Worksite health promotion, coworker support,and motivation for lifestyle change: Effects of a self-determination theory based cluster-randomized controlled trial on physical activity, cardiorespiratory fitness, and health

Abstract

Introduction: National surveys around the world repeatedly report that adults are not physically active enough to obtain various health benefits. The worksite represents an important context for physical activity (PA) promotion initiatives because it provides access to a large intersection of the adult population. Employers initiate health promotion programs in order to increase employees' health and reduce the costs of sickness absence. Existing networks among coworkers represent a source of social support that can be incorporated into the programs as an active ingredient. PA intervention studies based on the tenets of self-determination theory (SDT) have been proven effective in the context of health care and treatment. The present SDT based PA intervention study was adjusted to the context of a worksite health promotion program targeting employees working with transport, sorting, and distribution.

Aim: This doctoral thesis aims to contribute to the understanding of how interventions, situated in the worksite context, can be designed to increase autonomous motivation for behavioral change and produce health benefits regarded as both clinically relevant, and important to the worksite. The primary outcome variables were PA and cardiorespiratory fitness (CRF). The secondary outcome variables were biomedical markers (paper I), in addition to somatic symptoms and sickness absence (paper II). A SDT model of health behavior change was tested in order to assess mediating effects of SDT constructs (paper I-II). The thesis also aims to explore the development of PA behavior over a period of one year, and how behavioral patterns were related to competence and motivational regulation (paper III). Moreover, the thesis aspired to contribute to the theoretical understanding of peers as a provider of support for basic psychological needs (i.e., for autonomy, competence, and relatedness).

Methods: A cluster randomized controlled trial with a delayed-intervention control group. A total of 202 employees (M = 42.4, SD = 11.65, 76.2% men) agreed to participate, and six worksite locations (clusters) from the same company were randomly allocated to two conditions. The intervention group was offered six group-based sessions during 16 weeks. To establish a climate supportive of basic psychological needs, three active ingredients were combined during the sessions: talks and plenary discussions facilitated by a health and exercise advisor, a booklet consisting of individual reflection tasks related to behavioral change, and peer dialogue in small groups of coworkers. The baseline and post-test data collections included electronic questionnaires, in addition to objective assessments of CRF and biomedical markers. The follow-up data collection (12 months) consisted of questionnaires.

Main results: The intervention was moderately effective related to the primary outcome variable, CRF, albeit no between-groups effect was found for PA since both groups reported significant increases at post-test. The effectiveness of the intervention on secondary outcome measures was more mixed. Change in diastolic BP and HDL-C demonstrated a significant between-groups effect, and were considered clinically relevant. Changes in non-HDL-C and waist circumference were non-significant and clinically irrelevant. The intervention was also effective related to self-reported levels of somatic symptoms, albeit with small effect sizes. However, the intervention was not able to produce a statistically significant between-groups effect on sickness absence. The moderate effect sizes indicated that the intervention was able to incorporate coworkers as an active ingredient.

The SDT model of health behavior change was tested for model fit with two different sets of secondary outcome variables; 1) biomedical health markers, and 2) somatic symptoms and sickness absence. For the most part, the hypothesized associations between study variables demonstrated the expected direction and significant strength, particularly among motivational variables and primary outcome variables.

The analyses of possible subgroups related to changes in PA over a period of one year indicated that there were three distinct trajectories. The three trajectories differences related to motivational regulation and perceived competence for PA, in line with the tenets of SDT. The intervention was able to attract a subsample of relatively sedentary employees who increased their levels of PA considerably during one year.

Conclusions: The present study demonstrated the effectiveness of an intervention, both complex in nature and modest in dose, incorporating several sources of support for PA. The effects of the intervention on PA, CRF, some biomedical markers, and somatic symptoms are promising. SDT represents a valuable and practical framework for the design of PA interventions in the worksite. SDT also offers an understanding of the motivational antecedent of PA behavior, which has gained strong empirical support.

Paper I: Pedersen, C., Halvari, H., & Williams, G.C. (2018). Worksite intervention effects on motivation, physical activity, and health. A cluster randomized controlled trial. Psychology of Sport and Exercise, 35, 171-180. Doi:10.1016/j.psychsport.2017.11.004.

Paper II: Pedersen, C., Halvari, H., & Olafsen, A.H. (In press). Worksite physical activity intervention and somatic symptoms burden: The role of coworker support for basic psychological needs and autonomous motivation. Journal of Occupational Health Psychology, Doi:10.1037/ocp0000131. [Epub ahead of print].

Denne artikkelen ble tatt ut av den elektroniske versjonen av doktoravhandlingen i Brage på grunn av copyright-restriksjoner. / This paper was removed from the electronic version of this PhD-thesis in Brage due to copyright restrictions.

Paper III: Pedersen, C., Halvari, H., & Bentzen, M. (submitted and under review in Psychology of Sport and Exercise). Longitudinal trajectories of physical activity among employees participating in a worksite health promotion intervention: A latent class growth approach.