Unilateral Leg Training – History, Science, and New Concepts

Single leg training, often called unilateral leg training, is an important part of a well-rounded lower body training program. Unfortunately, a lot of confusion exists around its origins and its scientific benefits. Over the last 10 years, we have observed a few trends that have been both intelligent and creative. Coaches are spending less time arguing and have dedicated more energy to writing holistic workouts that are agnostic to pure ideology. Some philosophies have been stubborn to change, while others have overcompensated in the other direction.

This article isn’t going to be controversial, but it may influence you to either do more single leg training or more bilateral training. No matter what method you use, I am confident that you will feel freer to choose the program that better fits your needs.

Single Leg Training Is Here to Stay for Good

I remember that Pumping Gravity, a strength training seminar held in Providence, was extremely provocative, and it really cemented in me a set of foundational beliefs of how the body worked and how training could complement it. It was during the late 1990s and I was in college, so my leg training consisted of what I had done in high school and copying programs from other coaches. I am not embarrassed to say I chased numbers like a chef chases flavors and found that my training was too focused on maximal strength.

I treated single leg training like a beginner’s part of training, but quickly changed when I discovered that some very impressive throwers in track included single leg training as a main lift. This was heresy, as I thought single leg exercises were second-class training. As I was not a competitive lifter or emotionally attached to anything in particular, it was easy to convince me that an extreme power athlete’s training could help a team sport athlete or sprinter. From then on, I was sure that single leg training had value, but the culture still favored squatting and cleaning.

Ian King and other coaches produced great resources to support single leg training, and each year they became more mainstream. This backstory has a purpose: It’s an example of how my own experiences shaped my thinking, and I don’t want my bias or short time on this planet to skew a wider perspective. For example, I am an American and a former swimmer, but what would my experience be if I were in northern Europe throwing the javelin? What about as a Brazilian fitness coach in soccer in the 1960s? What about a French health provider in the 1900s? Imagine the golden age of the Greeks? Our experiences and exposure to different people can really impact our thought process and beliefs.

Like it or not, #SingleLeg training has survived the test of time, says @spikesonly. Click To Tweet

Like it or not, single leg training has survived the test of time. If you are not convinced that using a single support or double support with emphasis on one leg is valuable, you are not helping your athletes. Conversely, if you don’t understand anatomy and the nervous system and have tossed out bilateral lifting altogether, you are missing the boat on absolute benefits that may actually be safer and more effective. Most of you, like me, will fit in with the majority, using both options and wanting to keep iterating for a better result. This article will ask the tough questions of why we should pump the brakes on single-leg training or gently prod the late adopters of unilateral leg training.

Frans Bosch and the Accidental Revolution

Over 10 years ago, Frans Bosch showed athletes running up stairs with water jugs, cleaning with one leg, and even performing a few isometric exercises. I was in Chicago at the Level 3 Track and Field USATF conference and I was not a believer. After 12 years, I have yet to see an athlete produced through unstable training and single leg reflex exercises, but I actually think his presentation did more for reducing unnecessary volume in the weight room.

In the 1990s, the British track team were walking gods and inspired me to get into track and field. That group and the Canadian sprinters before and after were no strangers to the weight room. Near the USF track—under the stands, actually—was the weight room where iron was tossed around like a rag doll. I still recall the spider cracks on the concrete floor from a few sessions that were science fiction.

Every monster in the weight room will have a mirrored opposite: an athlete who refuses to train heavy or avoids the weight room entirely. The physiques of Ato Boldon and Maurice Greene were impressive in the 2000s, but Carl Lewis and Calvin Smith were not rewriting the weight room record books. Frans didn’t convince me that his exercises worked; he made me think about how important the track was for getting what you need. For countless years, we saw coaches refuse to focus on the track and use maximal strength—bilateral or unilateral—to get the job done. Now we know better, but we still have far to go.

@FransBoschBook made me think about how important the track was for getting what you need, says @spikesonly. Click To Tweet

A lot of us believe we know what really works on the track, and we know that sprinting begets fast sprinting, and all strength training is supportive. I learned quickly that many athletes are walking around touting an impressive squat, but only a few are breaking 10 seconds in the 100m. Fighting over weight room details is like fighting over table scraps: Sure, strength training is important, but we are missing the prime cut of steak. Single or double leg strength training for a sprinter isn’t that important of a debate, and team sport is less about absolute abilities and more about skills and harvesting talent. So, respectfully, I credit Frans for helping all of us downplay the weight room and get the most out of what we do, but the applications are still preferences to me. 

From Ancient History to Athletics Education

It’s hard to say who invented training, let alone strength training. Perhaps it was ancient Egyptians, maybe the Romans, perhaps an earlier society. Who cares? The fact is, we can easily spend years looking at pottery or relics for clues, but the past is behind us. I only like to spend time with history if it actually helps us today, not to prove that current experts are just reinventing the wheel. Yes, single leg training is older than any living human, but it’s about what is written and shared, not what could have happened in the past.

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Any of these “modern” exercises look familiar? Athletic performance isn’t new. It’s been around for centuries. pic.twitter.com/oG03BkhJTH

— Matthew Johnson (@StrengthCoachMJ) January 30, 2019

Training became more structured around the 1930s. Book publishers and countries found a reason to take exercise seriously, since the Olympic games and other competitions started to mean more. Professionalism in sport improved the profession of training for sport. Competitive sport was no longer circus entertainment with strongmen; it was measurable differences between winning and losing.

Still, the age-old desire of separating leg training for sport and leg training for bodybuilding is currently a problem. Exercise options were growing and evolving, but the prescription of programming workouts was so scattered that nothing was formally outlined until a few decades later. Some coaches and trainers were way ahead of their time, but we must judge a time period on what the majority of coaches were doing.

The age-old desire to separate leg training for sport & leg training for bodybuilding is a problem, says @spikesonly. Click To Tweet

From the 1960s to today, unilateral leg training has simply gone from accessory lift to primary lift, with various coaches promoting the exercises. For me, milestones were the work of Soviet experts in the 1980s, promotion of sports performance in the 1990s, and correspondence training in the beginning of this century. Now coaches are confident with using unilateral training as a primary option, but so far, the results have not indicated a shockwave of world records and injury-resilient teams. 

Thomas Graham Brown, Roger Enoka, and Armin Kibele

We need to look at classic studies and respect those in the scientific community who make a difference. Coaches often view scientists as either allies or enemies, depending mainly on whether their research supports or refutes a personal belief. The following three men have made a big impact on my own education, and I know their work stands alone. Each of their contributions really changed the argument from what is best for everyone to what could be ideal based on the needs of that individual athlete.

In the early 1900s, Charles Sherrington helped physiology make a massive leap forward, and the laws named after him are still recognizable today. Reciprocal inhibition is basically the body allowing for a controlled contraction and relaxation of muscle groups. Agonist and antagonist activities are clear with simple movements such as the leg extension, where the hamstrings relax during contractions of the extensors of the knee. However, I make the argument we should give more credit to Thomas Graham Brown, a Scottish physiologist who took the concept further and focused on central pattern generators. While pioneering, Brown’s concepts were obscure and had to be rescued by another researcher, Anders Lundberg, and his cat experiment preserved Brown’s legacy.

I am a Tellezian with regard to technique training; meaning, you don’t need to coach something that is already there—you want to restore it if tampered with or not screw it up. That philosophy is rooted in the work of Brown and Lundberg, where central pattern generators do most of the work, and coaches should ask themselves what tasks access what we have instead of focusing on glamour cueing. Similar to teaching is training, and training with one leg is like cueing high knees: It seems to help, but really is just a sport-specific exercise disguised as functional training.

Coaches should ask themselves what tasks access what we have instead of focusing on glamour cueing, says @spikesonly. Click To Tweet

Roger Enoka is a living legend in sport science, currently at the University of Colorado. The first edition of his book was released nearly 30 years ago. While Neuromechanics of Human Movement is the title of the fifth edition now, the core concepts are nearly timeless. Roger’s study on the bilateral deficit was straightforward, but in a very rare change, I was more interested in his conclusion than the results of his research. Great researchers often produce instrumental findings, but I am always a fan of those that can draw conclusions with a reasoning and rationale that benefits coaches.

Finally, we have Armin Kibele, a German researcher cited in the pioneering snatch article from Klaus Bartonletz that was released in 1996. It was interesting that the bilateral deficit was addressed, and single leg snatches were researched to understand how neuromuscular qualities were modulated based on leg support. The research confirmed the work presented by the IAAF and other experts who were promoting single leg training. I didn’t get excited to use the single leg snatch or clean options, but I did focus on higher velocity plyometrics and isoinertial training because of Bartonletz’s spectacular review. In the 1980s, the bilateral deficit and facilitation were carefully explained, but due to bias, we see many coaches do one or the other instead of mixed methods. 

Classification and New Details of Single Leg Training

What is a single leg exercise? Technically, hopping and bounding are single leg training. Though the Bulgarian lunge is popular, it’s a bilateral exercise. When you perform single leg squats, while technically a unilateral movement, it’s easy to cheat and let the exercise give you a false sense of balance and strength. Therefore, here are some guidelines that I am confident most coaches want to know. None of the recommendations or changes I suggest will transform a program from poor to world-class, but I made a few mistakes when converting bilateral exercises to single leg, thinking it would be easy. In fact, going to single leg without doing your homework usually leads to disappointment.

The bilateral deficit, possible neurophysiology and motor skill acquisition, is just the same false promise with a different spin to it. Exercises are the least important variable in training—success is usually managing loads and making sure you don’t do anything stupid. Countless programs have used old-school systems that don’t include any single leg training, and a few programs today succeed without a single barbell. Those extremes are welcoming, but being different just to look innovative isn’t worth it. Here are a few nuggets I stole from coaches with whom I have worked side by side.

• Asymmetry or imbalances still exist, even with single leg training. Due to the conservative training loads, we will always see a few athletes who need to do a lot of added homework on one side, usually due to past injuries.
• Not all bilateral exercises convert well to single leg training, so be warned. One example is single leg squatting with external loads, which creates a bizarre co-contraction to muscle groups that should be relaxing or firing differently when in less static scenarios.
• It’s okay to do balance training with single leg exercises, but don’t expect a strength benefit. Remedial balance work is just creating comfort for new exercises that may be foreign to the athlete. Elderly patients are interesting subjects, but their outcomes are not interchangeable.
• When making a single leg exercise for a primary global strength solution, we need to be careful with loading just as much as with two legs. Overload that is extreme is still risky, even if the lumbar spine is given a small break. Don’t just look at compression and shear stress; look at contractions and how internal strain increases risk.
• Single leg strength isn’t as important as reducing redundant mechanical overload. Replicating or sport-specific training hasn’t helped the upside, and it’s likely the cause of too many of the injuries.

I could go on, but coaches need to be realistic with their expectations for single leg training. You can be great at lunges and step-ups, but they are small cogs to reducing non-contact injury. Expecting single leg training to stop the ACL problem in the NFL is wishful thinking. A combination of exercises matters, including bilateral exercises. The bilateral deficit doesn’t matter much when most soccer athletes can’t do a full Nordic hamstring exercise on their own.

Be aware that not all #bilateral exercises convert well to single leg training, says @spikesonly. Click To Tweet

When I see the single leg options for reps by players lose challenge, then a case for absolute methods may be in order. Most of what I see with spinal loading comes from back pain information, such as lumbar pathology. Risk can show up more with intensive plyos, given the fact it’s easier to have a kid jump off a tall box than to squat heavy with two legs.

What I Have Changed and Why

What really prompted me to add more single leg training and load the bilateral options heavier was the work of many of the coaches from Poland and Switzerland. Local coaches around the corner and in the U.K. made me rethink barbell options and small changes to exercise selection. Those with no access to even a weight room made me think about overload and repetition work. The variety of programs that get results is fascinating, and coaches who are adaptable in their training based on circumstances are also always fascinating.

I didn’t get interested in Bulgarian squats because I had inconsistent access to benches, a stark reality for those at small colleges and high schools. If I had to summarize what most coaches should change in their program, it would be the following three elements:

• Technique and refinement of biomechanics
• Anatomical personalization of exercises
• Unloading joint stress and distribution of workload

I am sure other variables and methods have changed in your training program or that of other coaches, but for me the research and practice weren’t locked away in a secret vault. Illustrations of these exercises exist in books from long ago when photography was seen as a luxury, so we should be a little ashamed we are back to single leg training again. Going full circle isn’t really progress, it’s just a long trip on a treadmill going nowhere.

Overall, I have decreased the volume, slightly reduced the intensity, and made more effort to choose what works best for the individual with supplementary lifts. Again, if you work with large or small groups, chemistry and energy are benefits of not individualizing the training. A less-experienced trainee can watch superior technique, and the efforts of a few may inspire the rest. Creativity and personality transform science into results with applied settings.

Not All Roads to Rome Are the Same

The old saying that all roads lead to Rome is true, but some roads are better than others. I view single leg training as the foundation, but bilateral training is timeless as the body hasn’t changed much over the last hundred years. Strength in the lower body is essential, but how a set of dumbbells or barbells are loaded on one or two legs isn’t going to make athletes radically better or worse when the sport itself has such an impact on results.

I find that a mix of single and double leg training is better than either one alone, says @spikesonly. Click To Tweet

Create a program that is safe, repeatable, effective, and rewarding. It’s likely that nobody else will experience the same environment as you do, since variables are dynamic in nature. I have used both single and double leg training, and find that a mix of the two is better than either direction alone.

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