An Interview with Dr. Stuart McGill, Part I
I'm not a betting man, but I'd put money down that you've heard of Dr. Stuart McGill. Whether you're a professional athlete or someone who just wants a stronger core, you probably know of him. And if by some chance you haven't heard his name, I guarantee that many of the core exercises you're currently doing have been influenced by him.
In 2002, McGill released his landmark text Low Back Disorders: Evidence-Based Prevention and Rehabilitation and it changed the way coaches, bodybuilders, athletes, and non-athletes approach core training. With his books, articles, seminars, and more than 30 years of clinical research with everyone from elite athletes to disabled workers, Dr. McGill established himself as the premier voice for core development.
But like anyone who achieves a high level of power and influence, eventually your name can end up on a hit list. Over the last few years there's been a trend to turn away from, even blatantly criticize, what Dr. McGill tried to teach us.
On one hand, science is about critical thinking, so questioning his methods is healthy and necessary. It's the only way to intelligently initiate progress. On the other hand, his message often gets watered-down and words get put into his mouth.
One notion about Dr. McGill is that he's "anti-flexion" with regard to the spine. Critics like to say that McGill overly emphasizes the plank and avoids any spinal flexion exercise because it will inevitably torpedo your intervertebral discs across the room and splatter them onto the wall like a Jackson Pollock painting.
Okay, maybe not that extreme.
But one thing's for certain: McGill is the latest victim of the straw man technique. If you're going to argue with a professor who has over 300 peer-reviewed publications, you better bring your A-game.
Having known Dr. McGill for years, and being one of the fortunate trainers who's worked next to him, it was always tough for me to hear these criticisms because they were usually based on things I was pretty certain he wouldn't say. Sure, he might agree that some statements could apply to certain populations under certain conditions, but many other accusations were just plain wrong.
That's why I was relieved when McGill said he wanted get some things off his chest. I could tell the typically mild-mannered doc was a bit aggravated by all the Internet chatter. He's spent his life testing, experimenting, and collecting data in order to help us train smarter. But his principles got lost in a sea of misinterpretations.
So with any luck, this interview will clear the air and re-establish Dr. Stuart McGill's true message. Then you can make an intelligent decision and determine if his approach is right for you or your clients.
Chad Waterbury: Okay Stu, I'm going to get right to the hot-button issue: spinal flexion. You and your research team have been branded as the scientists who are anti-flexion. What's your take on that?
Dr. Stuart McGill: Chad, thanks for this opportunity. People hear sound bites when I'm asked about a specific situation and then they generalize. I usually have flexion motion in every program and this will surprise those people who are misinformed about our work.
With the cat-camel motion on all fours, we've proven it to be the best way to take the spine through the range without load. This preserves the ability to do daily tasks that often flex the spine, such as tying your shoes. The cat-camel helps floss neural tissues and keeps them healthy. Also, that exercise helps align collagen during the healing process. It's appropriate for most painful backs.
CW: Now, in order to delve deeply into this topic it's important to define what flexion really means. Surprisingly, it can relate to different mechanisms of action. Let's start with that difference.
SM: First, there's flexion movement which is the kinematic variable, the act of flexing the spine, such as seen with a full crunch. This is often confused with the kinetic variable of creating flexion moment, which is the challenge that requires abdominal muscle to create force and support the flexion movement. Flexion moment may be generated whether or not there's spine motion. To exclude flexion moment training for a flexion movement-intolerant person is a poor strategy and creates unnecessarily weak people.
CW: Speaking of people who aren't weak, strongmen and powerlifters sometimes round their back while pulling a max deadlift. So this leads people to think that it's acceptable to lose the inward lumbar curvature since some of those strongmen don't get debilitating back injuries.
SM: First, let me explain a concept. Spine power results from force multiplied by velocity. To mitigate risk, spine power must be low. If the load is high, then velocity, or spine movement, must be low.
Similarly, high velocity movement must be accompanied by low force. With these powerlifters, the load is high, the spine is partially flexed forward – but not 100% flexed – and locked in this flexed posture. Since there's no velocity, the spinal discs are more resilient to herniation than if movement occurred. Thus, there's no flexion motion but there's flexion moment. So some competent deadlifters who rotate and extend around the hips instead of the spine reduce the risk.
CW: Nevertheless, a guy who pulls a big deadlift could reduce his risk of injury if he maintained a more neutral spine. Correct?
SM: Yes, but it's a game of tradeoffs. Having a shorter leg-to-torso length ratio with shallow hip sockets will allow a more neutral spine. This reduces lumbar joint compression and shear loads but requires more hip-extensor strength.
A flexed spine uses less hip strength but increases the hydraulic pressure on the posterior part of the disc. This increases collagen delamination and the risk of a bulging disc. So if a person lifts with a flexed spine, what they do for the rest of the day matters even more. For example, incorporating full motion crunches for this heavy lifting athlete would be a mistake.
The concept of cumulative loading would need greater consideration. In other words, lifting with a neutral spine increases the tolerable training volume. That alone is a real gift to many lifters and particularly athletes who use the deadlift as part of a larger training program.
CW: Let's clarify what you mean by delaminating collagen. In layman's terms this means a weakening of the disc structure.
SM: Disc collagen delaminates mostly from motion, but this weakening is accelerated under higher loads. Specifically, the fibers split apart allowing the nucleus to flow through. Therefore, locking the spine so no motion occurs until the end of the lockout is helpful. But this distinction only holds true with no prior cumulative delamination.
Usually there will come a point when accumulated delamination, or a further weakening of the disc, will allow the nucleus to travel through the annulus. Then the person will experience "flexion motion with load intolerance." Once this stage happens, deadlifting will cause debilitating pain.
Now for a paradox: If a guy has a long history of lifting with some flexion, the trabecular bone in the vertebral body will be strongly adapted. It appears as though stronger and denser trabecular bone reduces vertebral end plate damage and the ensuing delamination process. This characterizes the grand old men of powerlifting who have survived years of lifting with a flexed spine.
But a newer lifter has a higher risk since they don't have years of loading history to create the adaptation. But the loading is needed to stimulate the adaptation, and this is the most perilous time. Some will survive, but others will have the legacy of a problematic back.
CW: Now the guy has a nagging injury.
SM: Unfortunately, yes. Following this injury he will have to preserve a neutral spine even when he's lifting light.
CW: Sounds like a terrible way to convince a guy to deadlift or squat with proper technique. And this is why you always have to consider the risk versus reward relationship. Most guys can pull more weight if they round the spine, but it's extremely risky. The slightest extra move during flexion movement action could be debilitating.
Let's talk about bone for a minute. Trabeculae are thin plates and struts of calcified tissue in the innermost layer of bone. Research suggests that increased loading, such as with heavy weight training, can increase bone density by up-regulating trabeculae.
So the vertebrae in a heavy squatter are much stronger than in a non-lifter because he has more dense trabeculae inside the vertebrae. Not only does trabeculae make your bones stronger, but it also serves to maintain the joint shape that's critical for optimal distribution of the load.
Since most T Nation readers have years of heavy lifting under their belt, and their bones are much stronger, are they less susceptible to disc injuries caused by lifting heavy loads?
SM: Yes and no. The type of back injury depends on the size of the load and number of bending cycles. Under high compressive loads the trabecular bone within the vertebrae is what regulates the load bearing strength.
Fortunately, it's fatigable and adaptable, just like muscle tissue. As the nucleus pressurizes, it creates a doming effect on the endplate down into the vertebrae, and the trabecular bone is what backs it up. So progressive training over the years lays down bone that's heavily adapted to bear mammoth-compressive load.
CW: Okay, so heavy lifting strengthens the bone in your spine to deal with more heavy load compression. Does this increased bone strength make people less susceptible to the risk associated with low load flexion exercises such as a full crunch?
SM: Here's the "no" part of the answer. The story changes with lower loads and repeated bending. The heavy-boned spines adapted for lifting don't protect against bending. When the compressive load is lower, multiple bending causes a weakening effect.
Here's an analogy: if you bend a wire coat hanger back and forth it eventually breaks due to metal fatigue. In the spine, the matrix binding the disc collagen fibers together will fatigue and delaminations occur. The nucleus starts to work itself through these breached delaminations with repeated bends. My research team was the first to quantify this back in 2007.
CW: Stu, there's some controversy with regard to maintaining lordosis while in the deepest squat position. Some say it's acceptable and not harmful to allow the pelvis to posteriorly rotate in the hole, thus allowing the athlete to squat deeper. I don't allow any loss of inward lumbar curvature with my athletes based on what you've taught me. What risks are associated with this posterior pelvic tilt at the bottom of a full squat?
SM: I see too many ruined backs from those who believed they were immune from spine flexion during the deep squat or clean, including some of the trainers and coaches themselves. A few lucky ones are. It's unfortunate how many former athletes tell me they wish they listened earlier and made wiser choices.
Exercises are tools to get specific jobs done. The way an exercise is performed depends on the rationale for choosing that exercise. First, list the objective and then decide on the best tool. Usually the best exercise is the one that creates the largest effect with the minimal risk to the joints. If the purpose is to create hip extension power, then exercises such as weighted carries and sled drags have to be considered.
For bodybuilders wanting to develop the gluteal muscles, they'll need to address the two major neuromuscular compartments in the glutes. The high lateral glute is developed with loaded carries or with most one-legged resistive squat exercises. The low posterior glute is mainly challenged in the bottom half of the squat.
This is where the choice regarding depth and spine flexion needs to be made. Depending on the person's injury history, what they do during the rest of the day, their hip joint anatomy, the other exercises in their program, and specific exercise form, they'll need to choose how deep to squat.
In my consults with some college football programs I've found about one-third of the players have back difficulties by failing to make good decisions regarding squat and power clean form and depth. Those one-third have their athleticism compromised by back pain.
Of course, the safest choice over the long term is to not go deeper than the break point of where the neutral spine is lost.
CW: I agree. If an athlete wants to train the thigh musculature through a greater range of motion, single leg exercises should be incorporated into the program.
Moving on, I know it's not exciting to talk about genetics since they're factors we can't control. However, genetics do play an important role in this argument for or against repeated spinal flexion, correct?
SM: We've discovered that the shape of the disc determines its resilience to the number of bends it can survive with minimal collagen delamination.
For example, while an oval-shaped disc with a smaller radius is better suited for twisting actions, it's poorer at repeated compressive loading. On the other hand, a limacon-shaped disc is better suited to bear high compression but it succumbs to focal stresses at the back of the limacon with repeated bending. This is exactly what's seen clinically.
Slender spines that can twist well win golf tournaments, but those slender spines don't survive playing linebacker in the NFL. Then again, I don't know of any linebacker who can hit a golf ball far. Each spine is suited to withstand a unique stress and fail under another.
CW: So what about the people that didn't choose the right parents? They have a damaged disc that's causing pain, a loss of strength, and an inability to train with optimal intensity. Can we say the problem is delamination? If so, how long does that type of injury take to heal?
SM: The problem might be delamination or it could be an end plate fracture. It depends on the type of damaging load. Assuming it's delamination, that type of injury doesn't heal quickly – far from it. It takes about 10 years, on average, for collagen gristling to take place.
So just because a guy is without pain doesn't mean complete healing has occurred. Restoring the former strength and tissue toughness happens with long bones, but it doesn't happen with collagen.
Furthermore, the mechanics of the joint have been disrupted and this will generally cause more load on the facet joints. They will become arthritic within a few years. This arthritic cascade is accelerated by more motion and the spine will never be the same.
CW: If someone has an injury, what steps do you typically take in your lab/clinic to correct it?
SM: First, back injury is not a life sentence, but it needs to be cleverly managed. We can usually link the mechanical cause to the tissue damage. Radially delaminated layers or annular tears are created from a twisting injury. Focal disc herniations are usually caused by flexion bending, and end plate fractures are from compressive overload.
First we examine the patient's sport training, their movement patterns, and lifestyle to find the injury or pain mechanism. Then we confirm the mechanism with provocative testing to replicate the pain using combinations of motions, posture, and loads. Next we quantify the combinations that cause pain and those that don't. Then we create the rehab program to remove the pain. Finally, the program morphs into a performance-enhancement training program that bears in mind the original mechanism.
CW: Excellent, Stu. That's essential information for any physical therapist or corrective exercise trainer. Speaking of twisting injuries, there seems to be some debate on your position regarding dynamic rotational core training. Care to elaborate?
SM: Injuries form clusters that help reveal the cause. If a baseball team has more than one stress fracture, I look immediately at the strength and conditioning program. There you'll find the cause – poor exercise choice and programming.
Usually, there will be loaded twisting rotation at excessive speed. I consulted for an Olympic sprint squad from one country that was compromised because of lateral medicine ball throws into a wall. These athletes were rotating around the lumbar spine, which either delaminated the layers of the annulus or caused stress fractures in the pars. It was the fault of the trainer/coach who didn't know better, and the importance of technique when recommending a power exercise.
What they needed was better training techniques to reduce the spine motion and emphasize hip drive. This is a very important point: I notice which teams have specific injury patterns when other teams that play the same sport do not.
CW: So how do you recommend that T Nation readers train core rotation?
SM: I begin by quantifying the demands of the sport, and then the capabilities of the athlete. I design a training program to address any deficiencies between the two. Therefore, each program is different.
CW: Yes, that's the risk we take whenever we recommend an exercise. What might be ideal for one guy could be problematic for another. But throw us a bone and give us some recommendations.
SM: Okay, here are some examples. I might begin with shadow boxing to enhance the timing of muscular pulses to stiffen the core to enhance shoulder and hip explosive power. Then I might build some endurance with standing cable single-arm pushes and pulls, emphasizing core stiffness and crisp deliberate shoulder pulses.
In order to build more strength, I might use a modified bench press with the right side of the body on a bench and the left side suspended. This requires intense gluteal muscle drive as the heavy dumbbell is driven up in the left hand. This technique is also performed with the left side on the bench while you press with the right arm.
SM: Then I might consider landmines with an Olympic bar.
SM: Now if we're talking about a golfer who needs more rotational velocity, I would start with the hips, probably prescribing hip airplanes. Then I'd ensure torso pulse generation is timed with the hips.
Don't miss part II of the interview with Dr. McGill where he talks about core training for MMA athletes, what he thinks about the concept of doing a thousand sit-ups every day, and much more!