Back squat
The barbell back squat reliably builds the quadriceps, glutes and adductors and is one of the best-studied lower-body exercises in training research. Going deep (thighs at or below parallel) grows more muscle than half squats in randomized trials; it does little for the hamstrings or rectus femoris, so pair it with a hinge and a leg extension if you want those.
What the science says
- Builds the quads, glutes and adductors Strong evidence
In Kubo et al.'s 2019 randomized trial, 10 weeks of squat training increased MRI-measured knee-extensor volume by about 5% in both full- and half-squat groups, with the glutes and adductors also growing. Plotkin et al. (2023) found 9 weeks of back squats grew the gluteus maximus as much as hip thrusts, and grew the quadriceps and adductors more.
- Deep squats beat shallow squats for growth Moderate evidence
Bloomquist et al. (2013) found 12 weeks of deep squats (to about 120° knee flexion) increased front-thigh cross-sectional area more than shallow squats (to 60°). Kubo et al. found full squats grew the glutes (+6.7% vs +2.2%) and adductors more than half squats, though quadriceps gains were similar. Both trials were small (17 men each).
- Little growth in the hamstrings and rectus femoris Moderate evidence
Kubo et al. measured no change in hamstring or rectus femoris volume after 10 weeks of squatting at either depth, and Plotkin et al. saw little hamstring growth. The squat is a quad, glute and adductor exercise; the hamstrings need a hip hinge or leg curl.
- Deep squats are not inherently bad for healthy knees Moderate evidence
Hartmann et al.'s 2013 review of more than 160 papers concluded that concerns about cartilage and ligament damage from deep squats in healthy people are unfounded, and that heavy half or quarter squats with supramaximal loads may stress the knee and spine more. This rests on biomechanical and cadaver data, not long-term injury trials.
How to do it
Muscles trained: quadriceps, glutes, adductors
- Bar on the upper back (high bar) or across the rear delts (low bar), hands as narrow as your shoulders allow
- Feet about shoulder-width, toes turned out 15–30°
- Brace your trunk with a deep breath before each rep
- Let the knees travel forward and track over the toes
- Descend until the thighs are at or below parallel without the lower back rounding
- Drive up through the whole foot, keeping chest and hips rising together
How to apply it
Squat to the deepest depth you can hold with a neutral spine, usually thighs at or below parallel, and add load or reps steadily.
Who should be careful
For healthy adults the squat is safe when load is built up gradually and technique holds. Use safety pins or spotter arms when training close to failure, and end the set when depth or back position breaks down. Anyone with knee, hip or back pain or a past injury should get individual advice from a physician or physical therapist.
Frequently asked questions
Do I have to squat deep to grow my legs?
Deeper is better. In randomized trials, deep squats grew the front thigh (Bloomquist et al.) and the glutes and adductors (Kubo et al.) more than half squats, so go as deep as you can with a neutral spine.
Are deep squats bad for the knees?
Not for healthy knees. Hartmann et al.'s review found no basis for the claim that deep squats damage cartilage or ligaments, and noted that very heavy partial squats may load the knee and spine more.
Does the squat train the hamstrings?
Very little. Kubo et al. found no hamstring growth after 10 weeks of squatting, so add a hip hinge such as the Romanian deadlift or a leg curl.
Scientific references
- Effects of squat training with different depths on lower limb muscle volumes
- Effect of range of motion in heavy load squatting on muscle and tendon adaptations
- Hip thrust and back squat training elicit similar gluteus muscle hypertrophy and transfer similarly to the deadlift
- Analysis of the load on the knee joint and vertebral column with changes in squatting depth and weight load
More exercises
- Bulgarian split squat Moderate evidence
The Bulgarian (rear-foot-elevated) split squat trains one leg at a time and builds the quads and glutes with far less load on the bar than a back squat.
- Romanian deadlift Moderate evidence
The Romanian deadlift is a hip hinge that loads the hamstrings and glutes at long muscle lengths, and trials of stiff-leg deadlifts and similar hip-extension exercises show real hamstring growth, mainly in the semimembranosus and biceps femoris long head.
- Conventional deadlift Moderate evidence
The conventional deadlift trains the whole posterior chain and grip and is a core strength lift, but research on its growth effects is thin: trials either use other deadlift variants or measure strength rather than muscle size.
- Barbell hip thrust Moderate evidence
The barbell hip thrust grows the glutes, and it does so with little growth of the quads or adductors, which makes it a good targeted addition.
- Lunges Moderate evidence
Lunges (forward, reverse or walking) train the quads and glutes one leg at a time and highly activate the glutes.
- Leg extension Strong evidence
The leg extension isolates the quadriceps and is the best-supported way to grow the rectus femoris, the one quad head that squats and leg presses barely touch.