VO2 On-kinetics And Walking Economy Are Linked To Fatigue And Mood State In Older Women

Advancing age can trigger a maladaptive cycle highlighted by systemic deconditioning and physical activity avoidance. Maintaining mobility independence is thus an essential aspect of healthy aging. Regrettably, older women are often beset by persistent fatigue and mood disturbance, both of which can interfere with quality-of-life. PURPOSE: Since functional capacity enables greater mobility independence, we reasoned that the acute responses to submaximal walking may reveal important physiological factors linked to fatigue and mood state. METHODS: For this study, women aged 55-75 years were dichotomized according to mid-life (50-64 y; n = 14) or older (≥65 y; n = 11). Oxygen uptake (V̇O2) on-kinetics and walking economy (i.e., net V̇O2) were measured during a fixed-workload (0.89 m/s, 0% grade) treadmill task wherein mean response time (MRT) signified the duration to reach 63% of steady-state V̇O2. Daily fatigue was measured with the Fatigue Symptom Inventory (FSI) subscale, representing fatigue rating in the last seven days. Mood disturbance was measured using the Profile of Mood States (POMS) questionnaire. Between-group comparisons were performed with parametric and non-parametric equivalents where appropriate. Linear regression was used to evaluate independent relationships of interest. RESULTS: Between-group differences were not detected for daily fatigue, body mass index, or mental health history. However, older women had greater disturbance in the POMS Depression-Dejection subscale [middle age, 45(4) vs. older 50 (7); p = 0.042, η2 = 0.17]. Among all participants, MRT positively correlated with POMS total mood disturbance (r = 0.430, p = 0.036) and POMS Anger subscale (r = 0.457, p = 0.025). Regression modeling revealed that MRT and walking economy were independently related to and jointly explained 55% (R = 0.744; p < 0.001) of the variance in daily fatigue. CONCLUSION: The inability to establish directionality notwithstanding, it is reasonable that interventions seeking to improve MRT and walking economy may attenuate the burdens of daily fatigue and mood disturbance in older women. Based on these findings future work is warranted. Supported by the Indiana Clinical and Translational Sciences Institute funded in part by grant number UL1TR002529 from the NIH-NCATS