Quantity of Aerobic Exercise Training for the Improvement of Heart Rate Variability in Older Adults
Abstract Cardiovascular autonomic markers such as cardiovagal baroreflex sensitivity (CBS) and heart rate variability (HRV) decline with the aging process. Aerobic training (AT) may be able to improve HRV, suggesting that AT can alter neuroregulatory control over the heart, improving autonomic markers and cardiac protection. Together, age and AT can influence HRV, but not revert the overall effects of aging on the decline of physical performance and HRV. The aim of this study was to review studies and describe the volume of AT necessary to produce modifications in HRV in elderly individuals. The review followed the guidelines of the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA). The articles selected were indexed in PubMed/MEDLINE, Lilacs and Scopus. The used keywords were "aging", "heart rate variability", "exercise" combined with the Boolean descriptors "AND" and "OR" with the synonyms "elderly", "cardiac autonomic modulation", "aerobic training" and "endurance training". The filters "languages", "humans", "age" and "clinical trial" were applied in the selection of the articles. Initially, 940 articles were found, PubMed (n = 729), Lilacs (n = 16) and Scopus (n = 195), filters and searches led to the 287 potential studies. The keyword combinations provided 24 articles that were in agreement with the inclusion criteria, and after full reading of the texts, 17 studies were excluded. From seven articles, four showed increases in HRV in response to AT. In an older population, 8 weeks of AT is enough to induce positive changes on HRV. However, longer exercise protocols and higher intensities also seem to have some influence.