Howdy,
The squat is commonly programmed for developing the lower body when training both athletes and bodybuilders. However, there are frequent misunderstandings in the fitness industry about which muscles the squat actually trains…
So, long story short, the main muscles trained by the squat (whether half or full variations) are the single-joint quadriceps, the adductors, and the gluteus maximus. In contrast, the squat does not train either the hamstrings or the two-joint rectus femoris muscle (the contribution is minimal). Some research showed that neither the rectus femoris nor the hamstrings increase in size after full or half squat strength training. The gluteus maximus and adductors were trained very effectively. Also, full squat is good for maximal muscle development because it builds glutes and adductors more compared to half (90 degree or quarter) squat, therefore it’s better for that kind of goals. For athletes though, other vars are probably better in every sense. Let’s discuss a bit deeper…
“The adductor magnus is a huge muscle of your thigh. It has two main parts, the “adductor” part and the “hamstring” part. Basically, the muscle is big, attaches to different parts of the pelvis, and some fibers adduct the hip and some extend the hip. In fact, when the hip joint is in flexion (like at the bottom of a squat) the adductor magnus will act to create hip extension. In other words, it helps power your ascent out of the bottom of a squat. This is why many people will have sore inner thighs after a squatting work out, they are a big contributor to the squat!” – Dr. Ryan DeBell
The glutes are simply unable to contribute much at the bottom of a squat due to a short internal moment arm; their relative lack of contribution in the hole is also borne out by EMG research finding that glute EMG is substantially lower below parallel. Rather, the glutes primarily contribute as you approach full hip extension (which is why someone may have cued you to “squeeze your glutes” to lock out a deadlift). As I’m sure you’re aware, squats aren’t particularly challenging when you’re nearing full hip extension, so there was an argument to be made that, sure, glutes will contribute a bit to the squat, but squats probably won’t stimulate them enough to be a GREAT growth stimulus.
“…Now that we see the glutes growing substantially after squat training – slightly more than the quads, surprisingly – I think that tells us that, while the glutes aren’t very helpful in the hole, they’re probably kicking in enough through the midrange of the lift (i.e. the sticking point) that squats still provide your glutes with a great growth stimulus. As for the adductors, I’ve been all aboard the adductor magnus train since at least 2015. When I first started squatting, my adductors got WAY more sore than any other muscle in my body. I’ve also strained my adductors squatting multiple times, in spite of never straining any other muscle (to the best of my knowledge) when squatting. So, I was sold when Andrew Vigotsky told me that he and Megan Bryanton had found that the adductor magnus should be the primary hip extensor in the squat, based on predictions from musculosceletal modeling. However, for the past few years, that was the only piece of evidence I had to support that contention, beyond basic anatomy. The adductor magnus is a huge, monoarticular muscle (meaning it causes hip extension without also imposing a knee flexion moment, unlike the hamstrings) with a very favorable internal moment arm for cranking out a bunch of hip extension torque, especially in the hole . Researchers just ignored it, in favor of focusing on the quads and sometimes the hamstrings.” – Greg Nuckols
“Now, in one important study, the researchers looked at change in total adductor muscle volume, but that should primarily be reflective of the adductor magnus; the adductor brevis is tiny, and the adductor longus is actually a secondary hip flexor, so it’s doubtful that the adductor longus grew much in response to squatting. Seeing such robust adductor hypertrophy in this study provides us with direct evidence for what I’ve suspected all this time: Your adductor magnus is a major player in the squat (probably your most important hip extensor), and squatting does a great job building your adductor magnus.” – Greg Nuckols
So, interestingly, it’s not an adductor m. that secondarily contributes to hip extension. Rather, its primary function seems to be hip extension, and it also secondarily contributes to adduction. So, we now have clear evidence that squats target your adductors, which lends further evidence to the notion that the adductor magnus is one of the biggest contributors to a successful squat. Even though your glutes aren’t a big contributor to strength out of the hole, they can still contribute enough through the sticking point of the squat for the squat to be an effective glute exercise. …Squats aren’t a damn hamstrings exercise. We don’t have to just look at biomechanical function or EMG; we can see that, even in untrained lifters, squats just don’t cause hardly any hamstrings growth. …Longer ranges of motion are great for growth, but it may not hurt to dabble with partials, as long as you still have plenty of long-ROM training in your program.
Make sure to squat “straight down” (the classic back squat), don’t bend hips excessively (hip hinge) and consequently bend too much over like while doing “good morning” exercise because it will not be more “glute dominant” (plus load on your back is significantly increased in this way). Don’t be affraid of bending knees more because it should be like that – it’a a squat! When you bend over more than necessarily, you will feel less quad activation and actually more hamstring activation. When you stay more upright, you use a bit more quads, and when you lean more, you use a bit more hamstring, but glute activity isn’t markedly different. For example, one study showed it’s only 3.8% more glute activity when you lean forward drastically and reach the arms forward in the forward lunge. “Making a squat/movement more hip-dominant does increase the hip extension moment arm (and decrease the knee extension moment arm) and increase hip flexion, and you will sometimes see greater hamstring activity or greater length change in the hamstrings, but the differences in glute activation aren’t worth fussing in my opinion.” – Bret Contreras. So, long story short, hip-dominant and quad-dominant variations are both good for the glutes.
In the pic below, you can see not much difference in glute, ham, erector, or quad activity when it comes to different squat variations in trained women. The front squat used much lighter loads and still saw similar muscle activation. So, as Bret says: “Don’t obsess about what squat variation is best and simply choose the one that feels ideal for your body. We sometimes think too much about high bar or low bar, stance width and foot flare, depth, torso lean, shin angle, etc., but the most important thing is to gain strength over time, and this is far more likely to happen if it feels right for your body. Some people don’t like low bar and prefer high bar; some don’t like front squats and prefer back squats. Some don’t like sumo squats. Some don’t like going deep and prefer parallel. Our bodies are unique and we should therefore squat uniquely according to our anatomy and goals.”
In a front squat, the combination of sitting down and keeping the torso more upright is going to put more stress on the anterior chain – the abs and quads. In a back squat, where the torso is more angled and you have to sit back further, there is more stress applied to the posterior chain – namely the spinal erectors, glutes and hamstrings. But, there is one interesting study showing that the front squat produced around 25% greater erector spinae EMG activity than the back squat. What was even more interesting to me was that the front squat had no significant difference in erector spinae activity compared to the superman exercise.
Remember, the superman exercise has been shown by McGill to produce up to 6000 N (over 1300 lbs) of compressive force to the spine due to the activity of the back extensors! McGill has shown that exercises like “superman” and the classic Roman chair back extension exercise produce excessive amounts of compressive loads on the lumbar spine.
Most people don’t need to progress their extension exercises to this advanced of a technique (it’s a big question if most athletes need to as well because of the “daily overload” in that area they are imposed to, ok – maybe a little bit). Basic exercises such quadruped hip extension (and hip thrust later) and bird dog produce an adequate amount of EMG activity while saving the spine from excessive compressive loads. Many people suffer from low back pain due to chronic postural adaptations (causing anterior pelvic tilt for example) and a subsequently low ratio of erector spinae to rectus abdominis strength. Overloading these people with aggressive extension exercises are only going to fatigue the extensors more and cause more low back pain.
Last but not least, if you prefer to perform the front squat, at least make sure that the person has a solid base of back extensor strength and core stability before progressing to the squat. Because, it’s shown that many people who suffer from low back pain have lack of both erector spinae and abdominal/core strength/stability. Back squat is probably a better option if one suffers from low back pain (if we compare the two)…
…This is very interesting topic and we can disuss forever, but I think I gave you enough info you can make high quality food for thought of. Till next time…
PRACTICAL RECOMMENDATIONS
- As we said, the main muscles trained by the squat (whether half or full variations) are the single-joint quadriceps, the adductors, and the gluteus maximus. In contrast, the squat does not train either the hamstrings or the two-joint rectus femoris muscle (the contribution is minimal). Also, full squat is good for maximal muscle development because it builds glutes and adductors more compared to half (90 degree or quarter) squat, therefore it’s better for that kind of goals. So, this info is very important from the muscle building standpoint, and this is where bodybuilders and phisique competitors need to pay attention. In other words, isolation (single joint) moves often reigns supreme for this part of population (even if they keep switching compound moves in order to attack all the muscles, they will be simply more fatigued by doing so if training frequency and volume are high on a weekly basis – which will not allow full motor unit recruitment for most muscles and therefore max hypertrophy potential at least). Of course, they should keep some basic big lifts at least in order to produce proper amount of testosterone, which is important for hypertrophy. Athletic population should use compound moves as much as possible, and single-joint moves as accessory stuff (targetig weak links), some parts of rehab, or if we want to lessen further exhaustion of the entire system – in order to speed-up recovery (this is just one of many methods/theories);
- Your adductor magnus is a major player in the squat (probably your most important hip extensor, it also has some fast twitch m. fibers so…might be a great deal for jumping and running performance), and squatting does a great job building your adductor magnus. Therefore, doing squats (especially “sumo” variation – both hip extension and adduction a bit) is a very helpful strategy if you want to buid load tolerance on your adductors (especially deeper squatting) and partly “prevent” strains and(or) solve adductor discomfort. Of course, do isolated moves if you want to recover faster, change angles, etc. (i.e. copenhagen drills, rubber band…), but training motor control via compound moves is golden in every sense – because the body works as one unit. Remember that adductor muscles stabilize pelvis, adduct and flex hips as well, so consider strengthening in that manner too. Also, remember that proper mobility drills, along with proper motor control and similar, are important for groins health as well. One more interesting thing on adductors, take a look at sprinters: Sprinters dispaly much greater adductor muscle volumes than non-sprinters, and the adductor magnus contributes the most to overall adductor size. All of the adductor contribute to hip adduction. Yet, the adductor magnus is a hip extensor, while the adductor brevis, adductor longus, pectineus and gracilis are all hip flexors. They are all actually more relevant to sprint running than the more frequently-trained quadriceps;
- Make sure to squat “straight down” (the classic back squat), don’t bend hips excessively (hip hinge) and consequently bend too much over like while doing “good morning” exercise because it will not be more “glute dominant” (plus load on your back is significantly increased in this way). Don’t be affraid of bending knees more because it should be like that – it’a a squat! When you bend over more than necessarily, you will feel less quad activation and actually more hamstring activation. When you stay more upright, you use a bit more quads, and when you lean more, you use a bit more hamstring, but glute activity isn’t markedly different. You can adjust these things according to your goals, but I prefer having some extra exercises for specific issues. One study showed it’s only 3.8% more glute activity when you lean forward drastically and reach the arms forward in the forward lunge. For sports performance (and in general I would say, in most cases) don’t overthink it and “find” the most natural way of lifting the specific lift (because that’s how you play your sport – “naturally”, and those kind of details don’t really matter here if you are healthy). For general population, don’t obsess about what squat variation is best and simply choose the one that feels ideal for your body. We sometimes think too much about high bar or low bar, stance width and foot flare, depth, torso lean, shin angle, etc., but the most important thing is to gain strength over time, and this is far more likely to happen if it feels right for your body. Some people don’t like low bar and prefer high bar; some don’t like front squats and prefer back squats. Some don’t like sumo squats. Some don’t like going deep and prefer parallel. Our bodies are unique and we should therefore squat uniquely according to our anatomy and goals;
- In a front squat, the combination of sitting down and keeping the torso more upright is going to put more stress on the anterior chain – the abs and quads. In a back squat, where the torso is more angled and you have to sit back further, there is more stress applied to the posterior chain – namely the spinal erectors, glutes and hamstrings. You can adjust this according to your specific case/issues (especially general and athletic population). But, there is one interesting study showing that the front squat produced around 25% greater erector spinae EMG activity than the back squat. What was even more interesting to me was that the front squat had no significant difference in erector spinae activity compared to the superman exercise. All in all, explanation behind this isn’t easy, but you just need to remember a few simple things when we talk about practice: McGill has shown that exercises like “superman” and the classic Roman chair back extension exercise produce excessive amounts of compressive loads on the lumbar spine, so I rarely recommend these to anyone (basic exercises such quadruped hip extension / hip thrust later, and bird dog vars produce an adequate amount of EMG activity while saving the spine from excessive compressive loads); Many people suffer from low back pain (or discomfort) due to chronic postural adaptations (causing anterior pelvic tilt i.e.) and a subsequently low ratio of erector spinae to rectus abdominis strength/tension (overloading these people with aggressive extension exercises are only going to fatigue the extensors more and cause more low back pain). If you prefer to perform the front squat, at least make sure that the person has a solid base of back extensor strength and core stability before progressing to the squat. Because, it’s shown that many people who suffer from low back pain have lack of both erector spinae and abdominal/core strength/stability. Back squat is probably a better option if one suffers from low back pain (if we compare the two… if you have any doubt, the spinal erectors “weakness” isn’t problem/cause in most cases – so you don’t need to strengthen them panically, overall core stability is a bigger issue in my opinion)… Also, if you have knee issues, back squat is probably a bit better option. And, if you like back squat (squatting in general), good ankle dorsiflexion and(or) wider feet (plus toes out) position could help a lot when it comes to reducing spinal load (making your torso more upright works for most people I would say, disregarding the aforementioned research).
For the love of movement,
Luka