One of the most pervasive swing faults affecting millions of golfers is the tendency to come out of posture — or lose spine angle — during the downswing. This movement pattern, commonly known as "early extension," does far more than simply compromise accuracy and distance. It actively robs the golfer of both control and power, while significantly increasing the risk of injury in the lead hip and lumbar spine (lower back).
The unfortunate reality is that most golfers — and even many instructors — fail to grasp the true biomechanical causes behind this widespread fault, let alone how to correct it. Before we can address the fix, we need to understand what proper movement looks like when executed correctly, viewed from a revealing angle.
In the photo sequence below, we see footage of Tiger Woods striking a three wood. The image on the left captures Tiger after he has already initiated the club's descent during the downswing. What deserves particular attention here is that BOTH knees still maintain significant knee flex at this stage of the motion.
In the second photo, observe how Tiger's belt has risen considerably above its position during the transition (indicated by the yellow line), producing an almost jumping appearance — all while preserving the flex in his trail knee throughout the entire movement.
For the vast majority of amateurs, the glutes — the most powerful stabilizing muscles in the lower body — never get properly loaded during the downswing the way Tiger achieves by "squatting" during the transition. This squatting motion represents a tremendous source of both power and stability. In fact, many golfers fully straighten the trail leg before they even complete their backswing, eliminating any chance of engaging these critical muscles.
Even among those who do maintain adequate knee flex initially, many then make the mistake of aggressively pushing off the trail foot during the downswing, trying to spin the hips around at maximum velocity. The result? The club and arms get trapped behind the body, forcing the golfer to lose their spine angle just to make contact with the ball.
Let's examine more closely what happens during that first image of Woods from the down-the-line view. Below, you can see that both Tiger on the right and I on the left exhibit that characteristic "squatting" look during the transition — we have maintained or slightly increased the knee flex we established at the top of the swing.
From a biomechanics standpoint, this is absolutely critical for loading the gluteus muscle to generate power and maintain stability. If you straighten up during this phase, it triggers the dreaded "over the top" move that plagues so many amateurs, draining all the force from the powerful trunk muscles that should be driving the swing. If you want to see exactly where your own swing breaks down, try a free AI swing analysis — it measures these exact positions frame by frame.
Looking at the top-of-swing positions below, we can identify approximately 162 degrees of knee flex at the peak of the backswing. Preserving this degree of flex is the single most effective way to activate the trail glute at this critical moment, enabling you to harness the ground for leverage during the downswing — what biomechanists refer to as Vertical Ground Force (VGF).
As the downswing begins, this flex in the trail knee is maintained or slightly increased. (Note that the flex appears to increase more than it actually does because the rear leg externally rotates somewhat during the backswing.) This is precisely the moment where the dynamic loading of the glutes truly engages, igniting the powerful Stretch Shorten Cycle (SSC) that elite ball-strikers depend on.
Maintaining this knee flex rather than spinning the hips open and straightening up serves multiple purposes: it gives the arms critical extra time to work back down in front of the body, it delivers the club on a proper swing path, and it keeps the glutes actively engaged throughout the downswing for both power generation and postural support.
When the trail leg straightens prematurely — as it does for so many golfers, including Josh from the accompanying video — the glutes can no longer apply force into the ground. This loss of ground connection eliminates the foundation necessary for generating both power and directional control.
Without this essential movement pattern and sustained knee flex, there is simply no way someone my size can generate the clubhead speed I produce, which maxes out in the upper 120s mph. The large muscles of the lower body must be recruited to both support the rotation of the torso and to apply force while leveraging the ground as a platform. If you want to hit the ball farther, you MUST learn to use your glutes effectively!
Now let's examine what goes wrong when the trail leg straightens during the downswing — and in this particular case study, how the problem is compounded when the straightening begins even earlier, during the backswing itself.
In this example, the golfer has allowed the trail leg to completely straighten during the backswing, entirely eliminating any possibility of loading the glutes — the two largest, most powerful muscles in the human body — since they are already near full extension with nowhere left to go.
To experience this principle firsthand, simply stand up and perform a squat. As long as your knees remain flexed, you can actively push down into the ground through your glutes. But the instant you fully straighten your knees, that ability to push and leverage the ground using these powerful muscles vanishes completely.
For most amateurs, this straightening leads directly to the dreaded over-the-top move, which you can clearly see this golfer performing in the second picture. The shaft should be positioned closer to her trail arm than her lead arm at this point in the swing. With nothing left to power the motion except her upper body, this creates a lunge at the ball that produces an extremely weak shot.
For more skilled golfers, the problem manifests differently — the club gets stuck behind the body as they approach impact. This occurs because instead of straightening the trail leg and losing its utility entirely, they keep the leg flexed but then recruit the powerful glutes to spin the hips open far ahead of the arms and club. The result is a swing path that travels too severely from the inside, producing blocked shots and snap hooks. In both scenarios, maintaining proper knee flex throughout the sequence is the fundamental key.
Returning to the original photo of Tiger Woods, we can now appreciate where the real payoff lies in terms of power generation. Again, notice the yellow line drawn on his belt in the left frame. He occupies a tremendously powerful position here, his hips bracing as he actively works to deliver his arms back in front of his body.
The glutes serve as the primary muscles for stabilizing the lower body in the golf swing at impact, and they are perfectly engineered for this demanding task. As Tiger approaches impact, observe how dramatically higher his belt sits compared to its position during the transition.
This distinctive "squat and jump" appearance is Tiger driving his ankles into the ground during the transition to "anchor" himself and actively load the glutes by capitalizing on the SSC. This is the same pattern that separates elite ball-strikers from the rest — and it is precisely the kind of movement you can train. If you want to experience how proper loading feels in a guided environment, try a free AI golf lesson that coaches you through each phase in real time.
As he arrives at impact, his lead glute is pushing forcefully into the ground, propelling his body away from the clubhead and further accelerating the club at the very last instant — all while stabilizing his lower body against the tremendous forces of inertia created by the fast-moving clubhead. At impact, note that his trail knee, while rotated by his hips toward the target, still maintains its flex.
Teaching golfers this precise sequence can require weeks of dedicated practice, but the results are well worth the effort. However, if you don't have access to an instructor who can guide you through this critical movement pattern, we have a solution! Enter the "Anchor"!
The Anchor Training Aid
The Anchor stands alone as the one training aid on the market designed to address all of these golf swing ailments — not through gimmicky mechanisms, but through a foundation of pure biomechanics and sound movement science.
Developed by Boston Celtics orthopedic surgeon Dr. Brian McKeon — a world-renowned orthopedic surgeon and sports medicine authority — this aid has the potential to dramatically transform your downswing and put you into the same powerful positions that Tiger Woods achieves, positions you may have only dreamed of reaching before.
Of course, as with any training aid, understanding "HOW" to move and "WHERE" to initiate movement from is the key to maximizing its effectiveness. In the accompanying video, we discuss the precise principles and techniques that will make the "Anchor" an essential element in your training journey toward becoming a more powerful, consistent golfer.
The Anchor functions by locking the knee at a user-adjustable angle throughout the entire golf swing. The angle settings accommodate different builds and setup positions, ensuring a customized fit for each golfer.
Once secured in place, the trail knee remains flexed throughout the swing, enabling the golfer to actively engage the trail glute during every phase of the motion — preventing the "stand up" pattern during both the backswing and downswing. This constant proprioceptive reinforcement works to retrain the brain through focused repetition, building the neural pathways needed to maintain proper flex automatically.
The device physically prevents you from straightening up during the backswing and blocks the same fault during the downswing. Instead, by maintaining your flex throughout the motion, you will finally be able to feel your trail glute activate — perhaps for the very first time in your golf swing!
This powerful new sensation will transform your swing if you struggle with any of the problems described above. And best of all, the Anchor can be worn while playing actual rounds! You can quickly unlock the brace to walk to your next shot, then simply re-engage the tabs and you're ready to swing again!
You can see the Anchor in action in our video - Maintaining Right Knee Flex.
Ready to add power back into your golf game?
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Video Transcription: Anchor | Create Vertical Down Force
Chuck: It's not very often that I get excited about training aids. So many training aids out there are so gimmicky, and of course we've all seen the "Tin Cup" scenario, where he attached a million devices and his swing is all over the place and he's shanking it and doing all kinds of things.
Unfortunately, most training aids just lead you down the wrong path. They don't have a lot of basis for what they're trying to do, or why. That's why I've never tried to push or promote any training aids before, because I don't believe in them quite frankly, just because they're not based around sound fundamentals.
That's why this is such a big deal, an exciting deal, to me because the Anchor that we're going to talk about today is actually based on biomechanical principles. Gee, what a novel idea; how about a training aid that's based on science? This is one of the first ones that I've ever seen.
It's great because it's perfect for people learning the Rotary Swing Tour, or any golf swing, for that matter. It's so important for golfers to understand how the body works.
It's challenging at first, because you're learning new movement patterns and you're doing all kinds of things that may be unfamiliar to you if you have dysfunctional patterns. To have something to help accelerate the learning process is great.
The Anchor was actually developed by the Boston Celtics' orthopedic surgeon, Dr. Brian McKeon. He knows a little bit about knees. He's done quite a bit of work with knees, and he developed this product.
He saw so many golfers who struggled with common things in the golf swing; not being anchored and stable in the backswing, or straightening up in the downswing, and all these things. This training aid is hands-down one of the simplest and best ideas out there for helping you do so many right things in the golf swing.
Josh, we know that you've struggled with some things that this training aid helped you with, as well.
Josh: Yeah, absolutely.
I don't have as much trouble going back, although we'll see how that could help people, when they're going back, maintain their knee flex. For me, on the downswing I tend to push really hard with my trail side.
Chuck: That's very common. Very common.
Josh: Absolutely.
Whenever I would come down, I'd do one of two things when I pushed. I'd either push and raise up and lose my spine angle really badly, and straighten this leg...
Chuck: Yeah. Why don't you show that from down the line? That's probably 80 percent of the golfers out there. Let me step to the side of you here. We'll see that this move is so common.
Josh: From here, I would just push really hard, straighten the leg, and lose my spine angle.
Chuck: Exactly.
When we do that, all of our angles are changing. Also importantly, your hips rotate more than we need them to during the downswing, right?
Josh: Absolutely. I think as a result of that, too, my arms end up coming in real late and they're way behind my body.
Chuck: Exactly. When we have that happen - when the hips rotate really fast - the arms and hands get stuck back behind the body. They have so much farther to travel to get back down in front. That's probably the most common error we see for better golfers, especially golfers who have really fast hips and are more athletic.
They go really, really hard, and then the arms and hands are stuck and they just bomb it 30 yards right, or hit a big snap hook.
Josh: I've seen that.
[laughter]
Chuck: One of the things that we have to understand with how this aid works is that it prevents that from happening. It gives you positive feedback for what it should feel like to feel stable on the downswing.
The other common problem, Josh - and you said you didn't really struggle with this much, but we see it all the time in our lessons - is for golfers to straighten up on the backswing. That's typically more of a higher-handicap problem, but show what that would look like.
You can see the trail leg's fully straightened out. Now Josh can't use his glute anymore. This big muscle in his rear, the chunkiest muscle in his body, is actually fully extended here.
It's just like doing a squat. Once you squat down and you fully extend, you're done. You can no longer push on the ground and use it for leverage. He can't use the ground for stability or leverage to generate any power, so all he can do from here is just use his shoulders and arms that come down from the top.
Eighty percent of high-handicap golfers coming over the top and slicing, a lot of it's due to this. Once that leg is locked out, you can't use your lower body, really anymore, unless you do some sort of compensatory move to try and get the leg to do something, and good luck timing that, right?
It just makes a lot more sense to keep it anchored and engaged the whole time. Why don't we show how this works, Josh?
Josh: OK.
Chuck: All you need to do is get into his address posture. Once he's in his address posture, all he has to do is just flip these tabs - go ahead and flip them down. Yeah, just like that, then do the other one. There's one on each side.
Then just flex the knee a little bit, and try to stand up. At that point, it's locked in there.
Your knee can't move at this point. If you go ahead and go back to the top of your backswing, it's anchored in. Now, can you feel your trail glute activate?
Josh: Oh, absolutely.
Chuck: With his weight on his ankle, he can actively push into the ground. Now he can use the ground for leverage. I know an instructor who used to teach his golfers - maybe he still does - to set up to the golf ball like they're on an ice skating rink; just to feel really light on their feet.
Well, you need to have stability. We're trying to generate a lot of speed and power here, so that's not a real good image.
You want to feel anchored and braced to the ground, and this is what helps you do that. As soon as that knee is straightened up, that glute disengages and you're no longer able to apply any positive - the technical term for it is "vertical ground force" - pushing into the ground, using it for leverage.
Go ahead and go into the downswing. Let's see what would happen there.
[laughter]
Chuck: I can see you're trying to move the way that...
Josh: I can try.
Chuck: You're trying to move incorrectly at that point.
Josh is really trying hard to push off that trail side, because that's what he knows to do. His leg's not allowed to straighten up, so this is forcing him to stay in that position. We can go back one more step, and let's go into the transition.
As you start to come down, the proper feeling during this first move of the downswing is not to push really hard off that trail leg, which is your tendency. Obviously, we know we want to shift our weight by pulling ourselves over with the lead side, but part of that feeling is getting stable as we're starting to create acceleration in the downswing.
The feeling is going back to neutral, which is where you were at address, so you maintain the knee flex. It's almost like you're doing a little bit of a squat. That's an exaggeration, but what you should feel is that that knee flex stays the same, and that you can continue.
Now you can push both feet into the ground. Now, if you try and straighten your leg up, it's going to change your spine angle, right?
Josh: Mm-hmm.
Chuck: Of course it's preventing you from doing it, right?
The good thing is that this not only helps you feel and put yourself in the right positions on the way down, but it also helps give positive reinforcement throughout the whole swing. During the backswing we want to make sure that that trail leg is remaining flexed and we're pushing that trail heel into the ground.
On the downswing we don't want to straighten up and start pushing right away. We want to just anchor ourselves to the ground so that we feel we're pushing both feet into the ground a little bit.
Obviously, we're shifting to the lead side during that time. Specifically, you need to be very aware of that if you're a higher-handicap golfer, because most higher-handicap golfers don't move enough. They stay back on the trail foot and hit a lot of fat and thin shots. If that's you, make sure that you shift, but keep the flex in your trail knee.
For the better golfers who have a lot of speed like you do, it's really important to feel like you almost sit, to give your arms just a little bit more time to get back in front of your body while you're shifting your weight, and keeping that knee flexed.
How does that feel, if you make a couple of swings and you go into your downswing? How would that feel different to you?
Josh: To me, it feels like I'm covering the ball a little bit now, instead of popping up out of my spine angle, my body being way open and my arms being so late. They're much more on top of the ball, like I'm covering it.
It's a totally different feeling.
Chuck: That's a horrible feeling, especially for a better golfer. When you've got a lot of speed, you just don't know where the ball's going to go after you hit it because of the fact that, as I mentioned, when you start to spin your hips really hard and straighten up early, the arms just don't have time to fall back in front of the body.
It's just not going to happen unless you swung your arms insanely fast. Nobody can really sync that up very well.
What we have to do is get into the position where we almost increase the knee flex. We don't; it stays pretty much the same as it was throughout the whole swing. The brace gives you just a tiny amount of leeway to increase it just a little bit, which you could feel.
The worst feeling, again, is getting into this position where you've maybe even made a great backswing, and then all of a sudden you're here and you've spun your hips out, you're hurting your back, your club is stuck and you're just going to block or flip it.
This is going to prevent all those things and give you the reinforcement to get yourself into those great positions that all the great golf strikers end up in, especially the powerful ones.
This simple aid is not only a great way to train yourself when you're on the practice range, but you can also play with it. Josh, you can just flip those unlocked, just push the buttons in, twist it up, and then you have full flexion.
If you're walking or playing in your cart, or what have you, you can play with it during an entire round of golf to continue to get those repetitions. We know how important those repetitions are. Once that's unlocked, you can walk around just like normal. It feels like anything else.
Then show how easy it is to get everything set back up once you're in your posture.
There's four different settings on here. Josh is in the A setting, which is about where most RST golfers are going to be, which is the most minimal amount of knee flex. There's B, C, and D settings as well. You probably wouldn't use most of those.
B won't be that uncommon, just depending on your build, but C and D would probably be only used in extreme circumstances where you're on a really awkward lie or something like that. You wouldn't need that much knee flex.
Of course, now we're...
Josh: This is C right here.
Chuck: That's a lot of knee flex on C, so we don't really use those settings. If you're in a situation where the ball's well below your feet or something, you would have to adjust for that, but most RSTers are going to be in the A or B setting.
It's already marked on there for you, so all you need to do is just get into your golf setup, flex your knees, get into the A setting, lock it in, done. You're ready to swing.
You can see, for the first time, this is a training aid that's actually built on principles of biomechanics. Once that leg straightens up you can't use the glutes, you can't use the ground; it's just the way the muscles work in the swing.
Especially if you're used to spinning your hips, this will really help prevent that, to give you the feeling of being anchored - hence the name - that you need at impact.
You don't want to feel like you're spinning out and just hoping to throw the club back out in front of you and timing it at impact. You want to feel anchored and stable, and this is the perfect training aid to help you with that.
Watch part 2 now to see how you're moving your body in the opposite direction of the pros!
The Anchor
Pushing straightens the leg
The right leg is straight
Using the Anchor
The Anchor preserves knee bend
The Anchor provides positive reinforcement throughout the swing
Spine angle is maintained
Chuck demonstrates hip spinning and getting the club stuck
Just unlatch for full flexion
Position C
