Iris Kanera

126 Chapter 5 Physical activity The increase in moderate PA in the IC that was found in the main analysis (having KNW- access) was confirmed when testing the use of the specific PA module. The effect size of moderate PA-changes ( d = .32) was higher when testing the use of the PAmodule compared to the main analysis ( d = .25). In comparison with prior, web-based PA-only interventions, these effect sizes were similar or even higher than the earlier reported overall effect size of d = .14 (Davies, Spence, Vandelanotte, Caperchione, & Mummery, 2012). Possibly, the module PA was followed by cancer survivors who were actually “in need” and able to increase PA. This might indicate that the KNW-recommendation on PA could have targeted the desired subpopulation. The low number of module PA-followers ( n = 45) might possibly have caused power problems, which might be a reason for the non-significant results after controlling for multiple testing. Moreover, the raw data (Table 5.1) of increases in moderate PA (+150.73 min p/w) in the IC was notably higher as compared to the UC (+75.99 min p/w). This may be interpreted as a meaningful result, considering findings fromWen et al. (2011) that every additional 15 minutes a day or 90 minutes a week of moderately intense PA reduced all-cancer mortality. This dose-response relationship has been confirmed in recent publications (Arem et al., 2015; Samitz, Egger, & Zwahlen, 2011; Schmid & Leitzmann, 2014). The module PA was derived from an existing, basic web-based PA intervention for the general population aged over 50, named Active Plus (Peels et al., 2014b; Willems et al., 2015), which has been shown to be effective in increasing weekly minutes of moderate and vigorous PA after six months ( d = .24). The increase of combined moderate and vigorous PA was higher in the Active Plus intervention in comparison to the KNW-intervention (283 min vs. 238 min p/w). Reasons for these differences might be the target population (general population in Active Plus vs. cancer survivors in KNW) and the program intensity (three tailored sessions within six months in Active Plus vs. one combined tailored session followed by an evaluation four weeks later in KNW). In addition, the module PA was one of eight modules in the KNW, while the Active Plus intervention consisted of only the theme on PA. In addition, there might have been more selective attrition in Active Plus due to higher dropout (close to half of the sample). Dietary behaviors The effects of the KNW on dietary behavior are valuable to mention although they remained not significant after accounting for multiple testing. It is promising that participants who had access to the KNW showed a higher vegetable consumption. As can be concluded from the sub-analyses, this increase in vegetable consumption could not be explained by following the module Diet. Possibly, the increase in vegetable consumption might be attributed to other intervention components, such as one of the news items that targeted