Unilateral training

Unilateral training loads one limb at a time.^{1Haff and Triplett (eds.), Essentials of Strength Training and Conditioning, 4th ed., p. 437.} Lower-body examples include lunges, step-ups and what the NSCA text calls the single-leg squat or Bulgarian split squat.^{1Haff and Triplett (eds.), Essentials of Strength Training and Conditioning, 4th ed., p. 437.} Trainers use these exercises to reduce side-to-side asymmetries and in rehabilitation.^{1Haff and Triplett (eds.), Essentials of Strength Training and Conditioning, 4th ed., p. 437.}

The bilateral deficit describes how, during a maximal effort with both limbs together, each produces less force than it would alone; training both limbs together reduces that gap.^{2Zatsiorsky, Kraemer and Fry, Science and Practice of Strength Training, 3rd ed., p. 73.}

In practice

• Weaker, untrained and injured clients tend to show a bilateral deficit, and unilateral work may help them build strength.^{1Haff and Triplett (eds.), Essentials of Strength Training and Conditioning, 4th ed., p. 437.} The NSCA describes bilateral facilitation in stronger, trained clients and advises against unilateral methods as their way to develop strength.^{1Haff and Triplett (eds.), Essentials of Strength Training and Conditioning, 4th ed., p. 437.}
• Unilateral work offers specificity for one-sided daily and sport tasks and challenges trunk stabilizers more than bilateral work.^{3Schoenfeld and Snarr (eds.), NSCA’s Essentials of Personal Training, 3rd ed., p. 299.}
• Expect loads to change when switching versions, such as barbell bench press to dumbbell bench press, and teach technique before setting the training load.^{4Schoenfeld and Snarr (eds.), NSCA’s Essentials of Personal Training, 3rd ed., p. 418.}
• Training one limb also increases strength in the untrained limb, known as cross-education, which points to a neural contribution to strength gains.^{5Schoenfeld and Snarr (eds.), NSCA’s Essentials of Personal Training, 3rd ed., p. 90.}