Why do we LOAD weak tissues? The Wisdom of Wolff’s Law

If you are familiar with Wolff’s Law, you know that tissues get stronger when we load them. In the 19th century Wolff noticed this effect in bones, but we’ve since learned that a variety of connective tissues need to be challenged in order to be strong. 


This may seem counterintuitive, as it is natural to want to protect weak tissues. Acute injuries do require a short period of rest/protection to allow the healing process to begin, but those same tissues will need gradually increased loading that signals the body to continue to build up strength.


This might also be called the “use it or lose it” effect, as tissues that are not challenged get weaker over time. Send an astronaut into space they will return to earth with weaker muscles, tendons and bones, unless they have a resistance training program to make up for the lack of resistance and impact from gravitational forces. Additionally, the cardio-autonomic system will become deconditioned in people who don’t regularly practice the challenge of pumping blood against gravity, leading to dysautonomia in astronauts and patients on bedrest alike. The body simply won’t waste energy to maintain something that isn’t being used. 


The solution may seem obvious– keep challenging the tissues and systems that you want to be strong! Use it rather than lose it! Especially if tissues are weak, they need to be challenged in order to stimulate the body’s repair processes. Exercise science calls this the “overload principle”– you have to regularly give the body a challenge beyond what it is accustomed to in order for it to grow stronger to meet the demand. 


Makes sense, right? The tricky part is finding the right amount of “overload.” If the system hasn’t been sufficiently challenged, it won’t build stronger tissues. Too much and you risk injuring tissues (or flaring up pain that is intended to warn you of too much–possible threat.) 


If the target tissues are vulnerable, exercise can be dosed carefully and progressed gradually to reap the benefits and minimize risk– a process every rehab specialist is familiar with. The ideal dose (amount, type, intensity) will vary over time. Let’s look at Wolff’s classic example:


When a bone is broken, it requires 4-6 weeks of protection/immobilization in order for a bone callus to bridge the gap. This newly formed bone is weak, and will need progressively increased loads in the weeks that follow in order to grow stronger. If it is not appropriately challenged with weightbearing and muscle-tendon units pulling on it, the bone will stay weak and be at risk of a repeat fracture with even the minor challenges of everyday stress. But loading the bone too much too fast while it is still vulnerable is a risk for re-injury. 


This may seem precarious, but there is a happy middle ground of appropriate loading/stress/exercise that allows the body to repair and strengthen tissues so that they can handle progressively larger challenges safely. For people without underlying pathology, the window of what the body can tolerate and respond to by building strength is relatively large. 


For others, the window may be smaller. If you are generally hypermobile or have sustained a hypermobility-related injury, your tissues are more flexible but lack strength. However, these tissues will still get stronger if loaded, making it imperative that appropriate loading occur. 


When a ligament is stretched beyond what it can tolerate, we call it a sprain. The inflammatory phase of healing lasts 7-10 days, and during that time it is advisable to take it easy and let the healing process begin. But beyond 10 days, the ligament needs to be progressively challenged in order to rebuild as a strong and stable ligament. 


A recent study found that exercise improved strength of ligaments and tendons and recommended light activity through a limited range of motion for <10 minutes at a time to strengthen ligaments and tendons. This amount is usually manageable even for those who are challenged by chronic pain or dysautonomia. 


Graded activity allows for people to start with what they can handle and gradually work up to therapeutic doses of exercise that will challenge tissues and systems for optimal results. People with dysautonomia can progressively increase exercise to condition their cardio-autonomic system and reduce associated symptoms, as shown in Dr. Levine’s studies on graded exercise. An adapted version of the Levine Protocol has even been shown to be effective for patients with Long COVID/Post-acute COVID Syndrome. Working with a rehab specialist familiar with your condition can help to individualize a graded activity program so as to maximize gains while reducing risks. 


The science makes sense– our bodies are smart and they won’t waste energy building strength we don’t need. The human body builds strength on an as-needed basis. The right amount of stress and challenge allows us to grow and develop resiliency. To continue growing stronger, the amount of stress/challenge will need to be increased as the tissues/system is ready for more. It is a process that evolves over time, rather than a one-time exercise prescription. A program will need to be adapted based on how someone’s body is responding– if symptoms increase rather than decrease, adjustments are clearly needed! Even for highly educated rehab specialists, there is a bit of trial-and-error required. Patients can partner with a trusted rehab specialist to explore what will work best for that individual’s unique circumstances and goals.


Humans have a remarkable ability to adapt. With a bit of tenacity, creativity, patience, and perhaps some professional help along the way, we can find the amount of challenge that optimizes resiliency and allows us to grow stronger. 


Need guidance on how to safely strengthen your tissues or condition your cardio-autonomic system? Consider booking a health consult to develop an individualized plan of action. 


Baar K. Minimizing Injury and Maximizing Return to Play: Lessons from Engineered Ligaments. Sports Med. 2017 Mar;47(Suppl 1):5-11. doi: 10.1007/s40279-017-0719-x. PMID: 28332110; PMCID: PMC5371618.

Smith TO, Bacon H, Jerman E, et al. Physiotherapy and occupational therapy interventions for people with benign joint hypermobility syndrome: a systematic review of clinical trials. Disabil Rehabil. 2014;36(10):797-803. doi:10.31 09/09638288.2013.819388 

Sampath SA, Lewis S, Fosco M, Tigani D. Trabecular orientation in the human femur and tibia and the relationship with lower-limb alignment for patients with osteoarthritis of the knee. J Biomech. 2015 Apr 13;48(6):1214-8. doi: 10.1016/j.jbiomech.2015.01.028. Epub 2015 Feb 2. PMID: 25721769.