Resumen de Effects of trunk-focused exercise programs and how the training program and the individuals' characteristics modulate their impact
Trunk-focused exercise programs (TEP) refer to those training programs in which the main target of the exercises resides in the active and/or passive trunk/core structures. Although these programs have shown a positive impact in sport and health contexts throughout recent years, there are several limitations in the literature that hinder the understanding of TEP effect and their relationship to the individual and to the training load characteristics. In this sense, TEP are sometimes compared to exercise control groups and/or other exercise programs that include trunkfocused exercises. Furthermore, although the individual and the training program features are a basic aspect to optimize training programs, experimental TEP studies not always provide this information properly. To address these constraints, the present doctoral thesis includes two systematic reviews and an experimental study. The two systematic reviews aimed at an in-depth analysis of the literature on TEP both, to improve the knowledge about the trunk-focused exercise contribution to increase trunk physical fitness and ameliorate stroke and low back pain symptoms, and to better understand how the individuals and exercise programs characteristics modulate TEP effectiveness. Overall, although the quality of evidence was low, their results showed that TEP were effective to ameliorate stroke and patients’ non-specific chronic low back pain condition, with positive effects in all the outcomes analysed. Furthermore, the analysis of moderator factors revealed that TEP effectiveness in stroke patients seems to be higher when the initial trunk impairment is greater, the patients are older, and the intervention starts earlier. Importantly, the TEP impact on low back pain symptoms (mainly pain reduction) seems higher when a greater improvement in trunk and/or hip range of motion is recorded after the training program and participants have a lower body mass index. These results reinforce the importance of paying close attention to the individuals and to the exercise programs characteristics when designing this type of interventions. On the other hand, the experimental study overcomes some of the problems found in the systematic reviews, especially the lack of experimental works that objectively controlled the training load intensity. This study aimed at the comparison of the effects of a higher intensity and a higher volume core stability exercise (CSE) program on core stability, core endurance and whole-body dynamic balance in young physically active males, using a smartphone-accelerometer to control the CSE intensity. These study results showed the specificity of the effects caused by the CSE programs, with a larger increase in the lumbopelvic postural control during the execution of isometric CSE for the higher intensity CSE program and a larger core endurance increase for the higher volume CSE program. Interestingly, the performance of conventional isometric CSE in lying and quadruped positions during the CSE programs did not have a significant impact on the unstable sitting test, a sudden loading protocol and several wholebody dynamic balance tests. Altogether, the results of the studies included in this doctoral thesis highlight the importance of performing TEP to improve trunk performance, functional capacity, and health status in different populations. Specifically, the two systematic reviews showed how moderator factors related to both, the individual and the training program characteristics can play an important role in modulating TEP effectiveness, which should be considered to maximize and tailor the TEP benefits in stroke and low back pain patients. However, the quality of the evidence for all the outcomes analysed in these systematic reviews was low, and thus, higher quality studies are required to strengthen the evidence on the impact of performing trunk-focused exercises in stroke and low back pain rehabilitation programs. Regarding the experimental study, the training load control performed through the smartphone-accelerometer allowed to describe the specificity of the effects caused by a higher intensity and a higher volume CSE program in young physically active males. Further research is needed to characterize the dose-response relationship of CSE programs in different populations properly.
Keywords: trunk exercises, potential effect modifiers, rehabilitation, training load, wearable devices.
