Pulmonary VO2 on-kinetics and walking net VO2 associate with fatigue and mood disturbance in postmenopausal women

Postmenopausal women often experience fatigue and mood disturbance both of which interfere with quality-of-life. Since greater physical function aids psychosocial well-being, we hypothesized the acute cardiopulmonary responses during walking may reveal important factors linked to fatigue and mood disturbance. In this cross-sectional study, women of similar body mass index (BMI) aged 55-75 y were dichotomized to mid-life (55-65 y; 83.4 ± 8.4 kg/m 2 ; n = 14) or older (≥65 y; 81.8 ± 10.4 kg/m 2 ; n = 11) groups. A 6-minute walk test was used to estimate peak aerobic capacity (V̇O 2peak ). A treadmill task coupled with indirect calorimetry measured mean response time (MRT) – representing the duration to reach 63 % of steady-state net oxygen uptake (V̇O 2 ). Average daily fatigue and fatigue interference were measured with the Fatigue Symptom Inventory. General mood disturbance was measured with the Profile of Mood States (POMS) questionnaire. Age-group differences were not detected in fatigue ratings, MRT, or walking net V̇O 2 . However, older women had lower aerobic capacity ( p = 0.002, ES = 1.39) and greater disturbance in the POMS Depression-Dejection subscale ( p = 0.042, ES = 0.41). Among all participants, and independent of V̇O 2peak , MRT correlated with average daily fatigue ( r = 0.500, p = 0.015), fatigue interference ( r = 0.421, p = 0.046), and POMS total mood disturbance ( r s = 0.437, p = 0.037). Regression modeling revealed MRT and walking net V̇O 2 jointly explained 55 % ( R = 0.744, p < 0.001) of the variance in average daily fatigue. In conclusion, MRT and walking net V̇O 2 may serve as important points of intervention to alleviate fatigue and mood disturbance in postmenopausal women. • In postmenopausal women, V̇O 2 on-kinetics correlate with fatigue and mood disturbance – independent of V̇O 2peak . • Regression modeling showed mean response time and net V̇O 2 jointly account for 55 % of the variance in average daily fatigue. • Mean response time and net V̇O 2 may be important to alleviate fatigue and mood disturbance in postmenopausal women.