Are 90-degree joint angles really optimal: an evaluation of some recent claims.

Are 90 degree squats really all their cracked up to be?

In this article we break down why som of the claims made about 90 degree squats may not be all that accurate…

By Coach Hunter Bennett

Over the last few years, strength coach Joel Seedman has seen a rapid increase in popularity.

Largely due to an Instagram page full of elite athletes performing somewhat unique (and at times bizarre) exercises, his methods have become a common topic of conversation amongst exercise professionals across the globe.

And while we could debate the effectiveness of his “crazy” exercises for days on end, his most contentious point relates to squat mechanics – and specifically the statement that every human should squat the same, using precisely 90 degree joint angles at the knee and hip.

Now, as someone who has trained people for the better part of a decade, this immediately sets alarm bells ringing.

In the world of health and fitness, nothing is black and white.

As such, talking in absolutes is often a recipe for sub-optimal results (and in some cases, injury).

While I could simply give my opinion on the topic, I thought it might be more useful to explore Dr. Seedman’s rationale, and provide some evidence based responses.

Just to be clear, this is not a criticism of everything he has ever done, but rather a critique of the claims he regularly uses to support his recommendation that 90-degree joint angles are optimal for all movements.

Claim 1: “90 degree squats optimise athletic performance”

This argument is often made while citing research that shows a 90 degree squat results in greater levels of muscle activation (measured by EMG) than full or “ass-to-grass” squats.

I would first like to highlight that this finding is not consistent across the literature.

In fact, even one of the studies Joel uses to support this claim (cited on his website) found no difference in muscle activity between partial squats and full squats – and even go on to state that:

“It can be concluded that the front, full, or parallel squat can be performed for similar EMG amplitudes. However, given the results of previous research, it is recommended that individuals use a full range of motion when squatting, assuming full range can be safely achieved, to promote more favourable training adaptations.”

But that’s neither here nor there…

The thing I want to highlight here is that acute research like this should not be used to form conclusions about training methods. Instead, provides mechanistic information that will help generate hypothesises for future research studies.

For example, an acute study showing that parallel squats produce greater muscle activity might lead to the hypothesis that parallel squats will lead to greater improvements in athletic performance when they are implemented in a longer training plan.

But this cannot be inferred from the EMG data alone – it needs to be tested with a long-term training study.

And guess what?

When this hypothesis is tested with long-term training studies, the results are not all that favourable.

To date there have been two studies (one and two) demonstrating that training programs implementing full ROM squats will lead to grater improvements in speed and jump height than squats performed with a 90 degree angle at the knee.

For clarity, there has also been one study showing a 90 degree squat to be better than full squats for improving jump height – but in this study the participants in both groups also did power cleans, lunges, hamstring curls, and step ups as part of their program, without any limitations in ROM.

As a result, it is hard to discern whether the results of the study were strictly due to differences in squat mechanics, or due to the combination of partial squats within a larger training program

All of which suggests that despite some research showing that partial squats increase muscle activation (and some that show the opposite), full squats are superior to improve athletic performance when used in a long-term training program.

Claim 2: “90 degree squats optimise strength development”

I don’t intend to spend too much time here – but it should still be addressed.

The law of specificity states that training adaptations are tightly coupled with the specific mode of exercise performed.

With that in mind, if you perform 90 degree squats, you will get stronger at 90 degree squats.

Conversely, if you train using a full range of motion, you will get stronger across a full range of motion.

Seems obvious, right?

What I want to point out is that some key training studies (one and two) have demonstrated that training using a full range of motion will still cause a substantial improvement in strength at partial ranges of motion.

These improvements won’t be as great as if you trained at that specific range of motion, but it will still improve.

However, if you only train using a partial range of motion, then you will not see improvements in strength at a full range of motion (i.e., in a deeper position).

This is because when you use a full range of motion, you move through a partial range of motion (i.e., you still spend some time at 90 degree joint angles as you move into, and out of, the bottom position of a squat), and therefore improve strength in those positions.

But when you don’t go any lower than 90 degrees, you don’t spend ANY time at a full range of motion, and consequently don’t develop much (if any) strength at anything deeper than 90 degrees.

In summary, strength is specific to the joint angles trained. But using a full range of motion will cause positive adaptations across the full range of motion – something that will not occur if you only use partial ranges of motion.

Claim 3: “90 degree squats optimise muscle growth”

OK, so while some of Joel’s other claims might be explained by a different interpretation of the science, this claim is completely and utterly false.

There have been a myriad of studies exploring the effects of range of motion on muscle growth – and it is well established that exercises that take a muscle through a full range of motion promote greater growth than those that only use a partial range of motion.

Especially in the lower body.

This appears to be related to muscle length.

In short, exercises that place a significant amount of mechanical tension (i.e., load) on a muscle while it is in a lengthened state will lead to greater hypertrophy than exercises that emphasise load in a shortened state.

As deep squats load the quads in a longer position than a 90 degree squat, they are undoubtedly superior for muscle growth.

Claim 4: “Deep squats cause inflammation”

One argument Joel regularly makes is that using a full range of motion can increase inflammation, which may contribute to things like metabolic disease and insulin resistance.

Now, there is no research to date exploring if training at different ranges of motions cause different inflammatory responses.

However, we can look at some other data to provide an educated opinion on the matter.

First and foremost, all resistance training (no matter the range of motion) causes an increase in inflammation. This is your body’s natural response to tissue damage, and something that stimulates adaptation.

In fact, recent research has shown that if you provide people with anti-inflammatory medication while they conduct a resistance training program, they experience smaller improvements in strength and size than they would otherwise.

All of which would suggest that inflammation after training actually helps drive adaptation.

Importantly, this type of acute inflammation is separate from systemic inflammation, which is the associated with an increase in risk of disease and illness.

Strength training has been shown to cause modest reductions in chronic inflammation in a host of population groups, including older adults, diabetics, and breast cancer survivors.

For the sake of transparency, I should note that the resistance training methods (with regards to range of motion) used in these studies is unclear.

But given the fact that many of them used machine-based exercises that tend to promote a full joint range of motion, I think it is safe to assume that they regularly used exercises where 90 degree joint angles were exceeded.

As such, we can summarise that exercises using both 90 degree joint angles and a full range of motion will cause an increase in inflammation in the short term, which is quite important for adaptation.

Similarly, both types of training will improve measures of chronic inflammation in the long-term, which may contribute to improved health.

Claim 5: “Deep squats lead to a loss of joint range of motion, joint degradation, and joint pain”

This claim is often linked to the inflammation one above, whereby the inflammation caused by “extreme” ranges of motion (i.e., more than 90 degrees…) will cause a reduction in muscle length, limiting joint range of motion.

This comes with the suggestion that full ranges of motion will also lead to a decline in joint health and contribute to joint pain.

But is this really the case?

Starting at the top, there is a substantial amount of evidence clearly demonstrating the strength training using larger ranges of motion cause significant improvements in joint range of motion.

In short, full range of motion training makes you more flexible, not less.

And similarly, it does not appear to have any negative effects on joint health – and may even have a positive effect.

Research has shown that the articular cartilage in the knees of competitive weightlifters (AKA the kings of ass-to-grass squats) is markedly thicker than people from the general population. This suggests that the load placed on the structures of the knee leads to an increase in joint health, rather than joint degradation.

As an aside, even the suggestion that a 90 degree squat places less load on the knee joint is completely unfounded.

It is well established that force on the knee joint peaks at 90 degrees, and once we move to greater degrees of knee flexion (i.e., descend deeper into the squat), this force is distributed away from the knee and to other tissues (predominantly muscle).

All of which is to say that squatting to 90 degrees using heavy loads is arguably going to result in greater load on the knee joint (I have previously discussed this HERE).

Just to be clear, I am not saying that this is a bad thing – just that this argument against full range squats is not completely correct.

Claim 6: Most exercise science studies are flawed”

Now, this is my favourite – like, actual favourite.

And there are two reasons why.

Firstly, a common statement made by Joel is that most exercise science studies are flawed because – and I quote – “they are carried out by lab rats who have no clue how to properly squat and demonstrate even greater incompetence when it comes to coaching these basic movements.”

The reason I find this statement so hilarious is that Joel will happily cherry pick studies that support his argument, and then disregard the rest of the evidence that goes against his claims – while simultaneously stating that all scientific evidence is trash.

This is something that I find a little deceitful…

Secondly, I think this statement is hilarious because I know it is not the case.

Don’t get me wrong.

I cannot speak on behalf of every author who has ever conducted a strength study. But as someone who conducts research in exercise science, I know how thoroughly studies are planned, and how precisely they are executed.

Most people who enter this space don’t do it for the applause (of which there is very little).

They do it because they are passionate about the topic. Because they actively participate in strength training (many were previously coaches) and want to provide good-quality evidence to improve the profession.

And to refer to them as lab rats with “no clue when it comes to coaching” is more than a little offensive.

I mean, I conduct research, and I have over 10 years of coaching experience under my belt – and I am certainly not alone.

Should everyone squat ass to grass?

Now, just to be clear, I am not saying that everyone should squat deep all the time.

Hell, I would argue that some people shouldn’t squat below 90 degrees.

We all have different anatomy and different injury histories. As a result, a small subset of the population might not physically be able to get into a deep squat without compromising their positioning and technique.

As a result, 90 degree squats might be a good fit for them.

However, I would also argue that this is a very small subset of the population.

In my experience, most people can get into a fairly deep squat (crease of the hip dropping below the top of the knee) with some decent coaching and, at most, a small amount of mobility work.

As such, they should try and train using that range of motion to optimise the benefits.

And if you can descend deeper than that (i.e., ass-to-grass), then more power to you – use that range, keep your joints healthy, and become a strong and robust human being in the process.

 

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