Aging is associated with a progressive loss of skeletal muscle mass, which ultimately reduces the functional capacity. Accordingly, moderate- to high-load resistance exercise (RE) (i.e., > 65% of one repetition maximum) has been well established as an effective strategy to promote muscle mass accrual in elderly. However, there is substantial inter-individual variability in resistance exercise-mediated changes in muscle mass, with some elderly at the lower end of the spectrum showing only small or even insignificant increases in muscle mass (i.e., low-responders). Nevertheless, it has been suggested this may be a function of an insufficient RE stimulus rather than a definite reduced capacity to increase muscle mass content, warranting the notion that low-responders may benefit from modulations in RE variables. In this regard, RE volume has been demonstrated to be associated with increased muscle mass accrual after RE in a variety of populations. Therefore, it seems appealing to hypothesize that RE volume manipulation may constitute a potentially effective strategy to minimize low-responsiveness in elderly individuals. Furthermore, low-responsiveness also seems to be related to ribosome density, inflammation, and suboptimal activation of the myogenic program, responsible for regulating satellite cells and myonuclei content, along with the protein synthesis machinery. Therefore, the present study aims to investigate the effects of different RE volumes on muscle mass in low-responder elderly individuals. A secondary purpose is to investigate these effects on satellite cells and myonuclei responses, ribosome biogenesis, and inflammatory signaling. For such, elderly subjects of both sexes will undergo a 10-week, twice a week, RE training program. Each leg of a given subject will be randomly allocated, balancing for dominance, in one of the two possible conditions: 1) one set of 8-15 maximum repetitions and; 2) four sets of 8-15 maximum repetitions. Before the training period, all subjects will be submitted to a magnetic resonance imaging exam, one repetition maximum test, and one muscle biopsy in the vastus lateralis muscle (the right or left leg will be selected randomly). These same procedures will be performed after the intervention period, however, at this moment two muscle biopsies will be performed, one biopsy in each leg of a specific subject. After that, the muscle samples will be sent to The University of Alabama at Birmingham, United States of America, where all the immunohistochemical and molecular analyses will be performed by myself in collaboration with Professor Marcas Bamman and his research team. Dr Bamman is a world-renowned expert in the field, and his collaboration will significantly improve not only the study, but the candidate's PhD academic formation.
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