There are many names for this beauty, here a few common ones:
Bulgarian Split Squat
Rear Foot Elevated Split Squat
Barbell Split Squat
Set-up Standards: I have been gathering data on this sucker for years now, mostly with the DB version. I like the Barbell version better, only for the positioning aspect. With the bar on the back of your neck, it keeps the torso upright easier than with the DB version. The bench height I like to use is just below knee height. You can use lower or higher as many other Coaches recommend various heights, for the relationship I am trying to establish, use a bench height about 2" or 5 cm below the centre of your knee cap. Your front foot should be approximately 3 paces (3 of your feet length) from the bench. Prior to performing this test at a high effort, ensure your hip flexors are ready for action (warm, supple, and activated) as they play a significant role in this test and could be aggravated if not ready. Side note - this is by no means a true single leg test, it is attempting to get a large % of the eccentric/concentric movement from a single leg, however, the rear leg is strongly involved in the movement during both the eccentric and concentric phases. Your knee should track forward during this test, as I want the kinematics of the front hip, knee, and ankle to be somewhat similar to the high bar back squat.
Tempo: For testing I use a 30X0 tempo (meaning 3 seconds down with little to no pausing at the top or bottom). There will be some tempo issues from time to time, just do your best to stick to the tempo. If your rear leg comes off the bench because you become unbalanced, then you should not count that attempt as a true test due to falling of the tempo. Side note - when trying to compare your squatting, pressing, or any slow lifts from year to year, you had better adhere to a set tempo, otherwise you are not holding the variable of tempo constant (variables you can control for with testing should be controlled to make your testing, whatever the test, more valid and reliable).
Relationship: Right now, I see it as being 6 repetitions @ 50% of your 1RM High Bar Back Squat. If you score above the range, good. Then, maybe your squat needs to go up? If you score below the range, maybe you need work on your single leg strength? To truly establish a good number on your Barbell Split Squat, you need to have practiced the movement as there is a performance curve on this test (note - I did not say learning curve because a learning curve does not exist, a performance curve does. Any takers on why this is?).
High Bar Back Squat 1RM: Like it reads, it has to be a High Bar Back Squat. A Low Bar Back Squat number would not qualify. The 1RM High Bar Back Squat should be obtained without the use of a belt or knee wraps for the purposes of these tests. Footwear, whatever allows good balance on the floor and proper torso position throughout the lift. You should probably wear the same footwear for both the split squat and back squat. What is absolutely imperative is that your tempo in the High Bar Back Squat is 30X0 and your depth is well below parallel, not a competition squat depth. If you do not adhere to this standard 1) you are lying to yourself about how strong your squat is, and 2) you do not have a usable # for this test.
Future: Down the line I will get somethings together with a single leg vertical jump as well as front rack barbell split squat and front squat numbers to see if anything pans out. But, I like the bar on the back of the neck as I want to movement to be limited by lower body strength/stamina, and not a poor rack position and what not. It is important to try to establish relationships between movements as it will only lead to a better design of programming and therefore better optimization of your fitness.
Why is single limb training important: In the strength and conditioning community, this is common knowledge. I imagine this is because many Coaches that work with athletes playing professional sport will have the athletes do some amount of single leg work (amount dependent on how much the coach deems valuable) because many aspects of the sport occur with one leg only in contact with the surface/floor, not two. Single leg/arm work is an easy way to increase muscular strength/mass in the trained areas without as much risk of injury or the amount of CNS fatigue due to the lower loads involved. I believe it is also very important for longevity of the trainee for the previous mentioned reasons, as well as to assess any bi-lateral imbalances. In CrossFit, this is a very under utilized aspect of training. I would guess it is under utilized because people do not know how to place the movements correctly into their training sessions or their overall training plan. They should not be added in as "goat" work, or after a "metcon". They should find their way into your training session in a better, more well laid out format. For many there movements need to find their way into you training in the off-season, as this is the time to balance things out and re-build for the upcoming season. For some, these movements are needed all year round as some muscle groups for certain individuals need constant attention in order to keep their squat numbers up, keep their hips/knees feeling good, keep their shoulders healthy, or what not.
My current relation ship would look like this:
Barbell Split Squat = 200lb x 6 reps
High Bar Back Squat = 350lb x 1 rep
Relationship of Split Squat to Back Squat = 57% (i.e. I have sufficient single leg strength relative to my back squat capabilities)
I would be quite happy for you to post your results in the comment section or to e-mail me your scores for data collection purposes.