The deadlift, which measures overall body strength, is the last of three lifts in powerlifting competition. The starting position for the deadlift is with the lifter in a squat position, arms straight and pointing down, and an alternating hand grip used to hold a bar positioned in front of the lifter’s feet. According to the American Drug Free Powerlifting Association (ADFPA) rules at the time of this study, the barbell is lifted upward in a continuous motion until the lifter is standing erect with knees locked and the shoulders thrust back. Causes for disqualification included failure to wait for the referee’s “down” signal at the completion of the lift, any stopping or downward movement of the bar once the bar leaves the lifting platform, failure to stand erect with locked knees and shoulders thrust back, and any “hitching,” bouncing, or resting of the bar against the thighs during the lift. All deadlift trials analyzed in the current study were in accordance with these rules.
Strength athletes, such as American football players, often employ the barbell deadlift in their training or rehabilitation regimens. These athletes use the deadlift to enhance hip, thigh, and back strength. The deadlift is performed using either a conventional or sumo style. The primary differences between these two styles are that the feet are positioned further apart and turned out in the sumo style, and the arms are positioned inside the knees for the sumo style and outside the knees for the conventional style. Stance width, foot angle, and hand width differences between these two styles have not yet been quantified. Although both deadlift styles are used in training, the efficacy of one style over another is unclear.
Because the deadlift is considered a closed kinetic chain exercise (23), it can also be employed in knee rehabilitation programs, such as after anterior cruciate ligament (ACL) reconstruction. Numerous studies have already shown that the squat is an effective exercise during ACL rehabilitation (11,15,20,22,25,26,29). Because the deadlift is performed in a similar manner as the squat, it is hypothesized that the deadlift may provide similar benefits during ACL rehabilitation. The moderate to high hamstring activity that has been reported during the deadlift (28) may help protect the ACL during knee rehabilitation. However, which deadlift style would be most effective in knee rehabilitation has not yet been established.
There are seven known studies that have examined biomechanical variables during the barbell deadlift (2,4,5,8–10,17). Three studies examined lumbar spinal loads (4,5,8), two studies investigated the effects of intra-abdominal and intra-thoracic pressures (9,10), one study quantified joint and segmental angles (17), and the remaining study calculated joint angles and joint moments (2). However, only two studies have compared kinematic or kinetic parameters between sumo and conventional deadlifts (5,17). McGuigan and Wilson (17) performed a kinematic analysis using male lifers from two regional powerlifting championships. The only significant differences they observed were that the sumo group had a more upright trunk and less hip flexion at liftoff, and the shank range of motion was greatest in the sumo group. Cholewicki et al. (5) quantified lumbar loads and hip and knee moments between the sumo and conventional deadlifts during a national powerlifting championship. They found significantly greater L4–L5 shear forces and moments in the conventional group, whereas hip and knee moments were not significantly different between the two deadlift styles. One limitation to all previous deadlift studies was that two-dimensional (2-D) analyses (i.e., one camera employed to record a sagittal view of the lifter) were conducted in quantifying kinematic and kinetic parameters. Although trunk movements through spinal and hip flexion and extension occur primarily in the sagittal plane, flexion and extension movements at the ankle and knee occur in the sagittal plane only if the feet are positioned in that plane (i.e., pointing straight ahead). This is because the ankles and knees primarily function as hinge joints and thus move in the direction the feet point. Therefore, the lower extremities will move out of a sagittal plane as the feet turn outward. These will cause erroneous measurements of lower extremity joint and segment angles, ankle and knee moments, and moment arms. These errors may be minimal during the conventional deadlift, because the feet point either straight ahead or are slightly turned out, but considerable errors can occur during the sumo deadlift, because the feet turn out to a greater degree. Therefore, it was the purpose of this study to compare joint and segment angles and ankle, knee, and hip moments and moment arms using three-dimensional (3-D) analyses during sumo and conventional deadlifts. Mechanical work and predicted energy expenditure was also quantified. A secondary purpose was to compare kinematic and kinetic calculations between 2-D and 3-D analyses for both sumo and conventional deadlifts.
MATERIALS AND METHODS
Subjects.
Twenty-four male powerlifters served as subjects. Twelve of the subjects performed the conventional deadlift, whereas the remaining 12 subjects performed the sumo deadlift (Fig. 1). All subjects wore a one-piece lifting suit. Mean age, body mass, and body height were 47.4 ± 7.3 yr, 71.6 ± 10.8 kg, and 172 ± 8 cm, respectively, for the sumo group, and 46.4 ± 6.1 yr, 76.8 ± 22.7 kg, and 170 ± 8 cm, respectively, for the conventional group. All subjects participated in a national powerlifting masters’ championship that was sanctioned by the ADFPA. To participate in masters’ level powerlifting competition, all lifters had to be at least 40 yr old. All subjects signed a human consent form giving their approval to be videotaped and participate in this study.
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Figure 1: Sumo (top) and conventional (bottom) style deadlifts.
Data collection.
Two synchronized Sony HVM 200 video cameras were used to collect 60-Hz video data. One camera faced the subject’s left side whereas the other camera faced the subject’s right side, with each camera’s optical axis forming a 45° angle to the sagittal plane of the lifter. The cameras were positioned approximately14 m apart and faced perpendicular to each other, with each camera approximately10 m from the subject. To minimize the effects of digitizing error, the cameras were positioned so that the lifter-barbell system was as large as possible within the viewing area of the cameras.
For each camera view, videotaping began approximately 1 min before a subject starting his lift and ended approximately 1 min after the completion of their lift. Just before a subject beginning their lift, an external light source was activated in both camera views to help match video frames when viewing the two videotapes. Before and just after the subjects were videotaped, a 2 × 1.5 × 1 m 3-D calibration frame (Peak Performance Technologies, Inc., Englewood, CO), surveyed with a measurement tolerance of 0.5 cm, was positioned and videotaped in the same volume occupied by the lifter-barbell system. The calibration frame was comprised of 24 spherical balls of known spatial coordinates, with the X- and Z-axes positioned parallel to the ground, and the Y-axis pointing vertical.
Data analysis.
In powerlifting competition, a lifter is given three attempts during the deadlift to maximize the amount of weight they can lift. A lifter’s first attempt is usually submaximal, whereas their second and third attempts are near the maximal weight they are capable of lifting. Therefore, only second and third attempts that were successfully completed (i.e., ruled a “good lift” by a panel of three judges) were analyzed. Seventeen of the 24 lifts analyzed were third attempts. The seven second-attempt lifts were used because the third attempts were unsuccessful due to the lifter attempting a weight that was beyond their one repetition maximum (1 RM). Therefore, it was thought that all lifts analyzed were very near each lifter’s 1 RM.
Three events were defined during the deadlift. The first event was barbell liftoff (LO), which was defined as the first picture in which the barbell disks on both sides of the bar were no longer in contact with the lifting platform. Because both sides of the bar typically remained symmetrical throughout the lift, the left and right side barbell disks left the lifting platform at approximately the same time. Therefore, at LO the lifter was supporting the entire barbell load. The next event was at the instant the bar passed the knees (KP), which was defined as the first picture when the vertical position of the bar was higher than the vertical position of the knees. The last event was lift completion (LC), which occurred when the lifter was in an upright position with the knees and hips fully extended and the shoulders pulled back. At this time, the head judge gave the “down” command, signaling the end of the lift. Total lift time was defined from LO to LC.
A 3-D video system (Peak Performance Technologies, Inc., Englewood, CO) was used to manually digitize data for all 24 subjects. A 15-point spatial model was created, comprised of the top of the head and centers of the left and right mid-toes, ankles, knees, hips, shoulders, hands, and end of bar. All points were seen in each camera view. Each of these 15 points was digitized in every video field (60 Hz), which was adequate due to the slow movement of the lift (2,5,14). To minimize manual digitizing error, each point was digitized twice and averaged. Digitizing began 15 video fields (0.25 s) before LO and ended 15 video fields after LC.
A fourth-order, zero-lag Butterworth digital filter was used to smooth the raw data with a cutoff frequency of 5 Hz. A cutoff frequency between 3 and 5 Hz has been demonstrated to be adequate during lifting 1 RM loads involving slow movements (7,17). By using the direct linear transformation method (24,27), 3-D coordinate data were derived from the 2-D digitized images from each camera view. An average resultant mean square calibration error of 0.8 cm produced an average volume percent error of 0.239.
The origin of the 3-D orthogonal axis system was first translated to the right ankle joint and rotated so that the positive X-axis pointed to the left ankle joint, the positive Z-axis pointed anteriorly in the direction the lifter was facing, and the Y-axis pointed in the vertical direction. The vertical positions of the digitized left and right ankles were within 1 cm of each other. This axes system was initially used to calculate all joint moments and moment arms and joint and segment angles. Muscle moment arms were not quantified in this study. Because hip flexion and extension during sumo and conventional deadlifts occur primarily in the Y-Z sagittal plane about the X-axis, hip moments were calculated about the X-axis and hip moment arms were calculated in the Z-axis direction. Ankle and knee moment arms were also calculated in the Z-axis direction, which equates to a 2-D analysis using one camera to record a sagittal view of the lifter. These 2-D data were compared with 3-D data from the 3-D analysis. Because during the sumo deadlift the feet were turned out approximately 45°, ankle and knee flexion and extension occurred in a plane midway between the Y-Z sagittal plane and X-Y frontal plane established above. Therefore, erroneous moment arm measurements would occur if the above axes system were used for the 3-D analysis, because ankle and knee movements do not occur in the sagittal plane during the sumo deadlift. Because the feet are only slightly turned out during the conventional deadlift, relatively small errors would result in moment arm calculations compared with the sumo deadlift. Therefore, the axes system was translated to each ankle joint center and rotated so that the positive Z-axis pointed in the direction of the mid-toes, the Y-axis pointed vertical, and the X-axis was orthogonal to the Y- and Z-axes. Hence, for both sides of the body, ankle and knee moments were calculated about the X-axis, and ankle and knee moment arms were calculated in the Z-axis direction.
Linear and angular displacements and velocities were calculated for both the left and right sides of the body and then averaged. Relative knee and hip angles and absolute trunk, thigh, and shank angles were defined in accordance with previous studies (2,17). Trunk, thigh, and shank angles were measured relative to the X-Z horizontal plane (i.e., from a right horizontal relative to a sagittal view of the lifter’s right side). Knee angles were measured relative to the thigh and leg segments. Although the hip angle is actually formed between the pelvis and the femur, this measurement cannot accurately be determined without external markers affixed to these segments. Therefore, the hip angle was defined as the relative angle between the trunk (hip to shoulder segment) and thigh (hip to knee segment). As long as the trunk is rigid and straight, this relative angle approximates the true hip angle. However, during the deadlift, the trunk does not remain rigid and straight, because spinal flexion causes the back to round to some extent, especially when maximum weight is used. As the spine flexes during the deadlift, the shoulders drop downward, causing the hip angle measurement to decrease and underestimate its true value. To compare joint and segment angle differences between a 3-D and 2-D analysis, hip and knee relative angles and thigh and shank segment angles from the 3-D analysis were projected onto a 2-D sagittal plane. Foot angle was defined as the angle formed between the foot segment and the Y-Z sagittal plane. Stance width was defined as the linear distance between the left and right ankle centers, whereas hand width was defined as the linear distance between the left and right hand centers.
During 1 RM lifting, studies have shown (7,13) that the barbell initially accelerates at LO to a first peak velocity (acceleration phase), then decelerates to a minimum velocity (sticking region), accelerates again to a second peak velocity (maximum strength region), and finally decelerates until LC (deceleration phase). These lifting phases and regions were also calculated in the current study. The Schwartz score, which is used in powerlifting competition to determine the overall best lifter for an event, was used to normalize the barbell load to each lifter’s body mass and to compare relative loads lifted between sumo and conventional groups. A complete list of Schwartz coefficients for any given body weight can be obtained in official powerlifting rule books.
Because segment and barbell accelerations are very small while lifting maximum or near maximum loads, joint moments can accurately be calculated using quasi-static models (12,14,18,19,21). Lander et al. (14) found that joint moments varied less than 1% between quasi-static and dynamic analyzes during the squat exercise with near maximum loads. Left and right hip, knee, and ankle moments and moment arms were calculated at LO, KP, and LC and then averaged. Body segment center of masses and weights were calculated by using appropriate anthropometric data (6) and each lifter’s known mass. Joint moments and moment arms were calculated relative to both barbell weight and system weight. The system weight used to calculate joint moments was the sum of the barbell weight and the weight of body segments above the joint in which the moments were calculated. Therefore, the weights of the trunk, neck, head, and upper extremities were used to calculate system moments at the hip; the weights of the trunk, neck, head, upper extremities, and thighs were used to calculate system moments at the knee; and the entire body weight (minus the feet) was used to calculate system moments at the ankle. The geometric center of the barbell represented the center of mass of the barbell (COMbar). X, Y, and Z position coordinates were calculated for both COMbar and the center of mass of the system (COMsystem). Ankle moment arms (MAankle) were calculated as the distance in the Z-axis direction from the ankle joints to COMsystem or COMbar. Ankle moments were the product of MAankle and system/barbell weight. Knee moment arms (MAknee) were calculated as the distance in the Z-axis direction from the knee joints to COMsystem or COMbar. Knee moments were the product of MAknee and system/barbell weight. Hip moment arms (MAhip) were calculated as the distance in the Z-axis direction from the hip joints to COMsystem or COMbar. Hip moments were the product of MAhip and system/barbell weight.
Because bar motion primarily occurred in the vertical direction, vertical bar displacement was calculated from LO to LC and normalized by body height. Mechanical work, which was calculated relative to both barbell weight and system weight, was the product of system or barbell weight and total vertical displacement of COMbar or COMsystem. The system weight used to calculate mechanical work was the sum of barbell weight and body weight. Independent t-tests (P < 0.05) were used to compare kinematic and kinetic parameters between sumo and conventional deadlift groups, while paired t-tests were used to compare 2-D and 3-D comparisons.
RESULTS
Of the 110 powerlifters observed during the national powerlifting competition described in the current study, 70% used the conventional style, whereas 30% used the sumo style. However, of the 54 lifters in the heavier weight classes (90–125+ kg), 85% used the conventional style and only 15% used the sumo style. In contrast, of the 56 lifters in the lighter weight classes (52–82 kg), only 55% used the conventional style, whereas 45% used the sumo style. Therefore, it appears that heavier lifters more commonly use the conventional style, whereas lighter lifters are more evenly split between the two lifting styles.
Comparisons of joint and segment angles between sumo and conventional deadlifts are shown in Table 1. Compared with the conventional group, at LO the sumo group maintained a more upright trunk, positioned the thigh closer to the horizontal, and positioned the shank closer to the vertical. At KP and at minimal bar velocity, the sumo group had greater hip and knee flexion (i.e., smaller relative hip and knee angles), whereas the conventional group positioned the shank closer to the vertical and the thigh closer to the horizontal. From LO to KP, the conventional group extended their hips, knees, and shank through a greater range of motion than the sumo group. Throughout the lift, the feet were turned outward 10–15° for the conventional group and 40–45° for the sumo group. Table 2 shows joint and segment differences between a 2-D and 3-D analysis. For the sumo deadlift, a 2-D analysis was significantly different than a 3-D analysis for all measurements. In contrast, for the conventional deadlift a 2-D analysis was not significantly different from a 3-D analysis for all measurements except shank angle at KP.
Table 1: Joint and segment angles (mean ± SD) between sumo and conventional deadlifts.
Table 2: Comparisons of lower extremity joint and segment angles (mean ± SD) between two-dimensional (2-D) and three-dimensional (3-D) analyses.
From Table 3, the sumo group employed a foot stance that was 2–3 times wider than the conventional group, whereas the conventional group had a 17% greater hand width than the sumo group. There were no significant differences observed in loads lifted, body mass and height, age, lift times, and Schwartz scores. Vertical bar and system displacements from LO to LC were significantly greater in the conventional group. Furthermore, the total mechanical work done on the barbell and system were significantly greater in the conventional group.
Table 3: Anthropometric, temporal, and work comparisons between sumo and conventional deadlifts.
Select events and lifting phases are shown in Tables 4 and 5. Vertical bar velocity remained low throughout the lift. Minimum bar velocity occurred at slightly less than 50% of the total lift time and slightly more than 50% of the total vertical bar distance. The conventional group reached the first peak bar velocity significantly faster than the sumo group. Therefore, they spent significantly less time in the acceleration phase than the sumo group. There were no other significant differences observed.
Table 4: Select events during the deadlift.
Table 5: Lifting phases during the deadlift.
Joint resultant moments and moment arms are shown in Table 6. At LO, KP, and LC, ankle and knee moments and moment arms were significantly different between sumo and conventional groups. The sumo group generated ankle dorsiflexor moments exclusively, whereas the conventional group generated ankle plantar flexor moments exclusively. Although at LO both groups generated knee extensor moments, at KP and LC the conventional group generated knee flexor moments, whereas the sumo group generated knee extensor moments. Although both groups generated hip extensor moments, they were not significantly different from each other. Comparisons of ankle and knee moments and moment arms between 2-D and 3-D analyses are shown in Table 7. For both the sumo and conventional deadlifts, 2-D analyses were significantly different than 3-D analyses. The largest differences observed occurred during the sumo deadlift.
Table 6: Joint moments and moment arms (mean ± SD) between sumo and conventional deadlifts.
Table 7: Comparisons of ankle and knee joint moments and moment arms (mean ± SD) relative to barbell load center of mass between two-dimensional (2-D) and three-dimensional (3-D) analyses.
DISCUSSION
Bilateral comparisons.
In the current study, linear and angular displacements and velocities, as well as joint moments and moment arms, were averaged from the left and right sides of the body. There were no significant differences (P < 0.01) between bilateral measurements. Bilateral measurements generally showed a 2–3° difference in joint and segmental angles, a 2–3 cm difference in linear displacements, and a 3–4% difference in linear velocities. Bilateral differences in joint moment arms and moments (Fig. 2) were also minimal. The small differences observed between bilateral measurements demonstrate the symmetrical nature of the deadlift exercise.
Figure 2: Representative graph for bilateral comparisons of joint moments. Solid circle—right hip moment at barbell liftoff;open circle—left hip moment at barbell liftoff.
Joint and segmental angles.
Because there are no 3-D analyses conducted on the deadlift, the objective of this study was to compare 3-D kinematics and kinetics between the sumo and conventional deadlifts. It was hypothesized that joint and segment angles would show greater differences between a 2-D versus 3-D analysis of the sumo deadlift compared with a 2-D versus 3-D analysis of the conventional deadlift. Because during the sumo deadlift the feet were approximately 70 cm apart and turned out approximately 45° from the sagittal plane of the lifter, lower extremity movements occurred in a plane midway between the sagittal and frontal planes of the lifter in the direction the feet were pointing, whereas trunk movements occurred in the sagittal plane. Therefore, a 2-D analysis of the sumo deadlift relative to the sagittal plane of the lifter produced erroneous hip, knee, thigh, and shank measurements, especially the greater these movements deviated from the sagittal plane. This is clearly demonstrated from Table 2, where all joint and segment angles during the sumo deadlift were significantly different between a 2-D and 3-D analysis. Compared with a 3-D analysis, a 2-D analysis overestimated hip, knee, and shank angles and underestimated thigh angles. In contrast, during the conventional deadlift, measurements from a 2-D analysis were generally not significantly different than measurements from a 3-D analysis. During the conventional deadlift the feet were turned out of the sagittal plane only slightly. Therefore, body movements primarily occurred in the sagittal plane. From these data, it appears that a 2-D analysis is adequate in measuring joint and segment angles during the conventional deadlift as performed in the current study.
McGuigan and Wilson (17) conducted the only known previous study that compared kinematic parameters between the sumo and conventional deadlifts. Because their analyses were 2-D, it was hypothesized that lower extremity measurements between their study and the current study would show greater differences than trunk measurements. In the current study, hip, knee, thigh, and shank measurements were generally significantly different between sumo and conventional groups, whereas these same measurements were generally not significantly different in McGuigan and Wilson (17) (Table 1). Furthermore, compared with McGuigan and Wilson (17), the current study found smaller knee and hip angles and larger thigh angles. This is the same pattern shown in Table 2 between a 2-D and 3-D analysis. This implies that a 3-D analysis is needed to more accurately calculate lower extremity measurements during the sumo deadlift. In contrast, trunk measurements between the current study and McGuigan and Wilson (17) produced the same significant differences at LO, KP, and LC. This was not surprising, because trunk movements between sumo and conventional deadlifts occur primarily in the sagittal plane of the lifter. Therefore, a 2-D analysis is adequate in quantifying trunk angles.
Mechanical and physiological work.
When normalized by body height, the conventional group had 20–25% greater vertical bar and system center of mass (COM) displacements from LO to LC compared with the sumo group (Table 3). This is nearly identical to the vertical bar displacements reported by McGuigan and Wilson (17). This is not surprising because the sumo group had a stance width 2–3 times greater than the conventional group, which produced a lower COM. These lower COM displacements by the sumo group resulted in 25–30% less mechanical work performed compared with the conventional group.
Because the deadlift is considered a total body exercise, with all the major muscles of the body being active, a high energy expenditure results when performing this exercise. Brown et al. (3) used standard open-circuit spirometry during both active and recovery periods of the deadlift to formulate the regression equation V̇O2 = 2.63 + 0.80(Workbar), where V̇O2 is the total oxygen consumption (L) and Workbar is the total mechanical work (kJ) done by the lifter on the barbell during the deadlift ascent. These authors formulated this equation to predict the total oxygen cost while performing 1–4 sets of 3–20 repetitions during the deadlift. With a high correlation coefficient of 0.912, 83.2% of the variance between V̇O2 and Workbar was explained, which implies that the total estimated work during the deadlift can be used as a gross predictor of the total oxygen cost associated with mechanical work.
Powerlifters and other strength athletes in training typically perform the deadlift for 3–4 sets of 3–8 repetitions. Consider an 80-kg athlete performing both the sumo and convention deadlifts for 4 sets of 8 repetitions. Assume their 1 RM was 220 kg, and their total vertical bar displacement was 0.444 m for the conventional deadlift and 0.353 m for the sumo deadlift (data from Table 3). Because an 8-repetition load is approximately 80% of the lifter’s 1 RM (16), the athlete will perform the 4 sets of 8 repetitions with a load of approximately175 kg. Hence, the estimated total mechanical work done during the 4 sets of 8 repetitions would be 24.4 kJ for the conventional deadlift and 19.4 kJ for the sumo deadlift. Using the regression equation V̇O2 = 2.63 + 0.80(Workbar) (3), the predicted total oxygen consumption would be 22.1 L O2 during the conventional deadlift and 18.1 L O2 during the sumo deadlift. Because an oxygen consumption of 1 L equates to an energy expenditure of approximately 5 kcal, the 4 sets of 8 repetitions would produce a predicted energy expenditure of approximately 111 kcal for the conventional deadlift and approximately 91 kcal for the sumo deadlift. These values are actually slightly underestimated, because contributions from anaerobic glycolysis increase the total energy expenditure, and these effects were only partially accounted for by the regression equation. Because a typical 8 repetition deadlift set takes approximately 30 s to complete, the total time needed to perform 4 sets of 8 repetitions is approximately 2 min, plus the rest time between sets. Assuming a 1.5-min rest period between sets, which is similar to the rest period between sets used in formulating the above regression equation, the total time needed to perform 4 sets of 8 repetitions is approximately 6.5 min. This equates to an average rate of energy expenditure of approximately 2.9–3.5 L O2·min−1 (approximately14–17 kcal·min−1), which is relatively high compared with walking, jogging, and other common activities (1). The predicted energy expenditure during the deadlift is even more impressive considering 70% of this time was spent resting. Most of the energy expended during the deadlift occurred during the 2 min needed to perform the 4 sets of 8 repetitions, whereas a relatively smaller portion was expended during the 4.5 min of rest. Therefore, total body exercises like the deadlift not only enhance muscular development and strength, but also generate a high energy expenditure and have a high caloric cost. Furthermore, total body multi-joint exercises are more functional in movements of daily living and athletic endeavors compared with single muscle, single joint exercises.
Selected events and lifting phases.
Brown and Abani (2) reported extremely low vertical bar accelerations during the deadlift, with peak values 0.41 m·s−2 or less. Similar low vertical bar accelerations were also observed in the current study, as well as low vertical bar velocities (Table 4). Three velocity events were noted during sumo and conventional deadlifts: a) 1st peak bar velocity; b) minimum bar velocity; and c) 2nd peak bar velocity. The typical vertical bar velocity pattern (Fig. 3) during the deadlift was that the bar initially accelerated from LO to 1st peak bar velocity, slowed down to minimum bar velocity, again accelerated to 2nd peak bar velocity, and finally slowed down as LC approached. The COM of the bar actually began moving vertically before the barbell disks leaving the ground at liftoff (Fig. 3). The bar bent slightly as the lifter initially exerted an upward force on the bar with his hands, which occurred because the bar is not completely rigid. Nevertheless, the amount of bend in the bar was minimal. The vertical bar velocity curve shown in Figure 3 is the same general pattern observed during maximum or near maximum loads during the squat (18), but different than the vertical bar velocity curve presented by McGuigan and Wilson (17). This discrepancy in the deadlift may be due the fact that the lifters in McGuigan and Wilson (17) completed the deadlift in approximately half the time it took the lifters in the current study (Table 3). The approximately 4-s total lift time in the current study is in agreement with another study involving the 1 RM deadlift during a national powerlifting championship (5). This implies that the subjects in McGuigan and Wilson (17) may have underestimated their 1 RM. Although powerlifters in competition typically choose a weight that they believe represents their 1 RM, this weight is sometimes less than their 1 RM. This may be because they underestimate their 1 RM, or it may be a strategic move in order to defeat their opponent. In either case, the amount of weight they lift may actually be closer to 95% of their 1 RM, which will affect both lifting kinematics and kinetics. Because the lifters in the current study and in Cholewicki et al. (5) were national level powerlifters, they may have been more experienced than the lifters in McGuigan and Wilson (17), who competed in regional powerlifting competitions. A more experienced lifter can better predict their 1 RM in competition compared to a less experienced lifter.
Figure 3: Representative graph for vertical bar velocity. AP, acceleration phase; SR, sticking region; MSR, maximum strength region; DP, deceleration phase.
Of the 24 lifters in the current study, 18 lifters achieved maximum vertical bar velocity at their 1st peak vertical bar velocity, whereas the remaining six lifters achieved maximum vertical bar velocity at their 2nd peak vertical bar velocity. From Table 4, the mean 1st peak bar velocity was approximately 40–50% greater than the mean 2nd peak bar velocity. These data are different compared to a 1 RM squat (18), in which lifters typically reached their maximum vertical bar velocity at their 2nd peak vertical bar velocity. During the 1 RM squat, the mean 2nd peak bar velocity was approximately 40–50% greater than the mean 1st peak bar velocity (18), which is opposite the findings from the current study. The maximum vertical bar velocity during the powerlifting squat had a mean value of approximately 0.5 m·s−1 (18), which is approximately twice the mean value of 0.238 ± 0.083 m·s−1 observed in the current study. Maximum vertical bar velocities in the current study ranged from 0.108–0.456 m·s−1, which were less than the 0.580 m·s−1 reported by McGuigan and Wilson (17) for one subject performing the deadlift. This is not surprising since their subjects completed the deadlift in half the time as the subjects in the current study.
As originally defined by Lander et al. (13), the lift was divided into four phases (Table 5, Fig. 3): a) acceleration phase → LO to 1st peak bar velocity; b) sticking region → 1st peak bar velocity to minimum bar velocity; c) maximum strength region → minimum bar velocity to 2nd peak bar velocity; and d) deceleration phase → 2nd peak bar velocity to LC. The acceleration phase and sticking region for the conventional group consisted of approximately 16% and 27%, respectively, of the total lift time. This was different from the sumo group, who spent approximately10% more time in the acceleration phase (Table 5). Interestingly, approximately 18% of the total lift time was spent in the maximum strength region during the deadlift, whereas approximately 35–38% of the total lift time was spent in the deceleration phase.
The end of the sticking region has previously been reported as the “sticking point” (18). Because bar velocity is minimal at this instant, it appears to be the most difficult part of the lift. This is often where powerlifters fail in their attempt for a successful lift. In the current study, the sticking point occurred just after KP (Table 3), occurring at approximately 43% of the total lift time for the conventional group and approximately 47% of the total lift time for the sumo group (Table 4). These are similar to the relative times reported by McGuigan and Wilson (17). The sticking point phenomena may in part be due to mechanical principles of skeletal muscle, such as to the length-tension relationship. The greater a muscle shortens, the less tension it is capable of generating. Decreasing muscle moment arm lengths from KP to LC may also be responsible for the occurrence of the sticking point. The sticking point occurred at a slightly different body position compared with a 1 RM squat (18). The trunk was slightly more upright in the deadlift (approximately 50°) compared with the squat (approximately 39°), and the knees and hips were extended more in the deadlift (approximately 152–164° and 111–123°, respectively) compared with the squat (approximately 105 ± 6° and 70 ± 11°, respectively). These body position differences between the squat and deadlift occur in part because the barbell is behind the lifter during the squat and in front of the lifter during the deadlift.
Joint moments and moment arms.
Cholewicki et al. (5) conducted the only known kinetic comparison between sumo and conventional deadlifts. Their subjects lifted approximately the same amount of weight as the subjects in the current study. Because these investigators used only one camera in recording a sagittal view of the lifters, they performed a 2-D analysis and calculated moments and moment arms at LO about the lumbar spine, hip, and knee. Although a 2-D analysis is appropriate in calculating hip and spinal moments and moment arms during both the sumo and conventional deadlifts, it is only appropriate in calculating ankle and knee moments and moment arms if the feet are pointing straight ahead. Because the feet are turned out to a greater extend in the sumo deadlift (42°) compared with the conventional deadlift (14°), a 2-D analysis for the sumo deadlift will produce greater errors in ankle and knee moments and moment arms compared with the conventional deadlift. This is clearly demonstrated in Table 7. Although 2-D analyses were significantly different than 3-D analyses for both the sumo and conventional deadlifts, the largest differences occurred during the sumo deadlift. From Table 7, ankle and knee moment arms for the conventional deadlift were generally only a few centimeters different between a 2-D and 3-D analysis. In contrast, ankle and knee moment arms for the sumo deadlift were generally 20–25 cm different between a 2-D and 3-D analysis.
Similar to data from Cholewicki et al. (5), there were no significant differences in hip moments and moment arms between sumo and conventional deadlifts. However, unlike the knee moments in the current study (Table 6), knee moments from Cholewicki et al. (5) were not significantly different between sumo (18 N·m) and conventional (18 N·m) deadlifts. The knee moments calculated from a 2-D analysis (Table 7) are relatively similar in magnitude to the 2-D knee moments from Cholewicki et al. (5) but quite different than the knee moments calculated by a 3-D analysis (Table 7). Ankle moments have previously been reported only for the conventional deadlift (2), with these authors finding similar ankle moment magnitudes as the current study.
Joint moments and moment arms during the deadlift and squat have been reported with respect to the barbell COM only (2,5,19). Because joint moments are also generated by body segments, moments and moment arms relative to the system load (i.e., barbell plus those body segments that contribute to generating joint moments) were also calculated (Table 6). Although moment arms were generally only 1–2 cm different between the barbell COM and the system COM, system-generated joint moments were much greater than barbell generated joint moments due to the greater load of the system. During the sumo deadlift, ankle and knee moments were generally 40–50% greater with respect to the system weight compared with the barbell weight. Similarly, hip moments at LO and KP were generally 25–30% greater for the system weight compared with the barbell weight. Therefore, joint moment contributions from body segments should not be discounted when calculating the actual joint moments that occur during lifting.
One of the most interesting findings in the current study is that ankle plantar flexor moments and knee flexor moments were primarily generated during the conventional deadlift, whereas ankle dorsiflexor moments and knee extensor moments were generated during the sumo deadlift. In both deadlift styles, hip extensor moments were generated exclusively. This suggest that during the conventional deadlift the ankle plantar flexors, knee flexors, and hip extensors are primarily responsible for causing or controlling movements at the ankles, knees, and hips, respectively. Similarly, during the sumo deadlift the ankle dorsiflexors, knee extensors, and hip extensors are primarily responsible for causing or controlling ankle, knee, and hip movements, respectively. It can be hypothesized from these data that the primary lower extremity muscles involved during the conventional deadlifts are the hamstrings, gluteus maximus, gastrocnemius, and soleus, whereas the primary lower extremity muscles involved during the sumo deadlifts are the gluteus maximus, hamstrings, quadriceps, and tibialis anterior. Electromyography (EMG) should be employed during these two deadlift styles to test these hypotheses.
It should be noted that ankle and knee moments during the sumo deadlift are relatively large in magnitude compared with ankle and knee moments generated during the conventional deadlift. For example, at KP the system load COM is slightly anterior to the knee axis during the conventional deadlift (Table 6), thus generating a very small knee extensor moment. Consequently, the knee extensor moment due to the external barbell load attempts to extend the knees. To counteract this knee extensor moment, increased activity from the knee flexors generate a knee flexor moment needed in order to control the rate and extent of knee extension. This is one reason why the hamstrings may be more active and the quadriceps less active during the conventional deadlift compared with the sumo deadlift. Because the knee flexors are also hip extensors, they are attempting to extend the hip and flex the knee simultaneously. In contrast, because the system load COM is posterior to the knee axis during the sumo deadlift, a large knee extensor moment is needed to counteract the large knee flexor moment generated by the system load. This implies that the quadriceps may be more active during the sumo deadlift compared with the conventional deadlift.
If the external barbell load causes the knees to extend prematurely or excessively, the lifter will have to complete what is referred to as a “stiff-leg” deadlift, which occurs when the knees are at or near full extension. This decreases quadriceps activity, increases hamstring activity (28), and increases erector spinae activity due to the spine being in a more bent and rounded position. This also places the lumbar spine in a more vulnerable position, with a higher risk of injury (5). Although spinal forces and moments were not quantified, the more upright trunk position observed during the sumo deadlift may decrease spinal loads. Cholewicki et al. (5) have shown that compared with the conventional deadlift, the sumo deadlift generated a 10% reduction in the L4/L5 moment and an 8% decrease in the L4/L5 shear force. This suggests that the lower back may be at lower risk of injury during the sumo deadlift. However, the conventional deadlift may be more effective in strengthening back and hamstring musculature. An EMG analysis is needed to test these hypotheses.
The authors extend a special thanks to Andy Demonia, for all his help and support in collecting the data, and a special thanks to Tom and Ellen Trevorah (meet directors), for all their support for this project.
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