How much flexibility do runners need for good body mechanics and running economy? – @fenixfeet

The Olympic Summer Games are in the rearview mirror, and what a spectacle they were. Among the astonishing feats of sporting prowess, gymnastics performances are especially branded in my mind. No exercise scientist could fail to be awed by how these champion athletes channeled power, flexibility and grace into meticulously crafted performances. With every jump, flip and spin, I visualized muscle filaments contracting at the microscopic level, in perfect harmony between flexibility and strength.

Your question concerns this complex relationship.

Stretching an elastic band causes it to store potential energy, which is released when the band springs back to its original length. Thicker, stiffer bands hold more energy and exert more force when they shorten. Your muscles have many of the same properties. Sprinters, for example, tend to have stiffer Achilles tendons that store energy during the landing phase of the run and release it during the push-off phase, making the movement more efficient and powerful. Sprinters also have stiffer muscles than untrained people when running at speed (1). By contrast, muscles that are too stiff and inflexible limit the joint range of motion, diminish performance in some events and increase the risk of injury in others. Hence, my amazement at the gymnasts who manage to consolidate the best of both worlds.

That’s the abridged background. Now, let’s answer your question. Ultrarunners don’t need much flexibility and probably benefit from more stiffness. A classic study from the University of North Carolina in the 1990s found that inflexibility in certain body areas conferred better running economy, perhaps by increasing elastic energy storage and return (2). Nor do we need exceptional flexibility because we’re not taking the long strides you see in your typical elite 10k runner. Ultrarunners tend to shorten their stride lengths in long distances, relying instead on stride frequency. This not only improves running economy but may also reduce injury risk by decreasing the center of mass, vertical excursion, impact shock and energy absorbed at the hip, knee and ankle (3). My advice is not to be overly concerned with flexibility unless it negatively affects your range of motion and predisposes you to injury.

How can we strengthen the tendons and ligaments that cause tendinitis in the foot and ankle? – @miwakeller

Lower limb tendinopathy, which is a broad term for “general tendon issues,” is quite common in runners. Various studies suggest the prevalence is 5-10%, depending on the runner's level and weekly mileage. Tendinitis has the suffix itis, which, in modern medicine, denotes "characterized by inflammation." Bronchitis is inflammation in the bronchi (the tubes that carry gases to and from the lungs); arthritis is inflammation of the joints (from the Greek arthro-, meaning “joint”); tonsillitis is inflammation of, you guessed it, the tonsils. A sudden injury can cause tendinitis, but it’s more commonly due to overuse and repetitive strain.

Why are you suffering tendinitis while your buddy runs more miles and suffers fewer injuries? That depends entirely on what’s causing your issue. It could be improper technique, inadequate warm-ups, muscle imbalances (i.e., lack of strength that places an undue load on a particular area), biomechanics, recovery and even genetics. If this is a recurrent problem, speak to a qualified, experienced physiotherapist. If you do, in fact, have a strength or technique deficiency, they’ll identify the issue and design a bespoke program to fix the problem at its root cause.

Why do nagging injuries magically go away 50 miles into a 100-miler? – @denzil_jennings

This is a common occurrence in ultrarunning, albeit anecdotal, and a phenomenon I can personally attest to. Six weeks out from my first 100-miler back in 2012, I strained a muscle in my lower back. I couldn’t train for the remainder of the lead-in, but the insolence of youth saw me trying my luck. I had severe tightness and shooting pains down one side of my leg for the first 40 miles. And then, as if by magic, it disappeared, as if the strain had finally admitted defeat and packed up its toys. Of course, no injury just “goes away.” It likely recedes into the background, temporarily submerged in a sea of inflammation and fatigue, only to return at a less convenient time, perhaps worse than before.

Several mechanisms may explain why you perceive less pain over time. In the short term, within 15-30 minutes, it tends to be explained by the “warm-up effect.” Exercise increases blood flow, increases body temperature and alters the contractile properties of the muscles. This can often allow minor niggles and trigger points to slowly ebb away. Exercise also triggers the release of various neurotransmitters that reduce pain perceptions—we know this as the “runners high.” However, both of these occur acutely, long before you hit the 50-mile mark.

If I had to speculate on the cause of the phenomenon you’ve described—where injuries that have plagued you for months seemingly disappear when you’re about to begin to most grueling part of a race—I’d put my money on beta endorphins. Ultramarathons tend to become most demanding when you’re exhibiting the most physiological strain and, in turn, the least psychological motivation. This intersection usually arises in the middle third of a race: a region of a 100-mile event where most DNFs occur (4,5) and which I’ve come to call no man’s land because it’s unknown, unclaimed and it’s where people usually get lost. When systemic inflammation is most pronounced, endorphins are released to dampen pain (6), attenuate the stress response and reduce inflammation through a suppressive effect on inflammatory cytokines (7). Your body attempts to lessen the “injuries” you’ve sustained and facilitate healing. It’s numbing rather than fixing the problem: run long enough and those same niggling injuries might return with a vengeance. So, tread lightly.

REFERENCES

1. Kubo K, Miyazaki D, Yata H, Tsunoda N. Mechanical properties of muscle and tendon at high strain rate in sprinters. Physiol Rep. 2020;8(19):e14583. doi:10.14814/phy2.14583

2. Craib MW, Mitchell VA, Fields KB, Cooper TR, Hopewell R, Morgan DW. The association between flexibility and running economy in sub-elite male distance runners. Med Sci Sports Exerc. 1996;28(6):737-743. doi:10.1097/00005768-199606000-00012

3. Schubert AG, Kempf J, Heiderscheit BC. Influence of Stride Frequency and Length on Running Mechanics. Sports Health. 2014;6(3):210-217. doi:10.1177/1941738113508544

4. Brager AJ, Demiral S, Choynowski J,
et al. Earlier shift in race pacing can predict future performance during a single-effort ultramarathon under sleep deprivation. Sleep Sci. 2020;13(1):25-31. doi:10.5935/1984-0063.20190132

5. Richard M. Diving into Ultramarathon DNF Data. iRunFar. February 28, 2024. Accessed August 16, 2024. https://www.irunfar.com/diving-into-ultramarathon-dnf-data

6. Sprouse-Blum AS, Smith G, Sugai D, Parsa FD. Understanding Endorphins and Their Importance in Pain Management. Hawaii Med J. 2010;69(3):70-71.

7. Pilozzi A, Carro C, Huang X. Roles of β-Endorphin in Stress, Behavior, Neuroinflammation, and Brain Energy Metabolism. Int J Mol Sci. 2020;22(1):338. doi:10.3390/ijms22010338