Being able to identify and correct weaknesses in powerlifting is a critical aspect of long term progress. But one of the issues that some athletes run into is selecting the exercise best suited to fix their deficiency. In this article we’ll explore some fundamental concepts of biomechanics to elucidate what exercise(s) should be used to address this weak point and build more muscle and strength in your quads.
First we need to introduce the term Torque which is defined as a twisting force that tends to cause rotation (1). To express torque we use the equation T = F * r * sin(theta)
T = torque
F = linear force
r = distance measured from the axis of rotation to where the linear force is applied
theta = the angle between F and r
Another way to express torque is T = F*r. In this equation we multiply the linear force by the distance from the axis of rotation. For simplicity sake we’re going to use this equation. Lets take three types of squats for our example: the low bar squat, the high bar squat and the front squat.
The red dot in the image represents the barbell and its relative location. You can see that in each squat variation the line of force (the dotted line) changes in relation to the hip and knee joints. In this case the knees and the hips are the primary axis of rotation and since we know that the calculation for torque is F * r we can determine which variation has the most impact on the quadriceps.
To keep things simple we can assign arbitrary numerical values to each variation to demonstrate how each squat variation loads your musculature. The load of the bar will remain constant at 100N (newtons) in each variation.
In the image above the numbers located between the dotted line and the joints represent the distance between the axis of rotation and the linear force. These are just units of measurement for the sake of this example and are not actual values from any data set.
Using these values we can calculate torque to see which joint generates the most torque for each variation. The chart below uses the distances outlined in the above diagram with a standardized force of 100N.
As you can see, the low bar squat generates the most torque in the hips, the front squat generates the most torque in the knee and the high bar squat has a relatively even distribution of torque between the hips and knees.
Since the quadriceps primary role is knee extension they are responsible for overcoming the external torque applied to the knee by the load (2). So we can see that front squats develop the quads the most. However I want to highlight a point; just because an exercise should theoretically produce a specific outcome does not mean the outcome is guaranteed.
There are many factors that could change the outcome, one such factor is technique (3). If you’re doing a high bar squat but on the ascent your hips shoot up and your knees travel backward then you change the leverages. So what was initially intended to develop your hips and quads relatively equally has now become a more hip and back dominant movement.
When one of my athletes is struggling with a particular part of a lift the first thing I do before prescribing a “corrective exercise” (and I use this term loosely) is to watch the lift. I want to first rule out technical errors that may be the cause of the breakdown in the lift. More often than not it’s a technical issue, so a specific exercise isn’t necessary and would likely do little or nothing to improve the main lift since it may not address the technical issue limiting the performance of the primary lift.
But lets assume that your technique is not an issue, and you still want to develop your quad musculature and strength. In many cases the front squat variation may be a good break to reduce training staleness or prevent overuse injuries. But since it’s less specific there is the potential drawback of spending less time practicing the competitive movement. So depending on where you are in your competitive cycle its implementation may or may not be appropriate.
As you get closer to your powerlifting meet your volume will decrease relatively and your exercises will become more specific as the intensity increases (4). So depending on the individual, the last month of a competition cycle may not be the best time to introduce front squats into the mix. However, you can still build significant strength and size in your quadriceps by implementing belt squats. This is one of my favourite exercises for a few important reasons.
The movement pattern is virtually identical to a low bar squat and since there is no axial load and the overall load has decreased it’s substantially less fatiguing than barbell squats (5). Because of this, the stimulus to fatigue ratio ends up in your favour. This is an effective alternative to front squats if you are getting closer to your meet and still want to spend a bit more attention on building or maintaining your quad strength.
Now that we’ve covered the basic biomechanics of torque, lets look at muscle physiology and how different phases of the squat relate to building muscle and strength. This is important because by understanding the force velocity curve and basic muscle physiology we can implement strategies to maximize the training benefit at each phase of the lift. The basic contractile unit of a muscle is called a sarcomere (6). These are arranged in a sequential stripped pattern along each muscle fiber as show below.
Within each sarcomere are actin and myosin filaments. When they receive instructions from the motor neurone to contract these actin and myosin filaments attach to each other and pull the Z lines closer together. This process is called sliding filament theory and describes the process of muscular contraction (6). What researchers have observed is that there is an optimal length by which the sarcomere can generate the most force. This is known as the length tension relationship (7).
When the sarcomere is stretched too much it can not produce force as effectively. The same is true when the sarcomere does not have enough tension. But there is a mid range by which the sarcomeres have the optimal amount of tension that allows them to generate the most force.
Lets look at how this impacts squatting in the real world. When you’re at the bottom of the squat your glutes and quads are maximally stretched. You’ll notice that this is also the point where most people fail; just coming out of the bottom. The reason people are able to grind through this weak point is because even though the torque angle puts you at a disadvantage the cross bridging is at it’s optimal length tension and can generate the most force (7). But once you grind through that initial sticking point the rest of the lift is relatively easy.
This brings up an important question though, if the points where we are weakest are when the muscle is too stretched and too short then why is the top of the squat easiest since this is the phase of the lift where there is too little tension? This is because at a full lockout position the bar is directly in line with your hips, knees and ankles. So your joints are stacked and can manage the load easily.
So if the upper end of the squat is the easiest, and the bottom is most difficult how can we manipulate the force velocity curve to get a better training stimulus on our quads? This is where accommodating resistance can be beneficial. Accommodating resistance is the use of bands and chains to alter the force velocity curve (8).
The diagram above is a representation of the relationship between force and velocity and can be understood through the equation F=Ma (Force = Mass x Acceleration). The greater the force, the greater the mass. The greater the velocity the smaller the force.
As we reach the top of our squat we decelerate and because our joints move closer to the line of force they don’t need to generate as much torque (1). However if we attach bands to the bar, the tension increases as we reach the top of the squat. So at the point where the squat should be the easiest, the linear force is actually the highest. This alteration to the force velocity curve allows you to get more training on your quads because it smoothes out the curve (8).
Next we have overspeed eccentrics. When you use a band, at the top of the lift the band has reached maximal tension and the kinetic energy is trying to shoot you back down into the bottom. This means as you begin your descent you need to resist against the force of the band which is trying to push you down at a faster rate than gravity (9). So the concentric and eccentric action is greater and the curve is smoother which improves rate of force development. There’s also the aspect of novelty that imparts positive training adaptations in your training when compared to using a fixed load (10).
There is some contention on whether the use of bands and chains has a substantial impact on powerlifting training. In this regard my experience is that it depends on the type of training you are doing. If you look at westside barbell they have maximal effort days and dynamic effort days. For a system that utilizes a lot of heavy days, utilizing bands and chains to develop speed and power can be highly effective.
This is because the dynamic days are lighter and promote recovery and also train the acceleration side of the force equation. But if you are primarily doing sub maximal training and high volumes, I’m not convinced that using bands and chains would be effective as a primary pillar of your training. Personally I do not use bands and chains much, but that’s because most of my training is sub maximal. If I were to utilize a high intensity approach to training I would definitely utilize the dynamic effort method.
This is something you will need to experiment with to find the best solution for your situation. But now that you understand the basic biomechanics of squatting, internal and external torque, muscle physiology and how to alter the force velocity curve by use of accommodating resistance lets give some practical takeaways for application.
Before deciding on prescriptive exercises to address weak points, ensure that the weak point is not simply a technical error. If it is, address the technique and the issue will self correct.
Front squats are primarily a quad dominant movement, low bar squats are a hip dominant movement and high bar squats have a more even distribution of load between the knees and hips.
Utilizing exercise variation can be an effective method to bring up lagging muscle groups or weak points. Alternate exercises distribute the load differently which you can use to preferentially targets specific muscles and/or motor patterns.
Exercise selection should factor in proximity to competition. As you approach your competition specificity increases. The competitive low bar squat is the primary tool during this time. Front squats, high bar squats and other variations are better used farther away from the meet (ie. during a hypertrophy or strength block).
As intensity increases throughout your training cycles and exercises become more specific the fitness to fatigue ration begins to intersect. One option to maintain a high level of fitness without generating significant fatigue is to utilize belt squats. These are far less fatiguing than barbell squats because there is no axial load.
The use of accommodating resistance (ie. bands and chains) can be used to increase RFD (rate of force production) and smooth out the force velocity curve. This presents a novel stimulus and if incorporated correctly can be an effective method to increase quad strength and hypertrophy. My personal opinion on the use of accommodating resistance is that best results are achieved when implemented in conjunction with a high intensity approach to training (ie. the maximal effort method or some variation of it).
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