Prior research by Frye showed that the powerlifting style squat (well sort of but not really), though quite safe for the knee joint, was inherently dangerous for the spine. I’ve always been uneasy regarding the methods and biomechanical calculations involved in Frye’s research, and thankfully new research by Swinton et al. has just arrived delving into the differences between the traditional squat, the powerlifting squat, and the box squat. This Paul Swinton dude is quickly becoming my favorite researcher. First he conducted a study on powerlifting practices, then a couple on deadlifts, then one on vertical jumping, and now this study (all of which I’ve reviewed either in my blogs, my TNation articles, or my research review service). If you’re not sure about the technique between the different types of squats, here are a couple of videos you can watch:
Box Squat Form (the study I’m reviewing utilized the high box squat which is second in this video)
I’ll try to sum this up quickly. The study examined 12 male powerlifters (average age was 27, average weight around 220lbs, average max squat around 485lbs, average years lifting experience 9 yrs) and utilized biomechanical equations, inverse dynamics, markers, 9 cameras (VICON), 2 force plates (KISTLER), and software (VICON) to calculate joint angles, joint torques (moments), velocity, peak power, rate of force development, and ground reaction forces.
What the Researchers Found that Was Not Surprising:
- The widest stance was the box squat, in the middle was the powerlifting squat, and the narrowest squat was the traditional squat
- During the eccentric component, the lifters sat back much more so in the powerlifting and box squats than they did in the traditional squat
- The powerlifting and box squats involved more hip abduction (knees out) than the traditional squat
- The powerlifting squat involved the most hip flexion
- The traditional squat involved more knee and ankle flexion
- Ground reaction forces, velocity, and power were reduced in the box squat due to the gradual shifts in loading between eccentric and concentric phases
- The powerlifting squat created the most hip extension torque
- The box squat led to the most “vertical” tibia of the variations
- Traditional squats allowed for the greatest velocity and power
- Powerlifting squats and traditional squats created the greatest force (very similar across loads)
What the Researchers Found that Was Surprising:
- The traditional and powerlifting squat involved similar torso angles (leans), and the box squat had the least forward torso lean out of the three styles
- The traditional squat displayed the highest loading on the spine (highest torque at L5/S1), as well as the highest loading on the ankle joints
- The use of a box decreased peak hip extension torque and spinal extension torque while increasing peak knee extension torque
- The box squat displayed the highest loading on the knee joints
- Rate of force development (RFD) was 3-4 times higher in the box squat than the other squats. This is INSANE!
- The study investigated experienced powerlifters who are skilled in the various squatting movements
- The study utilized a VICON with force plates, etc. which is a thorough way to investigate joint torques and other data
- The researchers are well-versed in powerlifting techniques
- Loads used in the study were 30% of 1RM, 50% of 1RM, and 70% of 1RM. Based on my experience, preventing forward trunk lean (which dramatically impacts torques at all the joints) during a maximal box squat is quite difficult. I wonder if the results would be different if maximal loads (or at least submaximal loads at 90% of 1RM or higher) were used
- Powerlifters might perform “traditional” squats differently than other lifters – the subjects in this study exhibited slightly more (only .5 degrees) forward trunk lean during the traditional squat than they did the powerlifting squat. I wonder if Oly lifters (obviously especially if heeled shoes are worn) or even lifters who simply stick to full squats most of the time would fare differently on this study
- The researchers didn’t attempt to explain the unusually high RFD shown in the box squat. I can personally relate to this – when performing dynamic effort box squats sometimes I feel very springy off the box even though the SSC should have dissipated
I’m sure this study will raise some eyebrows but I’m very well-versed in Biomechanics and the results actually make sense if you understand the interplay between the segment positions and barbell displacement in relation to the joint centers, but if I tried to explain it further I’d probably confuse my readers. In other words, this study seems very legit to me.
The box helps lifters sit back while staying upright (at least with submaximal loads), which actually decreases hip and spinal loads and increases knee loads (prior research by McBride supports this notion in terms of quadricep EMG activity – there wasn’t much of a difference between squats and box squats). The lifters paused for an average of 1.7 seconds during the box squat which most likely decreases contribution from the stretch-shortening cycle (SSC) and would explain the decreased force and power production. Something about the pause on the box really seems to help create a ton of RFD which could indicate that it transfers nicely to sport.
The researchers pointed out that knee loading isn’t the only factor to consider in determining joint safety – it’s also important to consider knee ROM and displacement of the femur relative to the tibia. For these reasons the traditional squat is most likely the hardest variation for the knee joint.
The box squat is clearly an excellent alternative for those with restricted ankle mobility (dorsiflexion) who are unable to perform a full range squat (ass to grass) as it will allow for an excellent training effect and the adherence to proper technical form.
Really this study just illustrates that when determining the safety of squat variations you don’t just have to consider how far you sit back, how far the trunk leans, or how far the knees travel over the toes; you also have to consider how far you shift forward or backward with the bar relative to the feet, as this influences joint torques considerably. For this reason, box squats and powerlifting squats could indeed be “safer” for the low back compared to traditional squats.