Why Having Stiff Muscles Is a Good Thing

We tend to think of flexibility as a positive, but that's not always true. Get-Fit Guy explains why muscle stiffness can actually be beneficial. Plus, learn how to make your muscles more powerful.

Ben Greenfield
4-minute read
Episode #210

In previous Get-Fit Guy episodes, I’ve talked about how long should you stretch a muscle to get optimal flexibility and the best ways to stretch to increase flexibility.

We tend to think of flexibility as a good thing. But it turns out that being too flexible can be a problem. In fact, there are certain situations in which having stiff muscles is actually a good thing.

Lower extremity stiffness in your quadriceps, hamstrings, calves, and ankles is considered to be a key attribute in the enhancement of running, jumping, and hopping activities. If you can store more elastic energy upon landing and generate more force output at push-off, you can reduce muscular fatigue and increase both speed and explosiveness.

What Are Stiff Muscles?

In exercise science, muscle stiffness is treated much like spring stiffness. Think about a spring. The more stiff and “springy” that spring is, the harder it is to compress and the more explosiveness it can potentially store as energy. A weak, stretchy spring on the other hand, stores less energy and produces less explosiveness..

Stiffness is measured in an exercise science laboratory as the quotient of force to length - and in the human body stiffness is quantified from both the level of a single muscle fiber to the level of the entire body as one giant spring.

A muscle or body system that stretches less and has fibers that are harder to compress or that are able to store more energy is considered to be more stiff, while a stretchy, flexible muscle is considered less stiff.

Here’s a great study that goes into the relationship between muscle stiffness and the spring measurements used in a lab.

Don’t Stiff Muscles Make You Susceptible to Injury?

You’d think that having stiff soft tissue would increase your risk of tearing, straining, or spraining a muscle, ligament, or tendon during activity, but it’s simply not so. Instead, research has shown that there is an “optimal” level of stiffness. Just like a very tight rubber band, extremely stiff muscles allow you to produce lots of force and explosiveness, but those muscles may indeed be more likely to tear or the bone attached to that muscle may be more likely to get a stress fracture.

In contrast, just like a very loose rubber band, muscles that aren’t stiff enough tend to be unsupportive of joints and lead to a higher risk of those joints being injured. Overly flexible hamstrings or quadriceps could potentially allow your knee caps to move around too much during a squat, run, or bike ride.

One study from Cal Poly in California compared running economy and flexibility in runners and found an inverse relationship between lower leg joint flexibility and running economy (for example, too much flexibility or not enough muscle stiffness in the Achilles tendons and the knee tendons).

In other words, the harder it was for a runner to touch their toes, the more economical their running was! So in a case like this, being super stretchy might not just make you more susceptible to injury, but may also decrease your performance.

Interestingly, the more fatigued you become while running, jumping, or performing other explosive movements, the less stiff and explosive your muscles become, and the more necessary it becomes for your joints to absorb the load instead. For example, towards the end of a marathon, your quadriceps, hamstrings, and calf muscles lose their springiness, which puts excessive strain on the knee joints. The more tired a muscle is when beginning an activity, the more likely this is to occur.

That's why going into any explosive or repetitive performance activity as fully recovered as possible is a very good idea!

See also: How to Recover After a Workout


All content here is for informational purposes only. This content does not replace the professional judgment of your own health provider. Please consult a licensed health professional for all individual questions and issues.

About the Author

Ben Greenfield

Ben Greenfield received bachelor’s and master’s degrees from University of Idaho in sports science and exercise physiology; personal training and strength and conditioning certifications from the National Strength and Conditioning Association (NSCA); a sports nutrition certification from the International Society of Sports Nutrition (ISSN), an advanced bicycle fitting certification from Serotta. He has over 11 years’ experience in coaching professional, collegiate, and recreational athletes from all sports, and as helped hundreds of clients achieve weight loss and fitness success.