Our results showed that participants in the lumbar and pelvic support groups reported significantly less pain intensity immediately after the intervention and after the 4-week follow-up than women in the control group. These results align with the findings of Patil's (17) and Mens et al.'s (19, 29) studies that reported women with PPGP could benefit from supportive pelvic belts to reduce pain in the postpartum period (17, 19, 29). Our results showed that the lumbar support group experienced more pain relief than the pelvic support group. It may stem from increased stimulation of skin receptors or compression of the soft tissues around the spine and pelvic joint receptors compared to pelvic support (42). Furthermore, it is possible that lumbar support has biomechanical effects on the lumbar area (43) and reduces mechanical loading to the trunk muscles in daily living (44) more effectively than pelvic support.
In this study, we assessed the effectiveness of lumbar and pelvic supports on pain, disability, and motor control in women with postpartum PPGP. Several studies have examined the effect of pelvic support in PPGP populations. Still, the absence of a control group (with no intervention) restricts the ability to determine the impact of such an intervention (17, 19, 30). A recent study showed that pelvic belts could improve pelvic pain in postpartum women with PPGP (30). However, the generalisability of their results was limited due to the small sample size (n = 16).
PPGP impacts the ability of women to perform activities of daily living (ADLs) and their quality of life (45). Concidering disability score measurements in the PPGP, only one study has directly compared the efficacy of a belt intervention in the postpartum PPGP (17). Patil et al. suggested that existing belts could provide more efficient support for the abdomen and pelvic areas if some modifications were made to their structures. In this case, the participants involved have minimal or no discomfort performing their daily activities (17). The findings showed that the lumbar and pelvic support groups had lower disability scores than the control group. However, a more remarkable improvement was observed in the lumbar support group after the 4-week intervention. As a broader support, the lumbar support could provide more comfort for participants in performing ADLs.
The Effort score during the ASLR has been used as a clinical parameter for the diagnosis and severity of PPGP (15). The study's results showed that the effort score during the ASLR improved when both lumbar and pelvic supports were used for the 4-week intervention period. However, there was a significant reduction in the effort score during the ASLR in the lumbar support group. It is generally believed that pregnancy is associated with pelvic misalignment (46) and instability, which can be alleviated by using a belt (47, 48). Based on these results, lumbar support could stabilize the lumbar and pelvic joints more effectively than pelvic support. The lumbar support also improves muscle function for load transfer over the pelvic region, providing more stabilization than the pelvic support (49).
The results showed that lumbar and pelvic supports increased the maximum isometric hip flexion force immediately after the intervention and after the 4-week follow-up. However, women in the control group exhibited limited hip flexion force. An explanation could be that involved women try to stabilize the pelvis with more muscle activity but cannot produce adequate muscle force to raise their legs (50). A previous study showed that using a pelvic belt positively impacted the ASLR and patients was able to raise their leg with no effort (51). The lumbar and pelvic supports might increase pelvic joint stiffness, which requires unloading sensitized ligamentous structures. This stiffness improvement could produce more normalized motor responses during the hip flexion test (50).
The pelvic support had minimal effect on trunk rotation muscle force when the intervention was terminated. In contrast, lumbar support improved trunk rotation muscle force during the intervention and follow-up periods. The following explanations for how the lumbar support could manage trunk movements have been proposed: improving proprioception, enhancing force closure muscle activity, and stiffening the trunk (43, 52–55). The enhanced proprioception may stem from increased stimulation of cutaneous mechanoreceptors (27, 28, 54). Aside from providing additional proprioceptive input, it has been suggested that lumbar support may also help regulate trunk movements and optimize lumbopelvic stabilization for normal load transference through the pelvis (43, 56, 57). Some studies suggest that lumbar supports increase trunk stiffness by making the entire spinal column more robust to perturbation (52, 55). Indeed, participants perceived added support just after wearing lumbar support and increased confidence in undertaking trunk movements (58).
The effect of orthotic interventions on proprioception in the PPGP has not been studied. In this study, proprioception was assessed by measuring the JPR of the hip joint in the standing position. This variable proved to be more accurate and reliable in the abduction movement of the hip joint than in the other movements (59). Our findings revealed no clinically significant differences in the reproduction of hip joint abduction between the groups after the intervention or during the follow-up period. JPR measurement in a standing position on the symptomatic side might lead to asymmetrical shear loading through the SIJ (60), making it unstable during load transfer (61) and aggravating the symptoms of PPGP (62). Further research with different test positions or continuous use of supports for longer than a certain period might affect the JPR of the hip joint.
We designed this trial with a wash-out period to explore each orthotic intervention's lasting effect (carryover of effect). Participants discontinued using support after the 4-week follow-up, and variables were assessed one week later. In the lumbar support group, variable improvements continued even after removing the support. Upon removal of the pelvic support, the pain intensity remained unchanged. Moreover, disability, effort score during the ASLR, and hip and trunk muscle force returned to their initial levels during the intervention. Therefore, a one-week wash-out phase might be more acceptable for future crossover studies using lumbar and pelvic supports.
Some limitations were identified in this study, which could be used to improve the design of future large clinical trials. First, we examined trunk rotators for gross trunk movement and ignored specific muscles in detail. Second, the hip joint reproduction error variable did not significantly change when supports were used in the intervention groups. A larger sample size or longer intervention time is recommended for future studies. Third, the findings provide evidence only for the pregnancy-related PPGP population and cannot be easily generalized to individuals involved in SIJ pain.
Despite these limitations, our study provides practical knowledge for treatment planning and clinical decisions for women involved in pregnancy-related PPGP. Early intervention for involved women might be required to manage worsening symptoms.