This study aimed at compare the effect of 16 weeks’ non-periodized and linear periodization combined training on the sleep quality of obese adults. Regarding the MCS, improvements were found in this component and in the domain of mental health after training only in NG. In addition, greater magnitudes of improvement were found in the MCS domains for the NG compared to the PG and CG, pertinent to the improvement of the psychological and social aspects, however, without statistical difference. Furthermore, a significant difference in time was observed for the functional capacity domain, with an increase in the score of the groups that underwent training, regardless of periodization.
The benefits of combined exercise on muscle structure, cardiorespiratory fitness, reducing systemic inflammation and metabolic markers in people with obesity are already evident 7,12,13, as well as the reduction of articulate and back pain 18. Thus, the improvement in functional capacity in the groups that performed the combined training is due to the aforementioned improvements; however, the different training prescriptions did not provide different results in this domain. The benefits of increased intensity, observed in studies with aerobic or strength exercises performed in isolation, 15,29, may be linked to the different forms of manipulation of the training load, with greater amplitudes than those used in the present study (40–69% HRres; 14 − 8 MR). This helps to explain the similar improvements observed in some domains PCS for both training groups.
Studies that have looked at the effect of combined training on HRQoL, and included overweight people, have conflicting results. Sillanpää et al., 23 observed an improvement in general health only among PCS, with a tendency to worsen the domains of role-physical and bodily pain in adults. Differently, Goldfield et al., 21 when analyzing the effect of training on adolescents, reported a significant improvement in functional capacity. Whereas, Baptista et al., 30 when evaluating the HRQoL of elderly people, observed improvement in three of the four physical domains (except role-physical), in addition to the PCS itself. It should be noted that the three studies cited used some form of training progression, making it impossible to compare them with studies with non-periodized methodologies. Therefore, the results of training interventions combined with and without progression are still inconclusive on their effects on HRQoL PCS.
The regular practice of physical exercises attenuates psychosocial disorders in different ways, either by improving the immune system and other physiological markers or else by the capacity for distraction and self-efficacy 17. In addition, improvement results in the MCS may precede the physical benefits, as they need greater stimuli for their adaptation, while the feeling of belonging to the group, distraction from stressful environments and a feeling of increased vigor provide psychological well-being, achieved even with reduced training volume 31–33. Evidence has suggested that exercising 30 to 60 minutes, three to five times a week, reduces mental burden, improving aspects of mental health 32, and in more severe disorders the practice is efficient, for example, improving depressive conditions 34. It is worth mentioning that the studied population did not have any diagnosed psychological disorder and, even so, it had positive effects on mental health. The improvement of this domain is of paramount importance in this population, and population-based evidence from the same region where the study was conducted pointed to a 45% increase in the prevalence of depressive disorder when there is the presence of CNCD 35.
In the longitudinal study by Chekroud et al., 32 higher intensities were associated with improved mental health in more than 1.2 million individuals. This corroborates the initial hypothesis that the program with linear periodization would present superior results due to the increase in intensity presenting superiority in other health parameters 5,7,12,14−16. Despite this, Reid et al., 22 when verifying the impact of progressive combined training on patients with type II diabetes mellitus and excess weight, did not report an improvement in MCS, which according to the authors was due to the excessive fatigue of the modality. This corroborates the findings of the present study, since more expressive results were found only in the group with no progression of intensity for mental health and MCS and, even if not significant, in role-emotional, social functioning and vitality. The difference in the frequency of training between the groups could explain the improvement of the MCS domains observed in the NG, but, despite 8.5% higher than the PG, it did not present significant differences between them, denoting not being a weighting factor for improvement 36. Another possibility are intrinsic factors linked to the practice of exercises, such as a taste for practice and motivation, exercising a direct influence on health parameters 36, but they represent a limitation of the present study since they were not evaluated.
The applied clinical design is one of the main strengths of this study, being an intervention lasting 16 weeks of training combined with different forms of periodization, using a control group for comparison, with randomization and blinding. Likewise, the equalization of the training volume allows the different periods to be compared in an equivalent manner. It should be highlighted the re-evaluation of the resting HR to adjust the participants' internal load to maintain the proposed intensity. Another important factor for the results is the sample of individuals with only obesity, free of other comorbidities. This reduced the eligible candidates for the study, but increased the representativeness of the HRQoL analysis in individuals with obesity.
As limitations, both the low adherence of the participants to the training sessions and the number of dropouts from the study must be considered when observing the results. It is likely that the participants in this research would benefit from greater effects by training more often, with consequent implications for HRQoL. Likewise, dropping out of the study may be due to low self-esteem, vitality and other negative psychological factors present in this population 37. Thus, more expressive results were not found in the PCS, possibly due to the low attendance of the participants to the training, given the need for frequent stimuli for the physiological adaptations to occur. It is likely that dropouts from this research are less aware of their health status, having a negative effect on their motivation 38. It is important to recognize that satisfaction, taste and pleasure when carrying out training is essential for the maintenance of individuals, therefore, there is the possibility that the training proposal used, without adherence strategies, is not sufficient to motivate this population 36. There is a possibility that the sample in this study was composed of some people with depressive disorder, or at least with symptoms, due to the low MCS score. The search for professional help and the clinical diagnosis of individuals affected by mental disease tend to take longer to happen, since the perception of symptoms and the perception of worsening health are mediators in the process, 39 not recognizing the presence of these diseases when questioned initially in that study.
In conclusion, non-periodized combined training is effective in improving mental health and MCS. However, it is not possible to state that the non-periodized model is superior to linear periodization, since similar results were found in the PCS between the training groups. From these results, we recommend that the training prescription combined with non-periodized structure, that is, with periodic adjustments of the internal load to achieve the physical and mental benefits of HRQoL in adults with obesity. Future studies should investigate the relationship between the proposed periodization and the improvement of HRQoL, contributing to greater understanding of the benefits provided in people with obesity, including different forms of periodization, such as the wave. Manipulations in the training frequency, duration and intensity proposed may expand the knowledge about the possible implications in HRQoL. These studies must take into account the low adherence of this population to training, inclusive, adopting strategies to maintain adherence to exercise programs.