## 3 Results
\begin{table}
\begin{tabular}{l c c c c c c c c c c c c c} \hline  & **Mean** & **SD** & **Min-Max** & **1** & **2** & **3** & **4** & **5** & **6** & **7** & **8** & **9** & **10** & **11** \\ \hline
1. Walking & 3587 96 min & 408.27 & 0-21,960 & – & & & & & & & & & \\
2. Moderate & 131.6 min & 55.76 & 0-2940 & \(-\)0.034 & – & & & & & & & \\
3. Vigorous & 40.73 min & 0-270 min & 0.61 & 0-2940 & \(-\)0.038 & 0.720 ** & – & & & & & \\ activity (IPAQ-s) & per day & & & & & & & & & & & \\
4. Walking & 591.29 min & 138.71 & 104.75\({}^{*}\) & 0.051 & 0.017 & 0.765 ** & – & & & & \\
4. (Accelerometer) & per day & & & & & & & & & & \\
5. Self-efficacy & 46.3 (a.u.) & 2.31 & 0-10 & 0.156 & 0.324 ** & 0.258 ** & 0.213 ** & – & & & \\ physical activity & & & & & & & & & & & \\
6. Pain & 7.10 (a.u.) & 1.83 & 1-10 & 0.086 & 0.082 & 0.021 & 0.046 & \(-\)0.272 ** & – & & & \\
7. Fatigue & 2.29 (a.u.) & 0.81 & 0-3 & \(-\)0.041 & \(-\)0.089 & \(-\)0.058 & \(-\)0.131 & \(-\)0.174 & 0.056 & – & & \\
8. Sleep & 2.60 (a.u.) & 0.68 & 0-3 & \(-\)0.045 & 0.018 & 0.056 & \(-\)0.049 & \(-\)0.147 & 0.261 ** & 0.185 ** & – & \\
9. Cognitive & 2.28 (a.u.) & 0.82 & 0-3 & 0.064 & \(-\)0.169 & \(-\)0.084 & \(-\)0.180 & \(-\)0.321 ** & 0.250 ** & 0.260 ** & 0.150 & – & \\
10. Anxiety & 11.86 (a.u.) & 8.86 & 3-21 & \(-\)0.082 & \(-\)0.060 & \(-\)0.006 & \(-\)0.104 & \(-\)0.154 & 0.228 ** & 0.080 & 0.087 & 0.084 & – \\
11. Depression & 9.46 (a.u.) & 2.36 & 3-21 & \(-\)0.119 & \(-\)0.217 * & 0.099 & \(-\)0.265 ** & –0.379 ** & 0.175 & 0.241 ** & 0.139 & 0.322 ** & 0.529 ** & – \\ \hline \end{tabular} Note. “\(p<0.05\),”\(p<0.01\); a.u. arbitrary unit.  
\end{table} 
Table 2: Pearson correlations. Regarding the medication, the only significant relationships were found between analgesics (pills per day) and the perception of exercise as intense (r = 0.258, \(p\) = 0.007), and with self-efficacy (r = 0.212, \(p\) = 0.025). Aim 2: Mediational Role of Self-Efficacy between Perception of Intensity of Physical Activity (Subjective Measure) and Walking Behavior (Objective Measure)  
Based on the results obtained in the correlational analyses and according to [PERSON] criteria [49] on mediational models, our predictor variable was the perception of intense physical activity, and our outcome variable was walking as a moderate-intensity activity (accelerometers). This finding is consistent with previous studies which indicate an overestimation by patients with fibromyalgia of the intensity of the physical activity that they carry out [28; 29]. Based on this finding, we intended to analyze the possible role of self-efficacy in this relationship according to the theoretical model proposed in Figure 1. The proposed simple mediation model resulted in uniformly acceptable model fits (\(R^{2}\) = 0.286). As hypothesized, perception of physical activity (vigorous) predicted the walking behavior registered by the accelerometer. Specifically, perceptions about the performance of intense physical activity were predictive of walking behavior (c\({}^{\prime}\) = 5.10, \(t\) = 1.01, \(p\) = 0.008, 95% Confidence Interval (CI) = 0.081, 1.44). In addition, a significant effect of the perception of intense physical activity on self-efficacy was observed (a = 1.63, \(t\) = 2.49, \(p\) = 0.014, 95% CI = 1.04, 1.34), along with an effect of self-efficacy on walking behavior (b = 4.63, \(t\) = 1.70, \(p\) = 0.022, 95% CI = 1.93, 5.21). The relationship between the perception of intense physical activity and walking behavior was explained by the mediating effect of self-efficacy (c = 3.16, \(t\) = 3.38, \(p\) = 0.004, 95% CI = 2.85, 4.72). Of all the symptoms considered as covariates in the model, only pain (B = \(-\)0.31, t = 0.13, \(p\) = 0.014, 95% CI = \(-\)0.54, \(-\)0.064) and depressive symptoms (B = \(-\)0.19, t = \(-\)2.99, \(p\) = 0.003, 95% CI = \(-\)0.31, \(-\)0.065) influenced the effect of perception of physical activity on self-efficacy but did not explain the total effect of the mediation model.