Not just a walk: differential psychological and physiological responses to park-based walking in postmenopausal women with different baseline happiness levels

Background Walking is known to benefit emotional well-being and physical health, yet its effects on the psychoneuroimmune system remain unclear. Psychological distress is common in postmenopausal women. Objectives This study examined psychological and physiological responses to walking in postmenopausal women with different baseline happiness levels. Methods Twenty-four postmenopausal women were stratified into higher-happiness ( n = 12) and lower-happiness ( n = 12) groups based on baseline scores of the Happiness and Life Satisfaction Scale. All participants completed a single 60-min walking session in a park. Pre- and post-walking assessments included heart rate variability (HRV), blood pressure, and salivary biomarkers (cortisol, α-amylase, lactoferrin, immunoglobulin A, total protein, and mitochondrial DNA (mtDNA)). Psychological status was evaluated using the Profile of Mood States (POMS). Results Salivary α-amylase/total protein (TP) significantly increased in both groups, while lactoferrin/TP rose only in the lower-happiness group. Salivary mtDNA decreased post-walking in both groups; a statistically significant reduction was observed only in the lower-happiness group. Following walking, both groups showed reductions in RR intervals, along with an elevation in heart rate. At both measurement time points, the lower-happiness group consistently presented higher mean heart rate and lower root mean square of successive differences (RMSSD) compared with the higher-happiness group. Psychological outcomes improved in both groups. The lower-happiness group had greater reductions in confusion, fatigue, tension, and anger, whereas the happy group showed increased vigor and self-esteem, along with reduced anger and depression. Conclusions A single 60-min park walk was associated with changes in salivary immune markers and improvements in psychological well-being in postmenopausal women. Differential responses were observed according to baseline happiness levels, with greater benefits observed in the lower-happiness group, highlighting the therapeutic potential of walking in natural environments.