Robert A. Panariello MS, PT, ATC, CSCS
Professional Physical Therapy
Professional Athletic Performance Center
New York, New York
During the past few years I have made a number of national and international platform presentations at both Strength and Conditioning (S&C) and Physical Therapy (PT) Conferences. While presenting at these conferences I have also attended my share of presentations, including single-leg exercise lectures, and had numerous discussions on this topic with both conference presenters and attendees. Over this period of time I have also read many citing’s of single-leg exercise performance in both the literature as well as on the internet. In recent years, there appears to be a trend by many professionals to supersede traditional bi-lateral leg exercises (i.e. squat, deadlift, RDL, etc.) in favour of single leg exercises. To be clear, I am not stating that there is the addition of single-leg exercises to the athlete’s rehabilitation and athletic performance training programs, but the actual replacement of traditional bi-lateral leg exercises with single-leg training in the rehabilitation and athletic performance (weight room) program design.
During my conversations regarding this topic of rehabilitation and performance training program design philosophy, the most common responses I receive are something to the effect of “Single-leg exercise is more sports-specific than bi-lateral leg exercises as we run on one leg, skate on one leg, etc.” as well as “traditional bi-lateral lower extremity exercises place the low back at risk of injury”. To be totally transparent I personally am not opposed the inclusion of single-leg exercises in the rehabilitation and/or athlete’s training program design as this category of exercise, when appropriate, does provide benefits to both the patient and athlete. I myself, when applicable, will also institute single-leg activities with both the patients and athletes that I train. However, with that stated, the question remains if bi-lateral leg exercises should be removed from the rehabilitation and performance training environment? Prior to making the decision to discard bi-lateral leg exercises, the rehabilitation and strength and conditioning professional should review the advantages and benefits of bi-lateral leg exercise performance, some which will be the topic of this discussion.
Are all single leg exercises really single leg exercises?
During the process of selection from the single-leg exercise category for the athlete’s program design some professionals consider exercises such as the lunge, the Bulgarian Squat/Rear Foot Elevated Split Squat (RFESS), etc., single-leg activities. During the performance of these exercises one will note that both feet are in contact with a stable surface area. (As a side note, with regard to the “Bulgarian Squat”, during my time studying the science of S&C in Bulgaria with the National Weightlifting team under the supervision of their Head Coach Ivan Abadjiev, I did not witness, not once, the performance of a “Bulgarian squat” nor any other type of single-leg work being performed by any weightlifting athlete. The same may be said during my time studying at the Soviet Institute of Sport in the former USSR as well as my time studying in the former East Germany.)
During the performance of these types of “single-leg” exercises, although the emphasis of applied stress may be placed at a primary extremity i.e. the front leg, isn’t the secondary extremity i.e. the rear leg also sharing the applied load? Isn’t the rear leg also assisting in body balance and control during the exercise performance? So are these exercises truly single-leg exercises or are they also bi-lateral in nature? However, with a traditional bi-lateral exercise leg posture the body achieves a greater (wider) platform of stability. This enhanced stability allocates many advantages during weight intensity exercise and athletic performance. As an example, if the rear leg was eliminated as a pillar of stability from the split leg exercise performance resulting in a true single-leg exercise such as the pistol squat, could the same levels of exercise weight intensity possibility be utilized?
Are the exercises that are performed in the weight room really “sports specific”?
As previously indicated, many statements for the utilization of single-leg exercise performance includes the notion that these exercises are “sports-specific” as the examples commonly sited are activities such as running or skating that do comprise a period of single-leg support. However, conversely, it could also be stated that no exercise performed in the weight room is sports-specific. To defend this position it is important for the Rehabilitation and S&C Professional to acknowledge the distinct differentiation between the relationships of an athlete’s “athleticism” vs. the athlete’s level of “skill”. For example in review of the jump shot in the game of basketball two basic important factors occur, (a) the athlete must jump high prior to shooting the basketball and (b) the athlete must be able to effectively shoot the basketball at the peak height of the jump. The ability of the athlete to jump high is dependent upon their “athleticism” whereby successfully shooting of the basketball (scoring) is based upon their level of “skill”. As a basketball player trains in the weight room to improve the physical qualities that correlate to optimal basketball performance, this will often include an improvement in their vertical jump (athleticism) performance. However, one may also ask what also occurred in the weight room to enhance their ability to improve their shooting accuracy (skill)? The answer is likely nothing.
The weight room provides an environment to enhance the athlete’s physical qualities (strength, power, elastic abilities, and speed) in an attempt to improve athleticism. The S&C Professional does little if anything to enhance an athlete’s level of skill as that is the responsibility of the skills (head or assistant/position) sport coach. The athlete enhances their skill level by repetitively practicing the skills of the sport as well as those necessary for their specific team position of participation. In discussions with my good friend Derek Hansen, the protégé of world-renowned sprint coach Charlie Francis, Derek would remind me that Charlie would state that nothing in the weight room is anywhere close to the velocity and output of sprinting. The utilization of heavy load intensities was utilized by Charlie for “recruitment” purposes that may indirectly transfer to the track via a conversion/transition period. Charlie would always characterize his weight training programs as “general” strength work as specific strength work occurred during training on the track. He was also of the opinion that sport specificity did not exist, particularly when comparing an athlete’s training to competition as the athlete’s training is never completely specific to their competition efforts. Charlie was of the belief that the athlete needed a specific minimum number of competitions to prepare them for their peak race performance. He believed that 100m sprinters needed at least 6-8 races and 400m runners needed no less than 4-6 races for this preparation philosophy.
During the rehabilitation of a post-surgical rotator cuff in a throwing athlete one of the end stages of rehabilitation is the implementation of a long tossing program. Long tossing is a mechanism of enhancing the physical quality of strength in the athlete’s throwing shoulder/arm. How does successful long tossing enhance the pitcher’s strike to ball ratio/accuracy (skill) from the pitcher’s mound? In other words how do long tossing activities improve the pitchers proficiency in throwing strikes? It really doesn’t. Therefore, are these exercises as well as the exercises the athlete performs in the weight room really “sport specific”? I am personally of the opinion that they are not.
What about the “single-leg” statements that occur during the discussion of running and skating activities?
Certainly during running and skating there is a period of time where the athlete is supported on a single extremity. However, does this mean that the contribution of bi-lateral leg training is not an important contributor to this phase of the movement cycle? The running gait cycle comprises 3 phases, the swing, the float, and the stance phases. In review of a single leg during the running cycle, 60% of the cycle is spent with the foot off the ground (swing + float phases) and 40% of the cycle is spent with the foot is in contact with the ground surface area (Figure 1).
Since a minority component of the running gait cycle occurs with the foot in contact with the ground surface area, the athlete must take advantage of this brief ground contact time (stance phase) by placing as much force into the ground in the allotted period of time. Two of my mentors in the field of S&C, Hall of Fame S&C Coaches Al Vermeil and Don Chu have taught me this concept over 30 years ago. Their lessons in training were based on the fact that the greatest athletes in the world are the one’s that apply the greatest amount of force into the ground surface area in the shortest period of time. This concept has been documented in athletics and sprinting by many including Ralph Mann and Peter Weyand.
Other than sprinting during track and field competition, one would have to observe if most sports are dominantly played with each leg in an alignment in front of each other or are most athletic activities performed with the feet positioned at their hip width alignment or wider, the same foot alignment that occurs during traditional bi-lateral exercise performance. Most athletic activities also begin and end on two feet. This includes the start of a sprinting or running activity as well as jumping, blocking, skating, fielding a ground ball, throwing, swinging, cutting as in the instance when a football player “jump cuts”, and of course deceleration type activities such as landing from a jump. Since most athletic movements are initiated on two feet, optimal force must then be applied at the time of the initiation of movement via a bi-lateral leg posture.
Ice skating is another interesting reference often included in the “single-leg” discussion. In a research paper by Bracko, who identified and analyzed the different skating style characteristics of National Hockey League (NHL) forwards, the highest mean percentage of skating time spent by a NHL forward during participation in an NHL hockey game occurred on a two foot glide (double leg stance), more than any other type of skating position. In fact Bracko noted “The primary difference between a high and a low point scorer was that a high point scorer spent more time on the ice, and had a higher mean percentage of time spent in a two foot glide with and without a puck.” One may also inquire what is the position of the lower extremities and feet of arguably the most important player on the ice, the goalie.
What are the advantages of “traditional” bi-lateral leg exercise performance?
There are a number of advantages to the traditional bi-lateral leg exercises when compared to single-leg exercise performance. These advantages include, but are not limited to:
1. Exercise Weight Intensity (Load) – High weight intensity is required for the body’s adaptation to build strength, power, elastic abilities and speed. The more stable the foot (feet) and lower extremity position, the heavier the load that may be lifted. Heavier loads enhance the physical quality of strength, the physical quality from where all other physical qualities cultivate. Strength is also the foundation for the application of optimal levels of force. Heavier loads may be applied to the athlete during traditional bi-lateral lower extremity strength exercise performance such as the squat, RDL, and deadlift when compared to the weight intensities applied during the performance of these same or similar type exercises when executed on a single lower extremity.
Load is also very important in the recruitment of a muscle’s motor units (MU) as well as fast twitch (FT) muscle fibers resulting in a greater overall muscle fiber contribution and force output during lower extremity exercise performance. Heavier weight intensities will also enhance a muscle’s rate of force development (RFD) and ground reactive forces (GRF’s) as well as the development of soft-tissue structures such tendon and ligament strength (Davis’ law) and bone density (Wolfe’s law). Ask the athlete for their interpretation of the contribution of the musculature of the shoulders, arms, back, CORE, hips and legs when lifting a heavy weight as compared to the effort of lifting a lighter weight during the same type of exercise performance. There likely will not be any surprises upon hearing their response.
2. Velocity – Barbell velocity has been demonstrated to be a very important factor in the development of the physical qualities of power and speed. If this were not accepted why do so many coaches measure barbell velocity during training with tendo units and other similar types of equipment? Higher exercise performance velocities will occur with a bi-lateral exercise posture when compared to the exercise velocities generated during single leg exercise performance. During a specific exercise performance with the weight intensity remaining consistent, higher exercise velocities will assist to recruit more MU and FT muscle fibers as well as enhance RFD and GRF’s when compared to the same load lifted at lower exercise velocities.
An additional benefit of high velocity training is the effect upon the body’s joint co-activation index. This concept was taught to me years ago by Charlie Francis and Al Vermeil. At the time, the three of us were hired as consultants to work together with an NFL team. A simple co-activation index description, with regard to the weight room setting, is that slow-strength type movements are usually correlated with heavier weight when compared to the weight intensities of power movements performed at higher velocities. Time is not a factor when performing strength-type exercises. The slower exercise tempo associated with lifting a heavy weight results in joint stability as both the agonist and antagonist muscle groups of a particular joint work together simultaneously. Thus, the co-activation index of these two muscle groups working together to stabilize a joint during a strength exercise performance is close to, or at, a 1:1 ratio.
High-speed exercise movements for the development of power and speed are dependent upon a brief factor of time. These high-speed weight room exercise activities (i.e. the Olympic lifts) require an emphasis of high contribution from the agonist muscle group while the antagonist muscle group of the joint(s) must have as low a contribution to exercise performance as possible. This emphasized contribution of the agonist muscle group allows for a shift in the co-activation index in favour of the agonists resulting in optimal high-speed propulsion, as well as a fluid motion of the body in the desired direction of movement. Tudor Bompa has also exhibited that the highest skilled athlete’s have the ability to completely relax their antagonist muscle groups during movement and that rigid and rough movements are a result of poor coordination between the agonists and antagonists.
In the area of sport rehabilitation RFD, GRF’s and improvement in the co-activation index are criteria that need to be instilled in the athlete as well. Angelozzi has demonstrated that post-operative ACL reconstruction athletes restored their strength to 97% of their pre-injury strength levels at 6 months post-op. However, in the same period of time the RFD was measured to be only 63% of documented pre-injury levels. In fact it took approximately one year for the RFD to reach 90% of the pre-injury level. In the area of sports rehabilitation high-speed weight exercises should be implemented appropriately and without risk to the athlete, as soon as safely possible, to enhance both RFD, GRF’s, and to induce a proper co-activation index for optimal high speed athletic performance. Higher exercise performance velocity is another advantage for the incorporation of traditional bi-lateral lower extremity exercises.
3. Lower extremity exercise and foot position – Most athletic activities are not only initiated and conclude on two feet, but often occur with each foot positioned at hip width if not outside the alignment of the hips, not usually with one foot aligned in front of the other. Remember when your sport coach taught you/told you to assume an “athletic position”? Where was the alignment of your feet positioned? What is the athlete’s common foot position when applying force during blocking, tackling, wrestling, jump cutting, jumping, landing, and yes even skating? Which lower extremity posture of the common sports of participation i.e. football, basketball, baseball, soccer, golf, etc. provides the athlete with the base of support that optimizes both stability and force production, a posture with a single-leg support, a foot position in a straight alignment with each other, or a posture with the feet positioned at hip alignment or wider?
Performing traditional weighted bi-lateral leg exercises will result in low back injuries
“Performing traditional weighted bi-lateral leg exercises will result in low back injuries” is another response provided to me during the bi-lateral vs. single-leg exercise discussion. As previously discussed stress is necessary for adaption to occur. Hans Selve has demonstrated with his General Adaption Syndrome (G.A.S.) Model that stress must be applied to the body for the disruption of the homeostasis of the body and for supercompensation and adaptation to take place. Therefore, for an athlete to enhance the physical qualities required for athletic participation, unaccustomed levels of high stress must be applied to the athlete for this adaption to take place. Therefore, it may be stated for this adaptation to occur, regardless of the exercise performed, single leg or bi-lateral leg, applying unaccustomed yet appropriate high levels of stress (intensity) to the exercise performance will result in the exercise not being 100% safe for the athlete. Since unaccustomed high levels of exercise stress are necessary for adaptation (improvement) to occur, and these applied levels of stress place a risk to the athlete’s anatomy during the exercise performance, one may ask is there truly a safe exercise? All high-intensity weighted exercises (applied stress) have a risk component. Thus, the only phenomenon occurring with “safe” exercise performance is a wasting of training time as a truly “safe” exercise will not apply the necessary level of stress needed for supercompensation and adaptation.
Traditional bi-lateral leg work will apply stress to the low back i.e. back squat exercise, deadlift, RDL’s, etc., however single leg as well as the split leg posture exercise i.e. lunge, Bulgarian/RFESS, etc. place high levels of stress to the Sacroiliac (SI) joint which has been documented to be responsible for approximately one-third of all low back pain. Why is this SI-joint statistic ignored during the same bi-lateral vs. single-leg exercise discussion? The fact is that no exercise performed with an significantly applied load is 100% safe, as it is the talent and responsibility of the S&C Professional (the art of coaching) prescribing the exercises to be performed, as well as the appropriately prescribed exercise weight intensities and volumes (program design), that will assist to prevent injury.
One other notion to assist in the prevention of weight training injuries taught to me by my friends and mentors, Hall of Fame S&C Coaches Al Vermeil, Al Miller, and Johnny Parker is the preparation of the athlete prior to the ensuing participation in performance training. This concept is not implemented as often as a coach, parent, or athlete may like as often times the athlete is brought into the weight room, and whether the athlete is physically ready or not, they are required to immediately execute the prescribed training program design. If the athlete is to squat during training, shouldn’t the low back be prepared prior to the initiation of the squat exercise performance? The same may be said of the anatomy of the SI-joint prior to single- and split-leg exercise performance. Preparation of the anatomical area in question for the eventually application of high-stress training will also assist to reduce the risk of weight room injury and the discarding of a valuable exercise.
What about exercise fatigue?
It is well documented how excessive fatigue negatively impacts joint biomechanics and muscle force output during athletic performance. If this were not true then why does a pitcher have a pitch count? Excessive fatigue will also have a negative effect upon weight room exercise technique, force output, as well as enhance the risk of injury.
My friend and former competitive Olympic style weightlifter, now a coach and researcher with a PhD in biomechanics Dr. Loren Chiu raised an interesting concern during a conversation that occurred between us years ago. Dr. Chiu pointed out that during single-leg exercise performance, since each leg is exercised individually, twice the amount of repetitions per exercise set must be performed when compared to bi-lateral leg exercise performance. Therefore, fatigue due to exercise performance may more readily occur following prolonged single-leg exercise execution when compared to bi-lateral leg exercise execution. This is especially true with regard to the musculature of the body supporting the weight intensity as the time under tension is twice that when compared to bi-lateral lower extremity exercise performance i.e. a set of 10 repetitions in a bi-lateral lower extremity exercise becomes a set of 20 repetitions as each leg of a single-leg exercise must perform 10 repetitions independently. This matter of exercise fatigue should be an important consideration during the program design of single leg and split stance exercise performance.
I am not against the implementation and utilization of single-leg exercise performance during both the rehabilitation and performance training of athletes. I myself utilize this category of exercise performance, when appropriate, with both my patients and athletes. However, there are circumstances where bi-lateral leg exercises provide many superior benefits in both the rehabilitation and performance training setting when compared to the single-leg exercise performance. To underestimate these benefits and to exclusively perform single-leg or split-leg in-line posture lower-extremity exercises would be a disservice to both your patient and athlete.