Supplement prediction model 129 Table 4 Hierarchical stepwise regression of exercise adherence on selected theory of planned behavior, psychological, past exercise and fitness, disease, and demographic variables (n = 196) Step/ predictors R2 F df b 1 b2 b3 b4 b5 1. Intention 0.169 39.34 194 0.956*** 0.723*** 0.707*** 0.633*** 0.630*** 2. Alliance 0.248 31.88 193 0.258*** 0.189*** 0.204*** 0.207*** 3. Depression 0.319 29.97 192 -0.643*** -0.589*** -0.525*** 4. MRC 0.356 26.44 191 -1.239** -1.225** 5. Education 0.376 22.85 190 1.389* Note: ***p = 0.000, **p = 0.001, *p = 0.01; df = degrees of freedom; b1-b5 = standardized regression coefficients for model 1 to model 5 Predictors of intention Significant moderate to large correlations were found between exercise intention and PBC, attitude, and alliance. Significant small correlations were found between exercise intention and subjective norm, depression, and MRC score (Table 5). Table 5 Significant Spearman’s correlations with exercise intention Predictor r p PBC 0.57 0.00 Attitude 0.42 0.00 Subjective norm 0.16 0.01 Alliance 0.36 0.00 Depression -0.18 0.01 MRC-score -0.17 0.01 Note: PBC: Perceived Behavioral Control; MRC-score: Medical Research Council dyspnea scale as a measure of disability in patients with chronic obstructive pulmonary disease These six variables were examined in a stepwise HMRA, entered in the following blocks: 1. TPB variables (PBC, attitude, and subjective norm), 2. psychological variables (alliance), and 3. disease variables (depression and MRC-score). With PBC, attitude and subjective norm in the model, only PBC and attitude predicted exercise intention (R2 = 34.5%). When adding alliance to the model, all three variables (PBC, attitude, alliance) explained intention (R2 = 37.9%). Finally, adding depression and MRC-score resulted in only PBC, attitude and alliance predicting intention (R2 = 37.9%). Three variables entered the final model, PBC, attitude, and alliance, and explained 37.9% (large effect) of variance in exercise intention (Table 6).
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