Squats build strength in nearly every muscle below your waist, but their benefits extend well beyond bigger legs. They improve jump height, protect bone density, make everyday movements easier as you age, and burn a meaningful number of calories. Few exercises deliver this much return for a single movement.
Muscles Worked During a Squat
Squats primarily target the quadriceps (front of the thigh), glutes, and hamstrings. Your calves, lower back, and core muscles all work to stabilize your body throughout the movement. This combination is what makes the squat a “compound” exercise: it trains multiple large muscle groups simultaneously rather than isolating one.
One common belief is that front squats hit the quads harder than back squats. Research using electromyography (sensors that measure muscle activation) doesn’t support this. Quad activation is essentially the same between front and back squats. The real difference is that back squats generate more hamstring activation. Front squats can match the quad stimulus of a back squat with a lighter load, which can be useful if you’re working around a back issue or prefer the more upright torso position.
Adding small modifications changes the emphasis. Squatting with a resistance band around the knees or actively pressing the knees outward increases activation in the gluteus medius, the muscle on the outer hip that stabilizes your pelvis during walking and running.
How Squats Improve Athletic Performance
Squat strength has a direct, measurable relationship to explosive power. A study on young female volleyball players found a strong correlation (r = 0.88) between one-rep-max squat strength and vertical jump height. After a training period that increased squat strength by 69%, vertical jump height improved by 9%. That may sound modest, but in sports where inches matter, like basketball, volleyball, and track, a 9% gain in jump height is significant.
The connection makes intuitive sense. Jumping, sprinting, and changing direction all require your legs to produce force against the ground quickly. Squats train exactly that pattern: pushing your body upward against resistance. When squat strength is measured relative to body weight, the correlation to jump height becomes even stronger (r = 0.95), meaning the athletes who were strongest pound-for-pound jumped the highest.
Effects on Bone Density
Weight-bearing exercise stimulates bone remodeling, and squats load the spine, hips, and legs, three areas most vulnerable to osteoporosis. In a small study on progressive back squat training, 11 out of 14 participants increased their bone mineral density. One participant who started in the “osteopenic” range (below-normal bone density) improved enough to be reclassified as normal.
This matters most for people over 40, when bone density naturally begins to decline. The mechanical stress of squatting signals your body to deposit more mineral into bone tissue. Bodyweight squats provide some stimulus, but heavier loaded squats create a stronger signal.
Everyday Mobility and Fall Prevention
Getting off a low couch, climbing stairs, picking something up from the floor: these all involve the squat pattern. Leg strength is one of the strongest predictors of independence in older adults. Research published in the American Heart Association’s journal Circulation found that people ages 70 to 79 with stronger quadriceps had a lower risk of dying over a six-year follow-up compared to those with weaker quads.
Squats also train balance and joint stability. As you lower into the movement, your ankles, knees, and hips all move through a controlled range of motion under load. This builds the kind of strength that helps prevent falls, not just the ability to lift heavy weight in a gym, but the ability to recover when you stumble on an uneven sidewalk or catch yourself stepping off a curb.
What Happens at Your Knees
The idea that squats are bad for your knees is one of the most persistent myths in fitness. The actual biomechanics tell a more nuanced story. Anterior shear force (the type that stresses the ACL) peaks between 30 and 60 degrees of knee bend, which corresponds to a partial or half squat. As you descend deeper, that force actually decreases. So stopping at a quarter squat to “protect your knees” may expose them to more of the specific force people are trying to avoid.
Posterior shear force, which loads the PCL, peaks around 90 degrees of knee flexion (roughly a parallel squat) and decreases as you go deeper or shallower. Compressive forces increase fairly linearly with depth. In a study of a powerlifter squatting 250 kilograms (about 550 pounds), compressive forces peaked at nearly 7,000 Newtons at the bottom of the squat. For most recreational lifters using moderate loads, these compressive forces are well within what healthy knee cartilage can handle and may actually help maintain cartilage health over time.
The practical takeaway: if you have healthy knees, full-depth squats are safe and may be preferable to partial squats for minimizing certain shear forces. If you have an existing knee condition, your ideal depth depends on the specific issue.
Calorie Burn and Metabolic Cost
Squats aren’t a cardio replacement, but they burn more calories than most people expect. The metabolic cost depends on intensity. Light-effort squats (bodyweight or easy loads where you can hold a conversation) carry a MET value of about 3.5. Vigorous squatting with heavier loads pushes the MET value up to 8.0, comparable to running at a moderate pace.
For a person weighing 140 pounds, that translates to roughly 58 calories burned in 15 minutes of light squatting and up to 133 calories for 15 minutes of intense squatting. A heavier person burns proportionally more. Beyond the calories burned during the session, squats build muscle mass, which raises your resting metabolic rate over time. Each pound of muscle burns more energy at rest than a pound of fat, so adding muscle through exercises like squats contributes to a slightly higher daily calorie burn even on days you don’t train.
Hormonal Response to Squatting
Heavy compound exercises like squats trigger a temporary spike in testosterone and growth hormone. In trained men, moderate-intensity lower body exercise (around 70% of max effort) produced a 27% increase in testosterone immediately after the workout. Higher-intensity sessions (90% of max) produced a smaller, non-significant bump of about 17.5%. In both cases, levels returned to baseline within 60 minutes.
These acute hormonal spikes were once thought to be a major driver of muscle growth. Current thinking is more skeptical. The increases are short-lived and relatively small in absolute terms. They likely play a supporting role rather than being the primary reason squats build muscle. The mechanical tension on muscle fibers during the lift itself appears to be the more important growth signal.
Cardiovascular Considerations
Squats improve muscular health, but heavy resistance training in general has a complex relationship with cardiovascular markers. A randomized study of healthy men ages 20 to 38 found that four months of resistance training (including squats) decreased arterial compliance in the carotid artery by 19%, meaning the artery became stiffer. Blood pressure itself didn’t change, and peripheral artery compliance was unaffected.
This doesn’t mean squats are bad for your heart. It means that if cardiovascular health is a priority alongside strength, combining resistance training with regular aerobic exercise is the best approach. Aerobic training improves arterial compliance, and the two forms of exercise together produce better overall outcomes than either alone.