE OF WEIGHTLIFTERS

Figure 1 - Positioning of the video cameras V1 and V2 and the cine cameras C1 and C2 with respect to the weightliftem' stage.

BAUMANN, GROSS, QUADE, GALBIERZ, AND SCHWIRTZ

Figure 3 - Body and barbell points to be digitized.

recorded by both the video and film cameras. Figure 3 shows the points that were digitized in the three-dimensional analysis from the films. Reduction of the video recordings was completed using a video digitizer, with the reference framework providing a suitable scale for the various sagittal planes involved in the movement.

Kinetics-Ground Reaction Forces. The measurement of ground reaction forces (GRF) in high level competition poses problems that are quickly obvious in weightlifting. Whereas external kinetics can be fully determined from the G W , the mounting of force plates may be difficult for several reasons. The insertion of the plates into the competition platform must not alter its mechanical or visual characteristics. Furthermore, the precision of the measuring apparatus must be maintained throughout the competition, and also, in this case, must withstand over 1,200 consecutive impacts from falling weights.

Ground reaction forces were measured using two Kistler force plates (600 x 1,000 mm) specially designed for this project. Particular attention was paid to precision, mechanical stability, and safety with respect to impact. The mounting frames were set in a four-tonne concrete block. The force plates were then firmly mounted on top and within precisely cut recesses in the competition platform. In order to avoid any mechanical contact between them, the 5-mm slits that separated the plates from the surrounding material of the platform were then sealed with a soft dustproof plastic. The output of all 16 measuring channels was fed into a Data General Computer through appropriate amplifiers. The data acquisition was triggered automatically as soon as a threshold of 300 N was reached and included all measurements during the previous 3 seconds as well. The sam- pling frequency was 100 Hz and the total measurement time on each occasion was 10 seconds. This system, using separate plates for right and left feet, per- mits measurement of the three GRF components, the coordinates of the point of application of the force, and the free pe~endicular moment.

Kinetics-Muscular Moments. An effective evaluation of technique and development of optimal methods of training a knowledge of the time histories of the various muscular moments (joint moments) is of utmost importance. From external kinetic data and three-dimensional kinematic information concerning the joint centers of the lower limbs, it is possible to calculate the net muscular moments around various joints in all three planes. It is important to note here that


these are net moments and that the effects of antagonistic muscular activity have not been considered.

The calculation undertaken here with respect to muscular moments around the joints of the lower limb are based on careful determination of the position of the joint center and of the GRF vector. Control tests showed that the moments created by the inertial forces of the individual segments of the body were consis- tently under 5 % . These inertial forces were therefore not included in the calcula- tions. In the results, only those muscular moments acting in the principal plane of movement are,reported, This plane of movement is defined by the relative position of the long axes of adjacent segments and is that which is associated with the motion brought about by the major muscle groups involved.

Results and Discussion

Barbell Kinematics (Two-Dimensional)

Trajectory of the Barbell. The movement of the b& is the result of forces the lifter applies to it. The displacement-time and velocity-time relationships are often seen at a practical level as the most important criterion for assessing lifting technique. A number of pathways of the barbell's movement are illustrated in Figure 4 and correspond to lifters from different weight categories. At the beginning

.5 m 1

I

Figure 9 - Barbell tmjektories~f different attempts. 0 = 'initial position, 1 = end of 1st pull, 2 = end of 2nd pull.

74 BAUMA NN, GROSS, QUA DE, GALBIERZ, AND SCHWIRTZ

of the first pull the barbell is moved toward the lifter. With the lowering of the knees a small opposite movement occurs, during which the second pull and the drop under the barbell again results in movement toward the lifter. In the case of nearly all lifters in Group A, the barbell's pathway does not cross a vertical reference line projected upward from the initial position of the bar. This applies to many Group B lifters too. As a rule, this movement ends with a jump backward in the drop under the barbell. Garhammer (1985) has already drawn attention to this jump, which is considered by Vorobyev (1978) to be a fault.

The patterns of Group A and B lifters from various weight categories are presented in Figure 5 for comparison. In particular the patterns show the maximum changes in horizontal displacement during the various phases of the lift. It is clear from this analysis that the new technique of pulling the bar toward the lifter is widely used, and the total variation in horizontal movements of Group A lifters is noticeably less than for Group B. The extent of these movements in- dicates the degree of instability involved or, as the case may be, the degree of correction needed to complete the lift. This parameter also serves as a measure of the additional acceleration and mechanical work that must be produced.

Vertical

110t kg Class

Figure 5 - Horizontal variations of the barbell in the weight categories 60 kg and 110 + kg. The horizontal bars represent the standard deviations of the horizontal excursions of the barbell at their extreme left and right positions, respectively.


The maximum height attained by the barbell increases as the weights of the lifters increase. This variable essentially depends on body stature, as can be seen from Figure 6. With very little variation, the height to which the bar is lifted in snatch lifts corresponds to 60% of the lifter's stature.

Velocity of the Barbell. The velocity-time relationship of the bar, particularly peak vertical velocity, is an important dimension as far as coaches are concerned. Figure 7 illustrates two typical velocity curves. The one on the left has two velocity peaks while the one on the right shows a steady increase in velocity to a single maximum value. The latter is characteristic of better weightlifters, and even in the case of a delayed rise in the velocity curve, Group A lifters seldom show any notable dip in velocity.

The absolute maximum velocity of the bar increases with increasing weight categories. The bigger loads that can be lifted by Group A are generally related to smaller maximum velocity values. These and other descriptive results of this section are summarized in Table 2.

As expected, the average power output (Pav) during the raising of the bar up to its highest point (BBH max) shows significant differences between Groups A and B, mainly due to the higher barbell weights lifted by Group A, and to a lesser extent, to the generally shorter duration of the lift.

The general trends allow the following differences to be identified with

Figore 6 - Correlation between maximum effective lift of barbell (BBH max) and body height (BH).


time [sl

Figure 7 - Different types of barbell velocities.

respect to Group A: (a) the maximum barbell height attained is less; (b) the maximum second peak is smaller; (c) the duration of the lift is shorter; and (d) body stature is slightly shorter. These characteristics reflect the better technique of the Group A lifters.

Kinematics of Body Motion (Three-Dimensional)

The classic phase structure of the snatch technique is based mainly on the changes in knee joint angle. In general the differences between first and second pull phases are identified. The first pull begins with the extension of all joints of the lower extremity (other definitions start the first pull with the lift-off of the barbell; Pietka & Spitz, 1978). The angle at the knee reaches a maximum and then decreases briefly, with the smallest angle reached marking the end of the first pull. The extension that then begins proceeds to a maximum, and it is this movement that is designated as the second pull. During this phase, maximum barbell velocity is attained, followed by the drop under the barbell.

Two-dimensional analyses of competitive movements are generally faced with certain problems. The first concerns the obstructed view of the knee behind the weights themselves over a fairly wide range of movement, particularly at certain critical points, which allows less than adequate precision in measurement. The second concerns the projection of body angles in a single plane, which may distort the true values. The extent of error in the two-dimensional estimation of knee angle, for example, is clearly illustrated in Figure 8.

One curve represents the true changing knee angle between the long axis of the thigh and lower leg calculated from three-dimensional data. The second, using the same basic data, represents the changing knee angle in two dimensions, that is, confined to the sagittal plane. The variation between the angles calculated

SNATCH TECHNIQUE OF WEtGHTLlFFERS 77

Table 2

Barbell Kinematics

Weight classlgroup

6Okg 75 kg 90kg l lO+kg A B A B A B A B

parameter Unit n-10 n = l 1 n=10 n=10 n-10 n = l l n-10 n=lO

- -

BBW

BH

BBHmax

BBHL

Vmaxl

BBHmaxlBH, ,

Pav

kg 130.8 7.5

m 1.57 0.04

m 0.83 0.05

m 0.88 0.05

m 0.10 0.02

mls 1.31 0.05

mls . 1.65 0.08

s 0.62 0.04

s 0.89 0.03

- 0.56 W 1269

I KNEB JOINT ANGLE lo1

Figure 8 - Comparison between three-dimensional and two-dimensional knee hgle.

90 '

,

0 , , I ' 1

- ' /

' ' -50 i -00 time Isl

1

78 BAUMANN, GROSS, QUADE, GALBIERZ, AND SCHWIRTZ

is clear to see and is about 15" at full bend. Such differences can vary according to the size of the true angle involved and the orientation of the plane of vision to the plane of movement. Thus it appears that a two-dimensional estimation of body angles (i.e., with one camera only) offers limited scientific application. A satisfactory solution to this problem is only possible through a three-dimensional analysis using two appropriately positioned cameras.

Figure 9 shows the characteristic curves of the angles of the lower limb as well as the velocity curve of the bar in Shalamanov's world record lift (143

Velocity of barbell h / s l

WORLD BECORD

I

BODY ANGUS to1

1 , , I w 2 4

1

Figure 9 - Velocity of barbell and angles of the lower extremity and angle between trunk and horizontal. TP1 and TP2 are the times of 1st and 2nd pull, respectively. TP1 = lift-off until min. of knee angle; TP2 = min. of knee angle until 2nd max. of knee angle (Pietka & Spitz, 1978).


kg barbell, 60 kg weight category). The knee angle increases to an initial maximum even before the lift-off of the barbell, followed by a pronounced bend at the knees until a minimum angle is reached (end of frst pull). Then there is a clearly shorter intensive extension made up to the second and absolute maximum knee angle achieved (end of second pull). The changes in angle at the ankle are generally similar to those at the knee, but of much less magnitude. The angle at the hip increases steadily over the two phases to a maximum that coincides well with the maxima of the other two joint angles. All three lower limb angles in fact reach their maximum values within 0.04 sec of one another at the end of the second pull. The angle between the trunk and the horizontal decreases slightly at the beginning of the first pull, as the increase in knee angle at this point is greater than that of the hip. Once the initial maximum knee angle has been reached, the trunk angle increases steadily to a maximum that coincides approximately with the foot-off, which precedes the action of dropping under the barbell. The maximum vertical velocity of the barbell is reached just before maximum extension of all the joints approximately 0.05 sec before foot-off.

Listed in Table 3 are the major kinematic results of 17 selected attempts from various weight categories. These data are purely descriptive and provide information on successful and unsuccessful lifts by world class athletes, including Shalamanov's world record (143 kg) and the Gold Medal winning lifts of

Table 3

Kinematics of the Body Motion

Joint angles0 Max. ang. ~el .~ lsec BW BBW Knee Hip TP1 TP2 Knee Hip

Subject kg kg maxl min max2 max s s P1 P2 P2

Shalamanov

Kritsky Trautman Senet Vardanyan

Erhard

Tsintsanis

Gunyashev

Krastev

80 BAUMANN, GROSS, QUADE, GALBIERZ, AND SCHWIRJZ

Vardanyan (177.5 kg) and Krastev (202.5 kg). The size of this sample, together with the enormous differences in anthropometric characteristics and lifting techniques between the various weight categories, does not allow these particular data to provide any worthwhile characteristics of better performances. Even when comparing good and poor lifts by the same athlete, the kinematic data do not reveal any particular trends. In fact, a comparison of the top lifters Shalamanov and Vardanyan reveals remarkable differences in all the measured parameters in both the first and second pulls.

As a rule, however, it appears that as the barbell weight (BBW) increases, the duration of the first pull also increases, whereas with the exception of Shalarnanov the duration of the second pull remains approximately constant at around 0.15 sec. This result agrees well with the findings of Vorobyev (1978). The maximum angular velocities around the knee in the second pull are also generally larger than in the first pull, and the extension of the hip occurs faster than at the knee.

Kinetics of the Body/Barbell System

The forces measured between the ground and the lifter do not represent the en- tire forces involved in the movements since, until lift-off, forces are being applied directly on the barbell from the competition platform. As soon as lift-off occurs, GRF with respect to the lifter accounts for all the forces acting on the system. Without careful kinematic analysis of the movements of the lifter and barbell, the effects of the GRF on the various parts of the system cannot be identified. The results with respect to external and internal kinetics are treated separately in the following section.

External Kinetics (GRV. Ground reaction forces were recorded separately for the right and left feet. Figure 10 shows an example of the forces recorded, giving not only an impression of the three orthogonal force components but also the degree of symmetry between right and left, though this aspect is not considered here. All three force components are of course included in the calculation of the muscular moments. In this section the results of the vertical component of the GRF during the technically most important phase (i.e., from the beginning of the lift to the drop under the barbell) will be presented. Figure 11 depicts a typical force curve combining right and left sides together with definitions of the specific parameters used.

The first intersection between the force curve and the line representing the total mass of the system (i.e., body weight + barbell) defines the point of lift-off of the barbell. Table 4 presents the numerical results of 17 lifts. The different maximum force values (Fzl and Fz3) rise steadily as barbell weight increases from 135 kg to 205 kg. The correlation coefficients between each of these values and the total mass of the system were both found to be highly significant (r > 0.97). There would appear to be a relationship between rate of change of force (RFz) and total mass, but this was not the case as no evidence of a relationship was found.

Figures 12a through 12j show the vertical force-time curves for 10 selected lifts from two weight categories (82.5 kg and 110+ kg). The scale used in each is the same, and the horizontal line in each represents the respective individual combined weight of the lifter and barbell.

500

0

-500 Isfl ----

Figure 10 - Example of all registered force components during snatch.

Figure 11 - Vertical component of GRF (Gold Medal in 110 + kg weight category).


Table 4

Selected Parameters of Ground Reaction Forces

BW BBW RFz Fzl Fz2 Fz3 Subject kg kg kNls N N N

Shalamanov 60 135 17.5 2573 1725 140 28.5 2532 181 1 143 20.0 2501 1749

Kritsky 82.5 140 12.0 2857 1668 Trautmann 140 7.0 2867 1675

145 6.5 2925 1785 147.5 6.4 2907 1773

Senet -150 24.0 3061 1663 Vardanyan - 175 14.5 3350 2218

1 75 12.5 331 0 2085 177.5 15.0 3312 2235

Erhard 134 - 145 14.5 3743 1701 Tsintsanis 136 160 9.0 3757 2080

- 165 12.0 3793 2556 Gunyashev 130 195 11.0 4060 231 2

- 202.5 11.0 4019 2453 Krastev 150 202.5 22.0 4335 2180

- 205 28.0 4290 2151

Internal Kinetics (Muscular Moments). The muscle moments, as pre- viously stated, are calculated from the carefully determined spatial coordinates of the center of the joints of the lower extremity and the resultant GRF vector. Despite the limitation that only net muscular moments are considered, they still represent a very important kinetic parameter that is closely related to the muscular control of the movement. The muscular moments of one leg are shown in Figure 13. The chosen example is typical of lower weight categories. When a curve is positive the extensors must be active, whereas when it is negative the flexors must be active (mathematically speaking, the curve for the knee should in fact be inverted). As the barbell nears lift-off and up to the end of the first pull, the moment about the hip joint becomes approximately constant while the moments about the other two joints decrease. The moment about the knee becomes negative, that is, the knee flexors become active. The relatively rapid flexing of the knees is only possible with the active support of the flexor muscles. At the beginning of the second pull all of the moments are once again positive, the knee and ankle moments reaching a second maximum during this phase before declining rapidly. Immediately before the foot leaves the ground (foot-off) all three moments reach zero.

These general patterns of the moment-time curves are very reproducible for individual athletes, though they change somewhat between athletes as a result of performance differences. In the heavier weight categories there is an essentially similar pattern in the first pull, although variations do occur in the second pull.


Figure 12 - Total GRF, vertical component for selected attempts in the weight categories 82.5 kg (a-el, and llO+ kg (f-j), respectively. The data given are namelweight categorylweight of barbell/ + = successful, - = unsuccessful.


Knee lad. lo1

Figure 13 - Muscular moments acting in the joints of the leg from beginning until foot-off. Top = knee angle.

The numerical results of 15 individual attempts are presented in Table 5. It is interesting to note the relatively small knee and ankle moments. Ranging from the 60 kg weight category to the 110+ kg weight category, the maximum values for the knee extensors lie between 65 Nm and 258 Nm. The knee flexors create maximum net moments of between 65 Nm and 161 Nm. From these figures, characteristic of competitive movements at the highest level, it is impossible to explain problems reported from the apparent overloading of the joint. The hip extensors must be active for a significantly longer period of time, which includes the first pull and adds up to between 0.4 sec and 0.6 sec. In addition they have to compensate for net moments 2-4 times larger than in the case of the knee, that is, from 260 Nm to 660 Nm. These values indicate the dominant role of the hip extensors in weightlifting and provide evidence of the massive loads to which the muscles and joint structures of the hip are exposed.

There is a high correlation between maximum moments at the hip and the total mass of the system (r = 0.95), which also means that increasing barbell weights leads unavoidably to increased loads on the hip (see Figure 14). The corresponding values for the knee joint show that the moments do not increase propor- tionally with external loads. In Figure 14 the second peak maximum moment about the knee (MK max2) and maximum negative moment in the opposite direction


Table 5

Extreme Values of Muscular Moments

BW BBW MF [Nm] MK [Nm] MH [Nm]

Subject kg kg Max1 Min Max2 Max1 Min Max2 Max

Shalamanov

Kritsky Trautrnann Senet Vardanyan

Erhard Tsintsanis

Gunyashev Krastev

1 Muacular Momenta Nml 0 0 ,

180 230 280 330 380

Figure 14 - Plot of selected moments in the leg versus system mass (BW + BBW).

86 BAUMANN, CROSS, QUADE, GALBIERZ, AND SCHWIRTZ

about the knee (MK min) are plotted against the total mass of the system. The correlation coefficients for the extensors (r = 0.61) and the flexors (r = 0.57) were found to be relatively weak and can perhaps be explained through differences in technique.

The moment at the knee joint is dependent upon the magnitude of the resultant GRF and the perpendicular distance between the line of action of this force and the joint center. Through changes in this moment arm, the moment about the joint will vary. Figure 15 shows an example using the heaviest weight category, comparing Gold Medalist Krastev (BW 150 kg, BBW 202.5 kg) and Group B lifter Tsintsanis (BW 136 kg, BBW 160 kg). The vertical component

Figure IS - Influence of the moment arm of GRF on the muscular moment at the knee.


of the GRF is larger for Krastev because of the greater mass involved. However, the maximum moment about the knee joint is quite the reverse, Krastev's in fact being smaller. The explanation lies in the,different moment arms of the GRF, Tsintsanis' being larger than Krastev's. The larger moment of the knee flexors in Krastev's case simply underlines the forceful support offered by the knee flexors at the end of the first pull.

This comparison demonstrates two things: first, that knowledge of the GRF alone is insufficient for deducing anything about the muscular activity involved, and second, that the position of the knee joint with regard to the GRF direction appears to be an important technical factor in this phase of the snatch. This factor can significantly influence the forces transmitted by the joint and surrounding musculature. The position of knee joint is certainly as important as the time history of the knee angle.

Summary and Conclusions

The results describe some important aspects of snatch technique. Since the origi- nal data come from world class athletes under the most demanding competitive conditions, they can be used as reference data not only for coaches and athletes but also with respect to future biomechanical research. Figure 16 summarizes the picture of the most important characteristics in a lift.

Most of the results with respect to the kinematics of the barbell and movement of the body are in good agreement with the results reported in the literature. The exception is the pathway of the barbell, which has clearly changed, coming more toward the lifter during the first pull. As a consequence there is a backward jump during the drop under the barbell, which Vorobyev considered to be a fault in technique.

The most important results appear to be those concerning the internal kinetics, namely the muscular moments. These parameters are closely related to the muscular control of the movement. In light of the present findings, it would appear that the division of the snatch technique into its usual pull phases is no longer entirely logical. Such a structure is derived from the kinematic characteristics of the movement of the barbell or change in knee angle (Vorobyev, 1978; Pietka & Spitz, 1978). An alternative to this has been suggested by Kauhanen et al. (1984), who based division of the technique into three phases on the sole criterion of minimum and maximum knee angles. According to this, the vertical component of the GRF could also be divided into phases of eccentric and concentric activity of the knee extensors. However, this would be a mistake and might lead one to draw false conclusions. It is in fact not possible to infer muscular activity from the measurement of knee angle and vertical GRF alone. As has been shown, it is the time history of the muscular moment that in fact gives insight into the detailed control of the movement. However, it must be noted that the moments calculated here are only net moments of force since antagonistic muscle activity has had to be neglected. Also, the problem of two-joint muscles has not been addressed, including for example the division of force between m. soleus and m. gastrocnemius. The problem remains unsolved, despite its obvious importance, because the effects on the results with respect to the knee and even the hip joints are unknown. The addition of EMG measurements would be an important consideration in future studies.


Figure 16 - Complete set of parameters. From top to bottom: body angles, barbell velocity, vertical component of GRF, muscular moments.

SNATCH TECHNIQUE OF WEIGHTLIFTERS 89 i t

Nevertheless, it seems reasonable to use muscular moments as suitable criteria for the overall structural characterization and division of the lifting technique. The biomechanical structure of the movement includes not only kinematic but also internal and external kinetic dimensions. It is not the ease of measurement but the essential system parameters and their interrelationships that are of prime importance when choosing appropriate scientific methodologies. If we are prepared to make such considerations in our analyses, we will probably increase our understanding of the weightlifters' movements. And finally, there is the problem of how the kinetic features of the movement can be translated into meaning- ful movement terms that can be understood and applied at the practical level.

References

Abdel-Aziu, Y .I., & Karara, H.M. (1971). Direct linear transformation from comparator coordinates into object space coordinates in close range photogrammetry. Proceedings of ASP/UZ Symposium on Close Range Photogrammetry, Illinois.

Enoka, R.M. (1979). The pull in Olympic weightlifting. Medicilte and Science in Sports. 11, 131-137.

Garhammer, J. (1979). Performance evaluation of Olympic weightlifters. Medicine and Science in Sports, 11, 284-287.

Garhammer, J. (1981). Biomechanical characteristics of the 1978 world weightlifting champions. In A. Morecki, K. Fidelus, K. Kedzior, & A. Wit (Eds.), Biomechanics VZI-B up. 306-3041. Baltimore: University Park Press.

Garhammer, J. (1985). Biomechanical profiles of Olympic weightlifters. Znteh t iml Journal of Spott Biomechanics, ,I, 122-130.

Kauhanen, H., HZikkinen, K., & Komi, 'P. (1984). A biomkhanical ardysis of the snatch and clean &jerk techniques of Finnish elite and district level weightlifters. Scan- dinavian Journal of Sports Science, 6 , 47-56.

Ono, M., Kubota, M., & Kato, K. (1969). The analysis of weightlifting movement at three kinds of events for weightlifting participants of the Tokyo Olympic games. Journal of Sports Medicine, 9 , 263-281.

Pietka, L., & Spitz, L. (1978). Kihematic-Bewegungsbeurteilung im Raum [Evaluation of movement in space]. In Bundesverband Deutscher Gewichtheber (Ed.), Lehr- beilage Gewichiheben, 4(1), 3-17.

Vorobyev, A.N. (1978). Weightlfig. Budapest: IWF. -

i '

Acknowledgments

This investigation was initiated and supported by the Subcommission for Bio- mechanics and Sport Physiology of the Medical Commission of the IOC (Chairman, Prince Alexandre de Merode). We are grateful to the Federal Institute for Sport Science (BISP) who supported the analysis, to Kistler Instruments for providing special force plates, and to Data Genetal for their computer assistance.

Thanks are also extended to The International Weightlifting Federation (President, G. Schodl; General Secretary, T. Ajan) and the Organizing Committee of the Swedish Weightlifting Association (C.-E. Hermansson, S. Johansson, B. Johanssori, and T. Tor- stenson) for their excellent support of this project.

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