Democritus University of Thrace, Department of Physical Education and Sport Science, Komotini, Greece

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1 UNSUCCESSFUL VS. SUCCESSFUL PERFORMANCE IN SNATCH LIFTS: A KINEMATIC APPROACH VASSILIOS GOURGOULIS, NIKOLAOS AGGELOUSSIS, ATHANASIOS GARAS, AND GEORGIOS MAVROMATIS Democritus University of Thrace, Department of Physical Education and Sport Science, Komotini, Greece ABSTRACT Gourgoulis, V, Aggeloussis, N, Garas, A, and Mavromatis, G. Unsuccessful vs. successful performance in snatch lifts: a kinematic approach. JStrengthCondRes23(2): , 2009 The purpose of present study was to determine kinematic characteristics of snatch movements that result in an unsuccessful performance, involving barbell s drop in front of weightlifter. The sample comprised 7 high-level men weightlifters competing at international level. Their successful and unsuccessful snatch lifts with same load were recorded with 2 S-VHS camcorders (60 Hz), and selected points onto body and barbell were digitized manually using Ariel Performance Analysis System. The statistical treatment of data showed no significant differences (p. 0.05) between successful and unsuccessful lifts in angular displacement and velocity data of lower-limb joints, trajectory and vertical linear velocity of barbell, or generated work and power output during first and second pulls of lift. Consequently, general movement pattern of limbs and barbell was not modified in unsuccessful lifts in relation to successful ones. However, significant differences (p, 0.05) were found in direction of barbell s resultant acceleration vector, suggesting that proper direction of force application onto barbell is crucial for a successful performance in snatch lifts. Thus, coaches should pay particular attention to applied force onto barbell from first pull. KEY WORDS kinematics, weightlifting, unsuccessful INTRODUCTION Weightlifting, and particularly snatch movement, is one of most technical competitions (2). Successful snatch lift performance is determined by weightlifter s ability to lift barbell overhead and keep it in that position until a confirmation signal sounds. This has to be done in no more Address correspondence to Vassilios Gourgoulis, vgoyrgoy@phyed. duth.gr. 23(2)/ Ó 2009 National Strength and Conditioning Association than 3 trials. However, many trials often result in drop of barbell during snatch movement. This is observed even with loads that athlete might be able to lift in next trial. The knowledge of factors that can make difference between a successful and an unsuccessful lift at a specific barbell load could increase frequency of an athlete s successful snatch lifts. At same time, it could reduce number of trials needed to lift a specific weight, conserving athlete s energy and increasing his or her possibility of lifting much higher weights. In past, several biomechanical parameters of snatch lift performance have been investigated during successful snatch lifts, using 2-dimensional (1,5 8,16,17) or 3-dimensional kinematic analysis techniques (3,14). Elite weightlifters have similar characteristics regarding ir limb and barbell movements during lift, independent of weight category (14), gender (12), or age (13). On or hand, nonelite athletes show different kinematic characteristics according to ir category (4) and gender (15). However, in both elite and nonelite athletes, a common movement pattern has been observed. The knees execute a characteristic extensionflexion-extension movement, where fist knee extension is defined as first pull, knee flexion is defined as transition from first to second pull, and second knee extension is defined as second pull (3,5,9,16). For a properly performed snatch lift, knee extension should be faster in second pull than during first pull, and hip extension velocity should be greater than corresponding velocity of knees (3,14). Regarding barbell s trajectory, bar is moved toward lifter during first pull and transition phase, and during second pull it is moved away from lifter s body. However, se anterior-posterior displacements of barbell should be small, to avoid pointless energy consumption for bar s horizontal displacement (3,9,14,16). Furrmore, for an effective lift, vertical linear velocity of barbell should be continuously increased until end of second pull, because existence of 2 clear velocity peaks would demand additional energy from lifter to overcome negative momentum of barbell during its velocity s decrease (2). Moreover, mechanical work done on bar for its vertical displacement should be greater during first than second pull, and mechanical power output should be greater in second pull (2,11,14). 486

2 Despite detailed analysis of snatch movement during successful lifts, re is a lack of corresponding data regarding kinematics of snatch movement during unsuccessful lifts, when barbell drops onto ground. The purpose of present study was to determine kinematic characteristics affecting drop of barbell in front of weightlifter during snatch movement. The research hyposis of current research was that significant differences in specific kinematic characteristics would determine final outcome of snatch movement. METHODS Experimental Approach to Problem To determine kinematic factors that make difference between a successful and unsuccessful lift, a large number of kinematic parameters describing both limb and barbell movements were studied though 3-dimentional kinematic analysis. Subjects The study sample comprised 7 high-level men weightlifters during national competitions. Two of m participated in category of 69 kg, 2 weightlifters participated in category of 77 kg, and 3 weightlifters participated in category of 85 kg. All subjects were members of adult Greek national weightlifting team and provided written consent for ir participation in study. Procedures were in accordance with Helsinki Declaration of 1975, and institutional review board approval was obtained for this study. Procedures Athletes successful and unsuccessful snatch lifts with same barbell load were recorded with 2 S-VHS camcorders (Panasonic PV-900) operating at 60 fields per second. The 2 cameras were positioned in a horizontal plane, 15 m away from subjects. The optical axis of each camera formed an angle of 45 with frontal plane of subject. That arrangement allowed movement to be viewed by each camera, both from side and from front. To determine kinematic characteristics of each lifter s body and barbell, selected points were digitized manually using Ariel Performance Analysis System (Ariel Dynamics). These points corresponded to great toe, ankle, knee, hip, and acromion of right side of body, as well as 1 point on right edge of barbell. The lift-off of barbell was used for temporal synchronization of 2 cameras, and 3-dimensional coordinates of selected points were calculated using direct linear transformation technique. For calibration of recorded space, a rectangular cube with 180-cm length, 90-cm breadth, 180-cm height, and 23 control points was used. The mean reconstruction errors expressed in RMS values were 3.2, 2.7, and 3.5 mm in X, Y, and Z directions, respectively. A low-pass digital filter with a cutoff frequency of 4 Hz that was selected through residual analysis of a wide range of cutoff frequencies was used for smoothing of raw position-time data. The movement was studied from beginning of barbell s lift-off to point at which lifter dropped under barbell; this period was divided into 5 phases, according to knee angle and height of bar: The first pull: From barbell s lift-off until first maximum knee extension The transition from first to second pull: From first maximum knee extension until first maximum knee flexion The second pull: From first maximum knee flexion until second maximum extension of knee The turnover under barbell: From second maximum extension of knee until achievement of maximum height of barbell The catch phase: From achievement of maximum height of barbell until stabilization in catch position with barbell overhead in successful lifts or drop of barbell in front of athlete in unsuccessful lifts Figure 1. Angular displacements of a) knee, b) ankle, and c) hip. a) A = angular position of knee at start of lift, B = first maximal extension angle of knee (end of first pull), C = minimum flexion angle of knee (end of transition), D = second maximal extension angle of knee (end of second pull). b) A = first maximal extension angle of ankle, B = second maximal extension angle of ankle. c) A = maximal extension angle of hip. VOLUME 23 NUMBER 2 MARCH

3 Unsuccessful Snatch Lift Kinematics Figure 2. Angular velocity of a) knee, b) ankle, and c) hip. a) A = first maximal angular extension velocity of knee, B = second maximal angular extension velocity of knee. b) A = first maximal angular extension velocity of ankle, B = second maximal angular extension velocity of ankle. c) A = maximal angular extension velocity of hip. To study movement of body, angular displacements (Figure 1) and angular velocities (Figure 2) of ankle, knee, and hip joints were calculated. The barbell s movement was described by anterior-posterior displacement of bar, maximum height of bar (Figure 3), vertical linear velocity, and vertical, anterior-posterior (Figure 4), and resultant linear accelerations. The external mechanical work and mechanical power output for vertical lift of barbell during first and second pulls were also calculated according to methodology described by Garhammer (11). Furrmore, angle u between resultant linear acceleration of barbell and vertical line passing through position of bar before lift-off was calculated, using equation u ¼ a cos a y a where a y was vertical component of barbell s linear acceleration, and a was resultant linear acceleration of barbell. Statistical Analyses For statistical treatment of data, t-tests and analyses of variance for dependent samples were used. The assumption of normally distributed samples was verified using Kolmogorov- Smirnov test, and level of significance was set at p # RESULTS The results reveal that re were no significant differences in durations of separate phases of lift between successful and unsuccessful lifts (Table 1). Moreover, no significant modifications were observed in knee angle at beginning of lift, in first and second maximal knee extensions, in minimum knee angle at end of transition phase, or in corresponding amount of knee flexion. The same was observed for first and second maximal ankle extensions and maximal hip extension (Table 2). Regarding joints angular velocities, t-tests revealed that maximum angular velocities of knee and ankle 488

4 Figure 3. Barbell s trajectory. A = barbell s displacement toward athlete, B = barbell s displacement away from athlete, C = maximum height of barbell, D = loss of barbell s height during catch position. joints in first and second pulls and maximum hip extension velocity were not significantly different between successful and unsuccessful lifts (Table 3). Analysis of variance for dependent samples showed no significant interaction between successful-unsuccessful lift factor and phase of lift factor, regarding maximal angular velocity of knee s extension (F 1,6 = 2.782; p = 0.146) and maximal angular velocity of ankle s plantar flexion (F 1,6 = 0.075; p = 0.794). On or hand, re was a significant main effect of phase of lift factor in both knee extension (F 1,6 = ; p, 0.05) and ankle plantar flexion (F 1,6 = ; p, 0.05) maximal velocities. These meant that in both successful and unsuccessful lifts, knees were extended and ankles were plantar-flexed significantly faster during second pull compared with first one. Regarding maximal extension velocities of hip and knee joints during second pull, no significant interaction was observed between successful-unsuccessful lift factor and joint factor (F 1,6 = 1.078; p = 0.339). However, re was a significant main effect of joint factor (F 1,6 = ; p, 0.05), which meant that in both successful and unsuccessful lifts, hip extended significantly faster than knee joint (Table 3). Regarding trajectory of barbell, no significant differences were observed between successful and unsuccessful lifts in maximum height of barbell or in horizontal displacement of barbell toward or away from lifter, nor were any observed in height of barbell at end of first pull, transition phase, and second pull (Table 4). Concerning vertical linear velocities of barbell, successful lifts were not found to be significantly different than unsuccessful lifts in barbell s maximum velocity, instant of maximum velocity achievement, barbell s absolute velocity at end of first pull, percentage of barbell s maximum velocity at end of first pull, absolute decrease of barbell s velocity in transition phase and its percentage in regard with maximum velocity of barbell, or in velocities of barbell at end of transition phase and at end of second pull (Table 5). Regarding energy characteristics of lift, no significant differences were observed between successful and unsuccessful lifts in work and power generated for barbell s vertical lift during first and second pulls (Table 6). Analysis of variance for dependent samples showed that interaction between factors successful-unsuccessful lift and phase of lift in mechanical work for vertical lift of barbell (F 1,6 = 2.554; p = 0.161) was not statistically significant, but main effect of factor phase of lift (F 1,6 = ; p, 0.05) was. This meant that in both successful and unsuccessful lifts, mechanical work during first pull was significantly greater than during second pull. No significant interaction (F 1,6 = VOLUME 23 NUMBER 2 MARCH

5 Unsuccessful Snatch Lift Kinematics 1.058; p = 0.343) of previous factors was found in mechanical power output for lift of barbell. Again, a significant main effect of phase of lift factor (F 1,6 = ; p, 0.05) was observed, but this time power was significantly greater during second than during first pull (Table 6). Furrmore, no significant differences were found between successful and unsuccessful lifts in selected parameters concerning position of body s limbs in reference to barbell s position in various phases of lift (Table 7). Moreover, no significant differences were found between successful and unsuccessful lifts in mean angle of barbell s resultant linear acceleration vector with vertical axis Oy (Figure 5) in any of distinct phases of lift, except from first pull (Table 8). Figure 4. Vertical linear velocity (a), vertical linear acceleration (b), and anterior-posterior linear acceleration (c) of barbell. a) A = first maximal vertical linear velocity of barbell, B = minimum vertical linear velocity of barbell during transition phase, C = maximal vertical linear velocity of barbell. TABLE 1. Duration (s) of separate phases in successful and unsuccessful lifts. First pull Transition Second pull Turnover under barbell DISCUSSION The results reveal that re were no significant differences in kinematic characteristics of lift between successful and unsuccessful lifts. However, direction of forces applied onto bar seems to be of decisive importance. Large deviations in line of force application on barbell from vertical in first pull, along with smaller ones during or phases of lift, can accelerate barbell in such a way that lifter might not be able to control barbell s movement and may drop it. Regarding durations of separate phases of lift, no significant differences were found between successful and unsuccessful lifts. The duration of first pull was longer than or phases of lift, and transition and second pull 490

6 TABLE 2. Selected angles ( ) of ankle, knee, and hip joints in successful and unsuccessful lifts. Knee angle at start of lift First maximal extension angle of knee Knee angle at end of transition phase Decrease of knee angle in transition phase Second maximal extension angle of knee First maximal extension angle of ankle Second maximal extension angle of ankle Maximal extension angle of hip TABLE 3. Angular velocities ( s 21 ) of ankle, knee, and hip joints in successful and unsuccessful lifts. Maximal angular velocity of knee during first pull Maximal angular velocity of knee during second pull Maximal angular velocity of ankle during first pull Maximal angular velocity of ankle during second pull Maximal angular velocity of hip TABLE 4. Barbell displacements in successful and unsuccessful lifts. Barbell s maximal height (m) Horizontal barbell displacement toward athlete (cm) Horizontal barbell displacement away from athlete (cm) Barbell height at end of first pull (cm) Barbell height at end of transition phase (cm) Barbell height at end of second pull (m) were particularly short in both cases. Moreover, re no significant alterations were observed in maximal flexion and extension angles of ankle, knee, and hip joints or in ir extension velocities. In both successful and unsuccessful lifts, knees were extended during first pull, and, during transition, y were flexed and moved in front under barbell, helping lifter to pass smoothly into second pull. After maximum flexion of knees, which determines start of second pull, hip, knee, and ankle joints were extended explosively and achieved ir maximum extension values at end of second pull (3,5,9,16). Furrmore, concerning joints extension velocities, same pattern was observed in both lifts. The maximal extension velocity of knees during second pull was always greater than corresponding velocity during first pull, and during second pull maximal VOLUME 23 NUMBER 2 MARCH

7 Unsuccessful Snatch Lift Kinematics TABLE 5. Vertical linear velocity of barbell in successful and unsuccessful lifts. Maximal vertical linear velocity of barbell (ms 21 ) Time of maximal vertical linear velocity of barbell (s) First maximal vertical linear velocity of barbell (ms 21 ) Minimum vertical linear velocity of barbell (ms 21 ) Vertical linear velocity of barbell at end of first pull (ms 21 ) Percentage of barbell velocity at end of first pull (%) Decrease in barbell velocity during transition phase (ms 21 ) Percent decrease in barbell velocity during transition phase Barbell vertical linear velocity at end of transition phase (ms 21 ) Barbell vertical linear velocity at end of second pull (ms 21 ) TABLE 6. Energetic characteristics in successful and unsuccessful lifts. Work during first pull (J) Work during second pull (J) Power during first pull (W) Power during second pull (W) TABLE 7. Relative position of foot, knee, and shoulder in reference to barbell s position, in selected time points, in successful and unsuccessful lifts, as well as anterior-posterior linear acceleration of barbell. Position of foot relative to barbell at start of lift (cm) Position of shoulder in front of barbell at start of lift (cm) Position of shoulder in front of barbell at end of first pull (cm) Maximal linear displacement of knee behind barbell in first pull (cm) Maximal linear displacement of knee in front of barbell at end of transition phase (cm) Position of shoulder behind barbell at end of transition phase (cm) Position of shoulder behind barbell at end of second pull (cm) Position of barbell relative to toes of foot at achievement of maximal height of barbell (cm) Maximal negative anterior-posterior linear acceleration of barbell (ms 22 ) Maximal positive anterior-posterior linear acceleration of barbell (ms 22 )

8 Figure 5. Barbell s trajectory and resultant linear acceleration vector in successful (a) and unsuccessful (b) lifts of 1 subject. Mean barbell s trajectory and mean resultant linear acceleration vector in successful (c) and unsuccessful (d) lifts normalized for total duration of lift. extension velocity of hip was greater than maximal extension velocity of knees, giving an additional acceleration onto barbell and contributing to execution of an explosive second pull (3,12 14). The transition from first to second pull is recognized as a particularly important phase. To be effective, it should be executed rapidly and with a small bending of knees (2). This allows storage of elastic energy into extensor muscles of knees during knees flexion and its use during following concentric contraction of knees, resulting in an explosive power output during second pull (5,9,16). It is remarkable that although work for barbell s lift was greater during first than during second pull, power output was significantly greater during second than during first pull in both successful and unsuccessful lifts (10,14). Regarding barbell s trajectory in successful as well as unsuccessful lifts, bar was moved toward lifter during first pull and transition from first to second pull; it was moved away from lifter during second pull and again toward lifter during turnover under barbell (9, 14). According to Isaka et al. (16), such small anterior-posterior displacement of barbell is indispensable for an effective lift, but its magnitude should be small to avoid loss of energy for horizontal displacement of barbell (3). Furrmore, a continuous increase in barbell s vertical linear velocity until end of second pull of barbell is important for an effective lift (2), whereas, according to Baumann et al. (3), existence of 2 clear velocity VOLUME 23 NUMBER 2 MARCH

9 Unsuccessful Snatch Lift Kinematics TABLE 8. Mean angle (u) between vector of resultant linear acceleration of barbell relative to vertical axis Oy in separate phases of successful and unsuccessful lifts. Angle u during first pull ( ) * Angle u during transition phase ( ) Angle u during second pull ( ) Angle u during turnover under barbell ( ) peaks is an indicator of an ineffective technique, as negative momentum of barbell should be overcome additionally from lifter (2). In present study, only 2 of subjects showed negative barbell accelerations during transition phase, in both successful and unsuccessful lifts. From above, it seems that skilled weightlifters show stable movement patterns of ir limbs and barbell. The failure of lift is judged by or parameters, such as line of force application on barbell, which is reflected by direction of barbell s resultant linear acceleration vector relative to vertical axis. In present study, only statistically significant difference in angle of barbell s resultant linear acceleration vector relative to vertical axis between successful and unsuccessful lifts was observed during first pull, showing decisive importance of appropriate beginning of lift. Although no significant differences were found in this angle in rest of phases, studying barbell s trajectory curves in combination with barbell s acceleration vector for each subject revealed obvious differentiations in way force was applied on barbell (Figure 5). So, absence of statistically significant differences in or phases might be attributable to great variance of barbells acceleration angles in se phases. PRACTICAL APPLICATIONS Summarizing findings of present study, it seems that skilled weightlifters showed a stable pattern in ir limb and barbell movement, no matter what final outcome of lift was. Dropping of barbell in front of an athlete during an unsuccessful lift principally seemed to occur as a result of erroneous directions of applied force onto barbell, beginning with first pull, which should receive particular attention from weightlifting coaches. REFERENCES 1. Barabas, A and Fabian, GY. Complex investigation of successful weightlifting exercises. In: Biomechanics in Sports V. Tsarouchas, L, Terauds, J, Gowitzke, BA, and Holt, EL, eds. Ans: Hellenic Sports Research Institute, pp Bartonietz, KE. Biomechanics of snatch: toward a higher training efficiency. Strength Cond J 18(3): 24 31, Baumann, W, Gross, V, Quade, K, Galbierz, P, and Schwirtz, A. The snatch technique of world class weightlifters at 1985 world championships. Int J Sport Biomech 4: 68 89, Campos, J, Poletaev, P, Cuesta, A, Pablos, C, and Carratalá, V. Kinematical analysis of snatch in elite male junior weightlifters of different weight categories. J Strength Cond Res 20: , Enoka, RM. The pull in Olympic weightlifting. Med Sci Sports 11: , Garhammer, J. Performance evaluation of Olympic weightlifters. Med Sci Sports 11: , Garhammer, J. Biomechanical characteristics of 1978 world weightlifting champions. In: Biomechanics VII-B. Morecki, A, Fidelus, K, Kedzior, K, and Wit, A, eds. Baltimore: University Park Press, pp Garhammer, J. Biomechanical profiles of Olympic weightlifters. Int J Sports Biomech 1: , Garhammer, J. Weight lifting and training. In: Biomechanics of Sport. Vaughan, CL, ed. Boca Raton: CRC Publishers, pp Garhammer, J. A comparison of maximal power outputs between elite male and female weightlifters in competition. Int J Sport Biomech 7: 3 11, Garhammer, J. A review of power output studies of olympic and powerlifting: methodology, performance, prediction and evaluation tests. J Strength Cond Res 7: 76 89, Gourgoulis, V, Aggeloussis, N, Antoniou, P, Christoforidis, CH, Mavromatis, G, and Garas, A. Comparative 3-dimensional kinematic analysis of snatch technique in elite male and female Greek weightlifters. J Strength Cond Res 16: , Gourgoulis, V, Aggelousis, N, Kalivas, V, Antoniou, P, and Mavromatis, G. Snatch lift kinematics and bar energetics in male adolescent and adult weightlifter. J Sports Med Phys Fitness 44: , Gourgoulis, V, Aggelousis, N, Mavromatis, G, and Garas, A. Threedimensional kinematic analysis of snatch of elite Greek weightlifters. J Sport Sci 18: , Hoover, DL, Carlson, KM, Christensen, BK, and Zebas, CJ. Biomechanical analysis of women weightlifters during snatch. J Strength Cond Res 20: , Isaka, T, Okada, J, and Funato, K. Kinematic analysis of barbell during snatch movement of elite Asian weight lifters. J Appl Biomech 12: , Rigler, E and Zsidegh, M. Sportwissenschaftliche untersuchungen im trainingsprozess ungarischer gewichber. In: Grundlagen des Maximal- und Schnellkrafttrainings. Bührle, M, ed. Schorndorf: Verlag Karl Hofmann, pp