Single Leg Training Research
For sake of clarity I’ll start by stating that I think both bilateral and unilateral training has a place in a well-rounded performance program. Trapbar deadlift and goblet squat are staples in our strength programming for developing athletes. ⠀⠀⠀⠀⠀⠀⠀⠀⠀
With that said, it seems that everyday we are seeing more and more evidence for the prioritization unilateral training over bilateral training.
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More research has recently demonstrated the power of the bilateral deficit and the superiority of unilateral lower body strength and plyometric drills for strength development and rate of force production when compared to traditional bilateral squatting.
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A study published in The Journal of Strength and Conditioning Research compared the effect of unilateral and bilateral plyometric training on single leg and double leg jumping performance and strength. They had unilateral jumping (hopping 🙄) and bilateral jumping groups perform the same total volume of plyometric training twice per week for 6 weeks and then tested Countermovement Jumps, Drop Jumps, Isometric Leg Press Strength and Rate of Force Development both bilaterally and unilaterally.
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Upon, looking at the results the researchers found that…
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“Unilateral plyometric training was more effective in increasing both single and double leg jumping performance, isometric leg press maximal force and rate of force development when compared with bilateral training.”
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A study published in The International Journal of Sports Physical Therapy compared barbell kinematics and muscle activation during bilateral and unilateral squat exercises. They compared three different types of squats: bilateral barbell squats, unilateral barbell squats with the free leg in front and unilateral barbell squats with the free leg behind.
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Researchers found that: ⠀⠀⠀⠀
“Unilateral squats with the same external load per leg produced greater peak vertical ground reaction forces than bilateral squats, as well as higher barbell velocity, which is associated with strength development and rate of force development, respectively.”
In summary, what both studies demonstrated was the power of the bilateral deficit. The research is representative of what we often see in that gym in that unilateral strength and power training can improve both unilateral and bilateral strength and power measures but it does not work the other way around. Structurally and neurologically we are unilaterally dominant creatures, designed to move in contralateral patterns with one limb at a time. By choosing training methods that are congruent with how our bodies are designed not only is it more effective but it also appears more efficient. Numerous studies, including the second one I referenced have found that we are able to achieve increased ground reaction forces and higher velocities with the same same external load per leg unilaterally as we can with bilaterally. This means higher motor unit recruitment and velocity of movement with less total load on the nervous system and spine. This may be especially important for athletes training with a history of back pain as they can pursue a training effect in the lower body without increasing training load on the spine.