Core training for runners: Focus on axial positional neutrality first.

Core training is a term often referring to abdominal exercises that are generally good for everybody including runners to perform for injury prevention and performance. The understanding of the public is shifting beyond just abdominal exercises, thankfully. The goal for this post is to broaden the frame on what core training is and its purpose.

(Axial) Spine, thorax (rib cage) with shoulder girdle, hip girdle

Let’s talk about muscles. So, what are your core muscles? Keep it simple. Just think of the muscles connecting your head to the neck, elbows and knees to your trunk, and all that are in between. In my view, essentially any muscles attaching to your axial skeleton, shoulder girdle, and hip girdle make up your core muscles.

Many professionals specializing in movement performance prefer to use the term “core control” versus “core training” as control implies actively aligning (positioning, orienting, or posturing) the axial system for movement. This could be from any position such as sitting, standing, lying down, et cetera. However, control does not necessarily imply improving the ability to generate force. So “core strengthening” may be used to describe making muscles stronger and/or fatigue resistant. Let’s consider core training as a blend of core control (timing and orientation) and core strength (the ability to produce force). For physics nerds, it may be better understood as kinematics and kinetics.

To enhance one’s understanding of core training, the concept of positional neutrality must be understood. Let’s define positional neutrality as the orientation of the axial skeleton, including pelvis and shoulder girdle, for maximum movement variability of the rib cage, spine, pelvis, arms, and legs relative to the individual. It’s the balance of muscle tension that establishes your starting alignment. In theory, the inability to position the axial skeleton in “neutral” results in either symmetrical and equal suboptimal 3-dimensional range of motion and/or asymmetric equal-and-opposite joint range of motion right versus left and/or skewed rotation observable in the trunk, shoulder, and hip joints unless there is compensation in the movement system. (I know. That’s confusing.) If only the body were this simple, though. One must also consider that there is a degree of asymmetry in the human body that is normal. Traumatic injuries, the parent’s you chose, Wolff’s law / physical stress theory, will also impact an individual’s positional neutrality. The fact is, determining positional neutrality is really difficult for a person to determine without assistance from someone else who knows what he/she is doing.
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Here is a contrived example of why establishing positional neutrality of the axial system is important: I want to run up a steep hill fast. When I push off my left leg, I need my right hip socket to be oriented in a way for me lift or pull my right knee high while still allowing my left leg to push me up the hill. If the start position of my pelvis is skewed in one direction and I go up the hill, the movement will be suboptimal on both sides for different reasons. I would be too good on one side, and not good enough on the other.  If you know Goldilocks, she likes the one in the middle that’s “juuuuusssst right.” Which is to say, if my pelvis is more optimally oriented from the start (positional neutrality) I may be just as good at pushing and pulling on my right leg and my left leg. In theory, this implies improved load distribution on muscles-tendon and joints. I like the sound of that from the perspective of joint health, muscle and tendon recovery time, longevity, and performance.

One of the blessings and curses of being human is an incredible ability to compensate or workaround non-optimal conditions, which is the argument against the need for establishing positional neutrality. But things start to get out of whack when loss of positional neutrality reaches a “not-so-well-defined” threshold that begins to push the available range of motion of joints in one direction. Let’s use another example.

Imagine your shoulder joint as a golf ball (humerus) on a perfectly vertical golf tee (scapula). Gravity is pulling the ball down onto the tee and air pressure is holding it evenly in place on all sides. There is no shear force on the figurative joint and it is happy. Now imagine a strong wind (hypertonic infraspinatus muscle) starts to push the golf ball forward onto the lip of the tee (labrum). The golf ball is no longer aligned in a comfortable resting position through the vertical axis of golf tee unless an equal and opposite force pushes it back onto the tee. Ease the pressure on the figurative labrum, and push the ball back on the tee with your index finger and thumb (subscapularis and supraspinatus). Now tip the golf tee sideways (alter the position of the shoulder socket resting position) so the ball almost falls off. Something has to hold it there, constantly, or it’s going to fall! Again, now there is constant shear stress on figurative joint and lengthening pressure on the labrum and tissues that lengthen over time with sustained stretch.  Is this a good start position?

This scenario in the human body has been described by Shirley Sahrmann as the loss of the PICR (path of instantant center of rotation) of a joint. Ligaments, cartilage, labral tissues, and muscles/tendons begin to adapt as an individual moves further from this ideal position of relative neutrality. The nervous system reorganizes into a new understanding of the body’s neutrality, which may not really be a healthy neutral like the golf tee not aligned with gravity. When ligaments, tendons, and muscle adapt to accommodate new joint position at the shoulder or hip, for example, a degree of instability or impingement toward one direction arises. You may or may not experience pain, but it depends on how much force through a specific range of motion you try to move through and how many times you do it. It just depends on how much it takes to sensitize the tissues.   I can’t tell you how much it will take, but your brain will. “Ouch!”

So what is the biomechanical goal of core training? From an injury prevention perspective, one might say that it is exercise designed for the purpose of restoring or maintaining positional neutrality of axial skeleton. That is to say, it is exercise designed to avoid the positions of instability or impingement defined as moving the extensibility of mostly passive structures (i.e. ligaments, cartilage, labrum) away from the neutral zone of a joint. Some very flexible individuals may have large ranges of motion in all directions (large neutral zone) requiring more control, while others may be very stiff in all directions (small neutral zone). Think of stretchy yoga girl versus 70 year-old stiff guy. So, static stretching may be a form of core training for very stiff individuals if the goal is to improve range of motion. However, pushing into instability where it is not needed through repetitive asymmetrical loading is UNWISE CORE TRAINING!

From a performance optimization perspective, there are two primary goals of core training for runners. 1.) optimizing muscle tension for fatigue-resistant powerful linear motion and 2.) maximizing gas exchange. In other words, core training should complement translation of forces from pushing on the ground into forward linear movement and pumping air into and out of the lungs by twisting the body back and forth repeatedly (A.K.A. running). Right and left alternating

IMG_3664exercise incorporating focused breathing, challenging the thighs-hips, upper arms-shoulders, and thorax is advanced exercise that an be modified in terms of degree of control, speed of movement, and resistance. Body weight exercises on all fours, planking exercises while holding static positions train core muscles. Supported postures on the floor either facedown or on one’s back may be the easiest to feel if the goal is to maintain a static core position. Establishing positional neutrality is where one should start. I believe this requires physical assessment by a professional to specifically determine areas of focus. But, an individual will learn to feel this position and may be able to achieve it while running without exercise before running. With only anecdotal evidence to support the statement, this is what FLOW feels like.

So what is core training? It is performing a movement that challenges the axial skeleton to maintain optimal position for movement of the extremities relevant to the desired task to be performed. It is a blend of control and strength. It is restoring or maintaining positional neutrality first of the axial aspect of the movement system. Its purpose is to maintain the PICR of joints of axial skeleton, shoulder, and hip joints. The abdominals are a big part of the equation, but so are many other muscles. For runners, I will generalize and say that the oblique abdominals, transversus abdominis, breathing diaphragm(s), pelvic diaphragm(s), Latissismus dorsi, multifidi, iliocostalis lumborum, serratus anterior, gluteus maximus, iliacus, gluteus medius, adductors, hamstrings, quadriceps, triceps brachii, et cetera, etc. etc. … are really important. My point is, all muscles are important and play a role in core training.  Ask yourself: What is going to get you to position yourself for the most movement variability from the start position?

In my opinion, exercise fads and programs today revolve too much around ‘mobility’ through aggressive stretching AND strengthening into extension and external rotation (opening up in front) because you don’t spend enough time there all day (sarcasm). For example, imagine sitting or standing all day with what your mother told you was “good posture” (in extension of your spine, perched on the edge of your seat), then going to the gym and doing more extension exercises like back squats, lunges, good mornings or straight leg deadlifts, pull-ups, bench press, Lat pulldown, snatch squats, stretching your hip flexors, gluteals, and avoiding a real curl up where your spine flexes because “it’s bad for your back.” Where is the logic? I am not saying any of those exercises are bad. They have a purpose, but you must look holistically at movement. If you want to make orange juice and all you have are lemons, good luck.

The key takeaways of core training:

  • Core muscles are those that are attached up from the elbows and knees to the axial skeleton, shoulder girdle and hip girdle. Don’t forget the diaphragm right in the middle of it all. Yes, breathing matters!
  • Core training begins with establishing a healthy start position first – Are you oriented appropriately for optimal movement of your arms and legs. Can you achieve positional neutrality?
  • Positional neutrality is the orientation of the axial skeleton, including pelvis and shoulder girdle, for maximum movement variability of the rib cage, spine, pelvis arms, and legs relative to the individual. It is the static observation of a dynamic system.
  • Core training is a blend of timing and body positioning (coordination) and force production.
  • Stretching can be considered core training if it safely enhances the ability to orient / position the body.
  • Learn exercises from an expert that optimize your start position for maximized movement variability without stretching or strengthening into instability or impingement.
  • Add challenge and variability to maintaining neutrality through the axial system during movement. The more specific to the intended task, the better the performance of that task will be. Don’t just do more extension based exercises or planking.

Where resistance training, task specific training, and core training begin and end is a gray area. Be fit, be strong, be coordinated, and keep moving!

 Head for the hills,

-Erik

Post script –

I am a firm believer that being thoroughly assessed by a physical therapist is the best first step to getting serious about exercise, which is why it is mentioned in the post. Assessment should involve a thorough, in-person, one-on-one evaluation ending with relevant patient education. How you move and understanding why you are doing an exercise or modifying a movement habit is important. That said, the goal is not to create fear of moving. The purpose is to empower all humans to move with the precision that maximizes the benefit of exercise and minimizes risk of acute injury or gradual onset of injury. It is far better to keep moving than the alternative.

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