Many fitness professionals regard deep squats as the 'King of the Gym'. The one exercise everyone should do and the best way to train your lower body and 'build a killer butt' (whatever that means). But why? What is it about squatting that makes it a superior exercise to anything else and is deeper always better? Stop sniggering and get your mind back on training...
The key things about squatting that make it great;
hip, knee and ankle flexion/extension (as used in walking, running, and jumping/landing)
loads of muscles contract (it's hard to keep anything relaxed if you're squatting heavy!)
apart from the deadlift, it allows the greatest weight to be lifted
it's a great test of general athleticism as it requires good balance and coordination
Squats vs other leg exercises:
There are a couple of exercise classifications that tell us how many joints move and much muscle mass is used during an exercise. Isolation exercises are movements that happen around one joint and so use relatively little muscle mass. In simple terms think of a biceps curl - only the elbow joint is moving through range and the focus is on the biceps brachii. In real terms however, the muscles of the forearm, shoulder and even trunk are actually contracting when you do a biceps curl, meaning the literal definition of isolation exercises doesn't truly exist. Semantics aside, compound exercises are ones that move multiple joints and do so using multiple muscles and muscle actions. The squat is one such exercise.
Using more muscles - and bigger muscles for that matter - means a greater mass can be moved. This means more stress on the neurological system, the thing thats helps us get stronger. Larger and more numerous joint actions also mean more coordination, more calories used, more application to general strength and human movement. This is typically the argument for including squats in a training programme and I agree that most people should perform some kind of squat pattern.
There is a place for both isolation and compound exercise in a training programme and my philosophy is to understand the individual needs of the athlete I'm working with before deciding upon the exercises we will use. Many paths lead to increased strength and each has pro's and cons. The great thing about the squat pattern is that it allows a huge variety and we don't need to be attached to only one way of performing it.
Squats place a high demand on the whole body. As such, prior injury and the consequent weak links can rule out full squats for some, back squats or front squats may be safe for some whereas other athletes are better off using only single leg squats or split squat and lunge variations. The point is that having a big exercise library and understanding the subtle differences in each movement is key.
Lets get deep:
Understanding squat depth is fairly simple - does the hip crease go below the knee?
Yes, it goes as low as I imagine a hip crease can go - deep squat as performed by olympic weightlifters.
Yes, just about - deep squat acceptable in powerlifting standards.
No, it stops just short - how most people squat in commercial gyms. Not a problem if they are intending a half squat but if they claim this is a full squat they'd be laughed out of a decent gym...
No, the hip doesn't even really crease... - this is a quarter squat. Again, that's fine if it's intentional but a bit embarrassing if you claim to go ATG (that's arse to grass for those not in the know).
Does depth matter? Does it change the outcomes?
In a recent study by Brad 'hypertrophy' Schoenfeld (and others) the muscle activation of all major lower limb muscles at different squat depths was investigated. It showed that the primary groups used in the squat are the glutes (glute max primarily) the quadriceps, followed by hamstrings, with assistance from the other glutes (gluteus med/minimus) and calf muscles (soleus). The degree of hip flexion and forward trunk lean will likely change the contribution of the glutes as will the degree of 'turn out' in the feet. Regardless, the biggest takeaway for most people should be that the vastus lateralis (VL) is most highly activated at 90 degrees and a more balanced quadriceps contribution occurs by squatting deeper - the study used 150 degrees of deep knee flexion (da Silva et al., 2017). The hamstrings work either way but are generally more active coming up from deep positions. The stabilising muscles do more work when loads are greater (no shit Sherlock).
Other recent studies (Hammond et al., 2016) looked at muscle activation too and agreed that glute max activation peaks around 90 degrees - possibly because if you only squat to parallel (90deg) then you can use more weight which would demand more from your hip extensors - the glutes, erector spinae muscles and possibly hamstrings too. Either way, they suggest squatting to parallel or below for most muscle activation and implied training effect from this activation.
Marchetti et al. (2016) looked at different depths of squat at maximal effort contractions and found similar things - the higher up you are (i.e. you are almost done extending your knees but you still have to extend the hips) the more the glute max works. None of which is ground breaking if you understand a little bio-mechanics. Schoenfeld is also named on this paper - he loves a squat EMG study!
The point to all the above research tends to focus on how to balance muscle growth/hypertrophy in order to either look better or balance forces around joints for injury prevention.
Where science has attempted to determine which depth of squat is best for sports performance there are some misleading headlines that need a little analysis...
Half squats improve sprinting speed more than deep squats - squatting half way down allows for both heavier weights AND faster movements, even at the higher loads typically. This means that velocity specific strength gains and overload in ranges more specific to sprint mechanics can be performed. However, sprint speed is made up of both vertical force production (as with a quarter squat) and horizontal force production (more similar to joint angles in a deeper squat or exercises such as hip thrusts, RDLs and deadlifts). Rhea et al. in 2016 showed that partial range squats improved sprint speed more so than parallel and deep squats but they did so in 28 fairly well trained athletes. Execution of the squat - loads used and speed intentions - may be the primary cause of adaptation rather than the squat depth alone.
Half squats improve jump height more than deep squats - maybe not! A 2012 paper suggested that full front squats and back squats were the most effective way to increase jump heights (Hartmann et al. 2012). As with the theory on sprinting speed, velocity and angle specific strength would suggest half and quarter squats would be more beneficial... Rhea et al. again would suggest that partial squats improve jump height more so than full squats due to speed and range of motion specificity. I tend to agree from what I've seen in practice.
How do I know if I should squat? Which I type I should do?
Schoenfeld has also written a paper on squatting kinematics and kinetics (movements and associated forces) which gives some good recommendations depending on injury profiles and training aims. You can read the full paper here.
As I wrote earlier, my opinion is that everyone should do some form of squat pattern. That doesn't mean every athlete I train is doing ATG back squats. The biggest question to answer is "can I squat maintaining a good spine position and get my hip crease below parallel without pain and without losing balance". I've done a youtube video on assessing your own overhead squat to help...CLICK HERE
Which squat you perform in your training programme will depend on many factors; what is your goal? what phase are you in relative to your sport? what squats have you done in the past and were you succeeding in getting better/stronger? what's your injury history like and has anyone ever recommended you don't do squats?
Just remember these key things when making an exercise selection:
Full squats use more muscle mass than half squats at the same load and take longer to perform. For fat loss they may be a better choice.
Full squats use a more balance quadriceps activation and so may provide protective training effects for healthy knees. Longer time under tension and greater range mean longer muscle lengths are strengthened and greater connective tissue benefits.
Half and quarter squats can be performed more explosively and so may carry over to jump and sprint speed increases.
Partial range squats allow more load to be lifted and so may be better when in a max strength phase.
Split squats are the single leg cousin of squats and can help balance left and right leg strength and flexibility. Therefore, more appropriate during periods of rehabilitation or training for unilateral based sports.
Single leg squats require a huge amount of stability and balance so can help improve knee control - similar to the split squat but allows less load to be moved due to the demand on remaining upright.
Squats can be done with a multitude of foot positions, stance widths, heel elevations or even using bands and chains (thats a whole other blog post!). None are right or wrong, only right for you at the time or not. Assess first, plan second, squat last.
If you've got knees, and hips and ankles I suggest you use them to their full range. To do so without squatting of some kind is ludicrous. With so many options, you'd be holding back your athletic development by not including them at all.
da Silva, J. J., Schoenfeld, B. J., Marchetti, P. N., Pecoraro, S. L., Greve, J. M. D. A., & Marchetti, P. H. (2017). Muscle Activation Differs Between Partial And Full Back Squat Exercise With External Load Equated. The Journal of Strength & Conditioning Research.
Hammond, B., Marques-Bruna, P., Chauhan, E., & Bridge, C. (2016). Electromyographic activity in superficial muscles of the thigh and hip during the back squat to three different depths with relative loading. Journal of Fitness Research, 5.
Hartmann, H., Wirth, K., Klusemann, M., Dalic, J., Matuschek, C., & Schmidtbleicher, D. (2012). Influence of squatting depth on jumping performance. The Journal of Strength & Conditioning Research, 26(12), 3243-3261.
Marchetti, P. H., Jarbas da Silva, J., Jon Schoenfeld, B., Nardi, P. S. M., Pecoraro, S. L., D’Andréa Greve, J. M., & Hartigan, E. (2016). Muscle Activation Differs between Three Different Knee Joint-Angle Positions during a Maximal Isometric Back Squat Exercise. Journal of Sports Medicine, 2016.
Rhea, M. R., Kenn, J. G., Peterson, M. D., Massey, D., Simão, R., Marin, P. J., ... & Krein, D. (2016). Joint-Angle Specific Strength Adaptations Influence Improvements in Power in Highly Trained Athletes. Human Movement, 17(1), 43-49.