The deadlift (DL) is a full-body strength exercise that is frequently performed in resistance training settings. It is most often used for strength and power development, as it allows for the use of heavy loads, which generate large muscular forces (3,10). It requires the lifter to grasp the barbell in a position similar to a squat, then elevate the load in a continuous motion through extension of the lower back, hip, knee, and ankle joints (2–4). It is crucial that the barbell remain close to the body throughout the lift, ensuring that the load remains closer to the lifter's center of gravity (19).
There are many variations of the DL exercise. One such variation is the hexagonal bar (HBar) DL. The HBar enables athletes to perform the DL while the load is positioned closer to their body, as the lifter is actually inside the frame of the bar. The HBar also enables the lifter to keep a more erect posture, reducing strain on the lumbar spine (12). However, little research has been done on comparison of the HBar with a conventional DL using an Olympic bar (OBar). To our knowledge, only one study (19) has examined this comparison and found that the HBar DL produced greater peak force, peak velocity, peak power, and 1-repetition maximum (1RM) compared with the OBar.
The isometric midthigh pull (MTP) is a static exercise in which an athlete generates maximum force against a stationary bar (1,5,17), whereas peak force and rate of force development (RFD) are easily measured. The isometric MTP has several advantages to gross measures of strength, such as reduced risk of injury, minimal fatigue, and low technical errors (5,7). Although isometric peak force has been shown to correlate well with dynamic performance, this seems to only be the case in movements with similar joint angles (1,15,16,23). Therefore, peak force produced during an isometric MTP correlates well with weightlifting movements (1,7,11,14), such as the second pull of the clean, yet correlation with an isometric DL is unknown.
The HBar is commonly used in many strength and conditioning settings. However, to properly use it with DL training, further research is needed to examine how it compares with the OBar. Therefore, the purpose of this study was to compare MTP and DL isometric strength between an OBar and an HBar, and their relationship to dynamic performance.
Experimental Approach to the Problem
This study used a repeated-measures design to compare isometric strength between an OBar and HBar and between an MTP and a DL. Subjects were required to attend 3 days of testing 24–48 hours apart and performed both lifts, using both bars. Subjects also performed a countermovement jump (CMJ) to compare isometric strength with dynamic performance.
Twenty resistance-trained men (age = 24.05 ± 2.09 years, age range = 20–27 years, height = 178.07 ± 7.05 cm, mass = 91.42 ± 14.44 kg) with at least 1-year experience performing the DL volunteered to participate. All participants reported previous experience using the hex bar. They were free from any musculoskeletal injuries. Before data collection, all subjects were notified of potential risks and gave written informed consent, approved by the University Institutional Review Board.
For the OBar MTP, the bar was fixed in a power rack at midthigh level and secured with the use of straps. A goniometer was used to ensure that the knee angle was 135 degrees. Hands were positioned outside the knees, using a self-selected grip (Figure 1). The HBar was secured at the same rack height as the OBar with hands grasping the low handles with a neutral grip (Figure 2). For the isometric DL, standard plate height was used for position of both bars (Figures 3 and 4) and knee angle was not controlled. The same grips were used for DL and MTP.
Upon arriving at the laboratory, subjects read and signed an informed consent document. Body mass and height were obtained using an electronic scale (ES200L; Ohaus Corporation, Pinebrook, NJ, USA) and stadiometer (Seca, Ontario, CA, USA). Before testing, subjects performed a dynamic warm-up consisting of 10 m of walking knee hugs, walking lunges, and Frankenstein walks. They then performed a CMJ. An EPIC jump device (EPIC Athletic Performance, Inc., Colorado Springs, CO, USA) was positioned next to the force plate. Subjects' reach was measured with the dominant hand. While standing on the plate, subjects performed 3 CMJ trials, with 1-minute rest between attempts. Although 3 trials were the minimum performed, subjects continued to perform trials until they could no longer successfully hit the vanes of the device. After the completion of CMJ trials, subjects held still in the bottom position of a countermovement, and ankle, knee, and hip angles were recorded.
Subjects were then fitted to both bars for both lifts. For the OBar MTP, a handheld goniometer was used to ensure a 135-degree knee angle. This bar height was recorded and maintained for the HBar MTP. Subjects were given lifting straps to secure their hands to the bar. For familiarization, they performed 2–3 trials with each bar and each lift with a warm-up of 5 pulls at 50% effort, 3 pulls at 75%, and 1 pull at 90%, with 1-minute rest between sets and 3-minutes rest between conditions until a consistent effort was shown. They were instructed to pull against the bar as hard and fast as possible for 5 seconds. Ankle, knee, and hip angles were recorded for both bars and lifts.
Subjects followed the same warm-up procedures as day 1. They then performed 3 trials each of either an isometric MTP or DL, using both bars. They were given 1-minute rest between trials and 3 minutes between conditions. On day 3, they followed the same procedures, using whichever lift had not been tested on day 2.
For all tests, subjects stood on an Advanced Mechanical Technologies force plate (AMTI, Watertown, MA, USA) sampling at 1,000 Hz. All data were collected and analyzed with custom LabVIEW (v2013, National Instruments, Austin, TX, USA) software. For the lifts, isometric peak ground reaction force (PGRF) and RFD were measured. For the CMJ, jump height (estimated from the force plate), GRF, and impulse were measured. The average of the 3 trials was used for analysis.
A 2 × 2 (lift × bar) repeated-measures analysis of variance (ANOVA) analyzed all isometric force variables. Significant main effects were followed up with simple ANOVAs. A 2 × 2 × 3 (lift × bar × joint) repeated-measures ANOVA analyzed joint angle. Significant interactions were followed up with dependent t-tests. Pearson correlations analyzed relationships between all CMJ and isometric force variables. Alpha was set at 0.05 to determine significance.
For PGRF and RFD, there were no interactions or main effects for bar. However, there were main effects for lift, with MTP being greater than DL (Table 1).
Countermovement jump values are shown in Table 2. Countermovement jump impulse was significantly correlated with RFD of OBar DL (0.52). Isometric PGRF of both bars and lifts showed significant correlations with CMJ GRF and impulse (Table 3).
For MTP ankle angle, OBar was less dorsiflexed than HBar and CMJ and HBar also had less dorsiflexion than CMJ (Table 4). For MTP knee angle, both OBar and HBar were more extended than CMJ (Table 4). For MTP hip angle, OBar and HBar were significantly more extended than CMJ. For DL ankle and knee angles, there were no differences between OBar, HBar, or CMJ, but CMJ hip angle was more extended than OBar and HBar (Table 4).
The purpose of this study was to compare isometric strength between Olympic and hexagonal barbells for MTPs and DLs and compare these with dynamic performance via a countermovement jump. The major findings were that MTP force was greater than DL for both bars, MTP joint angles were more extended than DL, and the strongest correlations were seen between DL force and CMJ impulse. These may be because of anatomical differences of body position between the MTP and DL, the joint angles of the lifts, and the need to maximize explosive force during efforts such as isometric pulls and vertical jumping.
Isometric MTP is a commonly used assessment to measure strength because of its similarity with the second pull of the clean. A characteristic of this lift is a knee angle of 130–140 degrees and an upright trunk, commonly referred to as the power position as it represents the point, during weightlifting movements, where the highest forces and power outputs are achieved (1,14). In comparing weightlifting and powerlifting exercises, Garhammer (11) reported average power output in the DL to be one-half to one-third of that developed during the snatch or clean, attributed to the lower vertical velocities generated throughout the DL. Additionally, in a review of existing studies of weightlifting and powerlifting, Garhammer (11) reported that power testing has more potential as a tool for predicting performance in weightlifting movements than powerlifting. The current study examined 2 separate lifts that are classically considered weightlifting specific (MTP) and powerlifting specific (DL). The DL is commonly used to generate maximum force, whereas the clean is used to generate maximum power (14,19,20). Despite the overlap, it has been repeatedly demonstrated that the development of strength and power are distinct qualities (17). Further, previous research has shown that the joint angle of isometric tests significantly impacts the relationship to dynamic performance (1,15). Therefore, the higher power production during weightlifting movements would result in greater outputs during the isometric task in a similar position.
The force differences between MTP and DL may also be because of anatomical differences between the positions. The conventional DL at heavy loads is commonly viewed as the most challenging movement for the lumbar spine (13,18,19), with liftoff to knee being the most difficult (4). Examining elite powerlifters, Cholewicki et al. (6) found that loads on the lumbar spine ranged from 14k to 17k Newtons during the DL. In contrast, the position of the MTP is often referred to as the power position (14). At MTP, greater extension angles at the ankle, knee, and hip allow for a more advantageous length-tension relationship of the muscles involved than at the DL position. The shorter a muscle, the less tension it is capable of generating (9,10). As the fibers are more optimally overlapped at MTP, greater force is able to be developed than at DL.
Because of the dimensions of the force plate, participants were required to perform the DL with a conventional stance. Although all participants had experience performing the DL with a hexagonal bar, many were powerlifters who used a sumo-style when performing dynamic DLs with an Olympic bar. This change in stance may have impacted some lifters' force production. During the sumo-style DL, the feet are positioned further apart and turned outward, with the hands positioned inside the knees (8–10,18). Because of the differences in biomechanical positioning, Escamilla et al. (9,10) found that sumo-style DLs resulted in 25–30% less mechanical work. Additionally, Cholewicki et al. (6) observed a 10% reduction in L4/L5 moment and 8% reduction in L4/L5 shear force when using the sumo DL vs. conventional. As subjects were performing maximum isometric actions, differences in forces on the body with the conventional stance may have affected their force-generating capability.
Despite greater force for the MTP, the strongest correlations were seen between DL PGRF and CMJ impulse. This is contrary to what was expected, as, unlike the DL, both the CMJ and MTP are often used as measures of explosive performance. Previous research has reported conflicting results in the relationship between isometric and dynamic performance. McGuigan et al. (17) found very strong correlations between isometric MTP and vertical jump height, and with 1RM squat and bench press. Thomas et al. (21) found that isometric MTP performance did not significantly correlate with vertical jump peak velocity or jump height; yet, it did correlate with peak force and peak power. As in the present study, previous research found low correlation with dynamic measures of performance and RFD (17,21).
As mentioned, multiple studies have found that the strength of the relationship between dynamic tasks and isometric performance are dependent on similarity of joint angles (1,5,15,16). The lack of correlation between MTP and CMJ could be attributed to the differential biomechanical characteristics of the 2 movements. The MTP uses an exclusive isometric muscle action, whereas the CMJ uses an eccentric muscle action followed by a very brief isometric and finally concentric muscle action (21). Thus, the CMJ uses the stretch-shortening cycle, unlike isometric actions. Additionally, MTP performance relies solely on maximal force production, whereas CMJ relies on both maximal force and velocity, a more complex relationship resulting in power (21).
In the present study, MTP ankle, knee, and hip joint angles were significantly more extended than DL and CMJ. However, there were minimal differences between DL and CMJ angles, with the only difference seen at the hip. This could explain the stronger correlations between DL and CMJ variables. Previous research has found the position of the knee during the first pull to be near the angle where knee extensor strength is approaching maximum (22). Additionally, both the first pull of the DL and CMJ require the application of high force in a short period of time (22). During a dynamic DL, an explosive concentric action is required to move the load from the ground; this high reliance on rapid strength production during liftoff is similar to that required to lift the body from the ground during a CMJ (22). Although rapid strength production is also required for MTP and dynamic weightlifting movements, our subjects were required to have experience with the DL, but not weightlifting movements.
Angle differences may be explained by the biomechanical characteristics of body position specific to each bar. At MTP, OBar knee angle was maintained at 135 degrees, with HBar initiated from the same rack height. This produced no difference in knee flexion between bars. Despite the similarity of knee angle, there were differences between bars as the HBar requires the lifter to be centered inside the frame while extending their joints and producing force vertically. With the OBar, the lifter is positioned behind the barbell. Therefore, these different body positions result in MTP ankle and hip angles with the OBar being significantly more extended than with the HBar.
The above anatomical characteristics are similar for the DL position, yet rather than controlling knee angle, pulls were always initiated from standard plate height from the floor. There were no differences in DL knee angles between bars, but the OBar ankle angle was significantly more extended than the HBar. This can likely be explained by the position of the lifter in relation to the barbell. With the OBar, the lifter was positioned behind the barbell, with more extension at the joints as mentioned previously. In contrast, the HBar positions the lifter inside the bar at a fixed position, resulting in greater ankle flexion than the OBar.
The findings of the current study indicate minimal difference in force between hexagonal and Olympic barbells. Therefore, regardless of bar selection, the position from which the pull is initiated may play the largest role in force production. However, athletes and strength coaches interested in vertical jump performance may benefit by initiating pulling movements from the DL position as evidenced by the high correlation with CMJ impulse. Because of similarity in joint angles between DL and the CMJ, deadlifting with either bar may be beneficial to athletes whose sports require frequent jumping.
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