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Tissue Adaptation for Runners

BY Carrie McCusker

While training often emphasizes muscular development, strong connective tissue may be the key to a long, injury-free running career.

The old adage that all runners eventually get injured is faulty. Rather, runners that don’t build mileage methodically or neglect to consider important factors like diet, shoe choice, mobility, flexibility, strength, and recovery are at higher risk for injury. The potential for injury is in fact greater in new or returning runners with lower mileage compared to seasoned, experienced runners with higher mileage. This indicates that running a lot of miles isn’t necessarily the reason athletes get injured. A major contributor to this discrepancy is tissue adaptation — a simple way of explaining how muscles, bones and connective tissue like ligaments and tendons adjust to load and stress through use and recovery.

What is connective tissue?

Connective tissue is sort of a catch-all way of describing what connects everything in your body together. This includes fascia, a thin wrapping beneath the skin surrounding all muscles, organs and blood vessels that provides support for the working parts; tendons, which connect muscle to bone; and ligaments, which connect bone to bone. Strong ligaments and tendons are essential for runners, and anyone who has experienced plantar fasciitis or torn an achilles tendon understands the tremendous impact and ongoing struggle to heal them once injured.

Why is connective tissue adaptation important to runners?

New and returning runners might focus on being “out of shape”, a subjective evaluation that’s often due to an accelerated heart rate and lower levels of oxygenation. While the development of the cardiovascular system and growth of adapting muscles will respond rapidly to the application of consistent stress through training, important connective tissues like ligaments and tendons are slower to develop. 

Because these structures have lower blood supply, it is critical to understand that connective tissue needs to experience stress systematically along the way. Runners should therefore implement slow and steady increases in their training load for tissue adaptation to properly develop. Consequently, jumping ahead with mileage because you feel good can lead to debilitating injury. Tendon and ligament injuries are much more difficult issues to navigate than those concerning muscle or bone because they take an even longer time to heal, and generally require surgery if the tissue is torn.

How long does it take for tissue adaptation?

The “Physical Stress Theory” proposes that changes in the relative level of physical stress cause a predictable adaptive response in all biological tissue. In runners, these adaptations include atrophy (decreased stress tolerance), maintenance, hypertrophy (increased stress tolerance), and injury. The goal of gradually building up training loads necessitates the transition from atrophy to hypertrophy, and then to a steady state of maintenance over time. 

Jared Buzzell, a physical therapist at Spectrum Orthopaedics in Portland, Maine, suggests it can take between six and twelve weeks for tissue adaptation to occur. “This is the timeline I give runners when we modify mechanics, change footwear, or especially for a newer runner when considering volume increases,” he says. Buzzell subscribes to the 10% rule, which means increasing weekly mileage by no more than 10%. While this number is a good rough estimate, a coach or PT can help choose a plan that is unique and appropriate for the individual. Buzzell notes that other factors can come into play, including age, nutrition, sleep, and injury type. With proper guidance and compliance, “the injured tissue will heal 50% within the first two weeks, 80% within six weeks, and 100% by the twelve week mark,” he says. 

How can runners improve tissue adaptation?

Having a coach is a great place to start when beginning a new running program, and a good one should help you to avoid overstressing connective tissue. If patient, any athlete can adapt by building their training slowly and methodically. Remembering that it takes time, consistency, and resolve to build a running base. 

First and foremost, Buzzell emphasizes that all runners should have adequate hip mobility to avoid compensation through the pelvis and spine. A good range of motion is essential. To advance this, he suggests quad massages plus hip flexor and lat stretching (especially for triathletes) to reduce tension on the pelvis and promote a more neutral position. Secondarily, assessing core and hip girdle strength in single leg stance can tease out any glaring issues. If an athlete cannot maintain “single leg stance with proper rib over pelvis alignment without losing control, the repetition of running will likely lead to tissue breakdown,” says Buzzell. Single leg stance drills with arm and leg movement can progress to exercises such as single leg deadlifts and other strength based work.

Drills that work the posterior chain and challenge the neuromuscular system can continue to promote efficient mechanics. Buzzell suggests scuff back walks, 100 ups, charging bulls and skater hops. Things like butt kicks, high knees and strides before a run can warm and activate,  adding to neuromuscular development. Building into a good resistance training program in conjunction with building mileage is widely recommended. 

Don’t forget that tissue adaptation takes time and patience. Getting a run analysis from your local PT, talking with an expert about running shoes, and then committing to a consistent training program that includes resistance training, mobility work and properly dosed mileage can create the foundation for an injury-free, long-lived running career.

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About Carrie McCusker

Carrie McCusker is a level 2 TrainingPeaks coach and a lifelong athlete who enjoys bringing individual attention to every level of athlete. You can find her on Strava and Instagram or check out her coach profile at TrainingPeaks.

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