Two Legs or One Legs? Bilateral or Unilateral? That is the question that is being viciously debated across the entire fitness industry. From high school strength coaches to the likes of Mike Boyle, everyone has an opinion and everyone is sharing it.
So I figured I would exercise my first amendment right and share mine as well. But more specifically also discuss the bilateral deficit.
Okay first to address the unilateral versus bilateral debate.
I am not an all or nothing person when it comes to training philosophy (cake? now that is a different story). I like to use Bruce Lee's quote which reads, "Absorb what is useful, discard what is useless, and ddd that which is essential, that is your own," to describe my training philosophy.
I believe that we should try to take the good and leave the bad from each person or idea we encounter. I think that unilateral training, both in the lower and upper body, is a valuable training tool. But like with any tool it is useless if you do not understand how to use the tool and when to use it. I have the same mindset toward any training technique or methodology and that goes for bilateral lifting as well.
I personally do not favor one over the other. I try to program a fair amount of each for my own programming, though I do end up having slight more volume in the bilateral section. My clients balance between the two depends on what I see during their initial and subsequent FMS evaluations. I tend to like to see a certain amount of symmetry in each leg during a unilateral exercise before I progress them to a bilateral version. This insures that any imbalance or asymmetry has been for the most part cleared up and is no longer a concern.
But again I think bilateral and unilateral exercises have a place in everyone's program. The frequency, volume, and intensity of the exercises is dependent upon the individual's training experience, postural imbalances, and their particular weak movement patterns.
Now to get to a more specific topic regarding the bilateral versus unilateral debate.
The bilateral deficit (BD) is a well documented phenomenon that describes the lower muscle activation observed during bilateral exercises versus unilateral exercises. Meaning that if you were to perform a leg extension with your right leg and then your left leg and added the total amount of muscle activation in each leg together it would be larger than the muscle activation observed when the leg extension was performed with both legs simultaneously.
A study published in the Journal of Applied Physiology performed by Vandervoot, Sale, and Moroz found significantly less integrated electromyographic activity was recorded from the quadriceps muscles of the dominant leg during bilateral compared with unilateral maximal voluntary contractions. The authors noted, "Bilateral strength was significantly lower than the summed unilateral value under isometric conditions."
Okay so we know that their is benefits for performing both unilateral and bilateral exercises. We have learned that predominance though towards bilateral lifting is not necessarily the best approach to training. This is due to the fact that unilateral exercises allow for a reduction of spinal loading and reduced injury potential.
But now that we know that there is a reduction in muscle recruitment during bilateral exercises, the question must be asked is their a possible way to prevent this down regulation in muscle activity. Perhaps their is a way to get the same recruitment patterns we see during unilateral exercises during the performance of bilateral variations.
This is exactly what one professor at the University of North Carolina wanted to find out. Peter Vint put together a study in which he had each subject perform three maximum effort key-pressing trails under four conditions including: unilateral single finger efforts, unilateral multiple finger efforts, simultaneous bilateral and decoupled bilateral single-finger efforts, and simultaneous bilateral and decoupled bilateral multiple finger efforts. The difference between the simultaneous and decoupled bilateral efforts were that during the decoupled exertions subjects initiated key-pressing force with fingers on the non-dominant hand; then after a short time subjects added fingers on the dominant hand. So that though the decoupled exertions began asynchronously, subjects eventually developed and maintained key-pressing forces from fingers on both hands throughout the rest of the trial.
What Vint found was pretty interesting and may offer a solution to the bilateral deficit. Vint found that compared to simultaneous bilateral exertions, temporal decoupling improved force production by 8.7% and 7.3% during single and multiple finger key-pressing.
What this means for us in the weight room is that it might be worth our while to experiment with the same procedure prior to performing a bilateral movement. Meaning we begin performing an exercise using one limb and finish the exercise using both limbs.
For example, if you were going to perform a bench press routine it might be possible to decouple the deficit and increase bilateral muscle activation by performing unilateral DB bench press prior to your sets on the barbell bench press.
I have been experimenting with this process myself and it seems to have somewhat of an effect. I was able to do get 275 pound on the bench press for 4 sets of 5 reps on friday something I have been unsuccessful in doing in prior training sessions.
I am not saying this should become a standard operating procedure every time you wish to perform a bilateral movement, but I definitely think it might be worthy of a place in the training tool box.
I definitely think it is worth giving at least one attempt during your next training session. What have you got lose?
Vandervoort, A., Sale, D., & Moroz, J. (1984). Comparison of motor unit activation during unilateral and bilateral leg extension. Journal of Applied Physiology, 56, 46-51.
Vint, Peter F., Susan M. Thompson, and Donovan A. Shaw. "TEMPORAL DECOUPLING IMPROVES FORCE PRODUCTION DURING SINGLE- AND MULTIPLE-FINGER, BILATERAL KEY-PRESSING TASKS."TEMPORAL DECOUPLING IMPROVES FORCE PRODUCTION DURING SINGLE- AND MULTIPLE-FINGER, BILATERAL KEY-PRESSING TASKS. American Society of Biomechanics, n.d. Web. 23 Dec. 2012.
GO AHEAD GET TO THE GYM AND TRY IT FOR YOURSELF!
Drop me a comment below about your application of this technique and how you felt about it!