Like a “Car with Good Gas Mileage,” Healthy Tendons Allow You to Waste Less Energy on the Run

Like a “Car with Good Gas Mileage,” Healthy Tendons Allow You to Waste Less Energy on the Run

When Karin Grävare Silbernagel was studying to become a physical therapist, she recalls hardly learning about tendons. “The tendon was kind of considered this inert structure that just connected the muscle to the bone,” she says.

Though she quickly learned when she started her clinical practice over 30 years ago how big of a problem an injured tendon could be. More and more patients came in complaining of pain, suffering from tendonitis and other tendon issues.

Now Grävare Silbernagel is the principal investigator on the Tendon and Ligament Research Team at the University of Delaware.

And any runner who has ever dealt with tendon issues knows, too, the time and energy it takes to come back. Lucky for us, tendons and how they can be optimized for athletic performance are being studied and talked about more than ever before.

Take this recent research published in Science Translational Medicine. Comparing mice to men, the researchers found that tendons that respond to mechanical stress can improve running and jumping abilities over muscles, in the case of one specific ion channel expression (Piezo 1). In mice with Piezo 1, tendons appeared to store more elastic energy.

“Tendons were able to stretch more easily and store larger amounts of energy, which allowed for greater flexion and greater instantaneous power produced by the ankle, whether alterations were innate or introduced after mice matured,” said senior author Hiroshi Asahara in a press release. “Muscle-specific alterations, however, did not result in improved physical performance.”

And while the ion expression is reliant on genetics, the research still reveals how critical tendons are to running performance in a sport that often overlooks prehab, cross-training, and other activities beneficial to tendon health.

Ultimately the researchers hope their findings can one day lead to new treatments for tendon-related disorders.

It’s great that more research is emerging, but what are you supposed to do with that information? First let’s dig into what tendons are and the role they play in your body while running.

It can be easy to confuse tendons and ligaments and their role in the musculoskeletal system. They are very similar in makeup–both being fibrous connective tissue–but ligaments join bone to bone, while tendons attach muscle to bone. Tendons help to propel the force generated by your muscles to move your muscles, and thus get your body in motion.

Though runners are well acquainted with the Achilles tendon as it lands in the top five most common injuries among runners, injuries of the patellar tendon (connects your knee cap to your shin bone), tibialis posterior tendon (attaching muscles on the back of your calf to your foot), and gluteal tendons (a common cause of hip pain) are also relatively common.

And yes, your tendons make a difference in your performance as a runner. Genetically speaking, people with longer Achilles tendons are able to run more efficiently according to a study published in the journal Medicine & Science in Sports and Exercise. That’s because as your foot strikes the ground, the Achilles tendon stretches. The longer that stretch, the more energy can be returned when your foot then pushes off. That energetic force is combined with energy created by contracting muscles, which is why the two body parts are often referred to as the muscle-tendon complex or unit.

It is unclear exactly how much of the tendons’ efficiency is due to genetics versus nutritional and physiological interventions. But what is becoming increasingly clear is that you can actually train your tendons to at least some degree. Physical activity promotes collagen turnover. And collagen makes up 80 percent of the dry weight of tendons.

Though people often complain about tightness, you do want your tendons to maintain a certain level of stiffness to get their job done. Grävare Silbernagel compares it to a basketball. “If you have a basketball, but don’t have enough air in it, you need a lot of energy to bounce it. But if you have the perfect amount of air, it can bounce back.”

On the other end of the spectrum though, tendons that are too stiff can become brittle and susceptible to injury, which is why a Goldilocks scenario is what you should aim for. Tight, but not too tight.

And that tightness varies even for the type of tendon and its principal function. Generally speaking, you want your Achilles tendon to be on the stiffer side in order to produce more force, for example. The tendons that attach to your hip flexors, however, should be more compliant (i.e. stretchier) for a wider range of motion.

Tendons, like muscle, respond to load-bearing exercises. Strength training for tendon health is something Grävare Silbernagel consults on with pro athletes, and has become a new hot topic in the last 10-15 years.

Grävare Silbernagel recommends heavy weight training to keep tendons healthy. “Looking at studies from strength training, if you do 50 percent of max voluntary contraction versus 90 [percent], the tendon responds by getting bigger and stronger if you have a little bit of a heavier load. And that load, you kind of strain it to actually stretch the tendon is kind of what you need to do,” she says.

Exactly how much load you need to train your tendons to prevent injury and also rehab injury, she doesn’t know, but it’s something she’s trying to find out. She calls it the holy grail.

Some coaches also recommend runners introduce mobility and plyometric exercises into their routine to combat hysteresis–a term used to refer to energy lost between the stretch and release of the tendon. Separate from the stiffness of the tendon, reducing hysteresis minimizes energy loss.

Experts also recommend similar load-bearing and plyometric exercises that can prevent injury in the rehab of the actual injury itself in almost a cyclical fashion. “After recovering from a tendon injury, doing a similar exercise program to maintain tendon health is advised to reduce risk for future injury/re-injury,” says Dr. Adam Tenforde, a former competitive runner and sports medicine physician at the Spaulding National Running Center.

Like building bone strength, tendons adapt to activity over time and are supported by proper nutrition and hydration, says Dr. Tenforde.

“Nutrition and hydration are important to help ensure appropriate components of collagen (protein) and caloric intake meets demand of sports to support overall health and being in a net positive energy state,” he says.

Along with the ‘holy grail’ of tendon-loading, Grävare Silbernagel also wants to learn more about how tendons adapt differently in women than in men–because they do. Research shows that women have a lower rate of tendon collagen synthesis following exercise than men, less mechanical strength in their tendons, and are also more likely to sustain a soft tissue injury from physical activity.

Without more information on sex-specific differences, female athletes won’t have the same fair chance to make the absolute most of these energy-giving propulsion mechanisms we call tendons.

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