Hello everyone, Joe from LEOMO here. In this 2-part write-up I want to take a look at the Squat. Specifically, I will examine sagittal plane mechanics for this movement.
To begin, the squat is a fundamental movement pattern seen in every day life as well as in competition and training scenarios. Whether your focus is improved overall function, competition lifting, endurance, or sport, the squat at its fundamental level can provide insight into many areas of your movement competency and can be a valuable tool for training. The focus of today's topic will be assessing squat movement patterns in the sagittal plane with endurance athletes.
We have two subjects in today's discussion. One a competitive Enduro cyclist, the other a competitive distance runner and former World Record holder in the marathon.
Purpose of this Analysis:Endurance athletes often participate in strength programs to support their primary training. For these athletes, the squat movement is a commonly targeted exercise due to it's functional applicability to their primary sport's movement patterns.
In this analysis, I will discuss:
1. The goals of the squat.
2. How to assess squat depth, torso vs tibial angle, and postural stability at the bottom of the movement.
3. How to apply external cues to increase the effectiveness of this movement.
What is the goal of a squat?
Simply put, the goal of a squat is to create force to move your Center of Mass (COM) vertically. With various movement limitations, we may see this perfect vertical displacement compromised.
When our hips, the primary driver of the COM in this movement, shift out from underneath the COM, it creates a lever that we must then generate additional force to correct or account for. To optimize our squatting effectiveness, we need to be able to move the COM vertically, while keeping our hips in the best position to minimize the total force needed to move a given weight.
The depth of the squat is important in determining which muscle groups will be targeted. To keep things simple, when squatting, a knee angle greater than 90° favors the quadriceps and knee extensors, and a knee angle smaller than 90° favors the hip extensors. In both cycling and running, knee extension and hip extension are primary components of the movements and thus both muscle groups should be trained. There are scenarios when we may opt to emphasize one over the other, but in general a full-depth squat to below a 90° knee angle is going to target both of these two primary muscle groups.
To capture this movement data, we placed one of our LEOMO motion sensors on the sacrum. Viewing the Pelvis GyroX output from that sensor (seen above), we can gain insight into the phases and quality of the movement. In this view, we can see James (Enduro cyclist) at the bottom of his unloaded squat. The red line in our Live Video Sync display lines up with the 2nd 0-cross of the GyroX data for that rep, and this 2nd 0-cross typically lines up with the bottom of the squat or the amortization phase of the movement.
Similarly, the 1st Pelvis GyroX 0-cross of a rep typically lines up well with close to a 90° knee angle.
This data will provide us with useful timestamps to compare other details of this movement. Additionally, if an athlete is not able to achieve a knee angle of less than 90°, then we will not see this same GyroX pattern.
Torso vs Tibial Angle:
Now that we have a way to view our squat depth with various timestamps, the next thing to assess is how well we are able to keep our hips under the COM for the full range of motion. I find that this is an area where many endurance athletes encounter movement challenges. A good way to ensure quality in this detail is to observe an athlete's Torso vs Tibial Angle throughout the full range of motion.
From the start of the movement to the very bottom, the angle of the torso and the angle of the tibia should match up as close as possible. It is common for runners especially, with slightly limited ankle dorsiflexion, to hit their tibial angle limit in the early phases of the movement, and then compensate by excessively tipping the torso forward to achieve the illusion of depth. This movement becomes more of a hip hinge than a squat.
We see this with our runner, Wilson Kipsang. While this is not inherently harmful, it does cause us to shift our hips behind the COM, creating an unfavorable lever (when top-loaded) as discussed above, as well as limits the depth of the squat. This may also be prevalent in athletes with long lower body limb segments, as is the case with Wilson.
In both James' and Wilson's cases, their dorsiflexion range is limited causing them to shift their hips out of line with the COM. To correct this in the short term, and allow them to continue training this movement pattern while they work on individual limitations, we will use a heel lift to help them achieve a more aggressive tibial angle.
By placing sensors on their torsos (sternum) as well as tibias (tibial tuberosity) we can view the angles of each of these segments relative to the ground and assess how external cues (heel lift in this case) are helping or hurting the movement.
In this view of James' squat (using the 2nd 0-cross of the Pelvis GyroX to indicate the bottom of the squat), we see that both tibias are achieving about 63° of dorsiflexion, while the torso is much more forward at 35.5° (90° as reported by the H-Angle output in Live Video Sync is perpendicular to the ground, while 0° is parallel to the ground).
With the addition of a 1.25" heel lift (above), we see an increased tibial angle of just 2-4° but a reduction in torso angle by 18°! The torso vs tibial angle is now offset by an average of about 6.5° when previously the offset was almost 30°. We can play with the height of this heel lift to adjust and tune this relationship, but this is already a great improvement.
Side Note: This is also a convenient way to assess dorsiflexion ROM symmetry in left versus right legs.
To read part 2 click here
Joseph Cavarretta, MS, ACSM-EP
LEOMO Sport Scientist & Coach