Single Leg Stability: A Fine Balancing Act

In my previous article, I introduced and discussed some basic concepts involving the importance of the gluteal muscle group towards human function and performance. The gluteal muscles are essential and unique towards how the human body operates but there are other components just as important. Before I talk about specific injuries and training concepts, I would like to touch on running mechanics and injuries in this department first. This will lay the groundwork for future discussions.

Did you say running mechanics and injuries?

I am sure I just grabbed your attention if you are an avid runner or OCR athlete. This is a very common issue, an issue that is mostly overlooked not only by coaches and trainers but also by athletes. The purpose of this article is to improve everyone’s understanding of the how and why of running injuries. We can then talk more about muscle function and exercise programs going forward with a better focus and understanding of the big picture concepts.

The importance of an “off-season” and taking the time to improve the foundation for a solid base of performance is crucial for an effective running career

Ensuring that all these muscles are functioning properly so they can perform during the dynamics of running is essential. An athlete should not have to sit out in the middle of a season and miss races due to an overuse injury. These deficits should have been addressed prior to the season and then focus should be on a maintenance program during the season.

Being a state level runner in high school and still a current athlete competing in the growing sport of obstacle course racing, I get it. I completely understand how much time goes into training and working towards wanting to achieve goals. When you get a system down and you see success, you want to keep pushing forward.

Mental focus is such a strong component towards human performance, which is a whole other topic within itself but it sometimes can work against us. Let’s face it; runners are some of the most stubborn athletes out there. Having treated so many in the clinic over the years, the same pattern is present over and over again.

It is safe to say that a person who is willing to go through discomfort for the challenge of completing a 5k, half marathon, marathon or even a sprint distance has strong will power. That will power can lead to the denial of something being wrong, such as developing an injury. Many runners just do not want to accept they may need to take a step back from their running volume and focus on some foundational training concepts.

The remarkable thing about the human body is that it will find a way to complete what needs to be done, even if it isn’t the safest or efficient method

Elite athletes are very good at doing this. They are so proficient in some areas that it can compensate for others. Those compensatory techniques will only hold up for so long before something fails. As an athlete you should use training to hone in on doing things properly as much as you can so when it comes time for a competition, if you compensate a little, your body can handle it. If you always are training compensation, failure will eventually happen.

When it comes to running injuries, the first thing topic I always hear about is footwear

One of the most common questions I get is “What shoe should I run in and should I change my shoes?” I will start off by saying that personally, the shoe is the last thing that I change with a runner in my treatment approach. I will discuss footwear going forward but I like to focus on improving the movement mechanics and deficits of the individual first.

If someone is unstable on one leg or demonstrates excessive patterns as compensation during running mechanics, changing a shoe will not matter. Many athletes feel if they cushion their feet to absorb the impact of ground reaction forces it will help resolve their issues and as this may provide temporary relief, it too will eventually fail.

The Importance Of Motor Control

One term that I want everyone to become familiar with is “motor control”. This basically is a fancy term for the body’s ability to complete a motion. An example is someone who can lie on their stomach and raise their leg straight up holding against good resistance. They then do the same in side lying, holding their top leg up against good resistance. These two tests can be indicative of “good gluteal strength.”

Now we have that same person, stand on one leg and do a single leg squat. They then have difficulty maintaining balance and control during the movement. The leg raise tests are indicative of strength; the single leg test is indicative of motor control. The individual can engage muscle groups against resistance BUT cannot recruit them all to complete a dynamic movement. This may sound straightforward but this too can be deceptive, because something we look for as therapists is compensation within these basic tests.

Sometimes an individual will recruit their lumbar muscles or hamstrings when trying to raise their leg up against resistance, which can be indicative of deficient gluteal activation and signs of compensation.

Now that we touched on some basic concepts, let's start to become familiar with some common running injuries.

The majority of complex injuries result from deficiencies in multiple areas including muscle strength, activation patterns, and mechanics

Even though running is a basic human function, many lack the ability to properly run. Poor mechanics produce a huge deficit in the efficiency of the movement.

The term “overuse injuries” is used to describe certain areas taking on more demand than they can handle and usually result from training errors. Achilles tendinopathy, calf strains, hamstring strains, hip flexor strains, tibial and foot stress fractures are all common things that are reported amongst runners. Increasing mileage, distance, and intensity at too rapid of a rate can lead to difficulty with tissue healing and adaptive changes. Add these factors on top of already strength deficient muscle groups, poor motor control, faulty mechanics and problems are sure to occur.

When joints and bones take stress from non-contact factors it means that the loading from the activity is too much for the structure to handle

If muscles are not working properly, then the stress is diverted to the joints and bones. Improving the efficiency of a runner by working on stride and striking rate as well as correcting abnormal movement patterns can prevent bone and joint stress injuries. This is where motor control comes into play.

Increased stress on a well aligned lower extremity can lead to increased bone loading and alternatively, normal forces applied to an abnormally aligned lower extremity can lead to increased bone stress. The worst-case scenario is a combination of abnormal forces coupled with a misaligned lower extremity, which will lead to serious risk for bone stress injuries. This is very common amongst runners who train insufficiently in the strength and stability department and focus too much on mileage and intensity.

A perfect example seen in runners and many athletes is the valgus and torsion collapse. What is that?

A good example is when an individual performs a single leg squat and the stance leg pelvic side drops, the knee moves inward or wobbles. Loss of balance, excessive foot movement, and torso rotation are compensations seen by the individual to help control the movement. SO if someone cannot complete this basic movement, then how are they expected to run efficiently?

During running there is the push off phase from single leg stance and then flight and then loading onto the opposite leg. Running can produce up to 2-4x bodyweight forces onto the body depending on height, weight, intensity, terrain, and surface. Imagine what is happening to all those unstable limbs during 10 miles on vigorous trails or hard pavement.

Common soft tissue injuries are iliotibial band syndrome and patellofemoral pain

Soft tissue is tissue other than bone, which consists of muscle, fascia, and fat. IT band syndrome occurs when the knee collapses inward (valgus stress) and since the gluteus and tensor fascia latae (muscles mentioned in the previous article) cannot control the limb properly, the IT band compensates and results in excessive pull. It has become common practice for many to resort to using a foam roller which may provide some relief but results in treating the symptom and not the source of the problem which is either muscle weakness or deficient motor control.

Patellofemoral syndrome occurs when the kneecap is not tracking properly over the knee joint so the under surface rubs onto the sides of the femur. It also results in stress onto the tissue surrounding the patella, which is called retinaculum and the patella tendon and quad tendon, which attach to the patella.

Focusing on improving muscle strength and stability is just as important as improving running mechanics

The muscles have to learn to work in a basic function with minimal loads before being put under excessive stress.

Progressing from single leg stability àsingle leg stability on dynamic surfaces à single leg stability with increased loads such as weights à increased loads on dynamic surfaces à increased loading and forces such as plyometric training would be the safest way to progress a program to compliment running training.

When running mechanics have been analyzed in studies it was found that increasing step rate heightened hamstring and gluteus maximus muscles during loading in the late swing phase. Gluteal muscles produce peak forces during loading in stance phase and hip extension moments as well. They also function to decrease the forward speed of the body’s center of mass during early stance so you basically don’t fall on your face.

The hamstrings work to help accelerate the hip into extension and also oppose the knee from accelerating into extension. This is why deficient hamstring function results in “pulls or strains” during increased speed such as sprinting. If the hamstring cannot function effectively to oppose the hip flexor function of the limb coming forward, it becomes overworked.

There is one analogy I want to leave you with. Think of building yourself as body armor. You work for months to perfect it for “battle” or in other words your competition season.

As you go through your season of competition it is going to take abuse. The more work you put into it during the offseason, the more it will hold up to the abuse and wear down at a lesser rate during the season. You will have time to do some maintenance and fixing up between competitions in season but the bulk of the work is done beforehand.

So now that you have an introduction to running injuries and concepts, it will make it easier to understand the more in-depth discussions about specific injuries. I will discuss proper exercises, programs and strategies implemented to prevent and treat them.

About The Author

Michael St. George, PT, DPT (@icore_stgeorge on Instagram) is a physical therapist who works for Excel Physical Therapy and Fitness which is a private practice that is based around the greater Philadelphia region and suburbs. He is FMS, SFMA, Y Balance and Motor Control Test Certified with 8 years of experience in outpatient orthopedics and sports medicine. His training consists of experience working with physicians and surgeons from the Rothman Institute and therapists in his field specializing in various manual techniques and advanced treatment procedures.


  • Nielsen, R., Parner, E., Nohr, E., Sorensen, H., Lind, M., Rasmussen, S. (2014) Excessive Progression in Weekly Running Distance and Risk of Running-Related Injuries: An Association Which Varies According to Type of Injury. Journal of Orthopedic and Sports Physical Therapy, Vol 44 (10), 739-747
  • Warden, S., Davis, I., Fredericson, M. (2014) Management and Prevention of Bone Stress Injuries in Long-Distance Runners. Journal of Orthopedic and Sports Physical Therapy, Vol 44 (10), 749-765
  • Lenhart, R., Thelen, D. Heiderscheit, B. Hip Muscle Loads During Running at Various Step Rates. Journal of Orthopedic and Sports Physical Therapy, Vol 44 (10), 766-774