Our study revealed that the DM group exhibited significant improvements in several key outcomes compared to the placebo group. Specifically, participants in the DM group showed enhancements in CMJ landing force, SJ concentric peak power, balance in both anterior-posterior and medial-lateral center of pressure, time to stabilization in the SLLH test, and peak landing force in both SLLH and LH tests. When comparing the DM group to the NHC group, no significant differences were observed across most variables. However, it is worth noting that the DM group displayed significantly better results than the NHC group in terms of LH peak landing force.
Manual therapy focused on DM significantly enhanced static balance in the anterior-posterior and medial-lateral center of pressure during the SLS test, possibly being justified be some underlying mechanisms. DM techniques targeted specific muscle groups and joint structures in lower limbs, possibly promoting proprioceptive feedback and neuromuscular control [24]. By applying manual forces diagonally across the region, these techniques may engage sensory receptors within muscles, tendons, and ligaments, eliciting proprioceptive signals that enhance the brain's awareness of limb position and movement [25]. This heightened proprioception allows for more precise adjustments in muscle activation and joint positioning, crucial for maintaining balance during single-leg stance [26]. Furthermore, DM can modulate neural pathways involved in postural control [27]. Research suggests that manual therapy techniques, including mobilization, can influence the excitability of neural circuits within the central nervous system, particularly those related to balance and coordination [28].
Our results also found that DM significantly improved the time to stabilization in the SLLH and LH tests, possibly also justified by eliciting proprioceptive feedback that enhances neuromuscular control and coordination. For example, a study by Espí-López et al [29] found that manual therapy techniques, including mobilization, led to increased dynamic balance possibly due enhancing proprioceptive ability. Also, research has shown that manual therapy techniques can influence cortical excitability and spinal reflex arcs, leading to enhanced motor output and coordination [30]. For instance, a study by Lehr et al [31] revealed that mobilization with movement significantly enhanced dynamic balance in health individuals.
By possibly improving proprioceptive input, diagonal mobilization facilitates more precise adjustments in muscle activation and joint positioning, which are essential for stabilizing the body during dynamic tasks like the SLLH and LH tests. Additionally, manual therapy interventions can modulate neural pathways involved in motor control and balance [32].
Our results also revealed that DM significantly improve landing force in the SLLH and LH tests, and CMJ. Although similar studies investigating this phenomenon have not been observed, a previous study revealed that high-impact landing forces were reduced through the implementation of augmented feedback information instructing individuals on proper landing techniques [33]. In our case, DM may have acted as a regulator of proprioception, facilitating improved coordination of muscle activity, thereby reducing excessive landing forces and promoting smoother force absorption. Additionally, by targeting joint restrictions and asymmetries, manual therapy techniques optimize the alignment of the kinetic chain, thereby reducing the risk of excessive loading and injury during landing tasks. Research has shown that manual therapy interventions can improve joint range of motion and biomechanical alignment. For example, a study by Stanek et al [34] found that manual therapy techniques improved tibial range of motion. These biomechanical improvements can enhance the ability to absorb and distribute forces during landing, resulting in reduced landing forces and improved landing mechanics.
While our study revealed promising results regarding the effectiveness of DM in improving various outcomes related to balance, neuromuscular control, and landing force, several limitations should be acknowledged. Firstly, our sample size was exclusively related with youth players, limiting the generalizability of our findings to elite populations. Future research should aim to test these findings with elite players aiming to ensure the robustness of the observed effects. Furthermore, despite our efforts to introduce a gentle approach in the control group to mimic a placebo effect, it may not effectively evoke the placebo response. This limitation is noteworthy, particularly in manual therapy, where the identification and implementation of placebos are not as straightforward as in other clinical trials. Additionally, the lack of a long-term follow-up assessment in our study prevents us from understanding the durability of the improvements seen with DM over time. Longitudinal studies are warranted to evaluate the sustained effects of DM interventions beyond the immediate post-treatment period. Furthermore, the mechanisms underlying the observed improvements with DM remain speculative and warrant further investigation. Incorporating neurophysiological assessments, such as electromyography or functional MRI, could elucidate the neurobiological mechanisms through which DM influences balance and neuromuscular control. Additionally, exploring the optimal dosage and frequency of DM interventions could help optimize treatment protocols for maximal effectiveness. Despite these limitations, our study provides valuable insights into the potential benefits of DM in improving balance and neuromuscular function, laying the groundwork for future research to address these gaps and refine our understanding of its therapeutic mechanisms and clinical applications.
From a clinical perspective, our findings indicate that DM can be integrated by practitioners to augment several performance parameters in young soccer players. These include enhanced landing force in CMJ, increased concentric peak power in SJ, and improvements in balance metrics such as anterior-posterior and medial-lateral center of pressure. Notably, DM should be applied cautiously, tailored to individual player needs to address specific imbalances. Furthermore, in the context of return-to-play scenarios, the incorporation of DM may offer additional benefits, potentially mitigating injury risks before training sessions or matches.