Bilateral facilitation describes a phenomenon where engaging one side of the body or brain improves the activity or performance of the other side. While some situations exhibit a “bilateral deficit,” where individual limb forces sum to more than a combined bilateral effort, bilateral facilitation represents the opposite effect. It indicates enhanced strength or coordination when both sides work together.
How the Brain Coordinates Bilateral Actions
The brain orchestrates bilateral actions through intricate communication between its two hemispheres. A major pathway for this communication is the corpus callosum, a large bundle of nerve fibers located in the middle of the brain. This structure acts like a bridge, allowing nerve signals to move between the left and right sides of the brain, coordinating senses, movement, and cognitive functions.
Sensory information received by one hemisphere is often shared with the other, demonstrating the importance of this interhemispheric communication. For example, when you type, sensory input from your right hand travels to the left side of your brain, and this information is then shared with the right side via the corpus callosum. This cross-brain communication allows signals from one hemisphere to enhance activity in the other, which is foundational to bilateral coordination.
The Role of Bilateral Facilitation in Everyday Movement
Bilateral facilitation plays a significant role in many common activities and motor skills, contributing to overall motor efficiency and coordination. In activities like walking, jumping, or riding a bike, both sides of the body work together in a coordinated manner. This synchronized movement is often more powerful or efficient than if each side were to act in isolation.
For instance, when performing bilateral exercises such as squats, bench presses, or deadlifts, both arms or legs work in unison to move a given load. This combined effort allows for heavier weights to be lifted and greater muscle recruitment, leading to enhanced strength gains compared to unilateral movements.
Utilizing Bilateral Facilitation for Recovery and Improvement
Bilateral facilitation finds practical applications in physical rehabilitation, athletic training, and skill development. In rehabilitation settings, particularly for stroke survivors, bilateral training is used to help restore motor function in an affected limb. The premise is that simultaneous movements of the unaffected limb can facilitate the performance and recovery of the weakened limb through neural coupling effects.
Various bilateral arm training (BAT) techniques exist, including bilateral functional task training and bilateral arm training with rhythmic auditory cueing. These methods aim to activate similar neural networks in both hemispheres, promoting neuroplasticity and cortical repair. While some studies show that unilateral and bilateral training can have similar effects on upper limb function, bilateral training may be more effective for increasing upper limb strength and improving movement quality. This intentional engagement of both sides can enhance motor learning, improve strength, and aid in neurological recovery.