5 New Reason to Train on One Leg
Single-leg exercises have become a staple in many strength and conditioning programs:
1. They allow athletes and bodybuilders to continue training around an injury.
2. They correct left-right strength and size asymmetries.
3. They improve general balance and proprioception.
4. They’re similar to athletic movements such as running and bounding and therefore have a strong motor carryover to sport.
When you dig a little deeper, there are even more hidden benefits that make single-leg exercise a powerful training tool.
More Explosive Power
Explosive power training has long been considered the exclusive jurisdiction of the bilateral (two-limbed) lifts. Heavy, complex movements like barbell squats, deadlifts, and presses stimulate the growth of cellular proteins. Lighter, ballistic strength exercises like barbell cleans and plyometric drills improve neuromuscular output, timing, and efficiency.
But that doesn’t mean single-leg exercises don’t have a seat at the power-development table. Unilateral exercises, which are performed from a small base of support and present a high degree of sensorimotor challenge, have been shown to improve Rate of Force Production (RFD), one of the most important factors that contribute to overall power output.
RFD is the physiological equivalent of a race car’s 0-60 mph time – it measures how long it takes a muscular contraction to get off the starting line before hitting peak levels of force production. RFD is typically divided into two-phases: The initial onset stage, which measures how quickly you can initiate a voluntary contraction, and the late stage, which measures terminal velocity.
Traditional bilateral resistance and/or explosive exercises improve RFD by developing the speed and amplitude of commands being generated from the pool of motor neurons in our brain. In other words, heavy-loaded exercises are excellent tools to improve your ability to generate outgoing (efferent) messages from “central command” to working muscle tissue.
Unilateral exercises, on the other hand, improve RFD in a somewhat reverse manner. The small base of support created by having only one foot on the ground at a time stimulates the pool of motor neurons at our spinal level (afferent), increasing their contribution relative to the overall force development equation. These types of improvements can be thought of as forcing “outside-in” adaptations, rather than traditional “inside-out” ones.
Although the research in this area is not as clear as we’d like it to be with regard to the exact mechanisms by which this occurs, we know that sensorimotor exercises improve RFD through some combination of improved motoneuron recruitment, firing frequency, and/or synchronization patterns in a way that’s just different from the way heavy resistance training does.
None of this is to say that you should ditch bilateral lifts in favor of unilateral ones; heavy bilateral lifts should always form the foundation of your power program. However, unilateral exercises may make for a far better, more response-specific power exercise option than they’re typically given credit for, especially in terms of improving early stage contractile power.
There are no clear-cut rules to maximize the power-enhancing properties of the single-leg lifts, but here are a few thoughts. First, single-leg deadlifts, single-leg squats, and strict step-ups are the most logical resistance training exercise choices, providing the smallest possible base of support and requiring the greatest proprioceptive response.
Second, using an offset load – holding a dumbbell or kettlebell on the opposite side of your working leg – seems to make sense. Asymmetrical loading increases rotational torque on the body, which in turn increases the balance demand and stimulates a stronger neural response.
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