Group of Scientists from Health Research Center, University of Almeria, Spain, published a systematic review of deadlift exercise and its variants combining published articles from 2002 till 2019. From initially selected 207 publications, 28 articles met inclusion criteria, and nineteen of these were eventually chosen for the review since they met excellent quality in the methodological process based on the PEDro quality scale (Table 1).

All studies contained :

• A cross-sectional or longitudinal study design
• Evaluation of neuromuscular activation during Deadlift exercise or variants
• Inclusion of healthy and trained participants, with no injury issues at least for six months before measurements
• Analyzed “sEMG amplitude,” “muscle activation” or “muscular activity” with surface electromyography (sEMG) devices

The deadlift is frequently performed primarily when the goal is the strengthening of the thigh and posterior chain muscles, specifically gluteus, hamstrings, erector spinae, and quadriceps. Thus, Deadlift is classified as one of the most typical resistance exercises for posterior lower limb strengthening, as well as its variants. Moreover, Deadlift has been mentioned in numerous studies comparing this exercise with other variants such as Stiff Leg Deadlift, Hexagonal Bar Deadlift, or Romanian Deadlift. It has also been contrasted with other less popular variants such as Sumo Deadlift, unstable devices, and elastic bands Deadlift, among others.

The main purpose of this research was to systematically review the current literature investigating muscle activation measured with sEMG of muscles recruited when performing the Deadlift exercise and all its best-known variants. The following results provided the researcher, clinician, and athletes with relevant information about the use of the best exercise to activate a specific muscle or group of muscles associated with the Deadlift and its variants.

Deadlift variants included were: the Conventional Barbell Deadlift (10/19 studies) and the Stiff Leg Deadlift (6/19 studies), which are followed by Unilateral Stiff Leg Deadlift (2/19 studies), Romanian Deadlift (2/19 studies), and Hexagonal Bar Deadlift (2/19 studies). The biceps femoris has been the most investigated muscle in terms of sEMG for the Deadlift exercise and its variants (13/19 studies). Gluteus maximus is the next muscle most evaluated (10/19) followed by vastus lateralis and erector spinae muscles (9/19). The semitendinosus and rectus femoris are positioned in fourth position (5/19) followed by vastus medialis, external oblique, and medial gastrocnemius (3/19).

Main findings of the study are:

• Erector spinae showed the greatest muscle activation during the Stiff Leg Deadlift exercise, and also showed a similar muscle activation than the gluteus maximus or biceps femoris during Deadlift and Hexagonal Bar Deadlift exercises.
• When comparing muscle activation within the hamstrings, there was a greater activation for the semitendinosus muscle than the biceps femoris during Stiff Leg Deadlift, which is even more pronounced when performing Unilateral Stiff Leg Deadlift.
• The concentric phase showed greater activation in the gluteus maximus and hamstring muscles than the eccentric phase for all exercises evaluated.
• The vastus lateralis showed greater muscle activation than the biceps femoris, and the rectus femoris showed greater muscle activation than the biceps femoris and gluteus maximus during Deadlift exercise.
• Erector spinae and semitendinosus are the most activated muscle in the Deadlift exercise.
• When comparing muscle activation within the hamstrings, there was a greater activation recorded for the semitendinosus muscle in comparison to that for the biceps femoris.
•  Erector spinae and quadriceps muscles are more activated than gluteus maximus and biceps femoris muscles within Deadlift exercises.

Apart from the above-mentioned Deadlift exercises, there are some other studies which focused on less conventional variants of this movement concluding:

• The Good Morning exercise appears to be an appropriate substitute to Romanian Deadlift when it is preferable to place the load on the back instead of lifting it from the floor. 
• Good Morning provokes a similar muscular pattern activation as Romanian Deadlift, but it showed more muscle activation for the semitendinosus and less muscle activation for the biceps femoris than Romanian Deadlift.
• Muscular activation presented during elastic bands Stiff Leg Deadlift was lower than that elicited during free weights Stiff Leg Deadlift, with significant differences when referring to the gluteus maximus, biceps femoris, and semitendinosus muscles.

As the authors concluded, Deadlift is an exercise frequently performed to improve the lower limb muscles, mainly biceps femoris and semitendinosus (hamstrings), and gluteus maximus. Based on this systematic review about the sEMG activity in the Deadlift exercise and its variants, it has been demonstrated that other muscles such as erector spinae and quadriceps are more activated than hamstrings and gluteus maximus, although some studies found conflicting results.

Deadlift exercise comprises a movement which could have a transference into daily life activities; also considered as one of the greatest compound lifts, as it involves several muscles groups coordination. A broad spectrum of Deadlift variants has been reported, so diverse applications for these exercises could merge, covering health, rehabilitation and performance environments.

Therefore, it must be considered that muscle activation would depend on the Deadlift variant performed. For instances, posterior thigh muscles would show greater muscle activity when performing exercises that holds the knees on a fixed and extended position (e.g. Romanian Deadlift or Straight Leg Deadlift). On the contrary, whether your goal is to maximize anterior thigh and lower back muscle activity, Deadlift would be the exercise of choice. Hexagonal Bar Deadlift also elicits a great anterior thigh muscle activity, but with a reduction on erector spinae muscle activity, turning this exercise into an appropriate Deadlift variant when athletes have lower back issues.

Hence, coaches, athletes and regular population ought to contemplate these findings when selecting the Deadlift exercise and its variants for their training programs, considering the individual training goals.

Reference:

Martín-Fuentes, Isabel & Oliva Lozano, José & Muyor, José. (2020). Electromyographic activity in deadlift exercise and its variants. A systematic review. PLOS ONE. 15. e0229507. 10.1371/journal.pone.0229507.