Differences in stance width between the conventional deadlift (CD) and sumo deadlift (SD) result in altered body position, which ultimately allows for differences in muscle activation and pulling mechanics.
Both McGuigan/Wilson and Escamilla et al have extensively analyzed the differences in the CD vs SD. The narrow stance of a CD requires increased ankle dorsiflexion (creating a less vertical shin) while the wide stance of a SD allows for a more vertical shin angle.
Additionally, the narrow stance of the CD creates a position with slightly more knee extension and a more horizontal torso (more hip flexion) when compared to the more vertical torso of the SD.
These differences in position are important for a few reasons:
1) Based on EMG data the two lifts maximally recruit difference muscles. CD shows much higher erector spinae activity and likely higher gluteus activity (some studies show higher glute activity in CD and some show no statistical difference), while the SD shows significantly more quadriceps activation. Interestingly, no significant differences were noted in hamstring activity.
2) With a more vertical shin and torso classically found in the SD, it has the potential to be a biomechanically advantageous position to lift a barbell from the ground due to the ability to keep the bar closer to the body, reduce hindering lever arms, decrease range of motion, and produce a more vertical bar path.
However, this DOES NOT mean that “sumo is cheating” or that the SD is universally easier for all lifters. On the contrary, due anatomical differences (ex: femur/torso/arm length and ratios), limitations in flexibility, and differences in muscular strengths, the CD can certainly still be the strongest variation for many lifters.
Additionally, McGuigan/Wilson found no difference in Schartz Scores (tool for assessing relative strength) between SD and CD in a national powerlifting competition.
Practical Application: Since the CD and SD activate different, large muscle groups to a significant extent, trainees seeking to improve general strength and athleticism should incorporate both lifts into a well-planned training program.
By: Bongju Kim Bro M.D. (@bros_md)