Deep Squats: Benefits, Risks, and How to Safely Squat Past 90 Degrees

Should you squat past 90 degrees?

Yes, for most healthy individuals, squatting past 90 degrees (often referred to as "deep squatting" or "below parallel") is not only safe but can offer significant benefits for muscle activation, mobility, and functional strength, provided proper form, mobility, and progressive overload are prioritized.

Introduction to Squat Depth

The squat is a foundational human movement and a cornerstone of strength training. Yet, few topics spark as much debate as squat depth. Specifically, the question of whether one should squat past 90 degrees – meaning the crease of the hip descends below the top of the knee, or the femur drops below parallel to the floor – is a common point of contention. While some historically warned against deep squats citing knee safety concerns, modern exercise science, anatomy, and biomechanics paint a more nuanced picture. This article will delve into the evidence to provide a clear, actionable understanding of squatting beyond parallel.

Understanding Squat Depth: Anatomy and Biomechanics

To understand the implications of squat depth, we must first examine the key joints involved: the hips, knees, and ankles, and how they interact with the spine.

• Knee Joint Mechanics: The knee is a hinge joint primarily responsible for flexion and extension.
  • Patellofemoral Joint: The joint between the kneecap (patella) and the thigh bone (femur). Compression forces on this joint increase with knee flexion. However, research indicates that peak patellofemoral joint stress occurs around 90 degrees of knee flexion, and can actually decrease slightly beyond this point as the quadriceps muscles' line of pull changes.
  • Tibiofemoral Joint: The joint between the shin bone (tibia) and the thigh bone (femur). Shear forces (forces that push the tibia forward relative to the femur) are highest at shallower squat depths (0-60 degrees), while compressive forces increase with depth. Ligaments like the ACL and PCL are designed to withstand these forces, and in a properly executed deep squat, the forces are distributed across a larger surface area, potentially reducing peak stress on specific points.
• Hip Joint Mechanics: Deep squatting requires significant hip flexion.
  • Glute Activation: As you descend past parallel, the gluteal muscles (gluteus maximus, medius, minimus) become increasingly active, particularly the gluteus maximus, which is a primary hip extensor. This makes deep squats superior for glute development compared to partial squats.
  • Adductor Engagement: The adductor magnus, a large muscle on the inner thigh, also acts as a powerful hip extensor, especially when the hips are deeply flexed.
• Spinal Considerations: The "Butt Wink": As you squat deeper, the pelvis naturally tucks under, causing a slight rounding of the lower back (lumbar spine). This is often referred to as a "butt wink."
  • A minor, controlled butt wink is often a natural consequence of reaching end-range hip flexion and may not be inherently dangerous for healthy individuals.
  • A pronounced or uncontrolled butt wink, however, indicates a loss of lumbar stability and can place undue stress on the intervertebral discs. This is often due to limited hip or ankle mobility, or insufficient core stability.

The Case for Squatting Past 90 Degrees (Deep Squat)

Numerous benefits are associated with safely performing deep squats:

• Increased Muscle Activation:
  • Quadriceps: While active at all depths, the quads remain highly engaged throughout the deep squat.
  • Glutes and Hamstrings: Activation of the gluteus maximus and hamstrings significantly increases as you descend below parallel, making deep squats superior for posterior chain development.
  • Adductors: The adductor magnus contributes substantially to hip extension in the bottom of a deep squat.
• Enhanced Range of Motion (ROM) and Flexibility: Consistently training through a full, pain-free range of motion can improve hip, knee, and ankle mobility over time, contributing to overall functional movement and reducing the risk of injury in daily life.
• Improved Joint Health and Cartilage Nutrition: The idea that deep squats "wear out" your knees is largely a myth. Weight-bearing movements through a full range of motion can actually promote cartilage health by facilitating the diffusion of nutrients into the cartilage and stimulating its repair mechanisms. The knee joint is designed for full flexion.
• Functional Strength and Athletic Performance: Deep squats mimic many movements found in sports and daily activities (e.g., picking something off the floor, jumping, running). Training through a full ROM builds strength that translates more effectively to these real-world movements and can enhance athletic power and stability.

Potential Risks and Considerations Below 90 Degrees

While beneficial, deep squatting is not without its considerations, particularly if proper form, mobility, and individual factors are ignored.

• Increased Joint Stress (When Form is Compromised): The knee joint is most stable under compression. If the knees collapse inward (valgus collapse), the back rounds excessively, or the weight is loaded too heavily without proper control, the deep squat can indeed become risky, leading to ligamentous or meniscal injuries. The danger lies not in the depth itself, but in the manner in which that depth is achieved.
• Pronounced "Butt Wink" and Lumbar Spine Safety: As discussed, an excessive butt wink indicates a loss of neutral spine and can place the lumbar discs under shear stress, increasing the risk of disc herniation or other back injuries. This is often a symptom of limited hip flexion mobility, tight hamstrings, or poor ankle dorsiflexion, forcing the pelvis to compensate.
• Individual Anatomical Variations: Not everyone is built the same.
  • Femoral Neck Angle and Acetabular Depth: Variations in hip socket depth and femoral neck angle can significantly impact an individual's comfortable and safe squat depth. Some individuals may simply not have the skeletal structure to squat "ass-to-grass" without significant compensation.
  • Ankle Dorsiflexion: Limited ankle mobility can prevent the knees from tracking forward over the toes, forcing the hips to compensate by tucking under, leading to a butt wink.
• Pre-existing Conditions or Injuries: Individuals with a history of knee injury (e.g., ACL tear, meniscus damage), hip impingement, or chronic low back pain should approach deep squatting with caution and ideally under the guidance of a qualified medical professional or physical therapist.

Who Should Squat Deep and Who Should Be Cautious?

• Ideal Candidates for Deep Squats:
  • Individuals with good overall mobility, particularly in the ankles and hips.
  • Those who can maintain a relatively neutral spine throughout the full range of motion.
  • Athletes and fitness enthusiasts looking to maximize muscle activation, build functional strength, and improve mobility.
  • Individuals without pre-existing joint pain or significant injuries.
• Those Who Should Be Cautious or Modify Depth:
  • Beginners: Should prioritize mastering proper form at shallower depths before progressing to deeper squats.
  • Individuals with Limited Mobility: Especially in the ankles or hips, which can force compensatory movements. Focus on improving mobility first.
  • Those with Specific Injuries: Such as severe knee osteoarthritis, hip impingement, or acute low back pain. Always consult a healthcare professional.
  • Individuals with Significant Anatomical Limitations: Some hip structures simply don't allow for comfortable, deep squatting without compensation.

How to Safely Progress to Deeper Squats

If you aim to squat deeper, here's a progressive approach:

1. Master Form at Shallower Depths: Before going deep, ensure you can perform squats with proper bracing, knee tracking, and a neutral spine at parallel or slightly above.
2. Improve Mobility:
   • Ankle Dorsiflexion: Incorporate ankle mobility drills (e.g., calf stretches, kneeling ankle rocks, elevated heel squats).
   • Hip Flexion: Perform hip mobility exercises (e.g., 90/90 stretches, pigeon pose, deep lunge stretches).
   • Thoracic Spine Mobility: Improve upper back extension to aid in maintaining an upright torso.
3. Gradual Progression:
   • Start with Bodyweight: Practice bodyweight deep squats to identify and address mobility limitations.
   • Use Assistance: Hold onto a TRX, door frame, or use a resistance band for support to allow deeper movement while maintaining form.
   • Elevate Heels: Placing small weight plates under your heels can temporarily improve ankle mobility and allow for deeper squats, but this should be a temporary fix while you work on true ankle dorsiflexion.
   • Light Load and Controlled Movement: Once comfortable with bodyweight, gradually add light weight, focusing on slow, controlled descents and ascents.
4. Listen to Your Body: Differentiate between muscle fatigue/stretch and sharp joint pain. Pain is a signal to stop and reassess.
5. Seek Expert Guidance: A qualified personal trainer or physical therapist can assess your individual mechanics, identify limitations, and provide personalized coaching.

Conclusion

The notion that squatting past 90 degrees is inherently dangerous for the knees is largely outdated. For most healthy individuals with adequate mobility and proper form, deep squatting is not only safe but highly beneficial for maximizing muscle recruitment, enhancing joint health, and building functional strength. The key lies in understanding your own body, respecting individual anatomical variations, prioritizing mobility, and progressing gradually. When executed correctly, the deep squat is a powerful tool in any comprehensive fitness regimen, leading to stronger legs, more resilient joints, and improved overall movement capacity.