Strength training is good for building muscle, losing fat, and making your muscles stronger. It’s easy to focus on your muscles during a workout, but your tendons are just as important. Just like your muscles, your tendons adapt and transform in response to exercise.
You might wonder how your tendons change when you train – do they grow stronger and more resilient? A new study has insights into what happens to tendons in response to training and its effects on physical performance, including jumping.
Know Your Tendons
First, know your anatomy. What are tendons? Tendons are tough fibrous connective tissue that attaches muscle to bone. When a muscle contracts, tendons pull on the bone so that movement occurs. Tendons are comprised of thick collagen fibers layered over one another, giving them the highest tensile strength of all soft tissues.
The fibers work like a rope, stretching as muscles contract but they also have the capacity to snap back into place when the muscle relaxes. Tendons make it possible for you to pick up something heavy, hold it in place, and then put it down again without the joint or muscle tearing. That’s convenient, right?
It’s clear that muscles change in size and strength in response to strength training, but what happens to tendons? They become stronger and stiffer and scientists now know why.
In a new study, researchers from ETH Zurich and the University of Zurich examined the molecular mechanism by which tendons change in response to exercise. They discovered that tendon cells have sensors that detect when a tendon’s collagen fibers shift as a muscle moves. When this shift occurs, calcium moves into the cells of the tendon. The calcium acts as a signal, telling the cells to produce enzymes that bind collagen fibers more tightly together. When the collagen fibers tighten, the tendon becomes stronger and stiffer.
How much your tendons stiffen in response to training depends on your genetics. According to research, some people of West African descent have a gene variant that causes their tendons to stiffen more in response to training. Therefore, people with this variant develop greater tendon stiffness when they train. Having stiffer tendons has an advantage; it gives them the ability to generate more lower body force, leading to greater vertical jump height.
The genetic variant, based on research, appears to be more important for fast jumping and has little or no effect on slow jump performance. That’s because tendons don’t play as much of a role in slow jumping. They also found that the genetic variant they identified, called the E756del variant, improved fast jumping performance by around 13%. One-third of people of African lineage carry this gene variant, while it is uncommon in other populations.
How can stiffer tendons help you jump higher? When you lengthen a tendon, it stores energy, and you release that energy when you jump. A stiffer tendon can store more energy to propel you into the air with greater force and help you achieve greater height.
Tendons Become Stiffer and Stronger in Response to Exercise Training
Tendons not only stiffen in response to training, but they also become stronger and thicker. One way to strengthen and thicken your own tendons is to lift weights. When you contract a muscle against resistance, it pulls on the tendon and the tendon pulls on the bone. The tendon also adapts to that pull over time.
Muscles become stronger by building new contractile elements, the components of a muscle fiber that cause the muscle to contract. The boost in contractile elements you get from strength training increases strength and muscle thickness. Tendons become thicker and stronger by building stronger collagen links, thereby giving the tendon more tensile strength and stiffness.
When Injured, Tendons are Slow to Heal
If you’re ever had tendonitis or tendinosis, you may noticed that it healed slowly. That’s because tendons don’t get a great deal of blood supply, Instead, they get most of their nutrients from the synovial fluid within the joint. Without an abundant vascular supply, tendon injuries heal slower. It’s not unusual for Achilles tendon injuries to take 3 to 6 months to heal. That’s why it’s important to train in a way that doesn’t place you at higher risk for a tendon injury.
Most tendon injuries are caused by stressing the tendon too much from repetitive movements. An example of this is Achilles tendonitis, a tendon problem common in runners who run long distances. This type of tendon injury happens because repetitive stress on a tendon forces the tendon cells, called tenocytes, to work harder to lay down new collagen.
However, the low blood supply to the tendon limits its ability to do this. If the tenocytes get too far behind, the tendon begins to degenerate at the microscopic level. You might not feel pain yet, but trouble is brewing behind the scenes. Keep training at the same level and you’ll end up with classic symptoms of tendonitis or tendinosis – pain with movement of the tendon, tenderness, and, possibly, swelling and slight redness.
Most of what people think of as tendonitis is tendinosis, degeneration of the tendon without inflammation. Less common is tendinosis, stress-induced degeneration of the tendon with inflammation. Both are uncomfortable and inconvenient, but the former is more common.
Tips for Preventing Tendon Injuries
- Wear supportive shoes that have enough padding to absorb impact if you run.
- Warm up before each workout by doing dynamic movements.
- Cross-train to avoid repetitive force on your muscles and tendons.
- Watch your weight. Excess weight places more impact on your muscles and tendons.
- Gradually increase the frequency and intensity of your workouts. Don’t increase running distance by more than 10% each week.
- Don’t focus just on cardio. Strength train too.
The Bottom Line
The response to tendons to exercise training is different than how muscles respond but both tissues adapt. Now you have a better idea of how.
References:
- Fabian S. Passini, Patrick K. Jaeger, Aiman S. Saab, Shawn Hanlon, Nicole A. Chittim, Matthias J. Arlt, Kim David Ferrari, Dominik Haenni, Sebastiano Caprara, Maja Bollhalder, Barbara Niederöst, Aron N. Horvath, Tobias Götschi, Shang Ma, Bettina Passini-Tall, Sandro F. Fucentese, Ulrich Blache, Unai Silván,
- Bruno Weber, Karin Grävare Silbernagel, Jess G. Snedeker. Shear-stress sensing by PIEZO1 regulates tendon stiffness in rodents and influences jumping performance in humans. Nature Biomedical Engineering, 2021; DOI: 10.1038/s41551-021-00716-x.
- Fenwick SA, Hazleman BL, Riley GP. The vasculature and its role in the damaged and healing tendon. Arthritis Res. 2002;4(4):252-260. doi:10.1186/ar416.
Related Articles By Cathe:
Tendons and Ligaments: How Do They Change with Age?
Flexible or Not? Factors That Affect How Flexible Your Joints Are
The Process to Start Rehabbing an Achilles Injury
How Resistance Training Shapes Tissues Other Than Your Muscles
Can You Strengthen Your Tendons?
