The characteristics of the participants are gathered in Table 1. The HIIT and EDU groups in terms of age, BMI, physical fitness, and PA levels presented values not statistically different. The EDU group was at slightly higher week of pregnancy. However, we have considered the observed statistically significant difference of 4 weeks between groups of no clinical significance. In the pre-intervention assessment, we did not observe any significant differences between both groups in any of the measured psychosocial parameters (Table 1).
Table 1 The characteristics of the study participants.
|
Group
|
|
|
|
Variable
|
HIIT
n = 34, M±SD
|
EDU
n = 20,
M±SD
|
Statistics1
|
p-value
|
Effect size2
|
Age (years)
|
31 ± 4
|
32 ± 4
|
Z = -0.675
|
0.500
|
0.185
|
BMI (height/weight2)
|
24.4 ± 2.8
|
25.4 ± 3.2
|
t = -1.141
|
0.259
|
0.322
|
Week of gestation
|
20 ± 4
|
24 ± 4
|
Z = -2.741
|
0.006
|
0.780
|
|
|
|
|
|
|
Initial VO2max (kg/ml/min)
|
25.6 ± 4.4
|
23.7 ± 3.6
|
Z = -1.505
|
0.132
|
0.417
|
Initial weekly PA (METs)
|
2625.3 ± 1823.2
|
2266.0 ± 1816.5
|
Z = -0.752
|
0.452
|
0.206
|
1 In case of variables with the distribution close to normal distribution we used parametric testing with Student t test and in case of variables with a distribution significantly different from the normal distribution we used non-parametric testing with Mann-Whitney U test.
2 In case of variables with the distribution close to normal distribution we used Cohen’s d for the evaluation of effect sizes and in case of variables with a distribution significantly different from the normal distribution we used rank-biserial correlation.
Bold type indicates significant difference in the outcome variable.
As additional information, 91% of women from the HIIT group and 90% from the EDU group had higher educational level. The remaining women had secondary education. 44% of women from the HIIT group and 50% from the EDU group had moderate level of physical activity. 38% of women from the HIIT group and 30% from the EDU group reported high level of physical activity. The remaining 18% of women from the HIIT group and 20% from the EDU group presented low level of physical activity. Groups did not differ either in their educational level (χ2 = 0.021, p = .885) or as a category of physical activity measured with the IPAQ (χ2 = 0.374, p = .829). Of note, the clinical score for depression symptoms was obtained by 5.9% of women form the HIIT group and 10% of women in the EDU group at baseline; and by 5.9% of women form the HIIT group and none of women in the EDU group during second assessment.
The severity of depressive symptoms
The results obtained in the ANOVA with repeated measures revealed a significant main effect (F = 6.530, p = .014, η2 = 0.112, observed power = 0.708), in the absence of an interaction effect (F = 0.878, p = .353, η2 = 0.017, observed power = 0.151), in case of the severity of depressive symptoms. However, when controlling for the week of birth (variable entered as a covariate in ANOVA) neither interaction effect (F = 1.506, p = .225, η2 = 0.029, observed power = 0.226) nor main effect remained to be significant (F = 2.010, p = .162, η2 = 0.038, observed power = 0.285). Further post-hoc analyzes showed that the groups did not differ in the severity of depressive symptoms, both in the first measurement (t = 0.277, p = .783, 95% CI: LL = -2.039, UL = 2.692, Cohen’s d = 0.078; HIIT group: M = 5.68, SD = 4.44; EDU group: M = 5.35, SD = 3.69) as well as in the second measurement (t = 1.620, p = .111, 95% CI: LL = -0.289, UL = 2.713, Cohen’s d = 0.399; HIIT group: M = 4.91, SD = 3.49; EDU group: M = 3.70, SD = 2.01). The change over time was non-significant in both the HIIT group (t = 1.620, p = .115, 95% CI: LL = -0.196, UL = 1.725, Cohen’s d = 0.278), as well as in the EDU group (t = 1.759, p = .095, 95% CI: LL = -0.314, UL = 3.614, Cohen’s d = 0.393).
Additional analysis with the Chi-square test showed that the groups (HIIT and EDU) did not differ in the presence or absence of clinical symptoms of depression (comparison of the observed and expected frequencies in each category: "occurrence of depressive symptoms", "no depressive symptoms") both in the pre-test (χ2 = 21.205, p = .130) and in the post-test (χ2 = 10.796 p = 0.460).
In the next step, we evaluate the associations between the severity of depression symptoms in the final assessment and age, BMI, level of education, week of birth, VO2max (at baseline and final), category of PA level (at baseline and final) as well as IPAQ METs (at baseline and final) in both groups. We found no significant correlations in the EDU group. However, in the HIIT group we found significant correlations between the severity of depression symptoms and category of PA level (at baseline) as well as IPAQ METs (at baseline and final). Based on the results of the correlation analysis, we performed series of regression analyses. The details for the significant correlations are presented in the Table 2.
Table 2 Predictors of the severity of depression symptoms during second assessment for HIIT group.
|
Severity of depression symptoms
|
|
R2
|
F
|
p-value
|
Beta
|
Baseline PA in METs
|
0.224
|
9.244
|
.005
|
-0.473
|
Baseline category of PA
|
0.219
|
8.990
|
.005
|
-0.468
|
Final PA in METs
|
0.230
|
9.548
|
.004
|
-0.479
|
METs- metabolic equivalents of tasks
PA-physical activity
Fear of childbirth
In case of the fear of childbirth, the ANOVA with repeated measure revealed that there is a significant main effect (F = 6.956, p = .011, η2 = 0.118, observed power = 0.735), in the absence of an interaction effect (F = 1.710, p = .197, η2 = 0.032, observed power = 0.250); see Figure 2. Additional, post-hoc analyses pointed that the groups did not differ in the case of the severity of fear of childbirth, both in the first measurement (t = -1.908, p = .061, 95% CI: LL = -5.160, UL = 0.118, Cohen’s d = 0.471; HIIT group: M = 32.29, SD = 5.09; EDU group: M = 34.81 SD = 5.64), as well as in the second measurement (t = 0.445, p = .658, 95% CI: LL = -3.211, UL = 5.041, Cohen’s d = 0.125; HIIT group: M = 30.76, SD = 7.52; EDU group: M = 29.85, SD = 6.89). The change (decrease in fear of childbirth) between pre- and post-intervention was significant in the EDU group (t = 3.060, p = .006, Cohen’s d = 0.684), but not in the HIIT group (t = 0.999, p = .325, Cohen’s d = 0.171). However, when controlling for the week of birth (variable entered as a covariate in ANOVA) neither interaction effect (F = 2.256, p = .139, , η2 = 0.042, observed power = 0.314) nor main effect remained to be significant (F = 1.584, p = .214, η2 = 0.030, observed power = 0.235).
In the next step, we evaluated the associations between the severity of fear of childbirth in the final assessment and age, BMI, level of education, week of birth, VO2max (at baseline and final), category of PA (at baseline and final) as well as Pa in METs (at baseline and final) in both groups. We found no significant correlations in the EDU group. However, in the HIIT group we found significant correlations between the severity of fear of childbirth and category of PA (at baseline) as well as PA in METs (at baseline). Based on the results of the correlation analysis, we performed regression analyses. The details for the significant correlations are presented in Table 3.
Table 3 Predictors of the fear of childbirth during final assessment for the HIIT group.
|
Fear of childbirth
|
|
R2
|
F
|
p-value
|
Beta
|
Baseline PA level in METs
|
0.145
|
5.439
|
.026
|
-0.381
|
Baseline category of PA
|
0.234
|
10.294
|
.003
|
-0.493
|
METs- metabolic equivalents of tasks
PA-physical activity
|
Physical and mental health
For the assessment of the differences in the physical aspect of health (reflected by the “Physical health” subscale’s score of the SF-12) between groups in the two measurements, repeated ANOVA measures revealed no significant main effect (F = 0.015, p = .903, η2 = 0.00, observed power = 0.052) nor interaction (F = 0.25, p = .876, η2 = 0.00, observed power = 0.053). Non-significant results were also observed when the week of birth was entered as a covariate in repeated ANOVA measures.
However, in case of the mental aspect of health (reflected by the “Mental health” subscale’s score of the SF-12) the analysis pointed at the significant main effect (F = 8.669, p = .005, η2 = 0.153, observed power = 0.823), in the absence of an interaction effect (F = 0.099, p = .755, η2 = 0.002, observed power = 0.061) (see Figure 3). Post-hoc analyses showed that the groups did not differ in the mental aspect of health in the first measurement (t = -1.995, p = .051, 95% CI: LL = -7.87, UL = -0.02, Cohen’s d = 0.562; HIIT group: M = 48.46, SD = 7.23; EDU group: M = 52.38, SD = 6.53), and in the second measurement (t = -1.791, p = .080, 95% CI: LL = -6.09, UL = 0.35, Cohen’s d = 0.522; HIIT group: M = 51.90, SD = 6.06; EDU group: M = 54.77, SD = 4.43). Of note, the increase in the mental aspect of health was significant only in the HIIT group (t = -2.652, p = .013, 95% CI: LL = -5.85, UL = -0.76, Cohen’s d = 0.476) and non-significant in the EDU group (t = -1.661, p = .114, 95% CI: LL = -6.04, UL = 0.71, Cohen’s d = 0.381). However, when controlling for the week of birth (variable entered as a covariate in ANOVA) neither interaction effect (F = 1.236, p = .272, η2 = 0.026, observed power = 0.193) nor main effect remained to be significant (F = 2.271, p = .106, η2 = 0.055, observed power = 0.366).
In the next step, we evaluated the associations between the physical and mental health in the final assessment and age, BMI, level of education, week of birth, VO2max (at baseline and final), category of PA (at baseline and final) as well PA in METs (at baseline and final) in both groups. We found no significant correlations in the control group. However, in the HIIT group we found significant correlations between the physical health and IPAQ (final) as well as between mental health and category of PA (at baseline and final) and PA in METs (at baseline and final). Based on the results of the correlation analysis, we performed regression analyses. The details are presented in Table 4.
Table 4 Predictors of the physical and mental health during final assessment for the HIIT group.
|
Physical health
|
|
R2
|
F
|
p-value
|
Beta
|
Final PA in METs
|
0.157
|
5.947
|
.020
|
0.396
|
|
Mental health
|
Baseline category of PA
|
0.160
|
5.533
|
.026
|
0.400
|
Baseline PA in METs
|
0.212
|
7.799
|
.009
|
0.460
|
Final category of PA
|
0.127
|
4.200
|
.050
|
0.356
|
Final PA in METs
|
0.167
|
5.818
|
.022
|
0.409
|
PA-physical activity
METs- metabolic equivalents of tasks
|
|
|
|
|
Covid-19-related fear
In case of the Covid-19-related fear, the results revealed that there were no significant differences between groups in the first assessment (F = 0.075, p = .785, η2 = 0.001, observed power = 0.058; HIIT group: M = 12.94, SD = 0.69; EDU group: M = 13.25, SD = 0.90). Of note, lack of significant results was observed when controlling for the week of birth as well. The analysis with the Mann-Whitney U pointed to non-significant results as well (Z = -0.535, p = .593; HIIT group: M = 11.41, SD = 0.76; EDU group: M = 10.30, SD = 0.97). The decrease in the fear of Covid-19 (measured with the Wilcoxon T test) between the initial assessment and final measurement was significant in the HIIT group (Z = -3.328, p < .001) as well as for the EDU group (Z = -2.661, p = .008); see Figure 4.
In the next step, we evaluated the associations between the COVID-19-related fear in the final assessment and age, BMI, level of education, week of birth, VO2max (at baseline and final), category of PA (at baseline and final) as well as PA in METs (at baseline and final) in both groups. We found no significant correlations in the HIIT as well as EDU group.
The exercise capacity (expressed as VO2max)
The analysis conducted with repeated measures ANOVA revealed both the significant main effect (F = 20.387, p < .001, η2 = 0.290, observed power = 0.993) as well as interaction effect (F = 16.928, p < .001, η2 = 0.253, observed power = 0.981), in case of the VO2max; see Figure 5. Post-hoc analyzes showed that the groups (HIIT and EDU) did not differ in the VO2max in the first measurement (t = -1.631, p = .109, 95% CI: LL = -4.241, UL = 0.439, Cohen’s d = 0.465; HIIT group: M = 25.59, SD = 4.37; EDU group: M = 23.69, SD = 3.58), however they differed in the second measurement (t = -4.076, p < .001, 95% CI: LL = -8.191, UL = -2.786, Cohen’s d = 1.149; HIIT group: M = 25.21, SD = 5.11; EDU group: M = 19.72, SD = 4.14). The change (decrease in VO2max) between pre- and post-intervention was significant in the EDU group (t = 5.125, p < .001, 95% CI: LL = 2.348, UL = 5.591, Cohen’s d = 1.146), but not in the HIIT group (t = 0.339, p = .737, 95% CI: LL = -0.924, UL = 1.292, Cohen’s d = 0.060).
The level of physical activity (based on IPAQ)
Further analysis with Mann-Whitney U test revealed that groups did not differ in the IPAQ MET in the first assessment (Z = 0.752, p = .452; HIIT group: M = 2625.27, SD = 1823.21; EDU group: M = 2266.00, SD = 1816.46). Similarly, no between-group differences were observed in the second measurement (Z = -1.506, p = .132; HIIT group: M = 3118.31, SD = 1995.15; EDU group: M = 23.69, SD = 3.58). The within-group analyses with the Wilcoxon T test revealed, that the differences between initial assessment and second measurement were statistically insignificant for both the HIIT group (Z = -1.410, p = .158) and EDU group (Z = -0.037, p = .970).