Validation of the German version of the state mindfulness scale for physical activity in a clinical sample.

Background: Mindfulness has been studied as a treatment option for a large range of psychological disorders and is associated with a multitude of positive psychological outcomes. There are now several scales for measuring mindfulness as both a trait and a state. As mindfulness potentially plays a critical role in maintaining physical activity habits, the State Mindfulness Scale for Physical Activity (SMS-PA) was developed to specifically measure mindfulness in a physical activity context. This study aimed to provide validity evidence for a German version of the SMS-PA (henceforth called SMS-PA-G) in a clinical sample.

Methods: We used baseline data from 129 participants in the randomised controlled trial 'New Ways to Cope with Depression'. The sample, which was screened for clinical depression symptoms, completed the SMS-PA-G and several other psychometric scales for capturing state mindfulness, self-efficacy, sense of coherence, anxiety, depression, and physical activity. We conducted reliability and item analyses and ran a confirmatory factor analysis. Also, we assessed construct validity through correlations with the abovementioned scales and through differences in SMS-PA scores between physically active and nonactive participants.

Results: The mean SMS-PA-G score in our sample was 25.3 with a standard deviation of 8.5. The item and reliability analyses provided satisfactory Cronbach's alpha and discriminatory power values. The confirmatory factor analysis showed that physical activity mindfulness can best be described via a bifactor model, with specific mind and body factors and a general mindfulness factor. We found the expected relationships with the attention subscale of state mindfulness, self-efficacy, and sense of coherence but did not find them with the awareness subscale of state mindfulness, depression, and anxiety. As hypothesised, physically active participants exhibited higher SMS-PA-G values than nonactive participants.

Conclusions: The SMS-PA-G is an internally consistent test instrument that captures respondents' general physical activity mindfulness and their attention to mental and bodily events. Whereas validity evidence was generally supportive of the SMS-PA-G, its relationships with other constructs require further investigation.

Trial registration: ISRCTN, ISRCTN12347878. Registered 28 March 2022, https://www.isrctn.com/ISRCTN12347878 .