Effect of Inspiratory Muscle Training on Diaphragm and Ab-dominal Wall Muscle Thickness With Fatty Liver Density in Elderly Women: A Randomized Controlled Trial

1. Introduction The aging process leads to various impairments in multiple physiological systems, including the musculoskeletal and respiratory systems. One of the primary consequences of this process is the decline in overall muscle strength, which directly affects an individual's functional capacity and ability to perform daily living activities. Although this reduction in muscle mass and strength is not directly associated with any specific disease, it becomes more pronounced in elderly adults with health conditions that limit mobility. Respiratory muscle weakness alone is considered a significant limiting factor for physical fitness and may lead to clinical outcomes, including impaired lung function, reduced muscle strength, and dyspnea.

Previous studies have reported that physical exercise provides a wide range of benefits for elderly adults, including improvements in functional capacity, reductions in infection rates, enhanced cardiovascular fitness, improved muscle fiber quality, and overall enhancements in quality of life. Aerobic exercise has been shown to exert systemic benefits, including improvements in respiratory muscle strength. Moreover, regular physical activity induces both local and systemic anti-inflammatory responses, offering protective effects against age-related chronic inflammatory pathologies (Silva et al., 2011, Can et al., 2019).

In this context, improving respiratory function through targeted interventions is vital for maintaining independence and decreasing healthcare burdens in aging populations. In recent years, IMT has gained increasing attention due to its dual role in enhancing athletic performance and improving functional capacity in elderly adults. IMT is a resistance training approach involving moderate-intensity respiratory loading, typically at 40-60% of maximal inspiratory pressure. It is performed over short durations while yielding significant improvements in muscle strength and endurance. Home-based protocols generally consist of breathing sessions conducted twice daily, five to seven days per week.

The practicality and safety of these home-based programs make IMT particularly suitable for elderly populations, including those with mobility restrictions. IMT has been reported to lower blood pressure in elderly adults with systolic hypertension , improve cardiac autonomic function, reduce sympathetic overactivity, and enhance vagal tone at rest in individuals with obstructive sleep apnea. Furthermore, IMT has been identified as a non-pharmacological intervention that enhances diaphragm function, supports postural balance, increases trunk stability, facilitates venous return, and ultimately reduces the risk of falls.

With advancing age, several age-related changes occur in the respiratory system, including reduced chest wall compliance, decreased elastic recoil of the lung parenchyma, diminished respiratory muscle strength, and a blunted response to gas exchange abnormalities. These alterations are associated with decreased exercise capacity, impaired walking performance, and reduced quality of life in elderly adults. The decline in respiratory muscle function renders elderly individuals more vulnerable to disease and disability; therefore, strengthening these muscle groups is crucial for reducing the risks of morbidity and mortality. Despite this, respiratory-specific exercise strategies, such as IMT, remain underutilized in geriatric health promotion efforts.