Bilateral and unilateral exercises are regular exercises found in every program specified by being double-limbed or single-limbed. Try not to get too caught up on the words bilateral or unilateral as your trainer (hi, it me!) likely won't name exercises "bilateral press" or "unilateral deadlift". These words are simply further descriptions on what is involved within your program.
Bilateral exercises are movements where you are using both limbs equally to produce force and complete the exercise. Examples of this are squats, bench press, deadlifts, or basically any exercise that does not say or require the exercise to be single-arm, single-leg, or alternating.
Bilateral exercises can be seen as compound exercises, accessory exercises, or isolation exercises. You'll notice in training programs, most of your main movements are compound exercises such as squats, bench press, overhead press, deadlifts, and rows, which are all bilateral exercises.
Unilateral exercises are movements performed single-sidedly. Examples of this are alternating step-ups, single-arm rows, singe-leg hip thrusts, or any exercise specified by single-sided or alternating.
Unilateral exercises can be used as main movements, accessory exercises, or isolation exercises. Unilateral exercises are often used to improve muscle imbalances, increase strength and endurance, and enhance activity-specific movements. For example, trail runners will likely have more single-sided exercises due to the nature of running. For another example, if someone's right arm is much stronger than their left due to playing tennis for years, we might program more single-armed exercises to encourage the left side to strengthen and to minimize the right side taking over in a bilateral upper body exercise.
Bilateral + Unilateral
Both types of exercises are important for a well-rounded training program. Only doing bilateral exercises can limit you on how much you improve muscular imbalances. On the flip-side, only doing unilateral exercises can limit you on how much strength you build in your bigger lifts (squats, bench press, deadlifts, etc.).
Ultimately, following a program created by a reliable personal trainer will allow you to make the most of your abilities.
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