You’re weight training to build muscle definition and strength and, possibly to lose weight. You’re focused on your muscles and probably don’t think about another facet of your architecture, your tendons. That doesn’t mean tendons aren’t important. It’s tendons that carry force from your muscles to your bones so that movement can take place. A bout of tendonitis will make it VERY clear that tendon health matters.
What Are Tendons?
Tendons are the connective tissue that attaches skeletal muscle to bones. One of the biggest tendons is your Achilles tendon. To feel it, slide your hand down to the base of your calf in the back. At the base of your calf muscle or gastrocnemius, you’ll feel a thick band. That’s your Achilles tendon. Tendons are made of strong, dense fibrous bands of connective tissue. Another type of tough connective tissue called a ligament connects bone to bone. Ligaments play a vital role in how MUCH a joint can move. These pieces of connective tissue limit joint movement, so you don’t end up with a painful dislocation. In this article, we’ll focus, in this article, on the tendon.
Tendons are tough and designed to withstand tension. Makes sense since they connect bones and muscles together and transmit force from the muscle to the bone when you contract a muscle. Although tendons are all made up of tightly packed bundles of collagen fibers, they vary in length based on genetics. For example, having long Achilles tendons gives you an advantage in running and jumping compared to someone with shorter tendons in this area. How your tendons are constructed also impacts how strong you are. The farther a tendon attaches from the axis of rotation, the greater strength potential that tendon and muscle combination has.
Can You Strengthen or Increase the Size of Your Tendons?
What about changes in strength and size? Tendons don’t increase significantly in magnitude but they do become thicker. In fact, you don’t want tendons to grow in size since it would impact the function of the joint. Another thing to know about tendons is they don’t receive the same quantity of blood supply that muscles do. Your muscles are much better vascularized than are your tendons. That’s why it takes so much time to heal an injured tendon. Without good blood flow, tendons don’t get the same stream of oxygen and nutrients that muscles do. That delays healing. In fact, a partial tendon tear can take four months or longer to heal.
As with muscles, you can increase the strength of tendons through training. By simply lifting weights, you’ll increase tendon strength. When you contract a muscle it pulls on the tendon and places stress on it. Your tendons adapt by thickening and becoming stronger so they can better deal with the added stress. Yes, you can strengthen your tendons but there’s a debate as to what type of training is best. Do you use heavy weights and low reps or high reps and lighter weights?
Heavy or Light Resistance
The ideal resistance for strengthening tendons is still open to debate. Intuitively you’d think that using heavy weights and low reps would maximize tendon strength. A number of coaches advocate this approach. However, others point out that using high reps and lighter weights boosts blood flow to the tendons and increases oxygen and nutrient delivery. The latter approach, using lighter weights and higher reps is beneficial in terms of injury prevention. When tendons have a good blood supply, they’re less likely to tear. Plus, if you do injure a tendon, an enhanced blood supply speeds up healing.
In terms of strength building, as with muscles, it makes sense that heavy is better. With heavy weights, you force the muscle to work harder. That force is transmitted to the tendon so that it has to adapt too. One thing to be aware of. Research shows that building tendon strength is slower than building muscle strength, partially because tendons don’t get the same degree of blood flow. Based on the results of one study, it takes weeks to months of weight training to create stronger, stiffer tendons. Blood flow to tendons also decreases with age, meaning it takes more time to strengthen them when you’re older AND more time to heal an injured tendon as well.
Training for Tendon Strength
The best approach might be to use a variety of weights and rep ranges – low reps and heavy resistance to strengthen and lower resistance and higher reps to enhance blood flow to the tendons. If you periodize your weight training workouts, you’ll expose your muscles and tendons to heavy weights AND light weights.
Adding a power component to your routine also helps build stronger, stiffer tendons. Stiffer tendons are able to generate more force. You can do this by lowering the resistance to around 50% of one-rep max and moving the weight as quickly as possible. Plyometric moves are another explosive type of movement that forces tendons to adapt. One study showed that plyometric exercises make tendons better energy transmitters, although it doesn’t increase tendon thickness.
Finally, exercise that emphasizes the eccentric or lower phase of a weight training movement is used to treat tendon injuries. For example, to treat an Achilles tendon injury, you might be instructed to do a calf raise on the good side and lower yourself slowly back down using the injured side. One study compared this approach to the conservative treatment of Achilles tendonitis among runners. The group that did eccentric exercises was able to run again after 12 weeks while the control group experienced no improvement. The question is whether eccentric movements actually strengthen healthy tendons. Still, including eccentrics in your training program has other benefits as well. Eccentrics create more muscle damage and, therefore, give you a greater potential for muscle strength gains and growth.
The Bottom Line
You can strengthen your tendons and make them stiffer through training. Since there’s some debate as to the best approach, the best bet is to include a strength, endurance, and power component during separate sessions. You can do this by periodizing your workouts.
National Federation of Personal Trainers. “Connective Tissue Training”
J Musculoskelet Neuronal Interact. 2011 Jun;11(2):115-23.
Mark’s Daily Apple. “Why Training Your Tendons Is Important (and 11 Ways to Do It)”
Int J Sports Phys Ther. 2015 Nov; 10(6): 748–759.
Br Med Bull (2012) doi: 10.1093/bmb/ldr052 First published online: January 25, 2012.
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