Performance Mobility, Part 2: Trunk Rotation

[Author’s Note: This is Part 2 in a six-part series on functional-mobility self-assessment and restoration for runners. Check out Part 1, an introduction to the series and a discussion of hip mobility, Part 3 on foot and ankle mobility, Part 4 on knee mobility, Part 5 on trunk extension, and Part 6 on hip abduction and rotation mobility. ]

Last month, I introduced the concept of performance mobility. To reiterate, there are certain fundamental motions required for healthy, efficient running. These motions are related to the hips, trunk (spine and chest), knees, and ankles. The purpose and utility of performance mobility are to provide runners with a way to self-assess their motion and, if need be, improve and restore it. Moreover (and perhaps most useful), if the motion is full and normal, there is no need to stretch any more!

This concept, and the first metric, covering hip mobility, drew a great deal of interest, commentary, and criticism. Allow me to point out and shed some more insights on some of the comments.

Stretching Worsens Performance Research

Several of you noted the substantial body of research demonstrating that stretching–namely static stretching, similar to what is noted in performance mobility–worsens performance by elongating the muscle-tendon unit and decreasing its power. I agree 100% with this theory. But it is important to note that there are many types of tissue mobility.

It’s well worth a trip back into the iRunFar time machine to January 2015, where I outlined the various types of tissue mobility in a similarly titled piece, Performance Flexibility: Joint, Spine, And Nerve Mobility For Runners. As the title implies, there are several types of mobility, besides the muscle-tendon, which is the primary unit studied in the literature.

The aim of performance mobility is not to elongate a muscle-tendon unit. Instead, it is to ensure that joint systems in the trunk, arms, and legs have full physiological motion.

Stretch Bands and Hinges

A good way to think of the difference in tissue mobility is by analogy. Consider the muscle-tendon as a stretch band. And while the stretch band cannot actively shorten the way a muscle-tendon does, it derives and stores much of its power in its elasticity. Indeed, the rationale of the anti-stretching research centers on the idea that overstretching the muscle-tendon reduces its elastic power. This could also happen with a stretch band: stretch too far and it may warp and lose tension.

Let’s continue our analogy. Beyond the stretch band is the hinge. A metal hinge is a good analogy for the articulation of a joint. One bone connected to another, and that unit must flex and extend. The hinge rides between two pieces, usually, a static wall and a swinging door. Compare that to a stable trunk and a swinging hip. For optimal function, that hinge needs to move through its full range, with very little friction. Seldom does a hinge have ‘too much motion,’ unless it becomes loose, thereby causing accessory motion (and uneven ‘swinging’ of the door). Otherwise, full motion is always preferred.

In the analogy, there is a stretch band connected on either side of the door–one to open it and one to close it. Implicit in the idea of performance mobility is that persistent range-of-motion loss is seldom due to tight stretch bands (muscles-tendons), but instead the result of a stiff, rusty hinge (joint)!

Moreover, a stiff, immovable hinge is far more likely to overstretch and damage the stretch bands! Thus, a regular check-in regarding ‘hinge mobility’ (and perhaps a spritz of WD-40) is extremely important in keeping that door fully and efficiently mobile! 

The following video demonstrates these two facets of performance mobility:

[Click here if you can’t see the video above.]

Performance Mobility is Not Evidence-Based

Others criticized the piece by arguing (as many do) that this theory lacks any research-derived evidence for its efficacy. And while I argued that much of what we do–as clinicians, as well as runners and coaches–does not have statistical evidence, yet still works, these mobility metrics are, indeed, scientifically and medically-derived.

The hip metric described in Part 1 of this series–the single-knee-to-chest test–is derived from an orthopedic special test called The Thomas Test. This is a ubiquitous sports-medicine test used to assess both hip and pelvic mobility (with associated muscle-tendon, joint, and other tissue mobility). All of the metrics outlined for performance mobility are grounded in the fundamentals of orthopedic tests and measures: what’s clinically normal and healthy, versus what is not.

In essence, the point of performance mobility is to bring these tests out of the examination room and into the hands of runners so that the runner can self-assess and stay ahead of any potential problem that comes from legitimate joint range-of-motion loss.

“The Research Says We Don’t Need to Stretch,” Part 2: Ultra Specificity

More argument for the need for vigilance with range of motion comes from the specificity of ultrarunning and ultrarunners. Fodder for a future ‘Stay the Course’ column is a primer on how to best interpret and apply research studies. Among many factors is external validity. Can the results of a specific study be applied to me? Specifically, the question is, can the results of a given research study be applied to ultrarunners? To help answer that, allow me to point out:

  • For most of the stretching research cited, the study involves a population of young athletes (or, commonly, military recruits) engaging in short, high-intensity exercise.
  • The average ultarrunner (and iRunFar reader) is roughly aged mid-forties, a working professional (sitting most of her or his day), and runs for a long time (four to 24 hours) at moderate intensity.

As such, many studies on mobility fail to address the unique characteristics, needs, and challenges of the ultrarunner. As stated two years ago in our article on performance flexibility, the need to monitor and restore full functional mobility stem from those unique ultramarathon challenges, which include:

  • Running for a very long distance and time
  • Cumulative impact stress, from both distance and terrain
  • Fatigue-induced reductions in good posture and range of motion

And on top of that, we have our population-driven factors, which include:

  • Age-induced reductions in tissue (namely muscle-tendon and joint) mobility (for those of us aged 40-plus)
  • ‘Professional’ factors, such as sitting at a desk or in a vehicle for eight to 10 hours per day or more

These combined factors are a compelling argument for vigilance in monitoring and maintaining functional mobility! My hope is that this additional insight will help clarify the importance and relevance of performance mobility, especially for ultra-distance trail runners. Now, onto the second metric!

The Trunk-Rotation Metric

The running motion is a multi-dimensional, whole-body motion involving not only a forward-and-back leg, but a lengthening and rotating trunk. This metric assesses both the quantity and symmetry of that whole-body motion.

Details: Flat on the floor, flex a leg up to waist level, and then fold that leg across the body while using the opposite hand to push the flexed knee toward the floor.


  • Equal, symmetrical motion (left versus right legs)
  • Knee gets (close) to the floor (maintaining opposite elbow to the floor)

Common Deficits:

  • Overall range-of-motion deficit: a failure to get the stretch thigh (flexed leg) at least parallel to the floor
  • Asymmetry: one side stiffer than the other


Loss of trunk mobility may indicate a ‘stiff trunk,’ which lacks the normal, slight amount of side-to-side rotation while running, or an overall posture deficit, usually a forward slump during running, outside of running like while sitting at a desk, or both. Asymmetry of motion is most detrimental. Note that the test itself resembles running: one leg straight, the other flexed and ‘driving.’ Commonly, the stiffer side (one that fails to twist as far) indicates a whole-body (leg and trunk) push-off deficit.

Joe Uhan performs the trunk-rotation test for performance mobility.

Restorative Exercises for Trunk Rotation

In this case, the restorative stretch is the same as the test: lying flat, flexing a thigh to the waist, and then folding across. There are a variety of ways to improve mobility. Prolonged holds (of 30 to 60 seconds) are useful in working on chronic-systemic (muscle-tendon as well as spine, rib, pelvis, and hip) stiffness. However, for those of you phobic of static stretching can also do repetitive on-and-off stretching of the knee toward the floor, using the hand.

Call for Comments (from Meghan)

  • So, did you pass Joe Uhan’s trunk-mobility test? If not, do you possess asymmetry between your left and right sides or do you have an overall loss of your range of motion?
  • We asked the same question in this series first article, and we’ll try it again here. What kind of flexibility training or stretching do you engage in, if any? Do you find that it helps you in specific ways? If so, can you describe them?
Joe Uhan: is a physical therapist, coach, and ultrarunner in Eugene, Oregon. He is a Minnesota native and has been a competitive runner for over 20 years. He has a Master's Degree in Kinesiology, a Doctorate in Physical Therapy, and is a USATF Level II Certified Coach. Joe ran his first ultra at Autumn Leaves 50 Mile in October 2010, was 4th place at the 2015 USATF 100K Trail Championships (and 3rd in 2012), second at the 2014 Waldo 100K, and finished M9 at the 2012 Western States 100. Joe owns and operates Uhan Performance Physiotherapy in Eugene, Oregon, and offers online coaching and running analysis at

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  • Joe,

    As one of those 40+ (sadly 50+ in my case) "professionally compromised" ultrarunners, I am in complete agreement with your stance on flexibility. I see so many people out on the roads and trails running with poor range of motion due to sitting all day, it's amazing. Some people can't even get their thighs in line with the trunk - literally look like they are running still sitting in a chair. This can't be efficient.

    If folks could just put a single caveat in front of all the stretching-related research, I think the controversy would go away. IF one already has full, unrestricted joint range of motion, especially in the hips, then stretching probably is not helpful to running performance. Unfortunately, in today's office-centric world, very few of us have that full mobility, and those who do, especially in the aging population, need to work consistently to maintain it.

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  • Joe, can you address one other theme that came up in the discussion - the distinction between static and dynamic range of motion, and the efficacy of stretching on increasing dynamic range of motion.

    As an example this is the type of thing many of us are used to reading from other sources that seems to represent closer to the new conventional wisdom (from Steve Magness):

    Even if you apply the ultra-specific thought process, running is dynamic, if dynamic ROM is what matters, why not assess that directly?

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    • Hey Luke,

      Thanks for the comment.

      I like (and generally like all of) Magness' post, and the difference between static (which is *usually* driven by bone-on-bone-joint motion) and dynamic (muscle-tendon) motion.

      Again, at the foundation of the "[static] stretching is bad" argument is what Magness argues: that some static stiffness can contribute to enhanced energy storage and propulsion. He goes a step further to argue that -- when you energize the system -- dynamic mobility greatly increases (e.g an active glute and stretch open the hip flexor, and vice versa).

      His examples, however, are mostly of joints dominated my dynamic tissues, namely the knee. In contrast, this month's metric - trunk rotation - is dominated by vertebral and rib motion (largely dictated by non-contractile joint tissues).

      So my argument is this:
      - Muscle-tendon tightness is generally good (to a point)
      - Restrictions of bone-on-bone-joint mobility is not good -- it represents "a brick wall" that even the strongest, most wound-up dynamic system cannot break-through.

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  • Glad to finally see someone NOT just saying "stretching is bad for you." That's all we've heard for a decade now. While I confess I haven't always had the exact reason for all the stretching I do, I do know it helps me feel better. I'm 55 and easily get stiff. I don't really see what I do as stretching, actually. I just kinda loosen up all my joints. It looks like stretching but I'm not trying to be a gymnast. Just want my joints to be a bit more flexible.

    You and Jay Dicharry are about the only two I'm finding who advocate any movements like these, it seems. Well, maybe many others do, but they call it Yoga.

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    • Thanks for the comment, Tim.

      Perhaps Jay and I are on the same page because our formal training is in physiotherapy first. This undoubtedly is a bias. However, I was a coach and runner before a PT, and I feel like this approach is a happy medium

      For you: keep in mind that Performance Mobility Metrics serve two purposes:
      1. If you don't have it, Stretch It
      2. If you don't have it...You May Be Doing Something Inefficient.

      My favorite quote: "The Best Exercise is Living Well" (~Joe Uhan). What that means: if you generally treat and move your body in an efficient way, you'll stay relatively mobile and strong (and thus, not need to do a lot of extra exercise).

      So for anyone who feels "the walls are closing in", constantly, with mobility loss, you have to wonder if there's inefficiencies in your stride, or in how you "live" (sit, stand, walk, etc).

      That said, in ultramarathon trail races, the demands are *so great* that even with max-efficiency, you're going to stiffen things. The key, then, is to NOT allow those walls to close in, over time.

      In conclusion:
      - keep doing your mobility work, but
      - be mindful of your efficiency (and if need be, get some folks to help you assess and troubleshoot)
      - try yoga! Many middle-of-the-road strength practices are a great combo of ***dynamic mobility*** using the running patterns!

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    • Actually, AFAIK the issue with stretching is that the muscles will not be able to transmit as much power to the surface you run, this sounds to me very much like road-running specific and stiffness to a certain degree is in fact a sought-for state for road runners, at least it is not frowned upon.

      I started rethinking that when I went over to trail and realised that I need to be able to bend my feet if I miss a step running down a hill without getting injured and this is exactly the "business case" for more elastic muscles.

      IMHO by applying the same principles to trail and ultra running that may be valid for road running we are forgetting about the need for specificity in our training.

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  • Thanks for the article, Joe.
    I'm just wondering about the hinge-joint analogy. If I don't mistake you, you state that mobility problems more often stem from an impaired joint function and as a result the muscle-tendon complex cannot function as intended. However, I would intuitively say it is the other way around. The muscles and tendons are the structures that stabelize and hold the joints in place. If they were absent your hinge would just fall apart.
    Furthermore, tendons actually act as a safeguard to not reach the physiological feasible range of motion of the joint. You would bruise your joint socket with every dynamic movement if they weren't.
    I'd say, the foremost reason for joint failure is based on a malfunction of the muscle-tendon complex. For example, cartilage degeneration is often a result of too much or to little pressure in the joint, governed by muscles and tendons. I believe non optimal joint function in terms of ideal force distribution is more often a result of asymmetric muscle tension than an actual evolutionary maldesign of the articular surface.
    Speaking in your analogy, the screws holding the hinge in place are the limiting factor and not the hinge itself. If the hinge gets distorted because one screw is lose you can use as much WD-40 as you want, it won't solve the problem.

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    • Hi, Romanair-

      Thanks for the comment. But I disagree 100%.

      From a physics standpoint:
      - muscles apply TORQUE through a joint. Force x Sine of the angle of application. All "movement" muscles apply rotatory torques. (Someone please chime in with phasic muscle group that applies a PURE compressive or distractive force!).
      - Conversely, a myriad of other (mostly) non-contractile tissues "stablize the joint". In the knee, for example, the collateral ligaments bind tibia to fibula in the way that "tie-downs" secure a load in a pickup truck bed. Additionally, other non-contactile soft tissue secure those bony ends, including a joint capsule and varous retinacula (speaking of the knee).
      - While muscles must work in harmony to rotate one bone on the other -- and a lack of smooth, coordinated motion can stress the joint (think shoulder or hip impingment of "the ball" not spinning efficiently, and "getting pinched"), the two greatest joint stressors, *by far* are:

      1.) asymmetrical loading of a joint surface (think knee buckling in)
      2.) chronic deficiency of full (bone-on-bone) joint motion

      For the former: bone and cartilage becomes stressed with too much load (think "knee buckling in" -- the outside of the femur/tibia is overloaded) on one side, while the other side (inner knee in this case), gets *not enough load*...

      For the latter: chronic "inaccessibility" of full joint range causes tremendous stress...but in ways most don't realize.

      How joint tissue - namely hyaline cartilage, which lines bony ends - gets nutrition is from motion. Cartilage has nearly no blood flow and relies on nutrition and hydration through full motion and even compression of the two bony ends. Think of it as two sponges on the ends of the bones, surrounded by a balloon filled with fluid.

      When motion is either chronically restricted or asymmetrical, quite simply, the sponge dries out. It literally dies, then is replaced by bone. This, by definition, is arthritis.

      So, I'm wrong: I don't disagree 100%. You did say, "degeneration is often a result of too much or to little pressure in the joint". But it's not because the quad is pulling more than the hamstring. This is a systemic alingment issue related to alignment and overall loading vectors (read: too much in the knee, not enough in the hip).

      I also agree with your statement that joints do not degrade due to "evolutionary maldesign of the articular surface". Absolutely.

      Here's my point: a joint system is far more than a group of muscles overlying it. It took years of making mistakes in the clinic (stretching only "the hip flexor muscle" and getting nowhere) to learn that, with chronic stiffness, the dysfunction -- that might've begun as an acute muscle-tendon tightness issue -- has now cemented itself "in the hinge": in the tissues of the joint, and that only interventions targeting the *whole system* could address that.

      Thanks for the comment, the challenge, and the discourse!

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      • Thanks for your detailed explanations and the constructive discussion!
        However, I’m still not convinced. Contrarily, I believe your line of argumentation rather proves my point right.
        Just that we are on the same page:
        I state, the root of joint “failure” lies within the muscle-tendon complex.
        You say, the root of joint “failure” lies within the joint itself.
        (Please correct me if I’m wrong)
        Concerning the biomechanics: The main function of muscles is to produce a movement or to counteract movement (stabilize), rather than purely compress or distract joints. BUT, latter is definitely a byproduct. The best example is the patellofemoral joint, where the quadriceps and patella tendon apply significant compressive and shear forces in the knee. Also being a perfect example of muscle forces governing the cartilage’s hydration/ nutrition. Furthermore, imbalances of the quads can lead to a dislocation of the patella.
        Yes, muscles produce torques, but they also play a crucial role when it comes to internal joint forces. These are kind of sort of important, since they may exert compressive knee forces 9 times the body weight in isokinetic knee extension (
        The buckling knee and the internally rotated tibia can very well stem from a muscle weakness or tightness in the hips or even somewhere else. Importantly, it often originates of a musculature problem. Even though, you disagree almost 100% with me, you say it yourself: “dysfunction — that might’ve begun as an acute muscle-tendon tightness issue — has now cemented itself “in the hinge””.
        The only (conservative) way you can manipulate joint integrity is via muscular training and stretching. Once the ligaments are overstretched or tightened, it’s the only way to stabilize or loosen (besides manual therapy) the joint complex.
        We probably don’t disagree at all, just that your hinge analogy makes one think joint failure comes from within; like if the friction and passive mobility properties of the joint get impaired, without the muscles and tendons having anything to do with it.
        Cheers, Roman

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  • i just started experimenting with the feldenkrais method to increase mobility and awareness. While body awareness has definitely increased, it's too early to tell whether this experiment will pan out. That said, your series of articles has been a good compliment to what I'm trying. Thanks for taking the time to put it all together for us!

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  • Hi Joe,
    Thanks for the articles, very informative.
    Just to check, in the picture, is your right shoulder touching the floor?

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