Equivalente metabólico em idosos: um contraponto à literatura

Abstract

The metabolic equivalent (1-MET) is a physiological concept that represents the energy cost of physical activities as multiples of the resting metabolic rate (RMR). There is a premise that the reference value for 1-MET would be 3.5 mL•kg-1•min-1, amount derived from oxygen consumption (VO2) at rest observed in a single 40-year-old man and body mass of approximately 70 kg. Despite its widespread use in the prescription of physical exercises, different factors can interfere with VO2 at rest, such as age, sex, body mass, muscle mass, fat mass, cardiorespiratory fitness, among others, making room for a question regarding its suitability for the elderly population. Therefore, the present Doctoral Thesis investigated the theme through two specific studies: the first, a systematic review, in which a state of the art survey was carried out on the values of 1-MET and the variables that influence it; The second, an original study, in which the influence of body composition and cardiorespiratory fitness on the variation of the real value of 1-MET in the elderly was investigated. The systematic review was performed through searches in the US National Library of Medicine (MEDLINE), Web of Science and Cochrane Library, Scopus and Sportdiscus databases using the keywords “metabolic equivalent”, “Basal Metabolism” and “Indirect Calorimetry” taken from Virtual Health Library and its synonyms for Medical Subject Headings, using AND logic operators between descriptors and OR between synonyms. The applied filters were “age” (≥65 years) and “species” (human); and the PICOS strategy was adopted as an inclusion criterion. In the end it was agreed that there is a strong relationship between changes in body composition and the reduction of 1-MET, with MLG being the main predictor of this reduction; and that the standard value of 1-MET that has been used, does not reflect the energy metabolism of the elderly, in view of the aging process. In the original study, the dual X-ray absorptiometry test was performed to determine body composition, cardiopulmonary test of maximum effort to determine VO2max, and indirect calorimetry at rest to determine 1-MET in 58 volunteers aged or older. over 60, of both sexes, physically active. The results of the Student's t test showed lower values of 1-MET when compared to the reference value of 3.5 mL•kg-1•min-1 (2.3 mL•kg-1•min-1; p <0.001 ); and the exploratory factor analysis showed two factors: the first was called “Body Size and Composition”, being responsible for explaining 53.4% of the variance, and the second, called “Metabolism”, was responsible for 23.0% of the total variance. Together, the factors explained 76.4% of the accumulated variance. It was concluded that the variables ASC, BMI, MG and VO2max, related to 'size and body composition' and to the 'metabolic component', are presented as factors that participate in the behavior of the 1-MET and together explain 76.4% of the accumulated variance and in particular, 1-MET and VO2máx have similar variations, raising the hypothesis that cardiorespiratory fitness may be the main influencing variable of 1-MET