The deadlift is an exercise that is often included in athlete strength and conditioning programs [1
]. Traditionally the deadlift has been performed using a conventional barbell (conventional barbell deadlift: CBD) and the main deadlift variations have come in the form of the technique used to perform the lift, with lifters applying a conventional (hands gripping the barbell outside of the legs) or sumo (hands gripping the barbell between the legs) [2
], in addition to different loading strategies [3
]. The introduction of the hexagonal barbell provided one of the most common deadlift variations used by strength and conditioning coaches for their athletes; however there is a paucity of research on the effect its use has on the mechanical demands of the deadlift [1
] (hexagonal barbell deadlift: HBD). Researchers have shown that significantly higher peak force, velocity and power can be achieved with the HBD [1
]. Furthermore, researchers have shown that the vastus lateralis makes a significantly greater contribution during the HBD. The biceps femoris makes a significantly greater contribution during the concentric phase of CBD, while the erector spinae makes a significantly greater contribution to the eccentric phase of the CBD [1
]. However, some researchers found no significant difference between CBD and HBD peak force [5
One of the potential limitations of these studies is that they used the combined method, combining force plate derived force data with motion capture system or linear position transducer derived barbell velocity. This method has been shown to significantly over estimate power during lower-body resistance exercises [6
]. Furthermore, because of the incompatibility between the typical conventional and hexagonal barbell lengths and most force plate dimensions, obtaining measures of work and power directly from the barbell may be more methodologically appropriate [6
]. This is because the force plate method relies on the assumption that barbell and body system mass do not change during performance. If, as is the case as the barbell leaves the ground during deadlift performance, they do then this assumption is violated and methodological integrity is compromised.
It should also be noted that recent research has questioned the use of peak instantaneous metrics like peak force and peak power [10
]. While these metrics are popular and can be useful, they represent a very small part of the movement of interest. For example, if data are recorded at 1000 Hz peak instantaneous values will only represent 1 millisecond. Therefore, it has been recommended that researchers and practitioners consider variables like mean force, the work performed and power achieved during whole phases of motion to get a fuller understanding of the mechanical demands of resistance exercises.
Therefore, there is currently a need to explore other mechanical variables of interest using appropriate methodology to contribute to the small but growing body of research. Doing so will help strength and conditioning practitioners make more informed decisions about the potential suitability and benefits of the CBD and HBD. Investigators have often quantified the mechanical demand of resistance exercises by studying the peak instantaneous values of variables like force, velocity and power [3
]. However, it has been suggested that mechanical demand should be quantified using data averaged over phases of interest, because this provides greater insight into the demand placed on the individual over the phase of interest, rather than the demand placed on the individual over what are typically very short sampling durations [12
]. Therefore, mean force, mean velocity, and mean power provide insight about how hard individuals must push or pull an implement to move it, and the effect this has on the implement, respectively. While studying barbell motion and deriving measures, like force, work, and power does not provide a comprehensive picture of the mechanical demand that is placed on the lifter, it provides researchers with a foundation from which they can decide whether the area requires further research. Therefore, the aim of this study was to compare the mechanical demands of the CBD and HBD. It was hypothesised that the HBD would enable participants to lift heavier loads. Additionally, it was hypothesised that the differences in hand placement (the HBD has handles outside the legs with the palms facing one another either side of the lower-leg) would result in significantly greater barbell displacement during the HBD, and this, combined with the heavier loads, would make significantly greater mechanical demands on participants.
Participants were able to lift significantly greater loads during the HBD (194 ± 20 vs. 183 ± 22 kg; p
= 0.003, ES = 0.503). The results of the comparison between the variables used to describe the mechanical demand of the CBD and HBD are presented in Table 1
. While the mean velocity of the barbell was significantly faster during HBD (15%, p
= 0.012, ES = 0.459), the total displacements of the two barbells were not significantly (1%, p
= 0.216) or practically (ES = 0.126) different. However, CBD duration was significantly longer than the HBD equivalent (20%, p
= 0.012, ES = 0.923). Furthermore, load was accelerated for significantly longer during the HBD (36%, p
= 0.004, ES = 1.778). Finally, mean force (6%, p
< 0.001, ES = 0.494), work (7%, p
< 0.001, ES = 0.512) and mean power (28%, p
< 0.001, ES = 0.889) was significantly greater during HBD.
The aim of this study was to test the hypothesis that the HBD enables the use of heavier loads and in so doing places a greater mechanical demand on the lifter. This was done by obtaining mechanical parameters directly from barbell motion and averaging them over the lifting phase. In general, our results supported this hypothesis. Significantly greater loads were lifted over a similar range of motion. Because the HBD was heavier, their displacement required significantly greater mean force to be applied to the Hex bar, meaning that significantly more work was performed at a significantly faster rate during the HBD.
To date, three studies have studied differences between the CBD and HBD [1
]. However, only one of these has compared differences between their 1RM [1
]. The results of the current study showed that participants were able to lift significantly more (Table 1
) during the HBD. This is contrary to the study that compared CBD and HBD and found no significant differences (181 ± 27 kg vs. 181 ± 28 kg) [1
]. The 1RM values presented by Swinton et al. showed that HBD 1RM was 8% larger than the CBD 1RM. Interestingly, the 1RM data presented by Swinton et al. [3
] and in the present study suggest that the improved leverages afforded by the Hex barbell facilitate the lifting of greater loads. Furthermore, the results of the current study show that these heavier loads are lifted through the same range of motion.
Although the total displacement of the barbell during the CBD and HBD was not significantly different, the duration of the lifting phase was significantly longer during the CBD. This resulted in a significantly faster mean velocity during the HBD, which agrees with related data (peak velocity) presented by Camara et al. [1
] and Swinton et al. [3
]. Interestingly, Camara et al. [1
] studied CBD and HBD with 65% and 85% 1RM, while Swinton et al. [3
] used loads ranging from 10% to 80% 1RM. Therefore, the current study is the first to study HBD with 90% 1RM and it shows that in spite of this heavier load, the Hex barbell is still displaced significantly faster. This may be explained by the fact that the barbell was accelerated for significantly longer during the CBD and because of the significantly smaller horizontal displacements that have been presented in the literature [3
]. The significantly faster velocity and longer time spent accelerating the barbell could make the HBD an excellent alternative resistance exercise for strength and conditioning coaches looking for a resistance exercise to maximize these qualities.
The significantly greater loads that were lifted during the HBD required a significantly larger mean force to displace them. This is to be expected, because ultimately the displacement of a mass is dependent on a combination of how much force is applied to it across the duration of the lifting phase (impulse) [10
]. While this finding suggests that the HBD may provide an excellent alternative resistance exercise for strength and conditioning coaches looking for a resistance exercise to maximize the force application, mean barbell velocity, in addition to how long the barbell is accelerated for, previous research must be considered. For example, Swinton et al. [3
] showed that the HBD was positioned significantly closer to the athlete (based on horizontal displacement from the start to end position). Furthermore, Camara et al. [1
] showed that the way the main muscles that contribute to deadlift performance are recruited changes when the Hex barbell is used. For example, they showed that the vastus lateralis makes a significantly greater contribution throughout the HBD, while the biceps femoris makes a significantly greater contribution during the concentric phase of CBD. Therefore, while the HBD may maximise some elements of mechanical output during deadlift performance, the strategy used to achieve these changes. This could have important implications for training outcomes. However, more detailed biomechanical analysis and training study based research is needed to corroborate this.
There were significant differences between the work performed displacing the barbell during CBD and HBD performance. Furthermore, because HBD lifting phase duration was significantly shorter, there were significant differences in the mean power achieved during CBD and HBD deadlift performance. Work performed during HBD has not been studied before and it would appear that the significant differences in the load that was lifted and therefore mean force, had a significant impact on this variable. Furthermore, because the effect that the Hex barbell had on phase duration was moderate to large the mean power achieved by displacing the larger HBD loads at a faster velocity was significantly larger. Not only does this finding agree with previous research [1
], it also suggests that, in addition to mean power been a more appropriate variable to quantify this capacity [10
], it is also sensitive enough to reflect differences that have been found in the inappropriate peak power alternative that has been used. Whether this means that mean power should be used over peak power is beyond the scope of this paper and readers are encouraged to read the recent review by Winter et al. [10
] to help inform their decision.
Although this study provides useful information that contributes to the growing body of research, it is not without its limitations. Given the amount of research that has been done into the most appropriate resistance exercise power, many may feel that the method used in this study was inappropriate. However, we would argue that, while that argument would be warranted if we’d studied resistance exercises where all of the lifter and barbell system load was on the force plate at the beginning, this isn’t the case during the deadlift. Comfort et al. [20
] overcame this limitation when studying power clean variations by instructing participants to start the movement from a position where the barbell was held off of ground. However, for obvious reasons, this was not possible during deadlift performance with 90% 1RM. Therefore, we feel confident that the linear position transducer method was appropriate for this study. Another limitation of this study could be found in our use of the linear position transducer. For example, Swinton et al. [3
] have demonstrated that load influences horizontal displacement during the HBD. One of the main limitations of the linear position transducer approach is that, with the exception of some commercially available systems, it cannot differentiate between horizontal and vertical displacement. Consequently, using a linear position transducer to record barbell velocity data may have resulted in some bias in the results because it relies on assumption that any horizontal barbell displacement is consistent across loads, and this may not be the case. Finally, the authors are cognisant that the mechanical parameters examined in the present study do not necessarily reflect muscle work or any differences in the movement strategies that might be employed to displace these two distinctly different barbells. However, in light of the results of this and other studies [1
] more detailed biomechanical analysis could be warranted to quantify these.
To summarise, the results of this study showed that significantly heavier loads can be lifted during HBD. Furthermore, they are moved through the same range of motion significantly faster, and the load is accelerated for significantly longer. These differences extend to the work performed and the mean power achieved in displacing the different barbells. Strength and conditioning practitioners should bear in mind that the strategies used to achieve these differences could have a significant effect on training outcomes.