Regardless of the debate about back squats and single leg squats every fitness professional and strength and conditioning coach will agree that both exercises and their variations are effective at developing leg strength, mass, power, etc….. Also, regardless of what side of the fence you are on regarding the squat debate, I think there is a time and a place for both exercises, but I will argue that there is always a time and a place for single leg strength when dealing with athletes that are performing their respective sports on foot (McCurdy, Langford, Doscher, Wiley, & Mallard, 2005).
Bilateral squatting does not induce nearly the stabilizing stimulus to the lower body that unilateral squatting does, and we can all appreciate the fact that most sports require the ability to exert force through single leg movements more often than bilateral movements. In fact, how many sport specific movements are performed bilaterally? The first one that comes to mind is the vertical jump, but when you think about single leg movements, many more sport specific movements come to mind. Oftentimes when working with someone who is particularly strong in the bilateral squat, if you get them on a single leg there stability, strength, and power dissipates. When so many sport specific movements occur from a single leg, this presents an obvious problem. This lack of stability, strength, and power on a single leg is a recipe for disaster on the field of play performance-wise and injury-wise.
When it boils down to it, professionals of this field simply need to swallow their pride on this issue and agree that there are benefits to both. Variations of both unilateral and bilateral squats should be in every program. One exercise isn’t necessarily better than the other, there is just good assessment of your athletes and good programming.
McCurdy, K., Langford, G., Doscher, M., Wiley, L., & Mallard, K. (2005). The Effects of Short Term Unilateral and Bilateral Lower Body Resistance Training on Measures of Strength and Power. Journal of Strength and Conditioning Research , 9-17.