Perceived fatigability and metabolic and energetic responses to 6-minute walk test in older women

Objective To determine the relationship between perceived fatigability and oxygen consumption, carbon dioxide production, respiratory exchange ratio and the energy cost of walking in older women. Design Observational, cross-sectional study. Participants Forty-eight community-dwelling older women were recruited from senior centres in Natal, Rio Grande do Norte, Brazil. Main outcome measures Participants were evaluated in two different sessions. In the first session, sociodemographic and clinical factors were assessed and accelerometers were delivered. In the second session, the 6-minute walking test (6MWT) was performed and expired gases were analysed. Self-reported levels of fatigue were evaluated on a numerical scale from 1 ('extremely energetic') to 7 ('extremely tired'). Severity scores for perceived and performance fatigability were calculated as the ratio of change in performance and fatigue, respectively, with walking distance. The O-2 cost of walking was based on the oxygen consumption rate and the 6MWT walking speed. Results No correlation was found between the severity of perceived fatigability and metabolic measures. However, the severity of perceived fatigability was significantly correlated with greater O-2 cost (r = 0.579, P < 0.01), physical activity (r =-0.654, P < 0.01), walking distance (r =-0.712, P < 0.01) and severity of performance fatigability (r = 0.690, P < 0.01). Conclusion Perceived fatigability was not directly associated with metabolic measures; however, greater severity of perceived fatigability was associated with an increase in the 02 cost of walking. Important relationships were also found between greater severity of perceived fatigability and poor functional fitness, high level of energy expenditure and lower level of physical activity. (C) 2015 Chartered Society of Physiotherapy. Published by Elsevier Ltd. All rights reserved.