--- id: back_squat name: Back Squat status: complete aliases: [High Bar Squat, Low Bar Squat] category: exercise pattern: [squat] equipment: [barbell, squat rack] difficulty: technical_complexity: 3 strength_prerequisite: 3 mobility_prerequisite: 3 muscles: - id: vastus_lateralis role: primary - id: vastus_medialis role: primary - id: rectus_femoris role: primary - id: gluteus_maximus role: primary - id: biceps_femoris role: secondary - id: semitendinosus role: secondary - id: erector_spinae role: stabilizer - id: core role: stabilizer # EMG data from two independent studies under different load conditions. # Values are % of maximum voluntary isometric contraction (MVC), concentric phase. # Do NOT average across studies — conditions differ. muscle_activation_studies: - source_id: yavuz_2015 doi: "10.1080/02640414.2014.984240" n: 14 population: "trained males" condition: load_pct_1rm: 80 bar_position: high_bar depth: parallel phase: concentric measurements: - {muscle: vastus_lateralis, mean_pct_mvc: 45.9, sd: 13.9} - {muscle: vastus_medialis, mean_pct_mvc: 52.3, sd: 18.1} - {muscle: rectus_femoris, mean_pct_mvc: 38.4, sd: 16.2} - {muscle: gluteus_maximus, mean_pct_mvc: 28.8, sd: 18.9} - {muscle: biceps_femoris, mean_pct_mvc: 18.7, sd: 14.9} - {muscle: semitendinosus, mean_pct_mvc: 15.0, sd: 6.9} - {muscle: erector_spinae, mean_pct_mvc: 41.1, sd: 14.0} - source_id: yavuz_2015 doi: "10.1080/02640414.2014.984240" n: 14 population: "trained males" condition: load_pct_1rm: 100 bar_position: high_bar depth: parallel phase: concentric measurements: - {muscle: vastus_lateralis, mean_pct_mvc: 48.5, sd: 17.2} - {muscle: vastus_medialis, mean_pct_mvc: 61.8, sd: 19.3} - {muscle: rectus_femoris, mean_pct_mvc: 42.1, sd: 17.8} - {muscle: gluteus_maximus, mean_pct_mvc: 47.3, sd: 27.7} - {muscle: biceps_femoris, mean_pct_mvc: 34.9, sd: 18.2} - {muscle: semitendinosus, mean_pct_mvc: 29.0, sd: 16.2} - {muscle: erector_spinae, mean_pct_mvc: 46.0, sd: 17.6} - source_id: kubo_2019 doi: "10.1371/journal.pone.0217044" n: 13 population: "resistance-trained males, 6±3 yrs experience" condition: load_pct_1rm: 70 bar_position: high_bar depth: parallel phase: concentric measurements: - {muscle: vastus_lateralis, mean_pct_mvc: 58, sd: null} - {muscle: vastus_medialis, mean_pct_mvc: 55, sd: null} - {muscle: rectus_femoris, mean_pct_mvc: 47, sd: null} - {muscle: gluteus_maximus, mean_pct_mvc: 42, sd: null} - {muscle: biceps_femoris, mean_pct_mvc: 28, sd: null} - {muscle: semitendinosus, mean_pct_mvc: 24, sd: null} joint_rom_required: ankle_dorsiflexion_deg: 20 hip_flexion_deg: 120 thoracic_extension_deg: 15 source: "NASM; Greene 1994" strength_curve: type: ascending sticking_point: bottom_third peak_force_position: lockout notes: > Hip moment arm peaks at the sticking point (~30–40% of ascent); hip extensor demand is highest there despite lower ground reaction force. source: "van den Tillaar & Andersen 2021, PMC8217455" injury_risk: joint_stress: knee: moderate lower_back: moderate shoulder: low common_injuries: - structure: patellar_tendon mechanism: overuse risk_factors: [high_volume, rapid_load_increase] - structure: lumbar_disc mechanism: flexion_under_load risk_factors: [poor_bracing, excessive_forward_lean] contraindications: - acute_knee_injury - lumbar_herniation variations: [front_squat, box_squat, overhead_squat] progressions: [box_squat] alternatives: [leg_press] sources: - source_id: yavuz_2015 title: "Kinematic and EMG Activities During Front and Back Squat Variations in Maximum Loads" author: "Yavuz HU et al." year: 2015 doi: "10.1080/02640414.2014.984240" credibility: rct - source_id: kubo_2019 title: "Comparison of muscle activation and kinematics during free-weight back squats with different loads" author: "Kubo K et al." year: 2019 doi: "10.1371/journal.pone.0217044" credibility: rct - source_id: van_den_tillaar_2021 title: "New Insights About the Sticking Region in Back Squats" author: "van den Tillaar R & Andersen V" year: 2021 doi: "10.3389/fspor.2021.681581" credibility: rct - source_id: nasm_squat title: "The Muscles Used in Squats: Squat Biomechanics Explained" author: "NASM" credibility: expert_consensus --- # Back Squat The back squat is a squat pattern defined by the barbell resting across the upper back. It is one of the most widely used compound movements in strength training, and one of the three powerlifting competition lifts. ## Execution 1. Position the bar across the upper traps (high bar) or rear delts (low bar) 2. Stance slightly wider than shoulders, toes turned out 15–30 degrees 3. Inhale and brace with a Valsalva maneuver, tightening the core 4. Flex hips and knees together, tracking knees over the toes 5. Drive up out of the bottom by extending the hips ## Common Faults - **Valgus collapse** — knees cave inward; typically from weak glute medius and abductors - **Excessive forward lean** — usually limited ankle mobility or insufficient core bracing - **Insufficient depth** — tight hip flexors or a miscalibrated sense of depth ## What the EMG Data Shows Activation increases non-linearly with load. The quadriceps (vastus medialis, lateralis, rectus femoris) are consistently the dominant prime movers. Gluteus maximus activation increases markedly only at very high loads (90–100% 1RM), suggesting the glutes are more load-sensitive than depth-sensitive in the back squat. Erector spinae acts as a stabilizer throughout, with activation in the 40–46% MVC range at 80–100% 1RM. The sticking point falls in the bottom third of the ascent, where the hip moment arm peaks despite a reduction in ground reaction force — this is primarily a hip extensor failure point, not a knee extensor failure point. ## Variations | Variation | Key difference | Best for | |-----------|----------------|----------| | High bar | More upright torso, quad-dominant | Bodybuilding, weightlifting accessory | | Low bar | Greater lean, hips and legs share load | Powerlifting | | Box squat | Fixed depth reference | Beginners, fear management | > For system-specific training applications, see each system's lens entry.