Are You Stiff Enough?

There are a lot of topics which get discussed in running circles. Volume. Intensity. Nutrition. Shoes… Rarely, in the top 5 of hot topics, will you find tendon stiffness. Yet, if you want to get the most out of your running, and maintain your longevity as a runner without the slow creep of pain and injury, it is important to understand the role that tendon stiffness plays. 

Tendon stiffness refers to the resistance of the tendon to stretching when force is applied.  In running, that force is primarily you hitting the ground. In this post, we'll explore the importance of tendon stiffness for runners, why it's beneficial, and how to increase it through strength training.

Think of Tendon Stiffness as Rubber Bands

Tendons are strong, fibrous tissues that connect muscles to bones. To understand the concept of tendon stiffness, let’s think of two different types of rubber band. 

One is new, thick, and very stiff (resistant to stretching) when you try to pull it apart. When you do manage to pull it apart (storing a lot of energy in it as you do), it snaps back as you let it go and release that energy. The other is old, thinning, and despite being easily stretched, it doesn’t release a lot of energy when you let it go. 

Similar to our rubber band analogy, tendons resist stretching when force is applied, and help to store and release energy efficiently.

Why is Tendon Stiffness Important for Runners?

Tendon stiffness is critical for runners for several reasons:

Speed: Tendon stiffness affects the speed at which the muscle can contract, which directly impacts running speed. The stiffer the tendon, the faster the muscle can contract, resulting in faster running speeds.

Efficiency: Tendon stiffness also affects running efficiency. The stiffness of the tendon helps to store and release energy as the foot strikes the ground and pushes off. The more efficiently the tendon stores and releases energy, the more efficiently the runner can move.

Reduced Ground Contact Time: Tendon stiffness plays a crucial role in reducing ground contact time. When the tendon is stiff, it can absorb more force without stretching excessively, which results in a shorter ground contact time. Reduced ground contact time can improve running performance and reduce injury risk.

Reduced Injury Risk: Tendon stiffness helps to reduce the risk of injury. When the tendon is stiff, it can absorb more force without stretching excessively, reducing the risk of injury.

What Happens When Tendon Stiffness Declines in Runners?

Declining tendon stiffness can result in the following:

Decreased Running Speed: Declining tendon stiffness can slow down muscle contractions, resulting in slower running speeds.

Decreased Efficiency: As tendon stiffness declines, the ability of the tendon to store and release energy decreases, resulting in a decrease in running efficiency.

Increased Ground Contact Time: Declining tendon stiffness can result in a longer ground contact time, which can increase the risk of injury.

Increased Injury Risk: When tendon stiffness declines, the tendon is less able to absorb force, which can result in an increased risk of injury.

Why Tendon Stiffness Should Not be Confused with Muscle or Joint Stiffness

It's important to note that tendon stiffness should not be confused with muscle or joint stiffness. Muscle stiffness refers to the resistance of the muscle to stretching, while joint stiffness refers to the resistance of the joint to moving. Unlike muscle or joint stiffness, tendon stiffness is beneficial for runners because it helps to store and release energy efficiently and reduce the risk of injury.

What Causes Tendon Stiffness to Reduce?

The lazy answer here is ageing - getting older. Like so many declines in our function, reduced tendon stiffness is far too readily written off as a part of the “natural ageing process”. This rationale perhaps gives people a get out of jail free card, excusing them from actually doing anything about this and many other physiological declines they might be experiencing. “I’m just getting old” is a common phrase to hear.

But rather than being baked into the cake of ageing, reduced tendon stiffness is more likely a function of factors we have control over - factors correlated with ageing rather than being caused by it.

One of the main causes is overuse and repetitive motions, which can result in inflammation and degradation of the tendons. In other words, simply running by itself can degrade tendons - especially when the volumes are forever high, and periods of rest and regeneration are few and far between. Improper training and not allowing enough recovery time after intense workouts can lead to decreased tendon stiffness.

Another cause is inactivity, where lack of use can lead to decreased tendon stiffness. Perhaps you are the type of runner who is either all in, or all out? You are either running crazy high volumes until you get sick or injured, or you are doing nothing at all.

My personal favourite cause of poor tendon stiffness is undernutrition and not fueling the body with essential nutrients (I am a Nutritionist first and foremost after all). 

Nutrition plays a crucial role in maintaining the health and stiffness of tendons. Perhaps the single biggest nutritional factor is a lack of high quality protein - both total protein and protein sources supplying collagen to the body. Protein is the building block for connective tissue. Without sufficient protein in the diet, the body may not have the resources it needs to repair and maintain the tendons.

After protein and the amino acids we derive from eating it, there are the micronutrients.  Vitamin C is essential for the production of collagen, a protein that makes up a significant portion of tendons. Vitamin D is also important for tendon health, as it helps the body absorb calcium, which is critical for strong bones and connective tissue. Magnesium is a mineral that helps regulate muscle and nerve function and is also involved in the maintenance of tendons.

Lastly, hydration is important for maintaining tendon stiffness. Dehydration can lead to decreased elasticity and increased risk of injury in the tendons. It's essential for runners to stay hydrated and replenish fluids lost during exercise to maintain tendon health.

What are the common nutrition problems I see in many runners, especially recreational runners? Not fuelling sufficiently, not eating enough protein or high quality sources, vitamin and mineral deficiencies (again, due to not eating enough), and chronic dehydration. 

Layer this on top of poor training structure, not doing any strength training, and insufficient recovery, and you have a recipe for low tendon stiffness and poor tendon health in general.

How Can You Increase Tendon Stiffness?

Strength training, and in particular, heavy strength training, is an effective way to increase tendon stiffness. Heavy strength training involves lifting weights that are heavy enough to challenge the muscles and tendons. By challenging the muscles and tendons in this way, the tendons become stronger and stiffer, which can result in improved running performance and reduced injury risk.

 Additionally, heavy strength training can help to improve overall strength and reduce the risk of other injuries, such as stress fractures.

Why are Runners Reluctant to Engage in Heavy Strength Training?

Good question. 

Despite the benefits of heavy strength training, many runners are reluctant to engage in it. This is often due to a number of misconceptions, such as the belief that heavy strength training will make them slow and bulky. However, this is not the case. Heavy strength training can actually improve running speed and efficiency, and it won't make you slow or bulky if you do it correctly.

There is also the reluctance to give up some running volume each week to go hit the gym. There can be a number of reasons for this, but nearly all stem from some element of fear (fear of losing fitness, fear of not burning enough calories, fear of not losing enough weight, and so on). 

My Top 5 Tips for Improving Tendon Stiffness

Engage in heavy strength training: Incorporating heavy strength training, such as lifting weights, into your routine is one of the most effective ways to improve tendon stiffness. This type of training helps to increase the density and strength of the tendons, reducing the risk of injury.

Incorporate plyometric exercises: Plyometric exercises, such as jumping and hopping (power training), help to improve the elasticity of the tendons and improve the stretch-shortening cycle, which is important for running performance. Note: You should be lifting heavy before you are doing a lot of plyometric work. Strength comes before power.

Cross-train with other forms of exercise: Engaging in a variety of exercises, such as cycling or swimming, can help to provide a change of pace and allow for different types of stress on the tendons, helping to improve stiffness.

Adequate recovery time: It's important to allow for adequate recovery time after intense workouts and activities to prevent overuse and fatigue of the tendons. This can include taking rest days (and recovery weeks!) or using active recovery methods, such as foam rolling or stretching.

Maintain a balanced diet: Eating a balanced diet that includes essential vitamins, minerals, and nutrients, such as protein, Vitamin C, Vitamin D, magnesium, and staying hydrated, is crucial for maintaining tendon stiffness and reducing the risk of injury. Additionally, consuming a diet that is low in processed foods and high in anti-inflammatory foods can help to reduce inflammation and support tendon health.

February 13, 2023 — Oska Inkster-Baynes

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