Abstract: Determinants of Physical Activity in Older Adults: Integrating Self-Concordance into the Theory of Planned Behavior

◆ Paula Stehr, University of Erfurt
◆ Constanze Rossmann, University of Erfurt
◆ Tabea Kremer, University of Erfurt
◆ Johanna Geppert, University of Erfurt

Engaging in physical activity is a promising strategy to increase the number of healthy years for older adults (Löllgen, 2013). However, physical activity levels are commonly too low (Guthold et al., 2018). Therefore, effective health promotion strategies are needed, that use theory in order to identify the relevant determinants driving physical activity behavior (Silk et al., 2011).
In this context, numerous studies refer to the theory of planned behavior (TPB; Ajzen & Fishbein, 2010) that has been confirmed in several meta-analyses. However, in the context of physical activity of older adults, research often finds significant effects for attitude and perceived behavioral control (PBC) on intention, but not for subjective norm (Alexandris et al., 2007; Gretebeck et al., 2007) indicating a need for theoretical adjustment. We propose to extend the TPB by integrating self-concordance, defined as the extent to which an individual’s goals reflect enduring interests and personal values (Sheldon & Elliot, 1999). Based on the self-determination theory (SDT; Deci & Ryan, 2008), self-concordance can be differentiated into external and introjected regulations (low self-determination) and identified and intrinsic regulations (high self-determination). We assume that this extended model is better suited to explain physical activity behavior for two reasons: 1) While subjective norms are only weakly related to behavioral intention, studies show that they are related to motivation (e.g., Brickell et al., 2006). 2) Fuchs et al. (2017) found that physical activity is driven both by the strength of the intention and its self-concordance. Moreover, habit strength was integrated as a moderator due to its pivotal role in physical activity (e.g., van Bree et al., 2013).
In order to test our model, we conducted a telephone survey with a randomly selected sample of German adults aged 65 year and older (N=865). We computed Structural Equation Modeling with SmartPLS 3 and chose Wold's (1975, 1980) Partial Least Squares approach, as it is recommended for novel theoretical models (A. Fuchs, 2011).
Our findings indicate, that focusing on intention strength only leads to an underestimation of the influence of both attitude and subjective norm on intention. While the relation between attitude and intention strength was rather weak, there was a strong relationship with self-determined regulations—especially for people not used to being active (low habit). In line with the above-mentioned studies, subjective norm was not related to intention strength, but had a strong positive influence on non-self-determined regulations indicating that high perceptions of subjective norms may undermine the self-determination of the intention to be physically active and, therefore, also reduce the probability of the actual behavior. Also, PBC was related to both intention strength and self-concordance (positively with both self-determined and negatively with external regulations).

These results show, that looking at intention strength only while neglecting self-concordance can lead to an underestimation of the role of certain behavioral determinants, which can lead to false conclusions in the development of campaign messages. With this, our study contributes to the existing research both theoretically and practically. Further implications and methodological limitations will be discussed.