Energy Utilization and Fatigue in Frail Older Women in Relation to Walking

Background and Objectives: Fatigue is one of the characteristics defining frailty. However, the mechanisms leading to fatigue are still poorly understood. Our objectives were to assess the efficacy of energy utilization (EU) during walking in frail older persons and their level of fatigue. Research Design and Methods: Clinical study of a convenient sample of frail older women. 10 healthy (H; 77 ± 4 year, BMI: 25 ± 3 kg/m2, MMSE: 29 ± 1) and 10 frail elderly women (F; 83 ± 6 year, 26 ± 5 kg/m2, 27 ± 3) were compared for their usual level of fatigue and changes in perceived fatigue and EU before and after walking. A 10 cm Visual Analogue Scale (VAS) prior to and following a 6-Minute Walk Test (6MWT) served to measure fatigue. EU was based on VO2 consumption adjusted for walking distance and measured using a portable Cosmed K4b2 indirect calorimeter. Participants underwent body composition measurements by DXA and venous blood sampling. Results: Groups had similar body composition and blood parameters. At rest, there were no differences in VO2 or energy expenditure, but the frail group had a lower heart rate. During 6MWT, between group differences were found for distance VO2, HR and EU. There were VAS changes in fatigue and a moderate correlation between the VAS of general fatigue and hsCRP. Discussion and Implications: Compared with their healthy counterparts, frail older women exhibited lower physical performance, efficacy of EU, and perceived more fatigue with activity. Inflammation was significantly correlated with subjective fatigue but did not characterize frailty.