Impact of Lower Limb Neural Mobilization on Neuromuscular Function and Calf Muscle Thickness in Elderly Individuals 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.

Traditional rehabilitation approaches for sarcopenia have primarily focused on resistance training, balance exercises, and nutritional interventions aimed at improving muscle mass and strength. While these interventions have demonstrated effectiveness, they may not fully address the neural components of muscle dysfunction. There is growing evidence to suggest that optimizing neural function can enhance the effectiveness of rehabilitation and lead to better functional outcomes. Neural mobilization is an emerging therapeutic technique that targets the peripheral nervous system and aims to restore the normal mobility and function of neural tissues. It involves the application of specific, controlled movements that promote the sliding and gliding of nerves relative to surrounding structures, thereby reducing mechanical restrictions, improving neural elasticity, and enhancing blood flow and axoplasmic transport within the nerve.

In the lower limb, neural mobilization techniques commonly target the sciatic nerve and its branches, including the tibial and common peroneal nerves. These nerves are responsible for innervating the muscles of the leg and foot, as well as providing sensory feedback necessary for balance and coordination. With aging, these nerves may become less mobile due to factors such as decreased tissue elasticity, prolonged inactivity, or degenerative changes in surrounding structures. Restricted neural mobility can lead to increased neural tension, impaired signal transmission, and reduced muscle activation. Neural mobilization techniques, such as slider and tensioner methods, are designed to restore normal nerve movement and improve neural function without causing discomfort. The slider technique involves simultaneous movement at two joints to promote nerve gliding, while the tensioner technique increases tension along the nerve pathway to improve its mechanical properties.

The present study aims to investigate the effect of lower limb neural mobilization on selective neuromuscular variables, specifically static balance, fall risk, and ankle muscle strength, as well as calf muscle thickness in elderly individuals with sarcopenia. This study is designed as a randomized controlled trial involving participants aged 60 years and above who meet the diagnostic criteria for sarcopenia. Participants will be recruited from community settings, outpatient clinics, or rehabilitation centers and will undergo a thorough screening process to ensure eligibility. Inclusion criteria include reduced muscle mass, decreased muscle strength, and impaired physical performance, while exclusion criteria may include severe cognitive impairment, neurological disorders, recent musculoskeletal injuries, or contraindications to physiotherapy interventions. Informed consent will be obtained from all participants prior to their inclusion in the study.

Baseline assessments will be conducted to evaluate all outcome measures. Static balance will be assessed using standardized clinical test which is single-leg stance test. Fall risk will be evaluated using validated tool, Timed Up and Go test. Ankle muscle strength will be measured using handheld dynamometry to quantify the force generated by the dorsiflexor and plantarflexor muscle groups. Calf muscle thickness will be assessed using ultrasound imaging to provide an objective measure of muscle morphology.

Participants will then be randomly allocated into an intervention group or a control group. The intervention group will receive lower limb neural mobilization in addition to OTAGO exercises, while the control group will receive only OTAGO exercises. Neural mobilization will be administered by trained physiotherapists using standardized protocols to ensure consistency and reproducibility. The intervention will be conducted over a period of 8 weeks, with sessions performed three times per week. Participants will be closely monitored for adherence, safety, and any adverse effects throughout the study period.

Following the intervention, post-assessments at week 4 and week 8 will be conducted using the same outcome measures as at baseline. Data analysis will involve comparing pre- and post 4th week and 8th week intervention values within and between groups to determine the effectiveness of neural mobilization. It is hypothesized that participants in the intervention group will demonstrate significant improvements in static balance, reduced fall risk, increased ankle muscle strength, and enhanced calf muscle thickness compared to the control group.

The expected results of this study are based on the premise that improving neural mobility can enhance neuromuscular efficiency. Neural mobilization may facilitate better nerve conduction, reduce mechanosensitivity, and improve the synchronization of motor unit recruitment, leading to more effective muscle contractions. Improved ankle strength is likely to contribute to better postural control and stability, thereby reducing fall risk. Enhanced proprioceptive input from the lower limbs may further improve balance and coordination. Additionally, increased muscle activation may stimulate muscle hypertrophy, resulting in increased calf muscle thickness.

In conclusion, this study seeks to explore a comprehensive approach to managing sarcopenia by addressing both neural and muscular components. By integrating neural mobilization into rehabilitation programs, it may be possible to enhance functional outcomes, reduce fall risk, and improve quality of life in elderly individuals. The findings of this study have the potential to contribute to the development of evidence-based interventions for geriatric rehabilitation and promote healthy aging in the growing elderly population.