What do we know about muscle activation in deadlifts?

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In a previous article, Chris Beardsley (@SandCResearch) discussed a study in which the biomechanics of conventional and sumo deadlifts were compared. At the end of the study, the researchers concluded that sumo deadlifts involved greater knee extension moments and therefore likely involved the quadriceps to a greater extent than conventional deadlifts.

They also noted that the sumo deadlifts led to greater ankle moments, which were dorsiflexion moments throughout the lift, while the conventional deadlift maintained plantar-flexion moments throughout the lift. They therefore concluded that sumo deadlifts likely made use of the tibialis anterior to a greater extent, while the conventional deadlift likely made use of the calf muscles to a greater extent.

Finally, they noted that while the conventional deadlift did display a slightly greater hip extension moment than the sumo deadlift, this difference was not significant. They therefore suggested that the hamstrings and gluteus maximus were equally active in both types of deadlift. However, without electromyographic (EMG) analysis of the muscles concerned during the two types of deadlift, the researchers commented that it was not possible to be certain. Consequently, they went away for a year and returned to examine this exact problem.

The Study: An electromyographic analysis of sumo and conventional style deadlifts, by Escamilla, Francisco, Kayes, Speer and Moorman, in Medicine and Science in Sports and Exercise, 2002

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What did the researchers do?

The researchers wanted to use EMG analysis to explore lower body and trunk muscle activation in deadlifts. Specifically, they wanted to compare activity in sumo and conventional deadlift variations. Because they like living dangerously, they also decided to compare the activity of the same muscles during both types of deadlift both with and without a belt. So they recruited 13 Division IA collegiate players, who were experienced in resistance training and had performed both types of deadlift in their training beforehand. The subjects performed four trials of deadlifts, including the sumo and conventional deadlifts, both with and without a lifting belt. The subjects used the same weight for each of the four deadlift variations, which was equivalent to their 12RM, although the researchers did not specify which deadlift variation the 12RM was obtained for.

During the trials, the researchers measured the EMG activity of the following muscles, using surface electrodes: rectus femoris, vastus lateralis, vastus medialis, lateral hamstrings (biceps femoris), medial hamstrings (semitendinosus and semimembranosus), lateral gastrocnemius, medial gastrocnemius, tibialis anterior, hip adductors (adductor longus, adductor magnus, and gracilis), gluteus maximus, L3 paraspinals, T12 paraspinals, middle trapezius, upper trapezius, rectus abdominis and external obliques.

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What happened?

Non-EMG measurements

The researchers reported that the average load across all subjects and deadlift types was 123.1 ± 18.6kg, which was the self-reported average 12RM of the subjects. The average foot angle for each type of deadlift was: 25.1 ± 8.7 degrees for the sumo deadlift and 7.0 ± 3.2 degrees for the conventional deadlift. So the athletes turned their feet out considerably more during sumo deadlifts than during conventional deadlifts. The stance widths for each type of deadlift were: 64.9 ± 16.9cm for the sumo deadlift and 32.7 ± 5.3cm for the conventional deadlift. The hand widths for each type of deadlift were: 25.3 ± 7.7cm for the sumo deadlift and 48.0 ± 8.7cm for the conventional deadlift.

EMG measurements

The researchers reported a number of significant EMG differences between the two types of deadlifts. They found that the sumo deadlift had significantly greater EMG activity in the vastus lateralis, vastus medialis and tibialis anterior than the conventional deadlift. They also found that the conventional deadlift had significantly greater EMG activity in the medial gastrocnemius than the sumo deadlift. The EMG activity of the various muscles measured is shown in the following chart.

Interestingly, although the previous study performed on conventional and sumo deadlifts, by Cholewicki (1991), found a significantly greater back extensor moment at L4/5 in the conventional deadlift than in the sumo deadlift, the researchers in this study did not find any difference at either L3 or T12. This may imply that the sumo deadlift is as effective a back exercise as the conventional deadlift. However, it is important to note that only two measurement points were taken and the weights used were relatively light (i.e. 12RM). The researchers reported that when lifting with a belt, the subjects displayed significantly greater EMG activity in the rectus abdominis but significantly less EMG activity in the external obliques, as can be seen in the following chart.

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What did the researchers conclude?

Comparison of sumo and conventional deadlifts

The researchers concluded that these results supported their analysis of the moments involved in the two types of deadlift that they presented previously. In the previous study investigating the moments, the researchers concluded that sumo deadlifts involved greater knee extension moments and therefore likely involved the quadriceps to a greater extent that conventional deadlifts. This proposal was supported by the current EMG study.

The researchers also noted that the sumo deadlifts led to greater ankle moments, which were dorsiflexion moments throughout the lift, while the conventional deadlift maintained plantar-flexion moments throughout the lift.  They therefore concluded that sumo deadlifts likely made use of the tibialis anterior to a greater extent, while the conventional deadlift likely made use of the calf muscles to a greater extent. This proposal was supported by the current EMG study.

Finally, they noted that while the conventional deadlift did display a slightly greater hip extension moment than the sumo deadlift, this difference was not significant. They therefore suggested that the hamstrings and gluteus maximus were equally active in both types of deadlift. This proposal was also supported by the current EMG study.

In summary, in this study, the researchers concluded that the sumo deadlift displayed greater quadriceps and tibialis anterior activity, while the conventional deadlift displayed greater calf muscle activity. They also concluded that there was no significant difference in the activity of the gluteus maximus and hamstrings between the two exercises.

Comparison of belt to no-belt lifting

The researchers concluded that the rectus abdominis and external obliques were the only muscles that were affected by the use of a belt during the two deadlift types. They concluded that when lifting with a belt, there was greater EMG activity in the rectus abdominis but significantly less EMG activity in the external obliques.

The researchers suggest that the increased rectus abdominis activity might occur with a belt because the belt provides resistance against which the rectus abdominis is able to contract, which enables a greater voluntary contraction than would be achieved without a belt.

The researchers suggest that the greater external oblique activity may occur when not wearing a belt because of the increased lateral stability that is required without this support.

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What were the limitations?

A significant limitation of this study was that the sumo and conventional deadlifts were performed using the same weight, which may not have been the same percentage of 1RM for each. Additionally, while the researchers were keen to compare the results of this study to the one that they performed to gain an understanding of the moments, this one was not performed using powerlifters as subjects but rather team sports athletes and this may have resulted in slightly different technique being used. Also, the EMG results that were presented were only mean levels of activity and there may have been variances in peak EMG that were therefore not reported.

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What are the practical implications?

Training to improve both deadlift variants should of course involve significant amounts of gluteus maximus and hamstrings work. However, the sumo deadlift should also include a greater emphasis on quadriceps and tibialis anterior strength, while the conventional deadlift will require greater calf muscle strength.

As the conventional and sumo deadlifts lead to similar EMG activities in the main leg and trunk muscles, this indicates that these exercises can perform very similar roles in a training program and should have good carryover to one another.

Wearing a belt causes greater rectus abdominis activity than not wearing a belt but reduces the activity of the external obliques. The use of a belt may therefore be useful for bodybuilders who wish to maximize the hypertrophy of the front abdominals but limit the hypertrophy of the obliques to emphasize the shoulder-waist ratio.

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