When I was a little girl I had a Gumby toy. My absolute fave thing about this toy was the fact that you could twist him into all kinds of shapes. Him and his horse. I could sit him on his horse with his legs around his head and his arms being used as legs. Good times. This toy, years later, has allowed me to come up with a clever name for this blogpost about being *too* flexible in your joints and ligaments aka hypermobile. Thanks Gumby.
Today we have the article on hypermobility and “over-flexibility” that I have been promising you. I asked my friend and fellow coach Miguel Aragoncillo (CSCS, BA in Kinesiology, Cressey intern, and cool dude) to help me out with this post, since I had the pleasure of learning from him and having his help with my own movement and pain problems. His insights and evaluation gave me a much better understanding of my body and why I was expericing certain nagging issues and what the underlying factors were. Right before my second powerlifting meet, which was in December of last year, I took the advantage to check out Cressey Performance for the day (my meet was in Boston), where I got to meet Miguel and hang out at the facility for the day. As you all know, Eric Cressey is so damn good at his job. That’s really the only way to put it. If you don’t read his blog, subscribe to his newletters or check out his videos, you are missing a wealth of information about how your body moves, performs, and common nagging issues that all lifters and exercisers experience. He balances being super smart and nerdy, with simple explanations for form, exercises, concepts etc. It’s no wonder that interning with him is a valuable experience. Getting to hang out with Miguel and have him apply stuff he learned to me and my situation was a godsend! Miguel programmed for me for about 3 months, using correctives to help what he called “bring me back to neutral” after identifying certain problems I kept having with my hips, posture, and proper muscular control. In the meantime, I grew in my knowledge of the body by leaps and bounds and stumbled (well really it was inevitable after awhile if I paid attention) upon my squat *epiphany* that I mentioned about a month ago (and which has gotten everyone all hot and bothered). That will be for another post, but this is the primer for it, and a pretty damn complete write-up of this common problem; hypermobility and joint laxity. Ladies, this post is directed to you mostly, because as you will see, we are the population who is affected the most. I’ll turn the floor over to Miguel below, and my comments and add-ons are centered in italics.
HYPERMOBILITY AND LAXITY
Whether you are an athlete with several years of lifting experience, or beginner just getting started, knowing if you have symptoms of hypermobility is imperative to making sure you aren’t hurting yourself or doing further damage to your body during your workout routine. In the following article, I will discuss what it means to be hypermobile, what to do about it, along with what to avoid if you do have some symptoms of hypermobility.
WHAT IS HYPERMOBILITY and LAXITY?
When discussing issues of mobility with clients and athletes, I am usually looking at the quality of their joints and ligaments and how they may allow extra movement during certain movements.
– When someone wants to start on a strength training program, lifting weights specifically. Its very important that they understand good movement. This is harder than it looks (take it from a shitty mover!), because well, who’s going to tell you that? You can watch videos, imitate, practice (all great ways), but sometimes without good coaching and a decent understanding of our joints and muscles, we still come across problems of
“Well, I can’t get into this position”
“I don’t feel I can get that low, it just stops”
“I feel weak and out of control trying to do that.”
“That exercise just doesn’t feel right”
– If you have ever asked yourself these questions, chances are you feel lacking in *mobility* aka the ability to move well. This is distinct from FLEXIBILITY, where you can touch your toes easy, twist your arms into a pretzel etc. What Miguel watches for is how well do you control your joints. If someone comes down into a deep squat, its not so much that they can get down there, its HOW they get down there.
Follow along the numbered list and watch the accompanying video, and you can get a better visual of what hypermobility looks like.
1 Flexion of the thumb to the forearm to make contact (L + R sides)
2 Extension of the pinky finger to 90° past the hand (L + R sides)
3 Hyperextension of the elbow past 10° or more (past neutral)
4 Ability to touch palms to floor without bending of the knees
5 Hyperextension of the knees past 10° or more
This video showed the quick tests to determine if you are hypermobile in certain joints. This is called the Beighton Laxity Test, and it is scored out of a possible scale of 9. Here I pass the test with flying colors. (5/9 is a often sign of hypermobility. It is certainly possible to do a few of these things with out diagnosing yourself as a hypermobile individual).
– Guess what my score was? Basically a 9. No shit sherlock.
Generally speaking, our joints have a certain amount of “give” or looseness. Think about a few sports injuries, or rolling your ankle when running or jumping, and you can begin to see what I mean by “looseness”. Individuals with extreme looseness of joints may be described as having ligament laxity.
– Anatomy lesson: Tendons and ligaments are connective tissue. They hold shit together. Ligaments hold BONE to BONE, whereas muscles turn into tendons and attach MUSCLE to BONE. Loose ligaments means that joint itself is flexible and loose. Outside of muscular considerations. This is someone who is “naturally flexible”. To give you an example, I stopped all my static stretching and aggressive hip mobility exercises after working with Miguel and guess what? I can still touch my hands flat to the floor without bending my knees. I can still sit in a deep squat and hyperextend my knees/elbows. I have flexible joints.
While this is a clinical definition of hypermobility, there are other signs of it, such as doing splits pretty easily, or doing some crazy shoulder things as well. If you’re a part of Cirque du Soleil as well, then that might be another sign that you are hypermobile.
AM I AFFECTED BY THIS?
Women have a greater predisposition towards having these symptoms. Barring the argument based on genetics and previous instances of laxity in parents and grandparents, women in particular can exhibit certain hormonal-related laxity symptoms.
– We all remember the cautions about EXTRA laxity in joints during pregnancy (which does not correspond to a good excuse to not exercise and act normal while baking a bun. Don’t start.)
You’ve probably heard a term “Q-Angle” thrown around, especially when discussions involve females and knee injuries and the anterior cruciate ligament (ACL). This term involves the angle of the hip to the patella along the femur, and it is of specific interest to note that many ACL prevention injury protocols (often aimed at youth female athletes) involve some aspect of “teaching” proper movement of the legs and hips, such as landing from a jump. In other words, these programs teach us to move better at the hip level, along with reducing unwanted muscles from firing.
Relaxin, estrogen, and progesterone, have been scrutinized and further research is needed in order to determine if there is a link with the menstrual cycle and subsequent release of these hormones, and its relation to ACL-laxity. (-1) in the knees.
– But in the meantime its pretty safe to say that this shit happens to girls more.
There is some relation with pelvic laxity in women due to childbirth and hormonal reasons. “Hisaw…first demonstrated a pelvic laxity which was dependent on the female hormones. …He believed that the responsible agent was a hormone, relaxin, which was produced in the uterus.” (-2)
Different populations are also affected by laxity to differing degrees. Chaitow and DeLany discuss in Clinical Applications of Neuromuscular Techniques: Volume 1, that this predisposition is also higher in those who have African, Asian, and Arab origin, not to mention the youth as well (due to developmental reasons). “Hypermobility is more common in people of African, Asian, and Arab origins where rates can exceed as high as 30% (as compared with Caucasians +/- 6%)…” (-3)
– Interesting bit o research. From working with teenagers I can say that this most certainly is extremely common in females, and some of my males. Just about every adolescent girl that comes in to work with me has knee valgus, bad lumbo-pelvic control aka their spine and pelvis are wiggling around, and no sense of core stability and neuromuscular control. Basically just beginners, but I notice that the males seem to have a faster “learning curve” for understanding control and stability and adjusting form. They typically are not as “loose”.
Whew! Alright, the difficult part is over. Let’s discuss what you can do about your hypermobility now, and how you can stop it from negatively affecting your movement and lifting.
WHAT CAN I DO ABOUT MY HYPERMOBILITY?
In my research, discussions, and personal experiences with hypermobility, symptoms are often VERY individualized. For example, Joy’s specific patellar tracking and hip issues may be specific to herself and other repetitive patterns seen not only in training, but also in day to day activity. Her hypermobility symptoms are drastically different than mine, and even among other athletes, such as baseball pitchers or gymnasts. However, no matter the situation, there is almost always a way to work around hypermobility conditions, whether you to love to lift for aesthetic or performance based purposes.
– YOU! Yes YOU sitting at home thinking “but I work out at home doing simple shit”, this applies to you as well. Want to get strong pain-free and build shapely muscles? This is important to that.
Even when discussing good exercise technique, there are a few things you need before starting, specifically good positioning aka good form, control of our everyday posture, and an understanding of how to control your core well (or how to work up to it). What it comes down to is; for hypermobile athletes and general lifters, control of your abs and glutes is critical.
When in doubt, squeeze your glutes, and brace your abs.
– See what I meant by simple? That region from your ribs to your ass is your CORE. Control and training of your abdominal muscles (front, side, deep), posture and breathing (diaphragm, inner ribcage muscles), low back muscles and the glutes (all three of them) are what comprise the core. Its not just the strip of six pack running down the front! Bracing your abs is similar to what you do before you come down in a heavy squat. GET TIGHT. I like to use the cue “zip up your jeans”. It’s not just sucking in your stomach though, and its not holding air as tightly as you would in a squat. Just imagine your spine, and all those muscles listed up there “holding you up”. Good posture is using those muscle to hold you up. Controlling them is so important to a stable pelvis and hip joint, strong core (which means a nice waist too) and good movement.
CONTROL YOUR CORE
First things first, control of the core is paramount to moving and performing at a higher level. Being hypermobile should naturally lean itself towards or away certain exercises depending on what someone needs more control of. Before prescribing any awesome exercises like lunges, squats, and deadlifts, I’d like to see control of the diaphragm. The parachute-shaped muscle that allows your lungs to move up and down in unison with breathing (inspiration and expiration).
Why the diaphragm, and not the elusive six-pack muscles? Your diaphragm will often control whether or not the rest of your upper body muscles are connecting properly to your abs, and then down towards your hips. While it is a little beyond the scope of this article to discuss the full function of the diaphragm, just know that if you tend to arch your lower back a lot, think of your obliques and diaphragm as the muscles that control and counteract the arch of the low back and help pull you away from this extension. This is what a having a functional core embodies!
– A little perspective for these photos from a couple years ago. At the time I could not actually walk in those heels. Literally. My knees were so loose and sore that I could only stand for short periods in heels. I actually had to hold the photographers arm to move to another setting for a shot hahah. This position you see me standing in was very comfortable for me, but my knees had constant pain. I was working out regularly at this time, doing spin classes, machine strength training, while meeting occasionally with a physical therapist friend who first opened my mind to how weak I was. I had also already had both kids at this time in case someone was wondering. He doesn’t know it, but his simple comments and insights triggered my curiosity and determination that I could walk and move pain free without surgery. He worked on me a bit as a favor to another friend, and though its taken awhile to get to where I am now (and boy am I still learning!), thank you to Daniel Gallucci for giving me just a bit of proper info that the hordes of orthopedists and athletic trainers never even bothered to mention while wrapping me up, prescribing anti-inflammatories and recommending I swim and not get too fat!
Why do you need to worry about controlling my core muscles? While your core musculature is certainly needed to get the elusive six pack look, believe it or not, the integrity of the core is vital to controlling the forces produced during big movements such as squats, lunges, and push-ups and overhead presses. Why? You can produce more force through the correct muscles when your core is lined up properly through activating the right muscles, in this case your diaphragm and other ab muscles.
– The minute I started on breathing exercises like the 90/90 Hip Lift and controlled breathing with a balloon, I felt a huge difference in how my glutes fired. In fact, I would say that prior to that, they were firing at less than half their capacity. The difference in how *in line* I felt moving was amazing. Miguel has some estatic messages hahahah from me about this.
Beyond the realm of exercise technique, breathing without respecting the diaphragm may encourage an over-utilization of the accessory muscles, namely the scalenes, upper traps, and sternocleidomastoid, among others, while under-utilizing the abdominal musculature along with the diaphragm of course. (-4)*
P.S. I take NO responsibility for this horrid photo. Miguel choose it hahahah, at least it does show them rather clearly.
– You need the big muscles to move the weight, not the small ones! They are categorized by their importance; accessory muscles. Not having the big muscles do the big work, you will not lift as effectively, powerfully or SAFELY.
We need to use THE RIGHT muscles to move big weight to avoid injury, pain, frustration and stalled progress.
FIRE THE RIGHT MUSCLES
You want to make sure you are firing the correct muscles for any given exercise. Believe it or not, certain movements can be performed incorrectly! For example, when doing a glute bridge, make sure to use your glutes, and not go into excessive extension of your lower back. If this basic idea isn’t followed, this could lead to possible injury in your lower back!
– Pretty duh, but its amazing how often when doing our everyday exericse we don’t pay attention to this. I can testify that for a long time I didn’t have the right “feel” to firing my glutes, lats and abs. Its a huge lesson now how underused the correct muscles really were, and it takes lots of practice to fix built-in strength; of the wrong kind.
Posture can be affected not only by exercise activity, but also by passive activity, or day to day activities. If you find yourself having not only symptoms of hypermobility, but also nagging injuries, ask yourself, “What are some activities that could contribute to my [insert pain]?” For example, if you complain of hip/knee/ankle pain in your right side, check out the position of your desk at work, your choice of driving position, or even your shoe choice. These factors could definitely contribute to your issues, regardless of the amount of exercise that you do.
If you find yourself hanging out in that position from time to time, there is an easy fix – get out of that hyperextension by – you guessed it – squeezing your abs and glutes!
– If you have a desk job and spend a lot of time sitting every day, stand up, walk around, flex the abs and ass, and quantify all that hard work in the gym!
EXERCISE SELECTION SHOULD GUIDE US TOWARDS OUR GOALS
Exercises such as deadlifts, squats, lunges, step-ups, and swings, along with the tools that we can use such as kettlebells, dumbbells, and barbells all serve a purpose – to help change our bodies. Whether your end destination is fat loss, muscle gain, or otherwise, you need to be aware that sometimes choosing some exercises may not be an optimal choice towards achieving that goal. If the path is riddled with hops, jumps, and an eventual dead end (injury), I’d like to steer away from that path and stick with a more basic path, that takes care of certain issues right off the bat, and allows for long-term progress.
The path you choose should involve the best exercise with the least risk. In this case, you can’t just go around low-bar back squatting high volume for days on end without experiencing some type of nagging pain in either the hips or shoulders. You have to ask yourself – what is the goal? If the goal is fat loss, or even just to feel better moving around, then perhaps you can look towards exercises such as kettlebell deadlifts or swings, or even just goblet split squats as an alternative for beginners or those who haven’t mastered good movment yet. Don’t be fooled either – split squats can get pretty intense when you control position, tempo, loading parameters, and other variables.
Just ask Joy…
– Ahhhhh the glory of variations!
HOW TO ADJUST YOUR TRAINING FOR HYPERMOBILITY?
1. Develop hyperstability to counteract hypermobility
Admittedly, I heard this advice from several coaches, and I’ve decided to run with it. If an individual is extremely loose, you need to equally be just as stable to overcome the extra mobility. For example, check out this picture of an Olympic lifter at the bottom of a snatch:
He shows signs of elbow hyperextension, along with some pretty extreme knee and ankle mobility at the bottom of this snatch. Although he shows these signs of mobility at these joints, he still has the ability to hoist 381 lbs overhead – he has developed “hyperstability” and this allows him to be both strong and flexible (albeit subjective form, but it is a max attempt I’m assuming).
2. Work on motor control
If you lack balance or don’t move very well, attacking your fat loss or other movement goals might be difficult to accomplish without gaining some type of control of your joints. I’d like to refer to this as developing “motor control”. Motor control is imperative to not only performance, but to prevent being a walking unstable mess of a person! Control the big joints before the smaller joints, and certain movements should fall into place. If you’ve ever had knee issues, let’s look at the hip joint before attacking your knee pain. Combine looseness of your knee joint or hips involving the elusive q-angle in women, and pelvic laxity due to hormones during certain times of the month, and I can begin to see a recipe for an alarming trend of knee and hip related joint laxity in many women for these reasons. Because you may be extra-loose at certain joints often means you need to develop muscular control surrounding these joints. Hopefully this connects a few dots, as developing control of your core will develop better control of your lower back (which could be prone to hyperextension aka “ducky butt”). Loose hip joints means you need better control of your glute muscles, as these are the muscles that control the bones of your hips!
To really harp on this, try this between your main exercises:
A1. Birddogs- 3×5 (Don’t arch your lower back!)
A2. Glute Bridge – 3×10
The second exercise can help activate a not-so-activated glute in between squats, which should theoretically help increase the amount of weight used, and help get a bigger booty in the process!
– We all seem to be getting the point about a strong butt. But just a reminder; the function of the glutes and core are intertwined. Take if from someone who was doing lots of “glute gaining” exercises regularly, but missing the part about controlling the diaphragm and breathing to pull my core straight. What did that mean? My low back was still taking too much of the load and my abs and glutes were not being allowed to fire correctly. Take a look at this video. Here I am moving a lot of weight, but do you see all the movement going on in my low back and hips, and how far forward I am? My inability to understand HOW to control my core properly was seriously stalling my progress and stressing out my hips.
3. Embrace partial range of motion movements
Pre-defined depths (tells you when to stop) to instill proprioception (managing your body in space) and to encourage motor control (having the right muscles control the weight) are a great choice for you if you have issues with control and balance of your joints. For example, box squats (or squats to a box), floor press, and rack pulls can be utilized by yourself to encourage appropriate learning and increased feedback, all within a certain range of motion that doesn’t go off into hyperextension (that nasty over arching again)! It’s like learning to walk before you sprint downhill.
– Such a great tip. Full range of motion is NOTHING unless you can control it. Thats’ where you will get injury from . Yes we want full range of motion, but if you lack control, shorten that a bit till you can get it down, than work up to it. Simple.
4. Don’t Stretch!
If you are hypermobile, then you more often than not do not need to stretch! Why is this? Because if we are in a state of hypermobility, stretching may not get rid of that tightness feeling. What you might be doing by stretching a “tight” hamstring is pulling on a hammie that is just in extension because it is “guarding” due to some type of compensation up or down our body.
Instead try foam rolling more to get rid of the feeling of tightness and work on activating the correct muscles before any exercise.
– Big problem right here. First off if you are hypermobile you are not really “tight” in the way that those who are not, could benefit from stretching. You are the opposite, but the feeling your muscles give you when you try to move of “tightness” is not really tightness! You will juse make matters worse. Check out Eric Cressey’s important post about how NOT to stretch.
5. Increase your muscle mass.
After taking the above into consideration, you should aim to increase muscle mass. This not only helps to burn fat at a quick pace, but theoretically, by increasing muscle mass, you create co-contraction of the muscles surrounding the joints. In other words, you will have more muscle to rely on in a passive state for motor awareness, which is better than having zero muscle on top of having zero clue where your joints lie, and possibly “hanging out on your joints” as a result of it all.
While all of the above is certainly a ton of information to digest at first glance, hopefully a couple of things to embrace is 1) muscular control – it just so happens to involve using your glutes and abs in an intelligent manner, and 2) movement education of how your individual body moves. So whether or not you show signs of hypermobility or not, appreciating control of certain muscles during exercising will help facilitate your results and help you get to where you want to go faster (and with less injury!).
– Miguel Aragoncillo has a BS, CSCS, & HFS. He graduated from Temple University with a Bachelor’s of Science in Kinesiology. His focus as a coach is to keep it simple: reduce stress, eat well, move properly, and move often. Besides training athletes and general population in the greater Philadelphia area, he also competes in powerlifting locally in New Jersey. He can be reached for consultations at his website and contacted through this e-mail.
So where do you take it from here? Here is an example of what your average overly flexible female should do in a training session.
1. Warmup correctly. I will change out certain exericses occasionally in my warmup but the basic structure remains the same. I start with foam rolling, and lacrosse balling of all my major body parts and then move on to simple exercises that get my muscles firing. Sometimes this is just lighter variations of what I plan to do that day. Pushups, or bodyweight squats. Other times I’ll throw in more targeted exercises like Lat Hangs or single leg glute bridges to really get the right muscles firing.
2. Film yourself so you can get an idea of what you look like moving. Pay attention to where you FEEL an exercise later. Usually this can mean pain or tightness and discomfort in the low back, front of the hips, front of the shoulders and upper traps/neck. Look your body will have to adapt, and aches and pains here and there is normal. Don’t be a p—y. But the point it with a little attention to what you are doing, you can tell if some nagging problem/injury just does not go away and is not part and parcel of getting stronger.
3. Decide if perhaps a shorter range of motion, or a lighter load with better movement in a certain exercise will serve you well! Check your ego and get it done right. Consider the following if you have:
Low Back Pain? > Breathing exercises for core work and glute activation, work on your hip hinge
Anterior Hip Pain? > Glute activation, hamstring activation, breathing exercises for core, work on hip hinge and “pulling” yourself down into squat movements
Sore neck or upper traps? > Lat activation, lower trap work, scapular stability/mobility, lighter back work that helps you feel your lats being used (sometimes this means VERY light)
Sore knees (under the kneecap or in general)? > Glute activation, glute medius activation, hamstring activation (so you can sit back into your hips properly), shorter range of motion squat/deadlift exercises till you can “take the knees” out of the equation, stick to non-impact strength training till your hips can properly take the load.
Weak abs and poor posture? > Breathing exercises for core, glute control, stability core work (planks, hollow body holds, pallof presses) as opposed to core work where there is lots of movement (leg raises, russian twists, ab wheels)
Here is what I did to make this simple for myself, and for programming general warmups for my athletes . I categorized certain warmup exercises and just pick a couple out of each category. Some I will use more than others, some were useful for a bit, and then I moved on, but once you get a better grasp of what good movement FEELS like, you will have less need for correctives, and extra shit all the time. Some of them overlap in effectiveness (glute marches are great of core stability and glute activation). Instead of linking all these vids, I will tell you to head on over to Eric Cressey’s channel, where you will find most of them, and/or the Postural Restoration Channel for breathing, and Bret for glute/hamstring.
Core Stability/Breathing /Lumbar Spine
- Glute Marches w/ shoulders on a bench on on the floor (only do these if you have a proper glute bridge down already)
- 90/90 Hip Lifts
- Glute bridges, or Hip Thrusts and/or single leg variations
- Wall RDL’s
- Bowler Squats
- Single leg RDL’s
- Deadhang Lat Shrugs
- Yoga Pushups
- Wall Slides
- Scap Pushups
- Quadruped Triple Extension
- Prone Lower Trap Raises
The best way to move well is to move well more. The only problem is when poor little you is stranded in the gym trying to figure out what moving well FEELS LIKE. That feel we want is the RIGHT muscles firing, and that’s what these exercises will help you accomplish. I want to explore this concept of “feel” later, having a wealth of experience in what moving WRONG feels like, vs what the changes felt like, but I won’t keep you too much longer. Remember that these exercises only serve an accessory purpose!
I hope this gave you a better idea of what hypermobility is, and whether its an issue for you, and then a starting point of how to fix it and get back to the important stuff. Like squatting and building butts. A great side effect of being aware of undesirable looseness and flexibility in your movements, is being able to more easily pin point great vs not-so-great movement in someone else. I can pick out people, athletes and random lifters who move really well and learn from what they look like doing it. A great example is Kristin Clever. She is bloody efficient. There’s another ex-military dude I watch at my college gym who yI can tell is tight in his hips (I would love to have him do hip mobility drills) but moves really well. Everything lines up, and his body and muscular development shows because of it. So if you ever catch me staring at you thoughtfully in a gym, just remember that I am appreciating or evaluating your mechanics. Not creeping. Well maybe a bit.
*Granted, this study elicits pursed-lip breathing techniques, which looks to be a similar technique to blowing up a balloon. The population used is those with COPD, and it cited overall improvements in ventilation through a shift in the muscles used with inspiration and expiration of breathing. The question is, if this technique helped such an extreme population, how much more can this help an asymptomatic, yet largely lumbar extension based clientele?
1- Ned, Heitz A., MS. “Http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1322903/.” Journal of Athletic Training 34(2) April (1999): 144-49. Hormonal Changes Throughout the Menstrual Cycle and Increased Anterior Cruciate Ligament Laxity in Females. Web. <http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1322903/>.
2- Carter, Cedric. “Persistant Joint Laxity and Congenital Dislocation of the Hip.” The Journal of Bone and Joint Surgery 46 B..No.1 (1964): n. pag. Persistant Joint Laxity and Congenital Dislocation of the Hip. Web. <http://www.bjj.boneandjoint.org.uk/content/46-B/1/40.full.pdf>.
3- “Clinical Application of Neuromuscular Techniques, Volume 1: The Upper Body [Hardcover].” Clinical Application of Neuromuscular Techniques, Volume 1: The Upper Body: Leon Chaitow, Judith DeLany: 9780443062704
4- Breslin, Eileen H., R.N., D.N.S. “The Pattern of Respiratory Muscle Recruitment during Pursed-Lip Breathing*.” CHEST 101 (1992): 75-78. CHEST. Web. <http://journal.publications.chestnet.org/data/Journals/CHEST/21638/75.pdf>.