KINEMATIC ANALYSIS OF THE POWERLIFTING STYLE SQUAT AND THE CONVENTIONAL DEADLIFT DURING COMPETITION: IS THERE A CROSS-OVER EFFECT BETWEEN LIFTS?

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1 KINEMATIC ANALYSIS OF THE POWERLIFTING STYLE SQUAT AND THE CONVENTIONAL DEADLIFT DURING COMPETITION: IS THERE A CROSS-OVER EFFECT BETWEEN LIFTS? MICHAEL E. HALES, 1 BENJAMIN F. JOHNSON, 1 AND JEFF T. JOHNSON 2 1 Department of Health, Physical Education and Sport Science, Kennesaw State University, Kennesaw, Georgia; and 2 Department of Physical Education and Recreation, University of West Georgia, Carrollton, Georgia ABSTRACT Hales, ME, Johnson, BF, and Johnson, JT. Kinematic analysis of powerlifting style squat and conventional deadlift during competition: is re a cross-over effect between lifts? J Strength Cond Res 23(9): , 2009 Many individuals involved in sport of powerlifting believe that squat and deadlift have such similar lifting characteristics that lifts yield comparable training results. The aim of this study was to compare and contrast biomechanical parameters between conventional style deadlift and back squat performed by 25 lifters competing in regional powerlifting championship. The 3-dimensional analysis incorporated 4 60 Hz synchronized video cameras for collecting data from 25 participants. Parameters were quantified at sticking point specific to each lift. Kinematic variables were calculated at hip, knee, and ankle. Paired (samples) t-tests were used to detect significant differences in kinematic mean scores for different lift types. The statistical analysis revealed significant differences exist between squat (0.09 m/s) and deadlift (0.20 m/s) vertical bar velocities. Differences were found for angular position of hip, knee, and ankle between lifts. The sticking point thigh angles were quantified as and for squat and deadlift, respectively. Trunk angles were (squat) and (deadlift). The results indicate back squat represents a synergistic or simultaneous movement, whereas deadlift demonstrates a sequential or segmented movement. The kinematic analysis of squat and conventional deadlift indicate that individual lifts are markedly different Address correspondence to Michael Hales, mhales@kennesaw.edu. 23(9)/ Ó 2009 National Strength and Conditioning Association (p, 0.01), implying that no direct or specific cross-over effect exists between individual lifts. KEY WORDS biomechanics, sticking point, sequential, synergistic, partial deadlift INTRODUCTION Surprisingly, controversy of wher deadlifts should be substituted with squat exercises during training continues to resonate throughout powerlifting community. Many individuals involved in sport of powerlifting believe that squat and deadlift have such similar lifting characteristics that lifts will yield comparable training results, with a crossover effect. Numerous coaches and competitors mistakenly continue to substitute various squat exercises into ir training programs in place of deadlift in hopes of miraculous performance improvements in deadlift. However, resemblance appears to be primarily restricted to submaximal deadlift loads typically used during early stages of a training program (10). Even though squat and deadlift appear similar from a simplistic mechanical standpoint, lifts are considered quite different when analyzed under maximal loading conditions, as used in powerlifting competitions. It is extremely difficult for an individual to identify minute movement pattern differences visually, but it is very easy to isolate variations using sophisticated motion analysis instrumentation. From a biomechanical perspective, squat and deadlift are much more different from one anor than currently believed by many in powerlifting community. Two basic strategies exist for lifting weights off of ground (i.e., deadlift) (9). One strategy is referred to as leg-lift, which displays a flexed knee position with a relatively vertical trunk position. The method demonstrates a movement that exhibits simultaneous and relatively equal angular changes about hip, knee, and ankle that closely resembles back squat movement. Conversely, back-lift strategy exhibits an extended knee and flexed trunk position during 2574

2 initial phase of movement, indicating a significantly increased rate of knee extension. The knee movement coupled with heavy weight lifting causes hips to rise rapidly, thus creating an increase in trunk lean. The leg-lift method demonstrates a reduced load on lumbar spine, which is considered safer, but knees are heavily loaded, whereas back-lift style subjects lumbar region to extremely high resultant forces and moments. Depending on lifting strategy, lower-extremity muscle groups are recruited in eir a synergistic (leg-lift) or sequential (back-lift) manner to generate necessary muscle moments. Bejjani et al. (2) reported that leg-lift method approaches straight leg technique when lifting extremely heavy weights caused, in part, by biomechanical constraints and inability to maintain lumbar lordosis. During heavy weight lifting, leg-lift method does not appear to be preferred strategy and may not be even possible (18 20). In summary, no one tends to use one method explicitly, but rar people use a combination of 2 different styles. However, when an individuals near ir maximal deadlift capacity, back-lift strategy appears to be most commonly used technique. To perform a comparative analysis, a common phenomenon specific to each of individual lift types was needed to serve as a marker for distinguishing differences between lifts. The event, described as sticking point, was selected because it has been reported to occur in various weight lifting movements, including back squat and deadlift (6,15,16). The sticking point of a movement is where upward momentum of barbell is momentarily decreased or stopped. This event is particularly important because success in weight lifting depends on a continuous motion of barbell past this region of lift. By isolating sticking point and identifying biomechanical constraints associated with this region, one could provide training implications that address lifting technique and possible implementation of specific assistance-type exercises. Numerous weight lifting analyses have focused on different squat techniques (1,5,7,12,14) or different Figure 1. Vertical bar velocity (squat). Figure 2. Vertical bar velocity (Deadlift). deadlift styles (3,4,8) to determine which method is best for strength development or lower-extremity rehabilitation (8,21), but a comparative analysis between lift types has never been reported. Investigating kinematics of both lift types concurrently while performed by a common subject pool could produce information that may challenge current training philosophies. METHODS Experimental Approach to Problem The objective of study was to compare back squat and conventional style deadlift to determine wher a biomechanical relationship exists between individual lift types. A competition setting was selected over a laboratorybased analysis because of different lifting strategies used, submaximal versus maximal loads. An all-out effort in competition as lifters attempt to set personal or state/national records is very difficult to replicate in a laboratory. For this reason, a competition environment was deemed best for addressing issue of training specificity in relation to squat and deadlift cross-over effect. VOLUME 23 NUMBER 9 DECEMBER

3 Kinematic Analysis of Squat and Deadlift The conventional style deadlift was selected for 2 reasons: a) fewer lifters use sumo style deadlift in competition (small subject pool), and b) majority of sumo style deadlifters do not perform back squat with a wide stance, so significantly different foot placement would affect biomechanical comparison. Only lifters that used a conventional-style deadlift and relatively narrow squat stance, heels approximately shoulder width, were selected for analysis. Similar foot placement was an important control factor for comparing individual lift types. Subjects The 25 male participants were competitors in a regional powerlifting contest, which also served as a national qualifier. The competition attracted lifters with varying skill levels, which provided a heterogeneous group of participants. Only lifters who successfully completed a squat and deadlift were randomly selected for analysis at conclusion of contest. Before competition, body weight ( kg), body height ( m), and age ( yr) were recorded after receipt of a signed consent from each participant. Before data collection, research project was reviewed and approved by Institutional Review Board at Georgia State University. Protocol Four synchronized video cameras (60 Hz) were used to quantify 3-dimensional analysis. The cameras were oriented to avoid any possibility of spotters, judges, and weight plates obstructing camera s view of competitors (i.e., body landmarks). A peak performance video/ analog motion measurement system was used to extract kinematic data from conditioned video signals (17), and n data were smood using a Butterworth digital filter (cutoff frequency 6 Hz). Four bilateral joint centers (shoulder, hip, knee, and ankle) and 2 podiatric landmarks (lateral aspect of calcaneus and lateral aspect of 5th metatarsal) were manually digitized. In addition, hand and bar contact points were included for deadlift to accurately measure bar velocity. Also, TABLE 1. Vertical bar velocity. Lift type Velocity (ms 21 ) Squat * Deadlift * Position 1 (begin ascent) Position 2 (peak bar velocity) Position 3 (sticking point) TABLE 2. Relative angles. Lift type 2576 barbell was assumed to be fixed at shoulder during squat, so shoulder joint markers were used to quantify bar motion. Contrary with previous studies, barbell end was not selected as a point for analysis because bar flex (oscillation) occurs throughout execution of lifts. Three stages were identified during deadlift: a) lift-off (LO); 2) knee passing (KP); and 3) lift completion (LC). In accordance with United States Powerlifting Federation (USPF) guidelines, competitors were allowed 3 lift attempts for each of individual lifts (11). The maximal load successfully lifted, for each lift type, was selected for analysis of each of lifters. Statistical Analysis Means 6 SD were calculated for each of biomechanical parameters. Paired (samples) t-tests were used to detect significant differences in kinematic mean scores for different lift types (a = 0.01). Calculated p values lower than 0.01 were considered evidence for statistical significance. RESULTS Absolute and relative angles were calculated geometrically along with 3-dimensional linear and angular kinematics of Relative joint angle (deg) Hip Squat * * * Deadlift * * * Knee Squat * * Deadlift * * Ankle Squat * * * Deadlift * * * P1 (begin ascent) P2 (peak bar velocity) P3 (sticking point)

4 following parameters: bar, shoulder, hip; knee, and ankle. It was observed that, during deadlift, certain body segments ascended before barbell LO, so ascent phase was defined as upward movement of barbell, unless orwise stated. Vertical Bar Velocity (Sticking Point) Each kinematic variable was reported at 3 different points: P 1 signified start of ascent phase; P 2 represents first point where vertical bar momentum begins to diminish; and P 3 represents first point of pronounced acceleration (sticking point) after previous phase. The sticking point is an important position because if lifter is unable to overcome inertia of lifterbarbell system and increase vertical velocity at P 3, lift will not be successful. Vertical bar velocity during ascent phase was used to identify sticking region. Figures 1 and 2 illustrate sticking point associated with squat and conventional style deadlift. A significant difference (p, 0.01) exists between squat and deadlift at P 1 but not at P 2 and P 3. Angular Positions Each parameter selected for analysis indicated significantly different (p, 0.01) relative angular positions at selected points. The hip and knee angular displacements for squat displayed relatively equal changes throughout sticking point region at and 10.25, respectively. The trunk demonstrated a decrease in angular position (2.66 ) during sticking region of deadlift, whereas hip extension increased (10.25 ). Similarly, during squat, trunk displayed minimal angular Figure 3. Squat Kneeangle vs. hip angle. TABLE 3. Absolute angles. Lift type Absolute joint angle (deg) Trunk Squat * * * Deadlift * * * Thigh Squat * * * Deadlift * * * Shank Squat * * * Deadlift * * * P1 (begin ascent) P2 (peak bar velocity) P3 (sticking point) Figure 4. Deadlift Knee angle vs. hip angle. VOLUME 23 NUMBER 9 DECEMBER

5 Kinematic Analysis of Squat and Deadlift TABLE 4. Segmental lengths. Lift type Arm (m) Trunk (m) Thigh (m) Shank (m) Squat * Deadlift * change (1.11 ), whereas hip exhibited of extension. The absolute thigh angle at sticking point for squat and deadlift were and 57.42, respectively. Knee Angle Versus Hip angle The deadlift showed 3 distinct or segmented phases defined by a dominant joint action: LO, knee extension; KP, hip extension; and LC, knee/hip extension. The squat lift produced a linear relationship between joint movements, illustrating a more synergistic or simultaneous movement. Anthropometric Measures These data were used in a quantitative manner to substantiate how segmental lengths may influence and alter moment arm lengths between different lift types. Only trunk length was significantly different (p, 0.01) between lift types. DISCUSSION A more detailed kinematic model would have been preferred, but USPF regulations would not permit use of reflective markers during competition, which could have potentially impeded performance of lifters. However, powerlifting championship setting provided an ideal opportunity to analyze individuals performing squat and deadlift while lifting extremely heavy loads. Even though lifts demonstrate fundamental differences and use different lifting strategies, a detailed analysis was used to address a common misconception that a cross-over effect exists between lifts. The most obvious differences between squat and deadlift are placement of barbell and lifter s body position during execution of lifts; however, kinematic differences between lifts are not as evident without motion analysis instrumentation. The deadlift, unlike back squat, consists only of an upward movement when performed in competition, so an analysis of ascent phase was selected for 2 primary reasons: a) it was common between lift types and b) it contained sticking point for both movements. The statistical analysis revealed significant differences between 2 lifts for selected kinematic parameters (p, 0.01). To identify sticking point for squat and deadlift, bar velocity was selected because it best represents performance and outcome of overall lift (Table 1). It was shown that sticking point of squat (Figure 1) and deadlift (Figure 2) not only occurred at different hip, knee, 2578 and ankle angular positions but also displayed different bar velocities. These findings support argument that sticking point mechanisms differ between squat and conventional- style deadlift caused, in part, by biomechanical and physiologic factors affecting muscle force production. Some of variability among kinematic parameters could be attributed to differing skill levels or differences in antropometric measurements between individual lifters. Furr research in this area should investigate how high-skill level competitors negotiate sticking point region as compared with lesserskilled lifters. The back squat exercise is considered paradoxical because of cocontracting antagonistic muscles of lower extremities during execution phase. Lombard and Abbott (13) described phenomenon involving bi-articulate muscles in a manner that joint movement is determined by dominant muscle moment about that particular joint regardless of muscle s multifunctional role. The relative knee and hip angular displacements during back squat movement display similar rates of change throughout sticking point region (Table 2). Figure 3 depicts a relatively linear relationship between knee and hip throughout ascent phase of squat, a condition during which cocontraction of rectus femoris and hamstring group (biceps femoris, semitendenosus, and semimembranosus) is evident. In this case, extensor muscle moment generated at hip by hamstrings is in excess of flexor muscle moment of rectus femoris. Similarly, at knee, extensor moment of quadriceps dominates flexor muscle moment of hamstring group (19,22). Bar velocities quantified during ascent phase of squat implies net extensor moment is diminished at sticking point region (Figure 1). In addition, mean absolute knee angle (Table 3) reported at sticking point is similar to past research findings (16). Conversely, deadlift exhibits different lifting mechanics as compared with squat, with most obvious being 3 distinct stages (Figure 4) identified during execution or ascent phase: LO, KP, and LC. Interestingly, se independent phases have never been clearly defined in previous research, and availability of this information could challenge current training methods that target sticking point in deadlift. The different phases were defined based on kinematics and furr identified by barbell location relative to anatomic landmarks. The LO phase begins with weight on floor and proceeds until barbell nears tibial tuberosity (approximately 6 cm distal to patella). The movement exhibited predominant knee extension throughout entire phase (Table 2), and trunk angle actually decreased, indicating an increase in trunk

6 lean during initial phase of lift (Table 3). The second stage was defined as distance between tibial tuberosity to a point approximately 6 cm proximal to patella. During this phase of lift, movement was dominated by hip extension with relatively minimal knee extension. An important note, KP stage includes sticking point position, which is located near inferior portion of patella. The final stage of deadlift (LC) transitions from KP phase until body is standing completely erect. The LC portion of lift demonstrated a combination of both hip and knee extension. The deadlift does not necessarily follow Lombard model because execution of lift is partitioned into 3 distinct phases. The segmental trunk length was defined as distance between hip and shoulder joint centers. The relative trunk lengths differed (p, 0.01) between squat and deadlift (Table 4), suggesting lifters demonstrated different postural positions during execution phase of lifts. During back squat, lifters were able to maintain lumbar lordosis with a slightly arched but rigid spinal column. However, deadlift exhibited a different trunk configuration, which suggests that under maximal load conditions, spinal column displays an abnormal curvature of spine during execution of deadlift. Specifically, trunk was unable to maintain lumbar lordosis, and a prominent kyphotic condition was evident at thoracic region of spinal column, which produced a rounded back posture. It has been reported that maximal and submaximal deadlifts demonstrate different lifting techniques and require different lifting strategies (10). In summary, sticking point for both squat and deadlift identified portion of lift where involved muscle groups are disadvantaged, possibly because of anatomic (bone architecture and alignment) and mechanical (resultant muscle forces and moments) factors specific to that region. The sticking point is a position common to each lift but occurred at 2 distinctly different locations during ascent. Three absolute conclusions are drawn from data, supporting reasons why lifts are different: a) evidence indicates that squat represents a synergistic or simultaneous movement, whereas deadlift demonstrates a sequential or segmented movement; b) both lifts demonstrate different sticking point locations, indicating different lifting strategies supported by angular position and kinematic measurements; and c) squat and deadlift exhibited different trunk configurations, which had a direct influence on lifting techniques under maximal load conditions. The kinematic analysis of squat and conventional deadlift indicate that individual lifts are markedly different, implying that no direct or specific cross-over effect exists between individual lifts. Furrmore, insight into possible causes for noted drop in vertical bar velocity at key positions during ascent cannot be clearly gained from results of this study. Because of complicated musculoskeletal mechanics of numerous bi-articulate muscles involved in execution of squat and conventional style deadlift, interpretations of resultant forces and moments are difficult. Although kinematic data reaffirmed that re may be changes in muscle action, mechanical disadvantages, muscle angle of pull, and muscle length-tension relationships near this part of movement, a biomechanical dynamic model is needed before musculoskeletal dynamics can be explained adequately. The scope of this analysis was to determine gross kinematic differences between back squat and conventional style deadlift. PRACTICAL APPLICATIONS Currently, a large portion of powerlifting community assumes that sticking point for deadlift occurs approximately at knee level. This assumption was supported by findings of this study; however, momentum began to diminish before sticking point. A popular exercise for training sticking point of deadlift is referred to as a lockout or partial deadlift performed using a power rack. Typically, lifters place barbell approximately at knee level and proceed to lift bar from this starting position until hips and knees are fully extended. In retrospect, as results suggest, starting partial deadlift at knees may be incorrect because findings from analysis indicated that vertical bar momentum began to decrease before bar reached knee position. Therefore, in contradiction with current training methods, barbell should be positioned approximately 6 cm below knees to target entire region, signifying a decrease in momentum including sticking point. The problem most people encounter while performing lockouts is inability to replicate body position specific to deadlift at that point of lift. Performing lockouts improperly on a regular basis could potentially have a negative affect on deadlift technique. Also, poor technique may inhibit recruitment process of involved musculature in regard to biomechanical factors affecting muscle force production. Contrary with popular belief, deadlifts should not be eliminated from training programs and replaced with squat exercises. Rar, deadlift should be properly and strategically placed in a periodized training regimen to maximize performance results. In conclusion, on basis of findings from this analysis, best way to improve deadlift is to deadlift. REFERENCES 1. Anderson, R, Courtney, C, and Carmell, E. EMG analysis of vastus medialis/vastus lateralis muscles utilizing unloaded narrow and wide-stance squats. J Sport Rehabil 7: , Bejjani, FT, Gross, CM, and Pugh, JW. Model for static lifting, relationship of loads on spine and knee. J Biomech 17: , Brown, EW and Abani, K. 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