Background: Psychological interventions are applied in sports worldwide, although it is still unclear whether and which methods have an effect on sports performance. Acceptance and commitment therapy (ACT) is a behavioral change model that targets psychological processes related to acceptance, mindful awareness, and values-consistent behavior, and has been adapted for athletes. Further, using the internet format to deliver psychological services has had a great impact in clinical psychology, although it is still an underexplored format for delivering psychological interventions in sports.Research aims: The overall aim of this thesis was to develop and evaluate the feasibility and preliminary effectiveness of an internet-based psychological intervention based on ACT (I-ACT) in an elite sports context (Studies II and III). It also aimed to develop and psychometrically evaluate a therapeutic tool and measure of values and values-based behavior in athletes (Study IV), and to review the current evidence regarding psychological interventions' effect on sports performance in athletes (Study I).Methods and results: Study I: A systematic review was conducted of studies investigating psychological interventions' effect on sports performance in athlete samples. Five meta-analyses using cluster robust variance estimation were quantitatively synthesized for studies with comparable research designs. Significant moderate effects were found for PST, MA approaches, and Imagery compared to no-intervention controls. The effects were no longer significant in the sensitivity analyses when inferior research designs (non-randomized trials) were removed from the syntheses.Study II: I-ACT was developed to focus on performance enhancement and to promote a psychologically sustainable sports participation. Four male elite ice hockey players took part in the intervention, and semi-structured interviews were conducted afterwards regarding their experiences. Data was analyzed using qualitative content analysis. Results suggest that I-ACT was feasible and acceptable in an elite sports context and relevant to their sport endeavor.Study III: A total of 55 elite ice hockey players in two separate I-ACT intervention cohorts participated. Each intervention cohort (outfield players in I-ACT1 N = 40; outfield players in I-ACT2 N = 10) was compared with a statistical comparison group based on players from the rest of the leagues (N = 1051) regarding objective performance outcomes (goals, assists, Total points, and PlusMinus). Goaltenders (N = 5) were investigated with save percentage as the objective performance outcome. A significant moderate effect in I-ACT2 compared to the statistical comparison group was found for PlusMinus, and the significant effect lasted at follow-up. No significant effects were found for the objective performance outcomes in the other intervention cohort (I-ACT1), nor in I-ACT participating goaltenders. Significant small within-group effects were found for ice hockey-related psychological flexibility and sleep quality in I-ACT players. No significant effects were found regarding subjective performance, life quality, or general anxiety. Linear mixed-effects models were used to analyze the results, except for goaltenders' objective performance, for which a within-group repeated measures ANOVA was conducted.Study IV: A therapeutic tool and measure of values and values-based behavior in athletes was developed called Bull's-Eye for Athletes (BEA). 155 athletes from junior elite to international senior level took part in the study. BEA was administered digitally and psychometrically evaluated using Rasch analysis. BEA demonstrated satisfactory psychometric properties in general regarding unidimensionality, local independence, invariance, and response category monotonicity. Although the results should be interpreted while considering the limited sample size.Conclusions: The effects of PST, MA approaches, and Imagery on athletic performance are unstable and should be interpreted with caution, and further randomized trials are required (Study I). The internet format was a feasible option for delivering an internet-based psychological intervention in elite athletes (Study II). I-ACT had an effect on objective sports performance in one out of two intervention cohorts. The results should be interpreted carefully in general, and I-ACT should be further evaluated in an RCT while also investigating mediators of change related to the ACT model (Study III). BEA offers a therapeutic tool and measure of values and values-based behavior in athletes. It demonstrated satisfactory psychometric properties in an initial psychometric evaluation. It should, however, be further evaluated with larger samples in various sports contexts and also in a longitudinal intervention study as a measure of values-based behavioral change in athletes (Study IV).List of scientific papersI. Reinebo, G., Alfonsson, S., Jansson-Fröjmark, M., Rozental, A., & Lundgren, T. (2024). Effects of psychological interventions to enhance athletic performance: A systematic review and meta-analysis. Sports Medicine, 54, 347-373. https://doi.org/10.1007/s40279-023-01931-zII. Reinebo, G., Björverud, L. G., Parling, T., Andersson, G., Jansson- Fröjmark, M., & Lundgren, T. (2024). Development and experiences of an internet-based acceptance and commitment training (I-ACT) intervention in ice hockey players: a qualitative feasibility study. Frontiers in Sports and Active Living, 6, 1297631. https://doi.org/10.3389/fspor.2024.1297631III. Reinebo, G., Jansson-Fröjmark, M., Parling, T., Andersson, G., Lindner, P., Lundgren, T. (in press). Internet-based acceptance and commitment therapy (I-ACT) for elite ice hockey players: A quasi-experimental multiple-cohort intervention study. International Journal of Sport and Exercise Psychology. https://doi.org/10.1080/1612197X.2025.2531840IV. Reinebo, G., Johansson, M., Jansson-Fröjmark, M., Wiklund, A., Ekman Öhrn, G., Parling, T., Rozental, A., Andersson, G., & Lundgren, T. Bull's-Eye for Athletes (BEA): A measure of values-based behavior in sport and a psychometric evaluation using Rasch analysis. Manuscript
Gustaf Reinebo (Thu,) studied this question.