Table 2

Measurement of behavioral determinants: items and psychometric properties
Determinant Item (on a 7-point Likert scale) Cronbach’s α
T0 T1 T2
Perceived behavioral control Exercising vigorously for at least 3 times 20 minutes this week is for me (completely possible – completely impossible) .76 .67 .70
Physical activity If I wanted to, I could exercise vigorously for at least 3 times 20 minutes this week (I completely agree- I completely disagree)
How much control do you experience on the amount of vigorous physical activity you have this week? (no control – complete control)*
The extent to which I exercise vigorously this week is mostly up to me. (completely agree- completely disagree)
Perceived behavioral control Eating at least 2 pieces of fruit per day this week is for me (completely possible – completely impossible) .40** .28** .30**
Fruit intake If I wanted to, I could eat at least 2 pieces of fruit per day this week (I completely agree- I completely disagree)
How much control do you experience on the amount of fruit you eat this week? (no control – complete control)*
The extent to which I eat fruit this week is mostly up to me. (completely agree- completely disagree)
Intention I intend to exercise vigorously for at least 3 times 20 minutes this week. (completely agree- completely disagree) .94 .90 .86
Physical activity I try to exercise vigorously for at least 3 times 20 minutes this week. (completely agree- completely disagree)
Intention I intend to eat daily at least 2 pieces of fruit this week. (completely agree- completely disagree) .96 .94 .93
Fruit intake I try to eat daily 2 pieces of fruit this week. (completely agree- completely disagree)
Perceived barriers (lack of time) I do not have enough time to engage in vigorous physical activity at least 3 times for 20 minutes this week, because of my work. (completely agree- completely disagree)* .71 .82 .76
Physical activity I do not have enough time to engage in vigorous physical activity at least 3 times for 20 minutes this week, because of my family life/ social life. (completely agree- completely disagree)*

*Negative items have been recoded for analyse.

**Cronbach’s alpha is unacceptable, even when items were deleted. Therefore, items have been analysed separately.

van Berkel et al.

van Berkel et al. International Journal of Behavioral Nutrition and Physical Activity 2014 11:9   doi:10.1186/1479-5868-11-9

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