Effect of Lower Limb Neural Mobilization on Selective Neuromuscular Variables and Calf Muscle Thickness in Elderly Population With Sarcopenia

Sarcopenia is a progressive and generalized skeletal muscle disorder associated with aging, characterized by a decline in muscle mass, muscle strength, and physical performance. It is increasingly recognized as a major contributor to frailty, disability, hospitalization, and reduced quality of life among older adults. With the global rise in life expectancy, the prevalence of sarcopenia is expected to increase substantially, posing significant challenges to healthcare systems and caregivers. The condition is multifactorial in nature, involving complex interactions between biological aging processes, reduced physical activity, hormonal changes, chronic low-grade inflammation, nutritional deficiencies, and neuromuscular degeneration. Among these contributing factors, impairments in the neuromuscular system have gained increasing attention, as they play a crucial role in determining muscle function, coordination, and overall physical performance in elderly individuals.

Aging is associated with structural and functional changes in both the central and peripheral nervous systems. There is a gradual loss of motor neurons, resulting in a reduced number of motor units, as well as remodeling of remaining motor units through collateral reinnervation. Although this compensatory mechanism may initially help maintain muscle function, it eventually becomes insufficient, leading to decreased motor unit firing rates, impaired neuromuscular transmission, and reduced efficiency of muscle activation. Additionally, peripheral nerves undergo age-related changes such as reduced nerve conduction velocity, decreased elasticity, and increased susceptibility to mechanical stress. These neural alterations can contribute to impaired coordination, delayed reflex responses, and decreased proprioceptive input, all of which are essential for maintaining balance and preventing falls. Consequently, the decline in neuromuscular function is a critical component of sarcopenia and significantly impacts the functional independence of older adults.

The lower limbs are particularly affected in sarcopenia, as they are responsible for weight-bearing activities, locomotion, and postural control. Among the lower limb muscle groups, the calf muscles, comprising the gastrocnemius and soleus, play a vital role in maintaining upright posture, generating propulsive force during gait, and stabilizing the ankle joint. These muscles are essential for activities such as walking, standing, climbing stairs, and responding to balance disturbances. A reduction in calf muscle thickness is commonly observed in elderly individuals with sarcopenia and is associated with decreased muscle strength, impaired mobility, and increased risk of falls. Measurement of calf muscle thickness using ultrasound imaging provides a reliable and non-invasive method to assess muscle morphology and monitor changes over time, making it a valuable outcome measure in clinical and research settings.

Falls are one of the most serious and common consequences of sarcopenia in the elderly population. They are a leading cause of injury, fractures, hospitalization, and mortality among older adults, and often result in a cycle of fear of falling, reduced physical activity, and further functional decline. The risk of falls is influenced by multiple factors, including muscle weakness, impaired balance, delayed reaction time, sensory deficits, and environmental hazards. Among these factors, deficits in neuromuscular function play a central role. Static balance, defined as the ability to maintain a stable posture while standing without movement, is a fundamental component of postural control and is essential for preventing falls during daily activities. It requires the integration of visual, vestibular, and somatosensory inputs, along with appropriate motor responses to maintain equilibrium. Impairments in static balance are commonly observed in individuals with sarcopenia and are strongly associated with an increased risk of falls.

Ankle muscle strength is another critical determinant of balance and fall prevention. The ankle joint is responsible for executing rapid and precise adjustments to maintain stability in response to external perturbations. The ankle strategy is often the first line of defense in maintaining balance during small disturbances. Weakness in the ankle dorsiflexor and plantar flexor muscles can compromise this strategy, leading to instability and increased reliance on less efficient compensatory mechanisms such as hip or stepping strategies. Therefore, improving ankle muscle strength is essential for enhancing postural control and reducing fall risk in elderly individuals with sarcopenia.