If you've been avoiding dumbbells, unilateral training can spark a muscle to respond when traditional methods begin to falter. IFBB pro fitness competitor Stacy Simons faced such a problem and started including unilateral movements to break through training plateaus. "I used to teach Spinning, and I lost a lot of size in my hamstrings. I incorporated standing and lying one-leg curls in my regular leg workout, and these exercises helped bring my hams right back up."
If you suffer from an injury such as a broken leg or arm, you don't necessarily have to swear off exercise. With unilateral movements, you can still train the noninjured limb. Studies have even shown a "cross-transfer" effect, whereby the nontrained limb sees some strength benefits when the other limb is trained. Also, because the body is forced to compensate for the absence of one limb, new neural pathways are developed that can result in more muscle-fiber recruitment overall.
A less-obvious but still important benefit: Stacy finds that training unilaterally allows for better concentration on perfect form. "When you're using both arms or both legs, you may start losing your form when you begin to fatigue. Doing one at a time, you can watch in the mirror and focus more intently on staying strict." She particularly enjoys this benefit when doing dumbbell shoulder presses. Since she suffers from a condition called spondylolisthesis, the forward displacement of one vertebra over another, she finds it easier to lift one lighter dumbbell overhead than two 45-pound dumbbells.
Even if none of the above situations applies to you, don't write off unilateral training; these movements have a place in everyone's workout. Go ahead and stick with the old stand-bys if you wish, but mix up your training every once in a while by adding some of the seldom-used exercises shown here, like the leg press, calf raise or sissy squat. Whether you're shaping up a problem area or just seeking new stimulus for muscle growth, you'll find that working out unilaterally is a useful tool.
