“More kilometers, more fun” is a quote attributed to legendary trail runner, Kilian Jornet. Indeed, more running often leads to more adventure, as well as more fitness and strength. This time of year, ambitious, aspirational runners–in preparation for warm-weather races and adventures–are tamping up their mileage: running more so they can run more.
Conventional wisdom tells us that the key to running farther and faster is to… well, run farther and faster! But more isn’t always more. The byproducts of more running include more impact, more muscle wear, and more stiffness. Thus, the more we run, the more likely we are to accumulate stiffness.
But what really gets stiff, and why should we care? How can systemic stiffness derail our running, and how can enhanced mobility truly improve running efficiency and injury prevention?
What Gets Stiff
Muscle cells and fibers are damaged even with short bouts of regular exercise. The body, in response to this stress, repairs the cells and lays down more fibers. This is the essence of strength development. Yet in the repair process, the fibers are often repaired and created in an irregular fashion. This irregular tissue is protectively stronger in the short term, but also stiffer and less flexible.
In theory, this tissue will naturally reorganize with time and moderate activity, but repetitive running can slow down this process. This process slows even further with increasing age. The result can be a progressive loss of muscle flexibility.
By definition, a joint is the articulation of one bone with another. Most joints include bony ends covered in shiny cartilage, surrounded by a fluid-filled joint capsule. Joint cartilage has poor blood flow, and instead gets its nutrition from the joint fluid, absorbing it like a sponge. As such, joints require full mobility to keep the sponge dampened.
The primary mechanism of arthritis is range-of-motion loss: the sponge dries out on the edges due to lack of full, periodic mobility, and the cartilage is replaced by bone.
The spinal column is the conduit of the entire nervous system. It is composed of 22 bones and multiple joint surfaces between each, as well as muscles surrounding all sides. The spine protects and promotes the flow of conscious and unconscious control of our entire body: the motor nerves that make our arms and legs work, as well as the autonomic nerves that control breathing, heart rate, digestion, and all other components vital to running.
Most runners understand muscle and joint flexibility, but few recognize the vital importance of spinal mobility. While it is a strong, resilient ‘organ,’ the spine is extremely sensitive to changes in mobility. Stiffness can cause significant dysfunction to those systems and derail efficient, strong running.
The nervous system is comprised of continuous, interconnected tissue that begins in the brain and spans out to the tips of our fingers and toes. Because nearly every nerve emanates from the brain and travels down the spinal column, the entire system is one continuous piece of tissue. That said, since the nerves that travel to the feet pass through the upper neck, it is possible–and uncannily common–for a neck issue to affect the legs. Indeed, ‘it’s all connected’ through the nervous system.
The nervous system can lose mobility when any part of the spinal column becomes stiff, or any tissue through which the nerve runs–including muscle, fascia (the protective and power-enhancing muscle covering), or even skin–becomes stiff or injured.
Nervous tissue is highly sensitive. When they lose mobility, nerves can become very painful or create tension in muscles, tendons, and joints in order to protect themselves. Conversely, the nervous system may weaken other muscles to protect vulnerable nerves.
This nerve tension is the most important tissue mobility. Trying to stretch a tight muscle or joint–without first addressing nerve tension–is a losing strategy, as the brain will always protect a tense nerve through muscle tightness.
A classic example of nerve tension is ‘hamstring flexibility:’ the sciatic nerve–the pain nerve powering the posterior and lower leg–runs its course from the posterior pelvis to the back of the knee. Stiffness anywhere in the spine–from the ears to the tailbone, and everywhere in between–can create tightness in the hamstrings that is unrelenting to any hamstring stretching. Most runners who complain of ‘tight hamstrings’ or achiness in the posterior thigh are experiencing sciatic nerve tension. And more often than not, the problem is coming from somewhere in the spine.
All that said, the nerves drive all flexibility in our bodies. For this reason, a mobile nervous system is extremely important to strong, efficient running.
How We Get Stiff
Stiffness is normal. It’s the byproduct of a gravity-dependent, impact activity. But here are some other factors that cause, exacerbate, or prolong stiffness:
- Poor running mechanics. Inefficient mechanics create more impact stresses, and attenuate them less.
- Poor posture. The spinal joints are designed to absorb some impact, but when taken out of their neutral position, they lose their shock-absorbing ability.
- Unforgiving running surfaces. Repetitive pavement (or even solid rock) running is more stressful than soft, varied surfaces.
- As we get older, all of our body tissues fail to bounce back as quickly as when we are younger. This difference becomes more marked in the late-thirties to early forties, and is progressive.
- ‘Not moving.’ Occupations involving a lot of immobility–namely sitting (but also prolonged standing in one place)–create significant stiffness.
- Poor hydration. Lack of consistent daily hydration can dry out tissues, impacting flexibility.
Some of these elements are avoidable; some are not. But how we deal with these factors dictates how stiffness affects runners.
‘A Bad Day’ or a Faulty System? Four Consequences of Mobility Loss
Let’s say a runner works really hard to prepare for a race: they run many miles, are diligent with strength training–including weights, core stability, and drills–and they study up on all the great material on the pages of iRunFar in preparation of their big event.
However, maybe their posture on and off the trail isn’t so great. Oh, and they recently had a rough fall, where they landed on their pelvis and tweaked their spine a bit. They are sore in the neck and back, but it’s no big deal.
But come race day, things don’t feel right: they’re working hard, yet they seem slow. Much slower than usual. The heart rate is elevated. And maybe their stomach is off, too. They brush it off, attributing it to a ‘bad day,’ and slog their way to a sub-par finish.
The question is: how much of that has to due with poor nervous-system function? How did their posture habits–or their recent fall–affect the true muscle function of their glutes, and their ability to push off with full power? Or how did their neck and back stiffness affect heart rate and digestion?
Runners will do anything–try any gear or new supplement–to save five to 10 seconds a mile. But a mobility issue in the joints, spine, or nerves could make a minute per mile difference, or more. Or make the difference between a finish and a DNF.
Losing mobility is so much more than feeling stiff. It can create a multi-system efficiency and power loss, as well as create and exacerbate tissue dysfunction and injury.
Let’s look more closely at four critical areas affected by decreased mobility.
Full muscle and joint tissue mobility is crucial to maximizing stride efficiency. Full hip mobility is paramount, along with ankle flexibility, for maximum leg efficiency.
But what about the spine? Having full spine mobility is extremely important for stride efficiency for two reasons:
An efficient spine lengthens, shortens, and rotates–slightly. The best, most efficient runners, have a stride that emanates from the spine. With each push off, the trunk lengthens slightly, while the opposite side shortens: the former facilitates the glutes to push, the latter uses the abdominals to drive the hip forward. This creates a slight trunk rotation, counter-balanced and enhanced by a strong arm swing.
An efficient spine is a strong, flexible, mobile spine that enhances arm and leg power. When it stiffens, the limbs must work much harder.
A tall spine creates strong hips. The pelvis is the connection between the legs and the trunk, and the orientation of the pelvis dictates where hip power is directed. During running, the pelvis should be forward-tilted, so that the hips are allowed to extend beneath and behind us. This creates the propulsive power of the hips. But this all starts at the spine. If we become too upright, or if the spine becomes too stiffly rounded, we lose that rearward pelvic and hip orientation, and lose significant hip power.
Runners with stiff legs and spines… well, they look stiff! They’re typically rounded in their middle-to-upper backs, or are fully upright, with a stiff trunk that swivels on top of a low back and pelvis. Hips fail to fully flex and extend, creating inefficient, shuffling strides.
Maintaining spinal neutral is vital for full stride efficiency. Keep the spine and hips mobile!
Decreased Aerobic Function
Running is an aerobic activity. Our ability to consistently get a full breath is vital to delivering maximal oxygen to working muscles. And full mobility of the trunk and rib cage–which can only happen with a neutral, ‘tall’ spine–is the key to deep breathing.
Unfortunately, trail runners are presented with several challenges to maintaining a tall-yet-forward-oriented spine, including:
- the fatigue of many miles and hours of running,
- long uphills that challenge our core-stability system and its ability to keep us from slumping over, and
- backpack hydration systems, which often facilitate slumped postures and decreased trunk mobility.
This stiffness creates to major issues affecting aerobic function:
Decreased lung volume. A stiff, rounded spine restricts rib opening, which limits lung filling. Our breaths are smaller and more restricted, and our maximal oxygen consumption goes down. Indeed, poor trunk posture creates a detrimental, high-altitude effect to running!
Increased sympathetic sensitivity. Another consequence of slumped, stiff spines is its effect on our other organ systems. The sympathetic nervous system–the ‘fight or flight’ nerves that controls heart rate, digestion, and other internal functions–has its cell bodies on the inner portions of our thoracic spine. Some physiologists believe that stiff spines create sensitivities in these nerves. When the ‘fight or flight’ nerves become sensitive, they’re more likely to create problems, including everything from higher heart rate to poor nutrient absorption and GI distress.
Indeed, having a stiff, rounded upper back is a lot more than looking a little slouchy! It can have severe consequences on running performance, and even one’s ability to simply maintain forward (and upward) motion in a high-altitude, mountainous environment–home to many of our adventures.
Here’s what we know so far:
- Muscles are driven by nerves.
- Nerves are continuous tissues that begin in the brain and travel through the spine.
- Nerves can become sensitized when mobility of the nerve, spine, or tissues surrounding it become compromised at any point where the nerve travels. This means that neck stiffness can affect the function of a nerve going to the big toe.
- Compromised nerves–as a self-protective response to tension–can deactivate muscles, creating significant functional weakness.
This is the real stinker. The nervous system will do whatever it takes to protect itself. If joints are poorly aligned, or if nerves are under tension in the system, they will deactivate muscles. The nerves that activate the muscles of the hips emanate from the lumbar spine and pelvis. Stiffness and dysfunction there can ‘pinch the power cords’ that innervate the hip muscles. But so can neck stiffness, as all the leg nerves must first pass through the neck!
These power cords are fairly resilient, but when there are multiple ‘pinches’ along their path–perhaps one at the neck and the low back–they can become significantly compromised.
This is not to be mistaken with a ‘pinched nerve’ or a ‘bulging disc,’ many of which create pain, parasthesias, and frank weakness affecting basic, daily function. Those are the most extreme examples on the spectrum of neuromuscular dysfunction stemming from a spine issue. Far more common are these mild inhibitions that occur from stiffness and tension in the system that often fly under the radar unless put to the test in maximal effort-activities–such as running a long, hard race.
Neuromuscular inhibition is a protective system that prevents us from pulling too hard on a nerve, or putting too much load on a stiff or unstable joint. But it just may be the most significant and least-known factor affecting running performance that should not be overlooked.
Pain and Injury
Lastly, spinal and nervous-system mobility loss can amplify and outright create arm and leg pain. Most runners (and healthcare practitioners who treat them) have a muscle-tendon-bone mentality to run injuries. A lower-leg issue is either a calf strain, tendonitis, or a fracture. For most, nothing else is possible.
But what about the nerves? If nerve tissue courses throughout the leg, what effect does the nerve have on pain generation?
To review, sensitive nerves can create pain, or create muscle or joint tension to protect that sensitivity. That said, many leg injuries are either exacerbated or all-out created by nerve dysfunction. Here are some examples of common running running complaints and (in parenthesis) the associated nerves that may be creating them:
- Anterior hip and medial thigh and quad pain (femoral nerve)
- Glute, hamstring and posterior thigh pain (sciatic nerve)
- Lateral knee and shin pain (fibular nerve)
- Medial shin pain (tibial nerve)
- Top of the foot and lateral ankle pain (fibular nerve)
- Plantar foot pain (tibial, medial plantar nerves)
Indeed, a full 25% of plantar-foot pain cases I see, clinically, are either amplified or outright caused by nerve issue that must be addressed at the neck, trunk, or low back.
Nerve dysfunction creates pain in two ways:
Nerve pain. A sensitized nerve can create pain anywhere along its length. Physiologists believe that happens when a nerve becomes inflamed, then ‘dumps’ the inflammatory waste down (or up) stream through a process called axoplasmic transport. That said, a pinched nerve in the neck may cause no pain there, but create pain in the leg.
Nerve-related pain tends to differ from muscle or joint-tissue pain. While soft-tissue pain tends to be worst with initial movement, or with prolonged load, nerve pain is more varied and unpredictable. Symptoms include:
- aching, throbbing, and/or burning;
- intermittent sharp, stabbing pain; and
- pain at rest (but often spine- or nerve-tensed positions such as sitting or lying down).
Protective tension. Nerves can generate soft tissue dysfunction by keeping certain muscles (or even tendons and joints) stiff to protect the nerves. Therefore, conventional soft-tissue treatments–massage, stretching, and strengthening–fail to fully resolve nerve tension-driven pain.
A Case Study in Systemic Mobility: ‘Plantar Fasciitis’
A 35-year-old female runner presents in the clinic with right-foot pain. Her foot pain is located on the plantar foot and medial ankle. Symptoms are worst during and after running. She is fairly stiff in the morning, but symptoms resolve quickly with weight-bearing. Examination found: mild tenderness on the medial plantar arch; range-of-motion loss in hips, and moderate (yet ‘normal’) stiffness in the neck, trunk, and low back.
Initial treatment consisted of increasing mobility to the ankle, foot, and lower leg, as well as the hips; hip and core strength; and gait training to improve hip drive and decrease overstriding.
However, after a few weeks, symptoms had improved only slightly, and the runner noted she continued to have sharp symptoms at rest, while sitting, later in the day. Further subjective revealed that the patient has chronic neck pain with “one or two headaches per week.”
Further examination found a straight-leg raise–a measure of sciatic-nerve mobility–was 100 degrees (beyond waist-level leg elevation) on the left, but only 70 degrees on the affected right side. Neck examination revealed significant stiffness, bilaterally, in the lower cervical spine.
Treatment included cervical (and upper-limb-nerve) mobilization. The patient complained of right arm parasthesias during treatment. Post-treatment, straight-leg raise improved to over 120 degrees, bilaterally.
Upon follow-up, the runner reported, “For a day after the treatment, my right arm hurt, but my foot pain was immediately gone the next day on the run.”
In summary, her foot pain was likely caused by overstriding, but exacerbated by the overall spinal stresses associated with running impact as well as a previous neck injury. Her mild right-arm flare, post-treatment, was some lingering nerve sensitivity that–along with the foot pain–abated quickly once nerve mobility was restored.
Mobility is more than flexible muscles. It is the key to maximizing stride efficiency, but also ensuring all the body systems–everything from heart, lung, and GI function to neuromuscular power–are firing on all cylinders, Yet, it is so easily overlooked or dismissed.
Thankfully, with a few tools–and, perhaps, breaking away from the mentality of ‘all I do is run’–dynamic mobility can be maintained, if not vastly improved for the bulk of runners.
In next month’s column, we will outline three activities that promote comprehensive joint, spine, and nerve-tissue mobility: foam rolling, yoga, and pool-running exercise.
Call for Comments (from Meghan)
- Have you been treated for a non-“muscle-tendon-bone” issue, as Joe has described, that has improved your ability to run? If so, can you describe the details of your experience?
- What loss to joint and spine mobility have you noticed as you get older? What have you been doing to mitigate the aging process?