Background: Four dimensions of inner strength were previously identified in a metatheoretical analysis: firmness, creativity, connectedness, and flexibility.Objective: The aim of this study was to develop an Inner Strength Scale (ISS) based on those four dimensions and to evaluate its psychometric properties.Method: An initial version of ISS was distributed for validation purpose with the Rosenberg Self-Esteem Scale, the Resilience Scale, and the Sense of coherence Scale. A convenience sample of 391 adults, aged 19 to 90 years participated. Principal component analysis (PCA) and confirmatory factor analysis (CFA) were used in the process of exploring, evaluating, and reducing the 63-item ISS to the 20-item ISS. Cronbach's alpha and test-retest were used to measure reliability.Results: CFA showed satisfactory goodness-of-fit for the 20-item ISS. The analysis supported a four-factor solution explaining 51% of the variance. Cronbach`s alpha on the 20-item ISS was 0.86, and the test-retest showed stability over time (r = 0.79). Conclusion:The ISS was found to be a valid and reliable instrument for capturing a multifaceted understanding of inner strength. Further tests of psychometric properties of the ISS will be performed in forthcoming studies. What this paper adds A new scale, the Inner Strength Scale, has been developed to estimate the four dimensions of firmness, creativity, connectedness, and flexibility. The Inner Strength Scale was found to have satisfactory validity and reliability. The Inner Strength Scale was found to be applicable to men and women of various ages.

This large cross-sectional study with participants from 65 to 80 years of age from Finland and Sweden showed that inner strength can be a resource for older people affected by disease. Increasing inner strength in older people affected by disease may be one intervention to support experiences of health despite disease.

The study population came from Sweden and Finland; still, despite the different backgrounds, patterns in the distribution of inner strength were largely similar. The present study provides basic and essential information about inner strength in a population of old people.

Inner strength is reported as an important resource associated with aging, health, and disease management. The aim was to explore inner strength in people (n ¼ 12) aged 65 years and older, who had experienced a crisis in life associated with a disease. The participants had self-rated their inner strength as high. We found that sources of inner strength were mutual love and support, and the fact that tough times have been managed before. Expressions of inner strength comprised focusing on possibilities instead of brooding, facing and take an active part in care and treatment, and being able to confront reality and pick yourself up again. Inner strength is a complex phenomenon. Increased knowledge of inner strength can serve as an aid in efforts to identify the need to promote inner strength.

The Swedish version of the 12-item SOC questionnaire showed deficiencies in a test of internal consistency because of two items in the ES subscale, and these two items were deleted. A consequence of the reduction is a weakening of the ES subscale and thereby to some extent the SOC questionnaire in total. Further testing is advisable. However, the 10-item SOC questionnaire was acceptable in a test of validity and reliability.