Recently there has been a growing interest in the athlete training world about the value of single-leg (unilateral) training. The question is if it is valuable to do exercises on one leg (lunges, split squats, etc.), or if doing only double-leg (bilateral) exercises, such as back squats, is most beneficial. There are many reasons that make single-leg training extremely valuable to athlete training. But first, think about this idea: almost everything athletes do is on one leg, so why wouldn’t we train single-leg exercise? Running, jumping, kicking, pitching, serving, skating, throwing, and the list goes on. All of these involve using one leg. There are so many reasons to train single-leg movements to improve athlete safety and performance.
As the late strength coach Charles Poliquin said, “You can’t fire a cannon from a canoe”. What this means is that if we do not have a stable base, we cannot create powerful movements. For example, if a soccer player does not have good single-leg stability, then they won’t be able to kick the ball with much power and accuracy. Training single-leg exercises is essential for developing strong and stable bases.
One of the biggest goals of athlete training is preventing athletes from getting injured. If an athlete does exclusively double-leg training, then in a game they encounter one of many single-leg movements that I mentioned before, how will their body respond? To keep athletes safe, we need to train them in patterns that they move in during their sports.
Something that often happens during double-leg movements is one side of the body will compensate for the other weaker side. This causes one side to develop more than the other side, which can lead to muscle imbalance and increased risk of injury on the weaker side. These things can easily be avoided by training single-leg exercises. It literally makes compensating impossible, as one side is taken completely out of the equation. Not only does this decrease injury risk, but it also has clear benefits in sports. One example is a soccer player being able kick the ball powerfully using both legs rather than being limited to only their dominant side.
One difference between single-leg and double-leg movements is how much weight is being loaded and where it is causing pressure. For example in a back squat, the weight is loaded completely on the spine, and this can cause lots of stress on the spine at heavier weights. Well if an athlete performs any kind of single-leg squat, we are essentially able to use half the weight, meaning half the load on the spine. Additionally, many single-leg movements allow the weight to be held in an athletes hands, taking the load completely off the spine. Overall, this makes them much safer.
Increased Strength Gains
Continuing from the idea reduced spinal load, this allows us to increase weight while still staying safe. It has been shown that athletes are able to use 60% of their double-leg weight while performing single-leg movements, primarily because of the decreased spinal load. This means we can use more than twice the weight with the same spinal load as a similar double-leg movement. There is also evidence showing that muscles perform worse while using both sides of the body verses one side (called bilateral deficit).
It is clear that single-leg movements have many benefits for athletes. Although double-leg movements should not be completely removed, single-leg movements should be a significant part of any athletes training program.