Unilateral training is an often-overlooked approach to fitness programming that can be a game-changer for your strength training goals. When you engage in unilateral strength training, you focus on training one limb at a time, instead of using both in tandem.
Incorporating unilateral training in your fitness regimen can help correct muscle imbalances, create more symmetry and functional strength, and enable you to perform daily movements more effectively. They also provide the added benefit of increased core activation and reduce the chances of injury.
While bilateral training has its place in a well-balanced program, adding unilateral training can supercharge your strength gains like never before.
Unilateral training vs. bilateral training
Bilateral movements use both limbs in unison to produce contractions and generate force to move a load. Examples of bilateral movements in daily life may include lifting a heavy box from the floor, squats, or push-ups.
On the other hand, unilateral movements utilise each limb individually to perform a required movement pattern. For example, step-ups, pistol squats, and single-leg Romanian deadlifts are examples of unilateral exercises.
Most of the exercises performed in a gym are bilateral. However, most activities of daily living include unilateral movement in some form. For example, when you walk or climb stairs, you’re using one leg at a time to move forward.
Similarly, when you’re opening a car door while carrying a bag of groceries, your body utilises unilateral movements to complete the action. Unilateral training helps you build the necessary neural connections to execute these fundamental movement patterns.
Benefits of unilateral training
Our bodies need to maintain a balance between muscular strength and synergy to produce efficient movement patterns. This is known as reciprocal inhibition, where muscles around a joint shorten and lengthen simultaneously to execute a movement. When we have muscular imbalances, certain muscles may compensate and pick up the slack for others, leading to movement dysfunctions.
Additionally, all of us have a dominant (stronger) and non-dominant (weaker side). When we do a challenging bilateral movement, one side often does more work than the other. This leads to unequal strength building and overuse injuries. It is compounded if one side/muscle group is injured, causing additional movement impairment.
This is why you often have to lift lighter weights when you’re unilaterally working a muscle group. While bilateral exercises enable you to lift heavy and build maximum strength, unilateral exercises push you to be more mindful of your muscle imbalances and work slowly to create a more symmetrical body.
What is bilateral deficit?
Bilateral deficit refers to the phenomenon where the total force created by both limbs working in unison is lower than the total force created by each limb unilaterally.
It can be a result of multiple factors, including inhibited neural activation, faulty muscle recruitment patterns, and differences in coordination between the dominant and non-dominant sides.
Bilateral facilitation, on the other hand, is the phenomenon whereby the maximal force produced during bilateral contractions is greater than the total force created in unilateral contractions.
Addressing muscular imbalance requires a multifaceted approach to improve the cumulative strength and coordination between limbs when they are used together. Unilateral exercises can help identify and assess any potential imbalances and muscular dysfunction, allowing you to introduce corrective strategies aimed at achieving optimum muscle recruitment and neuromuscular coordination.
Unilateral training and cross-education of muscle fibers
Cross-education refers to the phenomenon where unilaterally training one side of the body indirectly stimulates and enhances motor output (skill and force generation) of the same muscles in the opposite, untrained limb. Also known as the contralateral strength-training effect, this phenomenon was first reported in 1894 in a study conducted by the Yale Psychological Laboratory and has been studied extensively for its role in treating muscle impairments.
Simply put, if you have an immobilised limb due to strain or injury, training the same (homologous) muscles in the non-injured limb can preserve muscle strength, size, and motor function in the immobilised limb. This makes unilateral training especially beneficial for individuals with muscular imbalances and dysfunction.
According to a study conducted by Manca et. al, cross-education is primarily caused due to neurological mechanisms such as mirror illusion and can be accelerated by the use of eccentric contractions and high-intensity training. Due to its multiple benefits, cross-education is widely used in the treatment of orthopedic conditions and sports injuries.
Additionally, the principle of specificity states that with time, the human body adapts to the demands imposed upon it. Unilateral training can enhance the ability of the central nervous system for motor-unit recruitment leading to an improvement in force production and muscular definition.
The role of unilateral training in enhancing sport-specific performance
Most high-intensity athletic movements that require a change of direction or speed rely heavily on the use of one limb at a time. Therefore, unilateral training can be used in conjunction with other performance-enhancement modalities to improve athletic abilities and reduce the risk of injuries.
To understand the benefits of unilateral training in sports, we have to better grasp the concept of complex training. Complex training (sometimes known as contrast training) is a training modality that combines a heavy resistance exercise with a high-velocity explosive movement performed one after the other. These contrast pairings lead to certain physiological reactions such as post-activation potentiation (PAP) which further enhance muscular strength and power.
When unilateral training is used as part of a contrast training program, the addition of PAP can lead to greater improvements in single-leg strength and power, enabling the athlete to adjust their speed or change directions with ease.
Additionally, studies have shown that unilateral conditioning activities such as split squats and drop jumps can improve performance across a wide range of athletic tasks, including sprinting, jumping, and swimming.
The study further suggested that the effects of PAP rely heavily on the principle of specificity, with vertical drop jumps enhancing vertical jump performance and horizontal drop jumps improving sprint ability and change of direction. Therefore, it’s important to tailor the workout program to suit the client’s performance needs.
Mike Boyle, the author of Advances in Functional Training writes, “Single-leg training will promote greater muscle growth and greater muscle strength because it works more muscles…Single-leg strength is specific and cannot be developed through double-leg exercises. Having only one foot in contact with the ground forces the hip structures, the abductors, and external rotators to stabilise against movement both in the frontal and transverse planes”.
Integrated core training through unilateral movement patterns
Unilateral exercises such as single-arm dumbbell rows and side plank variations can be beneficial for your core muscles as well. When you engage one side of the body, your deep abdominal muscles have to work harder to stabilise your spine and reduce unnecessary rotational movements. This leads to increased core activation, lumbar support, and pelvic stability.
Should you do unilateral movements first or after bilateral exercises?
Both bilateral and unilateral exercises are beneficial in different ways and need to be incorporated into a well-balanced training program. The order in which you perform these movements depends on your goals and programming needs.
If your main goal is to maximise strength gain, you can start with bilateral exercises that will allow you to lift heavy followed by unilateral movements to target specific muscles.
However, if your main goal is to address muscle imbalance, you can incorporate unilateral exercises into a corrective strategy to address specific muscular deficiencies. In such cases, you can start the routine with unilateral exercises, followed by bilateral movements. This will activate the stabiliser muscles and prepare your body for heavier bilateral lifts.
Additionally, you can use both unilateral and bilateral movements in a specific workout by combining them into a superset. For example, you can select a unilateral exercise such as box step-ups, and alternate it with a bilateral movement, such as squats.
Manca, A. et al. “Contralateral Effects of Unilateral Strength and Skill Training: Modified Delphi Consensus to Establish Key Aspects of Cross-Education.” Sports medicine (Auckland, N.Z.) vol. 51,1 (2021)
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