Is the connectivity of the reticulospinal tract a predictor of strength gain and loss in older adults?

Sarcopenia is the progressive degenerative loss of muscle mass and strength associated with ageing. As part of the frailty syndrome, sarcopenia is a major obstacle to the independence, quality of life, and longevity of ageing adults, who are more likely to require hospitalisation and additional care. Age-related muscle weakness is the leading contributing factor to falls. Muscle mass has previously been the primary factor in defining sarcopenia; however, with ageing, there is a disproportionate loss of muscle strength compared to mass. It seems that muscle mass alone is not sensitive in finding individuals with functional limitations due to sarcopenia, thus it is plausible to suggest that sarcopenia might be a neurological process rather than a muscular one. The reticulospinal tract (RST) operates bilaterally, diverging in the spinal cord to innervate large groups of muscles in synergistic patterns. The RST is essential in gross force production and in a small sample of older adults, a positive correlation exists between grip strength and connectivity of the corticospinal and reticulospinal tract. This data set, implies that individuals who successfully maintain or enhance the connectivity of their RST (by being physically active) are stronger. However, this hypothesis remains untested. Therefore, the primary aim of this PhD is to examine whether the connectivity of the reticulospinal tract in healthy older adults is based upon their level of muscle strength? Understanding the connectivity of the RST in healthy older adults who have/are physically active compared to those that are not active, will provide important pilot data for investigating the connectivity of the RST in older adults with sarcopenia. If our hypothesis is correct, one prediction would be that lowered RST connectivity might predict those at risk of age-related muscle weakness and sarcopenia. The significance and impact of this research is that it will generate important new knowledge about the potential role of the RST for neurorehabilitation of individuals with sarcopenia. Training and or rehabilitation techniques that stimulate the RST, such as resistance-training could be a candidate for treatment or prevention of sarcopenia.