How much do you have to stretch to increase your flexibility?

The history of purposeful stretching can be traced back many centuries. Stretching was used by soldiers and competitors in the Greek and Roman empires, as well as in ancient yoga and martial arts practices in Asia. Fast forward to the present day, and stretching has become an extremely prevalent exercise modality. Virtually every athlete engages in some form of stretching before training or a competitive event. People often stretch to limber up in the morning or relieve stress at the end of the day. Of the many reasons why people stretch, however, perhaps the most common is to improve flexibility, which includes lengthening muscles and improving range of motion. But how many people know how to stretch in a way that makes them more flexible?

Let’s start with a basic physiology lesson. We know that soft tissues (e.g. muscles) have the capability to structurally change in length. This is described in Davis’s law, named after the 19th century Orthopedic Surgeon Henry Gassett Davis. Davis’s law states that tissues will physically adapt according to the mechanical loads placed on them. An example of this would be dedicated weightlifters, who can double the size of their muscles over the course of their careers. While the mechanism for changing muscle length is different than that for increasing bulk, when people provide their bodies with the correct environment for increasing flexibility, they should see adaptations follow.

Muscles are made up of tiny units that are responsible for their contraction. Depending on its size, there can be millions (or even billions) of these units in a single muscle. The body will add or subtract these basic units in response to mechanical stimuli, which will structurally change the length of the muscle. For example, if a muscle is held in a lengthened position for a sufficient amount of time, it becomes physically longer. On the contrary, if a muscle is held in a shortened position long enough, it becomes physically shorter.

With the principles of Davis’s Law in mind, exactly what stimulus is required to structurally lengthen a muscle? In other words, how much do we need to stretch in order to see a lasting improvement in flexibility?

To truly increase the length of a muscle, we know that a consistent and lengthy period of stretching is required. World-renowned physical therapist Jay Dicharry states in his book Anatomy for Runners that to see significant changes in soft tissue length, you should hold a stretch for 3-5 minutes at a time and perform this routine 4-6 days per week over 10-12 weeks. The American College of Sports Medicine recommends similar guidelines. It’s a slow process because we are physically remodeling the muscle to increase its length.

This stretching regimen is much more intensive than what is often suggested elsewhere. In the most popular stretching book ever written, aptly named Stretching, author Bob Anderson recommends holding each stretch for 10-15 seconds. Other sources recommend holding stretches for 30-60 seconds. While stretching for shorter periods might make you feel looser and even increase your flexibility, this is generally a short-term phenomenon. With shorter-duration stretches, you typically aren’t creating long-term physical changes in muscle length; rather, you’re most likely temporarily influencing the nervous system’s control over the muscle. Although stretching in this way can have other benefits, lasting improvements in flexibility probably isn’t one of them.

Now before you undergo a stretching program designed to increase muscle length, it’s wise to make sure you actually need to. It’s better to do nothing than be too aggressive with stretching, especially when flexibility isn’t an issue for you.

The most significant indicator that you need to improve your flexibility is if you lack the necessary range of motion to carry out your daily activities, sports, or exercise without compensation. We know that increased stiffness in one part of the body can cause compensatory movement in less flexible areas. The body will follow the path of least resistance, and if specific areas are too tight, this may mean performing less than optimal movement patterns.

On the other hand, if you can perform your daily activities, sports, and exercise without compensation, stretching to improve muscle length likely isn’t necessary. Most athletic trainers, physical therapists, chiropractors, and personal trainers should be able to assess your movement and flexibility and help you determine if a focused stretching program is right for you.

Improving flexibility is one of the many benefits of stretching, however it needs to be done the right way. The body can change if stressed in the right way, and becoming more flexible requires a few months of diligent stretching.

Dr. Jordan Duncan was born and raised in Kitsap County and graduated from the University of Western States in 2011 with a Doctor of Chiropractic Degree. He practices at Silverdale Sport and Spine. He is one of a small handful of chiropractors in Washington state to be credentialed in the McKenzie Method.