Most people treat lunges like a filler exercise. You’re at the gym, you’ve finished your squats, and you figure you’ll just knock out some walking lunges to "burn out" the quads. But then it happens. A sharp twinge in the patella. Or maybe you feel it all in your lower back instead of your glutes. Honestly, learning how to do correct lunges is harder than it looks because the move is essentially a controlled fall. If you don't stick the landing, you're just grinding your joints.
Stop thinking about lunges as a "leg day" staple for a second. Think of them as a stability test. Every time you step forward, your nervous system is screaming to keep you upright. If your form is trash, your body compensates by shifting the load to places that aren't meant to take it. We’re going to break down the mechanics of the perfect rep, the physics of why your front knee keeps caving in, and why the "90-degree rule" might actually be holding you back.
The Anatomy of a Perfect Rep
When you start looking at the mechanics of how to do correct lunges, you have to start with the "train tracks" concept. Most beginners try to step forward as if they are walking on a tightrope. This is a disaster. Your feet should be hip-width apart throughout the entire movement. If your feet are in a straight line, your center of gravity is totally screwed, and you’ll spend more energy wobbling than actually building muscle.
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Keep your chest up. Not "military parade" up, but naturally tall. You want a slight forward lean in your torso—about 10 to 15 degrees—to actually engage the glutes. If you stay perfectly vertical like a statue, you’re putting an insane amount of shear force on the knee. That slight lean shifts the load back into the posterior chain. It's a game changer for anyone with "crunchy" knees.
The back foot matters more than you think. You need to stay on the ball of that back foot. Don't let the heel touch the ground. Ever. Your back leg is your rudder; it controls the descent. As you lower down, that back knee should drop straight toward the floor, stopping just an inch or two above the wood or turf. If you're banging your knee off the ground, you're losing tension and risking a bruise that’ll haunt you for a week.
Why Your Knees Hate You (And How to Fix It)
We’ve all heard that your knee should never go past your toes. That’s a myth. Well, it's a half-truth that became gym dogma. Researchers like Dr. Aaron Horschig have pointed out that for many people, especially those with long femurs, the knee has to move forward slightly to maintain balance. The problem isn't the forward travel; it's the "valgus collapse."
Valgus collapse is just a fancy way of saying your knee is caving inward toward your midline. This is the ACL killer. It usually happens because your glute medius—that muscle on the side of your hip—is weak or just "asleep." To fix this, imagine you are trying to screw your front foot into the floor. Twist it outward without actually moving it. This creates torque and keeps that knee tracked perfectly over your second and third toes.
- Check your setup: feet hip-width.
- The descent: slow, controlled, 2-3 seconds down.
- The "bottom" position: front shin should be nearly vertical, or slightly forward.
- The drive: push through the mid-foot and heel of the front leg, not the toes.
If you feel like you’re falling forward, you’re likely pushing off your back leg too much. The back leg is for balance; the front leg is the engine. Drive through that front heel. You should feel your glute and hamstring fire immediately. If you don't, try wiggling your front toes while you’re at the bottom of the rep. If you can’t wiggle them, your weight is too far forward.
Variations That Actually Build Strength
Once you've mastered the basic forward lunge, you’ve gotta switch it up. Forward lunges are actually the hardest version to get right because of the deceleration required.
- Reverse Lunges: These are actually the gold standard for beginners. Because you're stepping backward, your front shin stays more vertical naturally. It’s much easier on the knees. If you’re recovering from an injury, start here.
- Lateral Lunges: We live in a world where we only move forward and backward. Lateral lunges force you into the frontal plane. They hit the adductors and the side of the glutes. Keep that trailing leg bone-straight.
- Bulgarian Split Squats: Okay, these aren't technically lunges, but they’re the "evil cousin." By elevating your back foot on a bench, you put almost 100% of the load on the front leg. It’s brutal. It's effective. It's probably why you can't walk the next day.
The "Core" Connection You're Missing
Lunges are a secret core workout. If your pelvis is tilting forward (anterior pelvic tilt), your lower back is going to take a beating. You need to "tuck" your tailbone slightly. Think about pulling your belly button toward your spine. This stabilizes the spine and ensures the stretch is happening in the hip flexor of the back leg, not the vertebrae of your lumbar.
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When you hold weights—whether they are dumbbells at your sides or a kettlebell in a goblet position—your core has to work double time to prevent "lateral lean." If you find yourself tipping to the side, drop the weight. Perfecting how to do correct lunges requires more than just leg strength; it requires a rigid, stable torso that can handle the shifting weight.
Common Mistakes and Quick Fixes
Most people "overstride." They take a massive leap forward, which overextends the hip flexor and makes it impossible to keep the torso upright. Your stride should be long enough that both knees can hit roughly a 90-degree angle, but short enough that you feel stable.
Another big one? The "walking" lunge "plopping." I see people in the gym basically falling into their next step. Each step should be a distinct, controlled movement. Step, stabilize, lower, drive. If you're rushing, you're just using momentum, and momentum doesn't build muscle.
Troubleshooting Your Form
- Wobbling? Space your feet wider (horizontally).
- Knee pain? Switch to reverse lunges and focus on a vertical shin.
- Low back pain? Tighten your abs and don't lean back so far.
- No glute burn? Lean your torso forward slightly and drive through the heel.
Actionable Steps for Your Next Workout
Don't just go out and do 50 lunges. Start small. If you haven't been doing these correctly, your stabilizer muscles are going to be weak.
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Start with static lunges (also called split squats). Don't even take a step. Just get into the lunge stance and go up and down. Do 3 sets of 10 on each leg. Focus entirely on that "screw the foot into the floor" trick to keep your knee stable. Once that feels like second nature, move to reverse lunges.
By the time you get back to forward lunges or walking lunges, your mechanics will be locked in. Your knees will feel better, your glutes will actually be sore for the right reasons, and you’ll realize that the lunge is actually one of the most powerful tools in your fitness kit. Focus on the tension, forget the "reps," and treat every single step like a skill you're trying to master.
Next time you hit the floor, film yourself from the side. Check your shin angle. If it's slanted way forward and your heel is lifting, you've got work to do. Adjust, reset, and push again. That's how you actually see progress.