For anyone who has Bulgarian split squatted before (also called the rear- elevated split squat or pitcher squat), you would know that it is a killer exercise.
In my opinion, it is one of the hardest exercises that exist, especially when using moderate to higher rep ranges.
In a previous article, we demonstrated that the Bulgarian split squat and back squat likely share a good carryover with one another.
Generally, the Bulgarian split squat is known as a unilateral exercise. That is, only one limb (a leg in this case) is involved in the execution of the movement.
For those unfamiliar with the exercise, one leg is placed behind your body and elevated, while the lead leg remains directly below or slightly in front of your torso. The lead leg squats up and down.
As we can see, calling this a unilateral exercise does have reasoning behind it. After all, only one leg is squatting.
However, I have heard some people question whether the Bulgarian split squat is truly unilateral.
The logic behind this argument relates to the elevated rear-leg.
Throughout the movement, the rear-leg remains in contact with the elevated platform.
Due to this contact, some have questioned whether this rear-leg could exert meaningful force during the movement. Such that this force could contribute to the full completion of a rep.
If this rear-leg could actually be the difference between a successful or failed Bulgarian split squat rep, then perhaps we cannot truly classify the exercise as unilateral.
In this article, we’ll be exploring just how much the rear-leg contributes to the Bulgarian split squat and whether we can truly call the Bulgarian split squat a unilateral exercise.
This study by Helme et al. aimed to determine just this.
The researchers recruited 26 men with at least 2 years of resistance training experience.
The participants performed the Bulgarian split squat with a range of incremental loads.
Note, a barbell was used with the exercise, and the rear-leg was elevated on a 40cm box.
Ultimately, the loads were classified into the following groups: 50-60% of a 5 rep-max load (5RM), 60-70% of a 5RM, 70-80% of a 5RM, 80-90% of a 5RM, 90-99% of a 5RM, and 100% of a 5RM.
A force plate was placed beneath the lead leg and rear-leg when participants executed their repetitions on the Bulgarian split squat. This force plate measured the vertical ground reaction force produced by each leg.
To test whether the Bulgarian split squat is truly unilateral, the researchers used two methods.
The first method assessed how increasing the load on the Bulgarian split squat impacted the amount of vertical ground reaction force generated by the lead leg and rear-leg.
For this method, if the Bulgarian split squat was truly unilateral, increasing the load should result in an increased amount of vertical ground reaction force produced by the lead leg, and not the rear-leg.
The second method assessed at what point during the Bulgarian split squat the rear-leg produced its peak amount of vertical ground reaction force.
If the rear-leg produced its peak vertical ground reaction force before the participant had achieved full depth (i.e during the eccentric phase), this would imply the Bulgarian split is unilateral.
If this did not happen, in other words, the rear-leg produced peak force during the concentric phase, this would imply that it is involved and helps out the lead leg in completing the exercise (the concentric phase is more challenging than the eccentric phase in the Bulgarian split squat).
There did appear to be a small positive correlation between load and the vertical ground reaction force produced by the lead leg. In other words, as the load incrementally increase, the lead leg produces more force to complete this lift. We can see this when looking at the table above.
For the rear-leg, there did not appear to be a correlation between load and the vertical ground reaction force produced. This is evident in the table above too. With incremental increases in load, the rear-leg produced roughly the same amount of force.
For the second method, peak vertical ground reaction force from the rear-leg occurred before the lowest point of the barbell during the movement.
Put differently, the rear-leg produced its peak force during the eccentric phase of the lift.
As demonstrated by the data, the Bulgarian split squat does indeed seem to be a unilateral exercise.
The results of the first method show that increasing the load on the Bulgarian split squat results in an increased vertical ground reaction force from the lead leg, but not the rear-leg.
If you go back to the table quickly, we can see the contribution of the lead-leg to total vertical ground reaction force production in percentage terms. Throughout all loading groups, the percentage contribution was fairly constant (84%). From this, it follows that the rear-leg produces roughly 16% of the total ground reaction force during a Bulgarian split squat.
Therefore, the ratio of lead-leg to rear-leg vertical force production is fairly constant throughout various loading, further demonstrating the rear-leg does not take over with heavier loads.
With regards to the second method, the peak vertical ground reaction force produced by the rear-leg did not occur during the concentric phase, it occurred during the eccentric phase. This suggests that the rear-leg does not help out the lead leg and increase force production during the hardest point of the exercise (the concentric phase).
To conclude, the Bulgarian split squat does seem to truly be a unilateral exercise.