3.1. Preliminary Analyses
Non-parametric comparisons to examine for possible differences in the baseline of both groups showed that significant differences in marital status, BMI, education level and number of children in their care did not exist. However, the average age of the FM group was significantly higher than that of the control group (U = 433.500; p = 0.007). For this reason, a square-root transformation of this variable was performed to obtain normality.
As expected, the FM group scored significantly higher than the control group in pain intensity, with averages on a scale from 0 to 5 of 2.22 (SD = 1.35) and 0.23 (SD = 0.49), respectively (U = 83; p = 0.000).
As expected, the two groups had significantly different scores on most of the scales to measure stress, as can be seen in Table 1
, except in positive impact of life changes (LES positive change score). Comparisons between groups showed that the FM group scored higher than the control group on severity of childhood abuse and neglect (CTQ), total presence of potentially traumatizing experiences (TEC total presence score), total severity of trauma (TEC total severity score), daily hassles (HSUP), occurrence of significant life changes (LES frequency) and negative impact of life changes (LES negative change score). The FM group scored lower than the control group on daily uplifts (HSUP).
In the REST-Q factors, the FM group showed significantly higher scores than the control group in the factors of “General/emotional stress” (U = 213.500; p
< 0.001) and “Performance-related/work-related stress” (U = 101.500; p
< 0.001), but lower scores in “General Recovery” (U = 225; p
< 0.001), as can be seen in Figure 1
3.2. Cardiovascular Responses to the Stressor Task
In the following analyses, only age was included as a covariate according to the preliminary analyses performed.
Regarding the mood variables, the mixed ANOVA showed a main time effect (baseline-task) for the following moods: anxiety (F (1,69) = 203.420; p < 0.001; η2 = 0.747), sadness (F (1,69) = 21.209; p < 0.001; η2 = 0.235), and anger (F (1,69) = 42.127; p < 0.001; η2 = 0.379). Specifically, participants reported being sadder, angrier and more anxious during the speech task compared to baseline. The interaction effect between time and group was not significant for any of mood variables, so no significant differences were observed between the groups in the three measures of mood change: anxiety (F (1,69) = 3.508; p = 0.065; η2 = 0.048), sadness (F (1,69) = 0.317; p = 0.576; η2 = 0.005), and anger (F (1,69) = 0.075; p = 0.785; η2 = 0.001). However, a certain tendency close to significance was observed in anxiety, with the highest values belonging to the control group.
At the cardiovascular level, the mixed ANOVA revealed that the individual main time effect (baseline-task) was significant on systolic blood pressure (F (1,72) = 167.045; p < 0.001; η2 = 0.699), diastolic blood pressure (F (1,72) = 213.828; p < 0.001; η2 = 0.748) and heart rate (F (1,72) = 210.843; p < 0.001; η2 = 0.745). Specifically, participants reported higher scores in all three during the task than at baseline.
Regarding cardiovascular baseline scores, no significant differences were founded in any variable examined between the groups: SBP (F (1,72) = 0.287; p = 0.594; η2 = 0.004); DBP (F (1,72) = 1.364; p = 0.247; η2 = 0.019); HR (F (1,72) = 2.062, p = 0.155; η2 = 0.03). In relation to the interaction between time and group, a significant effect on both systolic blood pressure F (1,72) = 6.889; p = 0.011; η2 = 0.087 and heart rate (F (1,72) = 14.704, p = 0.000; η2 = 0.170) was observed. Therefore, significant differences were observed between the groups in both measurements, with a higher change for the control group scores.
In relation to their expectations regarding how stressful they would find the task F (1,72) = 0.743; p = 0.392; η2 = 0.010, as well as their perceived ability to tackle the task successfully F (1,72) = 0.020; p = 0.887; η2 = 0.000, the ANCOVA test did not show significant differences between the groups in either of the two variables.
3.3. The Group as a Moderating Factor in the Relationship between Stress-Recovery Processes and Cardiovascular Response
Different moderation analyses were performed for baseline and reactivity measurements, as can be seen in Table 2
and Table 3
, respectively. This was done for the purpose of seeing if the stress-recovery state had an influence only in the cardiovascular reactivity period or also in the cardiovascular baseline period. It should be noted that given the previous analyses described, it was only appropriate to include age as a covariate for the analysis of the group’s moderating role on the relationship between Performance-related/work-related stress factor and systolic blood pressure. This made it possible to appreciate that the baseline measurements had no moderating effects. However, for reactivity measurements, three moderating effects of the group were identified, two of them for the relationship with the Performance-related/work-related stress factor (Beta = 1.78 for SBP and Beta = 1.10 for DBP) and the other for the relationship with the General recovery factor (Beta = 0.94 for HR).
In Figure 2
and Figure 3
, it can be observed that an increase in the Performance-related/work-related stress factor levels was associated with a decrease in systolic reactivity and diastolic reactivity; this was only the case for the control group, with no relationship between both variables in the FM group.
In the case of the General recovery factor, it was noted how an increase in this factor was related to an increase of heart rate reactivity in the stress task, but only in the FM group. This was not observed in the control group, as can be seen in Figure 4