Mental health is a real challenge for global society today. The COVID-19 pandemic also has a significant negative impact on people mental health through increased exposure to stressors. The
results of many scientific studies show a relationship between outdoor activity and increasing general mental health. Outdoor treatments in the natural environment are a part of the complex spa care in all famous spas in the Czech Republic. This study aimed to conduct a standardized Profile of Mood States questionnaire and to find out the effect of Nordic Walking training in the natural environment of Karlovy Vary on the mood states (tension, anger, fatigue, depression, confusion, vigour) of the participants. The questionnaires were completed by 36 participants (25 women, 11 men) aged between 20 and 65 years (average 45 years). Based on the statistical evaluation, positive changes were observed in most of the investigated mood states. First of all, significantly increased vitality and, on the contrary, decreased fatigue (p-value <0.001) were confirmed. The training also had a positive effect on the anger and depressive states, with a significant reduction in both cases (p-value <0.05). This study results have confirmed that Nordic walking training in the natural environment of Karlovy Vary forests has a positive effect on the mood states of the participants and their mental health. These results will be the basis for follow-up research investigating the impact of physical activity in spa environments on the mental health of visitors and residents of spa towns.